Wireless-sleep apnea monitoring system

Preface sleep apnea syndrome is a very common sleep breathing disorders, according to research in the United States, approximately 24% of the adult male and adult female, or 9% more than 200 million people suffering from this disease in China, Taiwan at least 35 000 people have this problem.

Whether in the diagnosis of patients generally suffer from sleep apnea refers to patients during sleep in apnea and hypopnea total more than 5 times per hour. Including apnea refers to sleep, appear for 10 seconds more respiratory air flow, low airflow ventilation means breathing does not completely stopped, only to the original 20% ~ 50%, while oxygen concentrations declined 4 percent of respiratory disorders. Current doctor diagnose sleep apnea syndrome often use night sleep apnea more physiological monitoring instrument that records all night sleep cycle, including apnea and breathing becomes shallow times, type, number, oxygen index, ECG changes, mouth and nasal cavity flow, thoracic and abdominal respiration, blood oxygen and other signals of the earlobe, snoring frequency. Use night sleep apnea more physiological monitors although accurate, but require them to wear a variety of instruments, must also be in a specific hospital professionals to conduct measurements, very inconvenient is also easy to affect patients sleep, so not suitable for long-term monitoring. Therefore General patients unless the very serious is not going to go into hospital for this check. What's more, many physiological sleep apnea monitor meter is an expensive instruments, General patients will not be buying their own measurement in the home, it is difficult to achieve universality. The system mainly directed against these disadvantages developed a simple, conscious of more low, affordable and suitable for home sleeping environment for long-term monitoring of the monitoring system to help physicians understand the patient's condition, and provides medical treatment process to improve traceability.

Research methods and system design for system block diagram 1.

This system consists of (1) physiological parameters meter and (2) the physiological parameters parser. Physiological parameters meter contains a physiological signal sensing devices, micro-controller. Physiological parameters parser is the use of Bluetooth wireless module receives physiological measurement meter as measured with physiological parameter data, analysis, and congenial operation screen is displayed, providing patients sleep physiology.

Figure 1 wireless-sleep apnea monitor system block diagram physiological parameters gauge · physiological signal sensing device heartbeat variations use of sensing components for optical sensors, the main use of human vascular cardiac contraction of blood flow and oxygen concentration will produce changes.

This system using optical coupler (CNY70) using optical reflection method detects vascular blood flow changes at the end. Figure 2-optical coupler CNY70 internal structure and principle of action.

Figure 2 optical coupler CNY70 internal structure and operation principle of the audio signal receiver is receiving sleep due to the obstructive snoring, this system uses a capacitive audio receivers as key components of the received signal, use receive wave pressure change vibrating membrane of displacement, causes the vibration film and aluminum shell of capacitance change with ultrasonic CT or weak, electric capacity to complete the conversion of impedance FET produces RECM, RECM REXT and change of partial pressure, resulting in a different output.

Figure 3-audio receiver internal structure and principle of action.

Figure 3 audio receiver internal structure and operation principle breathing sensor works is the use of breath will have ups and downs and chest, pulling the horizontal variable resistance resulting resistance value changes. · physiological signal sensing circuit 1. heartbeat sensor circuit diagram 4 block diagram for heartbeat sensor circuit.

Heartbeat is a change in the measurement sensor to signal to contain the DC bias voltage (DC Offset), heartbeat signal, breathing and muscle vibration, noise and high-frequency 60Hz, heartbeat signal to the desired signal, signal noise, therefore, be regarded as separate pre-filter circuit of hardware and software are two approaches to address different noise on the impact of the measure. Front filter circuit features can reduce software program for digital signal processing the required amount and time of operation, avoid causing signal processing delay. Figure 5 is the heartbeat of the waveform. Figure 6 as the heartbeat into digital signals of the waveform. Figure 7-heartbeat sensor circuit.

Figure 4 the heartbeat sensor circuit block diagram

6 the heartbeat converted waveform diagram 5 heartbeat signal waveform diagram before the conversion

Figure 7 heartbeat sensor circuit 2. snoring sensing circuit diagram 8 block diagram for snoring sensing circuit.

To the audio receiver measurements to snore signal contains a lot of noise and background noise, you must use the hardware filter high frequency, low frequency noise removal only snoring band signal, Smithson [1995] research shows snoring frequency is approximately 1 ~ 200Hz voice band, other sounds of frequency domain is broader. First of all by the audio receiver from the measured signals, signal amplification via 200Hz low pass filter to filter out other sound caused by noise. Figure 10 to convert the snoring signal digital signal of a wave. Figure 11 for snoring sensing circuit.

Figure 8 snoring sensing circuit block diagram

Figure 10 snoring signal converted waveform diagram 9 snoring signal conversion before the waveform

Figure 11 snoring sensing circuit 3. respiratory sensing circuit diagram 12 for respiratory sensing circuit block diagram.

Use of the ups and downs when thoracic breathing, pulling the horizontal variable resistance change resistance values resulting voltage change, by way of the signal amplifier, comparison to determine breathing circuit. Figure 13 for respiratory signal waveform. Figure 14 for respiratory sensing circuit.

Figure 12 respiratory sensing circuit block diagram

Figure 13 respiration signal waveform

Figure 14 respiratory sensing circuit · CPU and display power

Road, Figure 15 shows the CPU and the system shows the circuit. CPU is using shengqun Semiconductor Co., Ltd. produces HT46R24 microcontrollers, which consists of A Port and Port C driver 15 * 4 Chinese display-LCD, as physiological parameters data display, Port B to physiological parameters and timer input, while Port D the MAX232 quasi-phase conversion do serial transmission.

Figure 15 CPU and display circuit · firmware physiological parameters measurement ditital program are as follows: in the physiological parameters measurement to avoid reading into the body of the error signal when turning, the use of multiple read way avoid, when the signal changes, continuous read and each read room joined some time delay, after the signal read than on is the same, this way you can reduce the signal read error rates.

When processing is complete of physiological parameters information stored in the buffer with a micro-controller, and through the Chinese type LCD display as measured with physiological parameters. Bluetooth wireless module, the key will be stored in the micro-controller for internal buffer of the physiological parameters data via RS-232 serial transmission between your computer and personal data communication. Physiological parameters parser to Visual Basic6.0 as a development tool, via Bluetooth wireless module receives from physiological parameters meter physiological parameters transferred data, stored in a database and associate each time point of physiological parameters for analysis, connecting Excel treats each time point measurement of physiological parameter information for analysis and integration to graphs showing each point in time, let the physiological changes of status in the diagnosis of physicians.

Results in Figure 16, on the grounds of the hospital had the correct data is the actual simulation of the system measured curves of the diagram.

This system provides a set of normal sleep respiratory physiological parameter data and graphs to increase physician in comparison and judgment of convenience.

Figure 16 physiological parameters after PATA cable analysis results indicated above in Figure 16 is not suffering from sleep apnea sleep respiratory physiology; is suffer from below the sleep apnea patients sleep sleep physiology.

Table 1 as Figure 16 individual color curves represent meaning. Figure 16 curve analysis and comparison can be found, sleep apnea syndrome patients sleep apnea is usually accompanied by snoring, sleep apnea, heart frequency at the same time domain has a very significant decrease, so it can judge the suffer from sleep apnea patients in the long term is not acceptable for the treatment of sleep apnea, the heart is not in sleep a beating but easy to suffer from diseases of the cardiovascular system.

Concluding remarks in the design of single-chip microcontroller software, must be based on the timeline as a benchmark, measuring various physiological parameters, in order to identify the individual reconstruction physiological parameters.

In order for the physiological parameters measurement meter volume miniaturization, you must select a low consumption power and size of the smaller components, and use the micro-controller so that the overall power consumption is minimized. Bluetooth wireless transmission modules for low power consumption and high security of wireless data transmission equipment. Measurement in physiological parameters, you must set the physiological signal sensing device fixed to the patient's body, because sleeping head, body movement and flip, easily lead to measurement equipment for peeling and incorrect measurement data, incorrect measuring how much affect the physician's assessment of the symptoms. So the physiological parameters measurement meter sensor size must be small, fixed easily, easily fall off and avoid affecting patients with sleep, physiological parameters of data processing, you must first use filter, noise removal, it only shows the real Sleep disordered breathing on the physiological parameters of the waveform, this is easier to get accurate physiological parameters, thereby improving the accuracy of the diagnosis doctor. In addition, to meet the physiological parameters gauge within the circuit module, the system's power supply is very important. Traditional power handling is determined by the electricity company provides 110V 60Hz (Editor's Note: this indicator for Taiwan power) of power through a weight, volume, no small transformers, after rectifier and voltage in order to get the voltage required for the system, but this procedure because the temperature easily leads to heat not exactly the components easily damaged. In order to let the physiological parameters meter small volume, light weight, and will not produce high-temperature, physiological parameters gauge adopts the market 110V 60Hz converted to 5V 1A power converter, providing micro-controller, and then through the DC-DC-double group-power converters into sensing circuit module ± 5V power supply, compared to the past, not only the difficulty of reducing power design, making it more convenient to carry.

References: 1.

Mariano Cabrero-canosa, Elena Hernandez-pereira, and Vicente Moret-Bonillo, ‘Intelligent Diagnosis of Sleep Apnea Syndrome.’IEEE engineering in medicine and biology magazine, March 2004:72-81.2. Varady et al., ‘A Novel Method for the Detection of Apnea and Hypopnea Events in Respiration Signals.’IEEE Tran. Biomed. Eng., 2002; Vol. 49, September: 936-941.3. ASYALI et al., ‘Assessment of Closed-Loop Ventilatory Stability in Obstructive Sleep Apnea.’ IEEE Tran. Biomed. Eng., 2002; Vol. 49, March: 206-216.4. Varady et al., ‘On-line Detection of Sleep Apnea During Critical Care Monitoring.’ Proceedings of the 22"d Annual EMBS International Conference, July 23-28, 2000, Chicago IL.5. China Taiwan tssm

Several new high performance electrical amplifiers

Overview

Bio-electrical signals are very weak in detecting biological signal both strong interference, therefore, the design of high-quality electrical amplifiers has numerous technical difficulties.

This article describes the use of ADI produced integrated instrument amplifier and amplifier, the design of several new structure forms of bioelectricity preamplifier.

Figure 1-electrical design application a preamplifier

Figure 2 electrical preamplifier design application 2

Figure 3 electrical preamplifier design application 3

Several new high performance electrical amplifiers

A design application

The amplifier circuit consists of four parts: instrument amplifier A5 form of front-stage amplifier, operational amplifier A4 constitutes differential amplifiers after, DC compensation amplifiers A3 and A1, A2 form right leg drive circuit, circuit structure as shown in Figure 1.

The advantage of this circuit highlight is the introduction of the DC circuit, so that the original DC-coupled amplifier become AC coupled amplifier, to remove the effect of polarization voltage.

Because maximum polarization voltage can reach 300mV, AC coupled to reduce the effect of polarization voltage is required.

In this circuit, DC compensation amplifiers to offset DC offset. To ECG collection, for example, if the left arm DC offset + 300mV, right arm to 0V, differential input voltage-300mV. Assuming that the former class instrument amplifier gain is 5, then the instrument amplifier output amplitude will reach 1.5V, if after the class magnification of 50 or higher, the output does not appear to 75V and saturation. Because in this circuit, feedback loop provides a reverse voltage equal to the reference point, as this kind of linear and impact, polarization voltage being eliminated, output saturation does not appear.

However, the vast majority of integrated instrument amplifier gain and common-mode rejection ratio: the higher the gain, the more common-mode rejection ratio.

And integrated instrument amplifier as bioelectrical preamplifier, due to the presence of polarization voltage preamplifier gain only in dozens of times, this enables integrated instrument amplifier as preamplifiers of cmrr is not possible.

For the circuit, pay attention to when choosing devices: as the front-stage amplifier instrument amplifier low gain requires high common-mode rejection ratio, as a result of subsequent DC compensation circuit and the magnification level is minimal, so the instrument amplifier input offset voltage is too high.

For positive and negative power supply system, you can use analog instrument amplifier AD620. It has the following features: adjustable gain (1 to 1000); power supply range (2.3V ~ 18V); maximum input offset voltage 50 V; input bias current up to 1nA; gain low has a large common-mode rejection ratio (G = 10, cmrr 100dB minimum), meet the design requirements. For rear differential amplifiers operational amplifier A4, magnification mainly in this level, so there are required operational amplifier low input offset voltage. You can choose the ADI OP747 (four operational amplifier), OP2177 (dual operational amplifier), have a micro-v magnitude of offset voltage and good performance.

Design application 2

The circuit consists of four parts: parallel dual operational amplifier consisting of front-stage amplifier, RC coupling circuits, integrated instrument amplifiers back-level amplifiers and common-mode signal sampling driver circuit, circuit design, as shown in Figure 2.

The advantage of parallel dual operational amplifier is not sophisticated matching resistor, theoretically it's cmrr is infinite, and with its peripheral resistance matches.

But parallel dual operational amplifier output is the double-differential output signal, if only with single-ended output signal will no longer have this advantage. So this circuit in after the class uses an integrated instrument amplifier A5, will double-differential output signal is converted to a common single-ended output signal. Integrated instrument amplifier has a good performance, but because the cmrr proportional gain in differential mode, while devices exist high offset voltage and usually signal source in large DC offset voltage (such as the detection of polarized when physiological signal voltage and sensor zero offset voltage), in direct application of integrated instrument amplifier as preamplifier is not able to achieve the maximum of cmrr performance. So this circuit in after the class uses an integrated instrument amplifier, and uses the RC-coupled circuit isolation DC signals, thus making integrated instrument amplifiers achieve higher differential-mode gain, resulting in very high cmrr performance. Common mode sample driver circuit consists of two equal resistor R4, R5, and one by the operational amplifier A3 composition of follower. A3 of the input signal is taken from the a1 and a2 outputs two series resistance of the voltage Vc, i.e. when only the differential mode signal output V01 = V02, VC = 0, the operational amplifier A3 output voltage of 0 is equivalent to the Earth; and when both common-mode voltage and differential-mode signal input, the total output A3 contains only common mode input signal part VC = 1/2 (Vi1 + Vi2). Making common mode signal without RC coupling circuit pressure directly on the integrated amplifier input, avoids due to capacitance coupled circuit does not match the overall reduction circuit cmrr.

After the actual measured, as shown in Figure 2 uses the circuit diagram the parameter, the circuit cmrr in 120dB above.

Use this circuit to note selected devices: as after the class amplifier instrument amplifier input offset voltage to as small as possible, because after the class has a major role of amplification. Can the AD620 Adi, the input offset voltage of up to 50 V.

Design application 3

The circuit consists of four parts: Qualcomm network, and

With dual op amp amplifier with integral feedback circuit of Qualcomm differential amplifiers and common-mode signal sampling driver circuit, circuit design, as shown in Figure 3. The amplifier has two different from past other biological preamplifier features: 1. Qualcomm Network on the front-end amplifiers; 2. Amplifying circuit magnification is done in amplification that parallel dual operational amplifier.

In this amplifier design, the signal input of the Qualcomm network is not grounded, if you enter a common-mode voltage, there is no current flowing through the network (no common-mode current pathway), high-pass network points potential equal, won't change the common mode signal signal for differential mode, you can achieve a high common-mode rejection ratio.

In addition, because the internal resistance of the organism signal source is generally higher, so the design-time selection of great resistance as possible R1 and R2 (M class), you can better meet the needs of the circuit.

For a multistage amplifier system, the first level of magnification for large, as much as possible to reduce the noise amplifiers behind, so that the entire system of noise reduction.

But because polarization voltage and input offset voltage operational amplifier itself, fore gain not may be too large. Qualcomm Network better solution to the DC input voltage (polarization voltage), however, the operational amplifier itself by input offset voltage is magnified, still obviously affect the output of dynamic range. For example, the input offset voltage 1mV, 1000 times magnification, the amplifier output will reach 1V. Qualcomm Network resistor-capacitor will bring the noise impact on the system, this is past bioelectrical preamplifier design not the capacitance is placed in front of the system. The circuit uses Qualcomm differential amplifiers solve this problem. In the latter part of the differential amplifier feedback loop by adding an integrator, it has no effect on the AC signal, only on DC and extremely low frequency signal integration, offset by the impact. Right leg drive circuit through a follower access circuits, you can avoid right leg signal effect of the circuit, power frequency interference suppression.

After the actual measured, as shown in Figure 3 uses the circuit diagram the parameter, taking into account the problem of resistance, capacitance match the circuit cmrr can reach 123dB.

Design and application of the three, though the magnification is in the fore parallel dual operational amplifier, but former Qualcomm network, after integrating feedback circuit, dual operational amplifier requirements. As a back-level differential amplification of operational amplifier, because they do not make amplification, so do not specifically require a low offset voltage. In this circuit to make resistance as possible, so that the capacitor matching the best system performance.

Several comparison of bioelectrical preamplifier

Integrated instrument amplifier cmrr and gain.

Gain higher, cmrr. And integrated instrument amplifier as bioelectrical preamplifier, due to the presence of polarization voltage preamplifier gain only in dozens of times, this enables integrated instrument amplifier as preamplifiers of cmrr is not possible.

Combined with common mode driving technology of RC coupling circuit and integral feedback circuit, whether on the front or in the middle of the circuit are aimed at removing a magnified impact on biological signals of polarization voltage and devices in high offset voltage.

In the design of application a, front-stage amplifier by instrument amplifiers, gain lower, in order to achieve a high common-mode rejection ratio, instrument amplifier low gain with high common-mode rejection ratio.

The amplification signal DC components (including polarization voltage and instrument amplifier input offset voltage) by eliminating DC compensation circuit. Back level amplifier has a major task of amplification, operational amplifier input offset voltage has a high demand, not too large, high-gain amplifier, affect the output signal. In the design and application of the second, parallel dual operational amplifier as a top level amplifiers, gain low. It does not need sophisticated matching resistor, theoretically it's cmrr is infinite, and with its peripheral resistance matches. The amplification of the signal after common mode sample driver removal DC component. Instrument amplifier as after the class amplifier, the primary task of enlargement, since the cmrr proportional gain in differential mode, so you can achieve a high common-mode rejection ratio, but also require instrument amplifier input offset voltage is not too large, otherwise high-gain amplifier the signal output after impact.

In the design of the application, the front-end of Qualcomm Network filter addition polarization voltage, led as the front-stage amplifier parallel double amplifier can assume major enlargement task without causing the output saturation, and high-gain amplification can reduce system noise, and the operational amplifier itself by input offset voltage with high-gain amplifier by after the class Qualcomm differential amplifier feedback loop Integrator elimination.

However, it is necessary to pay attention to the design resistance, capacitance of matching, to achieve a high common-mode rejection ratio.

Conclusion

This article on several high-performance, low-cost electrical preamplifier provides an analysis of comparison, they skillfully use instrument amplifier gain and common-mode rejection ratio, combined with RC coupling circuit, integral feedback circuits and common-mode driver technology enables high performance amplifiers, suitable for detection of biological signals.

Handheld medical equipment power supply

When the range of medical equipment from hospital to emergency and family medical environment, its mobility will is determined by a number of factors.

In addition, the hospital's medical equipment often need battery support for patients in different hospital wards in the transfer.

Also, reproductive boomers people has entered the elderly, they still hope that scattered activities, this is the traditional fixed equipment for portable applications has created a demand for these devices to facilitate the activities of the sick elderly.

They include a diagnostic instrument, such as, in addition to fiber fibrillation ultrasonic equipment and blood Analyzer; there is also a device for patients, including insulin syringes, left ventricular assist device (LVADs) and wireless signal monitor life.

In addition, when multiple surgical instruments can only be used within a certain scope, some of the instruments are related to the use of battery-powered and get rid of this limitation.

Like electric plastic tools or endoscopic surgical equipment such as using battery power, the surgeon felt that flexibility brings great convenience.

Traditional battery pack contains the main energy supplied and integrated the remaining battery power, protection circuit, temperature sensor, display the battery or battery status led driver and serial data communication bus circuit boards.

External battery pack is a typical plastic shell that comes with the with the master can be connected with electrical interface external touch points and absorb vibration and maintaining internal and external components of the insulation.

Use profiles

Design a safe and reliable system for the first step is to accurately understand medical device use model called features, these features include the temperature range, discharge curves, charging, save life and transmission needs.

Application for mobile device selection of optimal battery, all external and internal operating temperature also are important considerations.

Manufacturers indicate the batteries in the ideal of constant current C/5 and + 20 ° c external temperature performance.

However, many medical devices are expected to be able to work at-20 ° c ~ + 60 ° c temperature range, and heat can charge and discharge process, lion and when battery system with temperature-sensitive components together, the combination of battery systems and equipment housings have maximum temperature threshold.

An inconsistent pulse discharge or typical defibrillators of pulse will cause the batteries to produce more heat, compared to non-uniform discharge curve, this situation can be faster to reduce battery capacity.

While charging the battery heat dissipation effects, should be taken into account in the design of battery systems.

Optimization property

To select the best batteries battery pack determines the field medical equipment works correctly, it needs to have full battery performance curve.

Learn about the voltage, charge and discharge cycles, load current, the energy density, charging time and discharge rate, and other indicators for handheld device select the cell in the first step, below to the standard to describe several batteries.

First of all be sealed lead acid batteries (SLA).

Rechargeable SLA's features include: rated voltage of 2V, Prism or cylindrical structure, large capacity, low cost and simple charging conditions. SLA batteries biggest challenges include: large bulky volume factors, linear voltage attenuation, lack of fast charge technology and on the high temperature and high self discharge sensitivity (this affects save life).

Followed by the NiMH battery.

Its features include: 1.25V rated voltage, the life of 500 charge and discharge cycles, 100Wh/kg average energy density, charging time is less than four hours, almost 30 per cent of the monthly discharge rate and strict size factor. In a demand for low-voltage or price sensitive places, NiMH batteries have a very good performance, 10 NiMH batteries can concatenate to increase voltage so that the total voltage reaches 12.5V.

Finally the lithium-ion battery.

Characteristics of lithium ion batteries included: 3.6V rated voltage and in the life of 500 to 1000 of charging and discharging cycles, the average energy density is 160Wh/kg, charging time is less than 4 hours per month average discharge rate of 10 per cent; 7 lithium-ion battery can be threaded together so that the total voltage reaches 25.2V.

Intelligent battery pack

Handheld and outdoor is the current trend of medical equipment.

Lithium-ion battery with higher energy density, lighter weight, more long work cycle, superior capacity retention and wide ambient temperature adaptability, relative to the same power of NiMH and SLA solution, it requires less number of batteries.

The Board of many advanced attachments promote a system of intelligent, these attachments including residual power, protection circuit, temperature sensor and serial data bus.

A smart battery pack, when the end user's discharge curve or characteristics adapted, can provide higher power utilization. Battery pack for the medical applications of worthwhile because it has the ability to monitor their own State, can accurately predict the remaining running time and work groups States sent to medical devices. These features allow the end user can use intelligent management device, but also to avoid unexpected failures or shutdowns. An intelligent battery pack can be used according to its history, such as making feedback traceability and guarantees provide convenience.

Security

Medical batteries must integrate multiple security systems and reliable protection circuit.

Where the activities of the safety circuit is to ensure that the battery of chemical substances remain stable State must factor. Safety circuit protection battery from overcharge and discharge, short circuit and extreme temperatures, the voltage shall be limited to the strict scope of work. Safety circuit through the battery temperature sensor at a particular temperature circuit breaker to prevent heat dissipation and overheating.

For multiple-cell battery pack, have an active cell balancing circuit is wise.

The circuit is placed in the battery pack in a particular key, as this makes the battery is no longer a risk of overheating.

How to deal with medical electronic equipment design challenges?

Medical electronic devices from weak and complex body signals in collecting valid information, and on the basis of this information to monitor, display, and the diagnosis of disease, while avoiding medical electronic devices causing damage to the human body, the technical staff in the development of medical electronics equipment faced many challenges.

Recently, the 2008 China International Medical Electronics Assembly (CMET2008) was held in Shenzhen, from scientific research institutions, and medical electronics TI, ADI, Xilinx, Altera, Actel, NI, and other international semiconductor vendor experts delivered a fantastic keynote and with many participating medical electronic Enterprise technician, medical electronics trends and increasingly complex design challenges for Exchange and discussion.

Large medical electronic devices used for semiconductor devices

Shenzhen Siemens El dit NI magnetic resonance company into Dr. "large medical equipment in electronic technology," keynote speech that large medical equipment mainly used for the diagnosis and treatment, and civilian or portable medical electronic devices development there are many different considerations.

For example in magnetic resonance imaging (MRI) system, generally using high-speed FPGA for sequential control, data transmission, and high-performance DSP is used for real-time security monitoring. Development of large medical equipment are rarely purchase devices from the market, but with the development of semiconductor suppliers, special-purpose device for large-scale development of medical electronics equipment and semiconductor vendors compare long-term relations of cooperation. The medical equipment of non-real-time data needs bus protocol control, Siemens, GE, Philips, large selection of medical equipment have CAN-bus, while using Ethernet Powerlink (EPL) has gradually become a trend, but the bus is not suitable for such as ECG, biochemical Analyzer uses this type of equipment. In addition, NI, also to those who intend to develop and magnetic resonance imaging devices supporting the use of test equipment business proposal, you must ensure that ancillary instruments are completely non-magnetic, otherwise it will cause the supporting apparatus and magnetic resonance imaging devices interfere with each other, so there is this program the best enterprise is to find magnetic resonance manufacturers.

Low power: portable medical equipment demand significantly

From different semiconductor vendor experts speech found that providing longer battery life, lower power consumption become portable medical equipment with common characteristics of semiconductor devices, and high-performance, highly integrated, portable medical devices use analog device's main features.

Figure 1: SRAM in soft errors and error fixing.

Figure 2: fixed error on SRAM FPGA logic has serious implications.

Actel Asia Pacific Technical Manager wearing Meng-lin recommended choice for medical device design FPGA to the reliability, the highest consideration.

Because SRAM FPGA to achieve ultra-low power work usually requires the device to standby and shut off the power source, in hibernation before will register state SRAM to non-volatile memory, which makes the design of FPGA on SRAM and cost a great deal of influence. (See Figure 1, 2) Actel low power FPGA using Flash Freeze technology reduce power consumption, support this technology, the device simply 1us can access low-power mode. The Flash Freeze process of FPGA devices provide low power characteristics and makes the contents of a register is maintained, so Flash FPGA has SRAM technology and fuse technology advantages of FPGA and could also be "-error". Dai Meng-lin stressed the Actel's proASIC3L family of devices is a real single chip Flash GPGA, than those who merely SRAM FPGA and Flash blend package FPGA devices with higher reliability and lower costs.

At this Conference, portable ultrasound imaging system to become a semiconductor vendor mentioned most medical electronics design.

Latest ultrasound imaging system using digital processing of signal chain, the higher the sampling frequency and direction of portable direction. In these new ultrasound system needs to display 3D and even 4D high quality color images. With the ultrasonic system design of complex, how to deal with the modern ultrasound imaging design challenges?, two large FPGA Xilinx and Altera recommend ultrasound beam generator (Beam Former) design using FPGA with DSP performance.

Figure 3: Xilinx's high-performance digital beam generator program.

Xilinx Asia Pacific DSP product and solutions marketing business senior manager Lin Hong SEO represents a portable ultrasound system trend is a growing number of data need to be processed more quickly, so the ultrasonic imaging system of beam generator will require greater use of programmable, high-performance DSP platform.

Xilinx's low-power FPGA provides by using DSP48 Slice full spectrum of high-performance FIR filters, FFT algorithm even floating-point operations, while also reducing costs.

Figure 4: Altera devices in the application of ultrasonic systems.

With the need to increase the number of probes, beam generator in a corresponding increase in the number of channels, it means more DSP features and more high-speed serial interface, and PCIe interface and new DDR2/DDR3 will also be new portable ultrasound system.

Altera senior technical marketing engineer Cho Min pointed out that, in the ultrasonic system design which uses high-speed Stratix III FPGA can cope with the high-performance beam generator by these challenges, because Stratix III device has a large number of DSP module implementation of filtering and weighted function and supports multiple channels at the same time, or only support DDR3 'sFPGA; at the same time as adopting programmable power technologies, optional core voltage and optimization of chip technology, Stratix III device power consumption is significantly reduced, thus becoming the industry's lowest power consumption of high-performance FPGA.

ADI medical device product manager Paul Errico said CW Doppler ultrasound system image quality requires constantly improved, therefore the design process should adopt high-performance analog devices, portable ultrasound system selection of highly integrated analog devices also allows lower overall cost.

Paul Errico in the General Assembly introduced the ADI for CW Doppler processing introduced the eight-channel high performance analog front-end chip AD9271, 4 I/Q demodulator AD8339 and ultra-low power 16-bit ADC AD7980. Of these, AD9271 integrated LNA, VGA and 12-bit pipelined ADC, not only can improve portable medical equipment image quality, smaller chip area and low-cost advantages, but also improve the battery life and reliability.

Figure 6: bipolar process and CMOS process on ultrasonic system front-end device parameters of control.

Coincidentally, TI in the General Assembly also introduced a highly integrated 8 channel analog front end AFE5805 analog front-end, which is to determine the image quality and overall system performance is critical, however, that a low-power analog front ends is in a package in the integrated LNA, VCA and ADC.

TI analog signal chain applications engineer Chen Hong sang at the Conference stressed that, in the face of CW Doppler ultrasound system of noise, bandwidth and space, and other design challenges, using bipolar process and CMOS technology to different functional modules of the parameters have different effects (see Figure 6), so the engineers to focus on analog front end function module technology.

LabVIEW rapid prototype built medical equipment

The 21st century is the century of the life and health, life sciences and the rapid progress constantly promoting human health and the disease itself, how to develop an innovative healthcare electronic equipment has become one of the focuses of the study.

Medical device research content involves many engineering research fields such as electronics, computer, information processing, optics, precision mechanics, etc.

With the medical treatment of the development, diversification and related engineering field technology continues to progress, medical electronic devices are becoming increasingly complex. General major medical device composed of multiple subsystems, the need to integrate a variety of sensors, machinery parts, electronic components, such as FPGA or microprocessor, etc, but also involves a variety of professional bus and the Protocol, its research and development cycle is quite long and may take 2 years to 3 years or even longer. So, how to shorten the whole medical electronic equipment system development time, improve the innovation degree will be market elements.

For some small companies, from fierce competition in a firm foothold and stand out is a very difficult thing.

Their core technical personnel may be experts in the field of biology and medicine, and master a certain patent or research results, but how do I in team personnel very limited circumstances, fast will patent or research results into products, and to guarantee product reliability and stability are very difficult. Therefore in the highly competitive medical electronics market, enabling rapid prototyping is the key. From another perspective, for universities, research institutes or the company's research and development institutions, they must focus on the future, have a forward-looking and innovative equipment research and development, so that researchers need to be concerned about how quickly some algorithm or theoretical research results for authentication, and to further build out the actual system until the products of their own research projects or patent industrialization, gets more support to enter into a virtuous circle.

To sum up, for medical electronics equipment developers, system itself in electronic, mechanical, sensors and other aspects of complexity and the demand of market competition, how to quickly prototype validation of research results and products of a leading to the market.

Through a unified platform to rapidly build prototype systems

System development generally can be divided into design, prototype verification, release of three phases.

Design phase for the product itself and which involves the concept of the algorithm, is a prototype verification; design of feasibility for validation or assessment; publication is the product of the final implementation. The main tasks during the design phase is determined by the development team in the biomedical, signal processing, image processing specialists or researchers use text and mathematical tools for algorithm or system design. Prototype verification phase, the main task is to be implemented on a hardware platform and verify designing algorithms and assess to further adjust the algorithm, this task is usually made with electronic engineering background of embedded system developers, VxWorks, QNX, Linux and embedded operating systems to be completed, they are using software tools and hardware platform directly related, such as CCS, VHDL, VDSP ++, etc. In general the two stages of developers and development platform is different, so the prototype phase of the developer must seamlessly design phase to attract and convert the results, if the system requirements needed to be amended or algorithm design some errors that will result in a large number of amendments to the prototype phase of the work and even rework. Therefore, the entire system development is a loop of the progressive process.

In order to reduce both the number of times between iterative stage, many development teams have taken sides move closer to each other, ask on the front of the algorithm designers on the hardware and the underlying programming have a certain understanding upfront embedded system developers also need to have some background in biology and medicine.

In this way, to a certain extent, to let the two stages between greater communication, but for developers of requirements is higher, but the lack of systematic, along with medical electronic systems became increasingly complex, cannot fundamentally solve the problem.

A more fundamental solution is to put these two phases of the transplantations to the unified development platform, which is a development platform integration algorithms and hardware: on the one hand, the introduction in algorithm design phase early hardware i/o for validation, you can find at an earlier stage and fix potential errors; on the other hand, uses the same algorithm design development environment, code can prototype verification process to be reused, thus simplifying the programming complexity, lowers the algorithm design and embedded developers, radically speed up the circulation of the progressive process, thereby reducing the system's development time.

LabVIEW: quickly build medical electronic prototype graphical platform

LabVIEW graphical development platform since its inception in 1986, has been working to simplify the complexity of the programming, the graphical programming has also become standard development tools.

For the development of medical electronics, LabVIEW provides hardware I/O introduced algorithm design, and through code reuse and commercialization, to publish embedded prototyping platform that simplifies the complexity of building a prototype system.

Interactive algorithm design emphasis on code reuse

Over the past few years, LabVIEW has extensibility into a variety of algorithms for design to better meet the needs of research and design staff.

In addition to the powerful graphical programming style, the LabVIEW now also includes a text-based math programming tools, continuous-time simulation, state diagrams and a graphical control design and simulation, model, to represent various algorithms and applications. At the same time, for digital filter and control models, digital signal processing algorithm development of interactive tools for the introduction of the medical electronics related algorithm design easier.

Signal processing is a lot of medical electronic systems critical parts, through LabVIEW and associated kits, designers can function by calling the out-of-the-box, quickly finish for example remove baseline drift, noise reduction, QRS detection, signal extraction applications, etc.

ByInteractive Quick VI (Virtual Instrument), as long as the menu is set to parameter to complete the Kaiser window FIR high-pass filter design to remove baseline drift. In order to further processing, or you can call the advanced signal processing toolkit-mania in Wavelet functions to filter out broadband noise.

For example, the fetal heart signal extraction and other more complex processing, developers can also use LabVIEW in ICA (ICA) algorithm to be applied.

As shown in Figure 1, the upper part is collected from the mother and the fetal heart's mixed-signal, and the bottom half is ICA after separation of the fetal heart rate signals.

At the same time, developers can also use LabVIEW built-in text mathematical tools to reuse existing algorithms, such as using the Mathscript node called MATLAB in development of .m file, and an interactive environment through LabVIEW on algorithm validation debugging, so with a variety of advanced mathematical and software integration.

With the introduction of the hardware i/o and fix potential problems found

As mentioned, if the system needs to be amended or algorithm design errors that will result in a large number of amendments to the prototype phase of the work and even rework.

So a solution is earlier to real-world signals and hardware into the design process, resulting in an early stage discovery and fix potential problems.

LabVIEW platform the most obvious value in algorithm design and hardware I/O a bridge is established between.

LabVIEW through the introduction of the i/o signals, and the design process and various advanced math and design software integration to help engineers to quickly add real-world data and theoretical models, thus enabling interactive design process faster, design time shorter.

Physical measurements and design and simulation completely different challenges, requirements and a wide range of measurement and control hardware tightly integrated, and to optimize the performance of processing a large number of channel data or high speed throughput.

LabVIEW through constant evolution, in physical measurement areas providing extremely high performance and flexibility to work with hundreds of data acquisition equipment and thousands of instruments and seamless integration.

Through code reuse and commercial platform to rapidly build prototypes

Most embedded systems developers currently using prototype evaluation board for system prototyping, but the prototype Board often only have a small number of analog and digital i/o channels, the also very little support for Visual, motor or synchronization capabilities.

In addition, only for the design concept of validation, designers often need special sensor or support special I/O and spends a lot of time and development resources to develop custom prototype Board.

To simplify this process, and remove the hardware verification and Board-level design amount work using flexible, commercialization of prototype platform becomes more and more embedded systems developers.

But for most systems, and prototyping platform must include the final release of the same parts, such as execution algorithms, real-time processor, used for high speed processing of programmable logic devices, or real-time processor interfaces connected to other parts. Therefore, if the commercial system does not meet all the requirements, so this prototyping platform must be scalable and supports custom. NI offers a variety of hardware platforms and LabVIEW integration, complete design, prototype verification to the publishing of the whole process. For example using LabVIEW and NI repeatable configuration I/O (RIO) equipment or NI CompactRIO platform, you can quickly and easily create a prototype of medical electronic devices.

Rapid prototype build instance: liquid nitrogen tumor therapy instrument

Medical device manufacturer Sanarus plans to develop an innovation-surgical equipment Visica2 (V2), implementation of the treatment process includes painless anesthesia, real-time ultrasound lesion localization and minimally invasive surgery.

To keep up with the product release schedule, the developers plan for four months to develop a working prototype of the system. In addition, under the investor demands, as soon as possible to achieve production to meet market needs.

Prepare the firmware for your device in General and to develop a custom circuit board cycle is very long.

Once the firmware or software layer problems will cause additional delays thus affecting the progress of your project. In addition since v2 is medical equipment that requires that the device must not contain any prejudicial to the performance of the system firmware and software errors; if not through 510 (k) certification required expendable test, the entire project will fail. Based on these requirements, you need a very reliable development programmes.

Because both integrated I/O development and programming features, CompactRIO is considered a flexible programme.

CompactRIO system consists of a 400 MHz processor, Ethernet controller, as well as the back panel of the 3 million Gates FPGA, LabVIEW FPGA Module can be on the back panel of the FPGA programming. Because LabVIEW FPGA is a graphical programming environment, biomedical engineers without VHDL experience can participate directly in the programming work. They can run in embedded controllers and liquid nitrogen pump pure resistive heating parts of control algorithm that management and control in the FPGA devices necessary input/output signals of interface, this resource allocation allows the construction of the prototype and the final system posted in the programming model is very similar to on. CompactRIO benefits clearly, the use of customized programmes need a few months time, NI programme took only a few weeks.

In addition, if you use the custom firmware, once the new demand will lead to cumbersome update process.

After using CompactRIO platform, code modifications become very easily. As the development platform is very flexible, as new functional requirements, the development process without delay. In addition, because the CompacTRIO has passed the EMC certification, this also ensures that when the prototype validation, regardless of the specialized design of EMC-related.

Summary

LabVIEW graphical development platform by providing design, prototype from algorithm to authenticate to a product launch, from software debugging and functional testing to production testing of unified environment that allows engineers and researchers can be on the same platform for product design and development, reduce cycle development and code correction, thereby speeding up the design process.

At the same time, through the CompactRIO embedded prototyping platforms, researchers can quickly be patent or research results into products, and to guarantee product reliability and stability, thus shortening the development of medical electronic devices.

Low power portable medical data recorder

Many medical applications requires no external power and data cable of the portable self-powered device, the most obvious example is the patients carry used to measure heart rate, body temperature and other health indicators of portable data recorder.

Of course, there are many complex applications even through external power supply, would need a small battery equipment secure redundant and equipment monitoring, such as hospitals, patient rooms, the environment controlled laboratory or storage device environment parameters (including temperature and humidity) continuous monitoring is required; the other portable device installation you will need an external power supply and network cable to the device easier and more flexible.

In some cases, such as the need for patients to carry medical equipment, freezer temperature detection equipment, no external power and network cables.

Portable medical equipment requirements which features? first, must be on-board power supply.

Usually available through rechargeable or non-rechargeable battery, although there are other ways (such as solar power), but this depends on the voltage and current requirements. No matter what kind of power supply, power supply efficiency must be high enough, and battery-powered portable device does not require a full load of work should be able to get to the "sleep" mode to minimize power consumption, dormant devices can be an external trigger signal or regular is "wake up", and then raise the operation rate (of course, power consumption will increase) in normal operating mode. The device should have between full-load work and "hibernate" modes of operation to perform some simple task (such as access memory or refresh LCD and LED display data), because devices typically only under certain conditions would need full-load operation capability (e.g. for sensor data filtering and decode), so that you can power and speed between a degree of balance.

Portable device even though support for wireless communication, but is not always guaranteed to be able to access the wireless network.

Depends on network conditions, a time machine in a wireless network environment, the next time it may be moved to does not have a wireless network environment, or may be caused by power outage temporarily turn off the wireless network. In these cases, if the device itself does not support wireless communication devices will need to keep collecting data stored for later upload to top level systems for data processing. There are a number of key data (such as environmental security failure data, configuration data, or device drivers) must ensure that the storage security, even if the battery fails or is removed or is missing.

Other characteristics of the portable device depends on the specific application requirements, the data can be directly through the analog sensor acquisition or through local network access to a subsystem read, portable device can only passively collecting data under certain conditions the voice alarm proactively through or to signal the alarm.

Some simple data acquisition equipment before the upload data without user intervention at all, while other devices (such as hand-held blood glucose meter or wristband-heart monitor) may require additional input and output device instead of the host system to change configurations or browse data.

Use MAXQ2010 design portable data logger

Although the industry has many options for microcontrollers, but Maxim company MAXQ series low-power microcontrollers, mixed-signal RISC MAXQ2010 characteristics that is ideal for battery-powered data acquisition devices.

MAXQ2010 have extremely low power consumption, high MIPS/mA ratio, only need a small battery current support portable applications, integrated 8 channel 12-bit ADC can collect many types of sensor data, and also supports many types of local serial interface (I2C, SPI, UART synchronous/asynchronous), can be used to access the host system and serial non-volatile storage devices, or relating to this device in the other subsystem communication.

MAXQ2010 according to the current task on computing capacity requirements by dynamically adjusting the clock frequency to change the power consumption, and when it has finished processing all of the data and events, a portable device to go to the lowest power consumption of Hibernate (stop) mode until you wake up again by application.

MAXQ2010 nuclear voltage only 1.8V, can greatly reduce power, 3V independent power supply of I/O can communicate with the external high-voltage logic. If you want to use as the lithium battery 3V button this single supply and do not want to use the dual power supply, you can use built-in integrated voltage regulator to nuclear power. In stop mode, the voltage regulator can be turned off to reduce power consumption.

MAXQ2010 to a variety of ways to read data from the sensor, if acquisition of analog sensor data, and can use built-in 12-bit ADC, multi channel support, 8-channel single-ended input.

MAXQ2010 from external sensors collecting data can be stored in backup battery-powered RAM or internal flash memory. On-chip clock based on real-time 32kHz (RTC) in the stop mode can work, according to the timescales for the data provider. If you want users to enter data or information that is displayed to the user is able to achieve MAXQ2010, it has a set of general purpose input/output pin (the largest packaging has 56), you can drive LED, read the mechanical switch settings, or scan through the ranks of the connected switch matrix. MAXQ2010 also has an LCD controller, you can direct drive 3V-segment LCD that supports up to 1/4-cycle multiplexing (COM1-COM4), its largest package provides 40 specialized driver pins, in 4 times the multiplex mode can drive 160 segment LCD display.

The data recorder based MAXQ2010 design examples

Like many used to collect or store data in the electronic device based on the data recorder adopts MAXQ2010 USB interface with the host (PC) communication.

However, because no USB interface MAXQ2010, we use FTDI FT232R chip company achieve USB adapter with UART.

Adopt the FT232R can give loggi design brings many benefits.

First, when the USB bus activity, The data logger can take advantage of the FT232R 3 .3V regulator output power supply, only one can be against diodes and battery-powered automatic switching, and because the regulator output (minus 0.2V diode forward voltage drop) voltage than the battery voltage after subtracting the diode drop in voltage high so that you can connect to the USB bus, the recorder no battery and power supply via USB Vbus. Takes two diodes (Figure 1) is to prevent a battery, output capacitor used to lower the load transient effect on the battery. Secondly, MAXQ2010 can utilize two serial interface (UART) in a direct and runs on personal computers, application communication, does not require any additional driver. Two serial ports by a built in USB connector on the virtual COM port connections. This design uses MAXQ2010 32kHz FLL based crystals as their own clock source (if you need to provide for RTC timing), it costs less than other crystals or resonant circuit costs are much lower. FLL circuit corresponds to a multiplier coefficient multiplier for 256, 32kHz Crystal oscillation frequency to 8.388MHz as MAXQ2010 clock.

Is calculated based on the data logger is MAXQ2010 consumes much current, can be considered: first, an external signal (such as buttons or sensors voltage jumps) micro-controller to wake from the stop mode; the system then through a single ADC channel read analog sensor voltage, the acquisition of sensor voltage values are stored in the data in RAM; at this point in order to save power, the micro-controller to return to the stop mode, but in about 60 seconds, the arousal of micro-controller was again (back in step 1).

Therefore, the calculation of the average current consumption and estimated battery life need microcontroller following parameters substituted the formula (1): tActive (complete all operations, including entering stop mode), iActive (this period of typical current values), tStop (keep stop mode), iStop (stop mode typical current), tExit (from stop mode is wake-up time), iExit (was woken by the typical current).

(tActive × iActive) + (tStop × iStop) + (tExit + iExit)

tActive + tStop + tExit

According to the above parameter values can be calculated from the average current of approximately 202nA; that is, if the power is an ordinary CR2032 lithium battery, the battery life can be estimated as 1138 hours.

Different battery manufacturers production of battery characteristics vary, CR2032 battery in 90% of discharge interval not exceeding 0.3V pressure drop, which means that the battery voltage drops to 2.7V before (after a diode drop back to 2.5V, meet single-supply operation at minimum voltage), micro-controller can work in 1024 hours.

Increased battery capacity or quantity, use rechargeable batteries, or when you are connected to the USB charging, etc. automatically while many measures are used to extend the battery life.

General average current is only slightly higher than the stop mode, the standby current, this is because the stop mode time far longer than the time the program runs, stop mode of the current play a leading role. Program loop code can be extended, such as measuring multiple sensor values or add other features do not significantly change the battery life. Of course, the use of other peripheral functions, such as LCD displays, LED indicates or serial port, and so will increase the power consumption, designers in the calculation of the actual battery life when you need to consider these features may increase power consumption.

Based on RF transceiver for implantable medical devices

Zarlink Semiconductor company for pacemakers, Nerve Stimulator, pump and other implantable medical devices applied a ultra low power RF transceiver chip, the data transfer rates, low power consumption, with unique wakeup circuit.

This article discusses how to use the RF transceiver for intimate communication system design.

Integrated circuit (IC) and medical device development over the past 30 years has been developed at the same time.

Circuit technology contributed to the development of increasingly complex, highly integrated and compact medical device development. At the same time, health care costs continue to rise and people living in the more affluent, more fat in the body, as well as longevity, have had to rely on the base station wireless connection of implantable medical devices of new application and treatment needs. Traditionally, implantable medical devices of communication system uses very short magnetic coupling, which requires the programmer and medical equipment to tightly coupled, usually data rate is lower than 50kbps.

In order to overcome the distance limits 402MHz ~ 405MHz medical implant communication services (MICS) band in 1999 enabled, then Europe would appear similar standards.

The band was possible with long distance (usually 2m), relatively high speed wireless link. In the human body due to signal transmission characteristics, and the band working user work-compatible (such as meteorological balloons, and other auxiliary meteorological equipment) and global availability, 402MHz ~ 405MHz band is ideal for this kind of service.

For implantable medical applications of the electronic system of the enormous difficulty of low power design.

For example, the vast majority of implantable pacemaker life require longer than seven years, the maximum leakage current in 10uA ~ 20uA magnitude. Because of the need to support the pacing and on current consumption requirements, communication systems current design of the equipment within the overall average life current does not exceed the total amount of the current design, i.e. 15% 2uA ~ 3uA. Implantable medical system of transceivers must periodically "view" or monitoring external communication devices, in the view, at a very low-power state to save energy.

Design considerations

In order to be able to use MICS band, implantable medical devices requires the use of ultra low power, high performance transceiver.

Implantable device transceiver design face numerous challenges, including:

(1) 400MHz communications for low power.

Implantation of battery power is limited, and implanted battery impedance is relatively high, which limits the current from the battery slot. (2) the communication phase, for the majority of implantable devices, should be less than the current limit in 6mA. (3) is sleeping and periodic "view" to wake-up signal, at a low power. (4) the minimum of external components and physical volume. Implantable-level components of expensive, high integration can reduce costs and increase overall system reliability. (5) data transfer rate is reasonable. Currently, pacing requirements for data transfer rates greater than 20 kbps, the future design of data transfer rate is much higher. (6) systems and data transmission reliability. (7) the selectivity and interference suppression capabilities, in particular, TETRA radio standards in Europe. (8) distance typically more than two meters. The longer the distance requires sensitivity to the better, because small antenna and the effects of loss and allows distance link budget. Antenna, matching, decay and loss of changes are large, losses may be as high as $ 40dB ~ 45dB.

ZL70101 MICS transceiver in the high data transfer rate of cases with excellent low-power characteristics.

Up to the data rate 800kbps, transmit and receive current is less than 5 mA. Circuit has a unique work in 2.45 GHz ultra low-power wake-up system, an average of sleep/monitoring current less than 250nA. System integration, just need three external components (Crystal and two decoupling capacitor) and a matching network.

Medical devices can be divided into an internal non-rechargeable batteries (such as a pacemaker) class and inductive coupling power class (such as cochlear implants).

The former is strongly mining system duty potential to save power. Transceiver for most of the time is off, so off current and cyclical find communication equipment need current must particularly low (< 1-2uA). At the same time, the two situations of the transmit and receive power is low (current < 6mA).

In 2.1V ~ 3.5V power voltages, ZL70101 peak current consumption receiving/transmitting 5mA, this < include basic RF transceivers and MAC current.

MAC to ensure that users receive high integrity data, automating the most link maintenance work. In addition, the MAC Protocol provides a savings in power, transmission of a packet of timer, the timer will be implanted device receiver off for some programming good time.

To enable to joules/bits defined total power consumption minimum, meet the requirements for using the receiver sensitivity, recommended implantable transceiver using data rates as high as possible.

Need a low data rate (or even low kHz range) systems should be buffered, working at the highest possible data rate, lower duty cycle to reduce average current consumption. To send a short pulse data saves power, reduce the time window of interference. In addition, the high battery impedance system, because a pulse from the capacitor discharge shorter power on decoupling requirements may be lower.

Transceiver allows users with the receiver sensitivity, from a variety of data rate (200 kbps to 400 kbps and 800 kbps).

In order to achieve this flexibility, the system uses 2 FSK modulation FSK or 4, 200 or 400 thousand characters, variable frequency deviation (see table 1). Through the use of film, digital filtering, you can reach the lower the number ofAccording to the rate and the corresponding higher receiver sensitivity. Transceiver has a MAC bypass work mode, in which radio frequency is fully available. In this configuration, users can develop custom protocol and data transfer rates.

Overall system architecture

ZL70101 works in Implantable devices and external base station (see Figure 2).

Base station includes emission 2.45 GHz wakeup signals of additional circuits. System once adopted 2.45 GHz wakeup signal start, through 402MHz to 405MHz MICS band transceivers and Exchange data.

ZL70101 MICS chip (see Figure 3) contains the three major subsystems: a 400MHz transceiver, a wakeup receiver 2.45 GHz and a media access controller (MAC).

According to the input pin of the State determines the chips used for implantation medical equipment, or base station Programmer's transceiver.

Transceiver with an intermediate frequency (IF) low band image rejection mixer superheterodyne structure.

Low-medium frequency allows filter and modulator minimum power consumption, and high data rate, zero-if architecture related flicker noise and DC offset. FSK modulation scheme reduces emission linear amplifier, thereby reducing power consumption, and you can use the simpler by limiting the receiver. As Figure 3 won the bid to half-duplex RF transmitter with 400 MHz transmitter subsystem contains a medium frequency modulator, a mixer and a power amplifier. IF modulator will be a one (two FSK) or two (4 FSK) asynchronous digital input stream into intermediate frequency. Upconversion mixer will convert the RF frequency medium. Note that transmit and receive mode is the same as the local oscillator frequency, allowing and dead time between.

You can register custom-4.5dBm ~-17dBm (500 Ω load), the step to less than 3dB programming emission power amplifier output power.

All RF input capacitance of internal antenna matching group can fine-tune match network, for a given power settings to achieve the maximum output power, receiver noise index best. Antenna tuned to automatically scale, which takes a peak with the ADC coupled detector, take one of the calibration control state machine.

400MHz receiver subsystem MICS band signal amplification, the carrier frequency transformation to MF.

Low noise amplifier (LNA) gain to 9dB ~ 35dB programmable. On implantation medical equipment transceiver, it is recommended that a higher gain settings, and the relatively low number of gain settings can be used to select the use external LNA's base station transceiver. LNA and mixer bias current of programmability that optimization is ideal for linear (IIP3), power consumption and noise index of flexibility.

Multiple phase IF filter to reduce the frequency and adjacent channel mirror interference, and limits the noise bandwidth.

Polyphase filter after the next limiting and a receiver signal strength indicator (RSSI) module. RSSI measurement consists of a 5-bit ADC conversion, you can use industry-standard SPI interface reads. The MICS no interference channel assessment program. Note that you must first define by MICS standard without interference of a channel assessment procedures with an external instrument to determine an appropriate available channel.

To do this, also developed a highly reliable medical applications customized private agreement by MAC address, including the following major features:

(1) use Reed-Solomon forward error correction (FEC) and cycle redundancy code (CRC) error detection techniques for error correction and detect.

Suppose the original radio BER 10-3, FEC and CRC after effective BER 1.5 × 10-10. (2) fault situations block to automatically transfer, and process control to avoid buffer overflow. (3) the ability to send emergency orders and MICS high priority information. (4) be capable of processing link watchdog to ensure that the communication was not successful for 5 seconds after the broken link. (5) provide link quality diagnostic and auto-calibration control.

Ultra low-power wake up the receiver

Because storage battery energy is most important, most embedded applications are seldom MICS on the RF link.

In the extremely low power applications, most of the time, the transceiver is a current very low sleep state. In addition to send emergency command, use MICS band systems must not interfere with channel assessment program, wait for the base station to start the communication. Implantation transceiver should periodically query base station do you want to communicate.

Wake-up system is a work in 2.45GHz SRD bands of ultra low-power RF Receiver, detect and decode a special packet, the packet from the base station Launcher, and then connect the remaining power chip.

Chip can also be started directly by pin control, such as base stations start, implant device sends emergency command or using selective wake-up system implantation equipment requires this way.

A brief summary of this article

Ultra low-power wireless technology for many implantation medical equipment it is critical, including pacemakers, defibrillators, Nerve Stimulator, drug infusion system, diagnostic sensors and rapid growth of implantable Diabetes Monitor.

However, with the implanted communication systems development and support of advanced diagnostic and treatment, and wireless performance on implantation medical device battery life does not affect is critical.