Infrared single-channel ECG telemetry transmission system design and operating principle (1).

ECG diagnosis of heart disease <P> important means, but for various reasons, difficult to capture the ordinary to the unusual ECG electrocardiogram. .Radio ECG or 24-hour Holter monitor, although able to effectively solve this problem, but expensive, hard for the family. .Infrared Biotelemetry with anti-electromagnetic interference, transmitting and receiving equipment is simple, low cost, easy debugging; without the need for frequency up; easy to use, the advantages of safety [1]. .With the rapid development of computer technology, computer has been the gradual deepening of the family, for the development of analytical, processing equipment, the family provides the basis for medical care. .To this end, we developed a single channel ECG telemetry infrared instrument, it is the computer for analysis, processing, display, storage, communication means, using infrared light as transmission media, real-time monitoring of the subjects. .Via modem, but also the telemetry data to the medical center for medical expert analysis, diagnosis, telemedicine is an ideal front-end and home medical monitoring equipment. .</ P> <P> 1 system design and operating principle </ P> <P> the machine to the computer as receiving, processing terminals, complete data reception, processing, storage, communications and other functions, real-time monitoring of subjects .. .</ P> <P> system uses a PCM-ASK modulation. .That the first modulation pulse code modulation, the second modulation using amplitude shift keying modulation. .PCM modulation with high precision, strong anti-jamming features. .ASK modulation, can enhance the resistance to ambient light, the ability of anti-electromagnetic interference, but also by choosing different sub-carrier frequency, multi-sets of telemetry systems to work simultaneously in the same area without interference. .Moreover, since the infrared emission control work in the off state, not only can reduce the power consumption of transmitting tubes, reducing the transmitter's size, weight, increasing the role of distance, have longer working hours, while, ASK modulation modulation circuit is simple, to achieve .easy, easy crystal frequency stabilization, improve system reliability. .Demodulation receiver, the data directly into the computer's serial port, greatly simplifying the hardware structure, and easy to use. .</ P> <P align=left> PCM modulator single chip, which will complete the signal sampling, A / D conversion, serial data output. .By comparison, we used produced MICROCHIP PIC16C71. .It is a low cost, low power, high performance, with on-chip A / D converter and 8-bit microcontroller program memory. .The command structure refined, fast, small, 18-pin package, there are four analog input channels, 13 I / O ports, four interrupt sources, the 5V power supply, clocked at 4MHz cases, a small working current .to 2mA. .</ P> <P align=left> integrated infrared receiver used as the infrared receiver module TEMS5380 receiving part. .It combines infrared receiver, conversion, filtering, amplification, shaping, demodulation in one small volume, high sensitivity, low power consumption, reliable and convenient debugging feature [2]. .Its center frequency is 38kHz, to transmit data rates up to 3000 baud, system block diagram shown in Figure 1. .</ P> <P align=center> </ P> <P align=center> block diagram of Figure 1 System components </ P> <P align=left> system works as follows: ECG amplifier and level adjustment circuit .zoom in and adjust the ECG signal to the A / D converter required level. .Microcontroller with 200Hz sampling rate of ECG sampling, A / D conversion, serial communication format according to A / D conversion result of additional start and stop bits to shift output. .Among them, a start bit, 8 data bits, 1 stop bit. .Code rate 2400bit / s. .In order to facilitate identification initiation, transmission, after the 10 yards, followed by sending the stop bit, until the next A / D conversion. .Gated serial output data control circuit. .Oscillation generated subcarrier frequency divider, when the serial data is high, the gate control circuit to open, sub-carrier signal through the gate circuit, driver infrared LED light. .VMOS tube driver circuit, it is a good switching characteristics, the output current, the circuit is simple. .</ P> <P align=left> infrared receiver module receives the signal, after conversion, filtering, amplification, demodulation, shaping, output serial data stream. .Telemetry system to increase the range of the transmitter in series of 6 infrared emission control, while at the receiving end of 4 parallel infrared receiver module, staggering their position to each other. .Infrared receiver module output or the door by the sum, and then by the level conversion, serial communication into a level required by the computer serial port into the computer analysis and processing. .</ P> <P align=left> computer work in two modes: real-time data monitoring mode and playback mode, before you can enter subjects information. .In real-time monitoring mode. .Display real-time display of ECG waveform and heart rate. .Abnormal ECG is detected, the computer sounds the alarm. .Press the memory key at any time before the 50 seconds can be key to the hard disk for data storage, in a monitoring process can store up to 21 minutes of data. .If you press the freeze button, ECG waveform is frozen on the screen, you can print out the ECG, after which you can press the Continue button to continue custody or guardianship mode press the Escape key to exit. .Exit monitoring mode, the results can be displayed. .</ P> <P align=left> in playback mode, enter the file name, you can choose any of the hard disk is stored in a playback of ECG waveform data, or data transmission through the network to the rescue center for further analysis expert .diagnosis. .</ P> <P align=left> 2 software design </ P> <P align=left>.