Ultrasonic transmitter chip design show-(1)

The field of medical imaging greatly benefit from the application of physics and Electronics Research and development, particularly in areas such as instrumentation equipment, image acquisition and modeling, and other fields.

With full non-traumatic, ultrasonic imaging mode in occupies a special place, which is the internal organs of provides a reliable way. Ultrasonic technology is used for medical purposes, there are more than half a century. However, this required device volume and complexity is expensive, until recently a number of discrete devices used exclusively to manufacturing.

Because semiconductor process technology, this trend is changing.

Now, you can fully use semiconductor IC for the manufacture of ultrasonic wave transceiver. Lower voltage IC technology now has significant high gain and low noise performance ultrasonic Receiver chips become reality. Similarly, in the higher voltage-side, there is growing concern about driving ultrasonic transducer transmitter IC manufacturing. This article provides an overview of the ultrasonic transmitter chip design some of the progress of many challenges.

Ultrasonic system overview: send and receive functions

In short, the principle of ultrasonic system is used for treating patients with sound, and then receive and process the reflected signals to patients with body image formation.

Sent to the body of the original sound waves generated by a transmitter, which generally consists of transmitter produces electrical pulse excitation. Similarly, a reflection of sound waves by transmitter receiver, and then convert back to last on the signal is processed to determine the relevant body part of the internal structure.

Figure 1 shows a complete medical ultrasonic system for typical structures.

Send realizing of the path can have several different ways. The path may consist of one beamformer and many level translators, gate drive and high-voltage switch, its output is sent to the ultrasonic transducer. In General, the transmitter by piezoelectric materials, it will be converted to high-voltage signals, that is, systems of sound waves to final output.

Figure 1 complete medical ultrasonic system for typical structure diagram

Some systems, the adoption of digital logic-driven output stage of the send path, from the beginning has been to maintain signal digital properties.

However, you can take a simulation mode to create and send a signal to the transmitter. It involves a beamformer output converted to analog format-to-analog converter (DAC). Then, send it to the transmitter before being used to produce simulated zoom.

Ultrasonic systems receive path, using a simulation method.

Because the received signal amplitude is far below the send signals, so the front-end including a low noise amplifier, then as a gain control module. Filter out non-related high-frequency components, the resulting signal through an analog-digital converter (ADC) converted to digital form, and the ADC output by beamformer.

Ultrasonic transceiver system of other important part includes a multiple channel activities interact multiplexers, and a control transmitter and receiver components between the signal flow of transmit/receive switching.

Transmit/receive switching of a key function is to send events during a receiver, because sending events involving excessive send line voltage, which is far higher than the receiver module.

Ultrasonic system requirements: send path challenges voltage range and frequency

To date, the description of the ultrasonic system can produce various signal image to meet the requirements of different Imaging modes.

In the extreme range, you can obtain B-display and harmonic imaging application requirements for high pressure (60 ~ 100V), low duty cycle (0.5 ~ 2.0%) signal. In one extreme case, you can get continuous wave (CW) Doppler-imaging mode requirements of low-voltage (3-10V), 100% duty cycle signals.

This means 1 ~ 20MHz base frequency range, the corresponding duty conditions, requires ultrasonic system of Dispatcher circuit ¡à 3V towns of ± 100V output voltage.

Obviously, the transmitter output ± 100V need some high voltage switch.

When the sender includes a IC, this requirement into a high-voltage transistor, and optimized to withstand large electric field. Similarly, they are low (< 10V) poor performance, and low-voltage typically used to run the CW. Design a dispatcher to meet the very far end of the voltage range of product specifications still, there is a serious challenge.

Wide range of output voltage does not manufacture ultrasonic transmitter devices of unique challenges, there are many more challenges.

Conversion rate

According to the previously mentioned voltage amplitude and frequency range, the dispatcher may have to produce up to 8V/ns of conversion rate.

Combined with the representative of the transmitter of 100 Ω and 300pF typical parallel load, then the transmitter in the most demanding cases will provide close to 3A of transient current (see Figure 2).

Figure 2 ± 100V power supply is typical of ultrasonic transmitter output, as well as the inflow of 100 Ω and 300pF parallel load corresponding to the instantaneous currents