MCP37231 datasheet(67/144 Pages) MICROCHIP

67 / 144 page

 2014-2016 Microchip Technology Inc.

DS20005322D-page 67

MCP37231/21-200 AND MCP37D31/21-200

4.10

Continuous Wave (CW)

Beamforming and Ultrasound

Doppler Signal Processing Using

CW Octal-Channel Mode

(MCP37D31/21-200 only)

In modern ultrasound medical applications, large num-

bers of transducers are often used. The signals from

these sensors are then coherently combined for higher

transducer gain and directivity. The signals from each

sensor arrive at the detection device with a different

time delay. Also, in multi-channel scanning operations

using the MUX, there is a time delay between acquiring

input signals (see Section 4.8.1 “Fractional Delay

Recovery for Dual- and Octal-Channel Modes”).

These time delays may need to be corrected before all

input signals are combined for the signal processing.

Digital beamforming is a digital signal processing

technique that requires summing all input signals from

different channels after correcting for time delay. The

time-delay correction involves the phase alignment of

the detected signals with respect to a reference.

Along with beamforming, many modern medical

ultrasound devices support Doppler imaging, which

processes phase information in addition to the classical

magnitude

detection

(for

brightness

imaging).

Ultrasound Doppler signal processing is used to

determine movement in the body as represented by

blood flow, which can help diagnose the functioning of

a heart valve or blood vessel, etc. In a traditional

ultrasound system, all of these functions are typically

accomplished with discrete components. Figure 4-23

shows an example of an ultrasound system

implementation using various specialized components.

The MCP37D31/21-200 device has a built-in feature

that can perform some of the functions that are done

traditionally using extra components. Continuous wave

(CW) digital beamforming and Doppler signal

processing features are available, but these are offered

in octal-channel operation only.

Figure 4-22 shows a simplified block diagram for the

ultrasound CW beamforming with DDC I/Q decimation.

Note that the sub-blocks shown after the MUX are

commonly used for all input channels.

FIGURE 4-22:

Example of Ultrasound System Building Block.

T/R

Switcher

Transducer

Array

HV MUX and

T/R Switches

AAF

Isolation

Clocks

Beamformer Central

Control Processor

I/Q

Processing

DAC

ADC

Doppler

Processing

Amp

ADC

VGA

LNA

Image and

Motion

Processing

(B Mode)

Color

Doppler

Processing

(F Mode)

Amp

Digital RX Beamformer

Video DAC/

Video Encoder

Video

Compression

Amp/

Filter

Amp

Audio

DAC

LNA-VGA-ADC Array (up to 256 Channels)

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