MCP37D11-80ESLASHTE datasheet(62/136 Pages) MICROCHIP

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MCP37D11-80: 80 MSPS 12-BIT PIPELINED ADC

DS20006381A-page 62

 2020 Microchip Technology Inc.

4.10.1

BEAMFORMING

Beamforming is achieved by scanning all inputs while

correcting the phase of each channel with respect to a

reference. This can be done using:

• Fractional Delay Recovery (FDR)

• Phase offset settings of each individual channel

• Gain setting per channel

While the CW input channel is multiplexed sequentially,

the phase offset can be added to the NCO output (each

channel individually). CH(n)_NCO_PHASE<15:0>, in

Addresses 0x86 to 0x95 (Registers 5-47 – 5-62),

corrects the time delay of the incoming signals with

respect to the reference.

The phase-compensated input signal is then down-

converted by a wide dynamic range I/Q demodulator.

The digital beamforming of the inputs is then obtained

by summing I and Q data from individual channels. The

combined I and Q data are fed to the half-band filter.

Equation 4-10 shows the I and Q data of an individual

channel with phase correction (phase offset), and the

resulting digital beamforming signal.

The processing blocks after the digital beamforming

are the same as the sub-blocks used in single-channel

operation described in Section 4.8.4.1 “Single-

Channel DDC”, except only limited decimation rates of

the FIR A and FIR B filters are used due to the

processing time requirement for summing the input

signals from all channels.

EQUATION 4-10:

BEAMFORMING SIGNALS

The NCO phase offset can be controlled by

0.005493164° per step. See

Section 4.8.4.6 “NCO

Phase Offset Control” for details.

4.10.2

ULTRASOUND DOPPLER SIGNAL

PROCESSING

Doppler shift measurement requires summing the input

signals from multiple transducer channels and mixing

them with a phase-controlled local oscillator frequency.

The resulting low-frequency output is then centered

near DC and can measure a Doppler shift produced by

moving objects, such as blood flow and changes in

blood pressure in arteries, etc. In traditional Doppler

measurement, many discrete analog components are

typically used along with a high-resolution ADC.

This device has unique built-in features that are

suitable for ultrasound Doppler shift measurements. By

utilizing these features, system engineers can reduce

many discrete components which are otherwise

necessary for an ultrasound Doppler measurement

system.

The following built-in digital signal post-processing

(DSPP) features in the MCP37D11-80 can be

effectively used for the ultrasound Doppler signal

processing applications:

• Fractional Delay Recovery (FDR): Correct the

time delay of signal sampled between channels.

See details in Section 4.8.1 “Fractional Delay

Recovery for Dual- and Octal-Channel

Modes”.

• Digital Gain and Offset adjustment for each

channel: See details in Section 4.9 “Digital

Offset and Digital Gain Settings”.

• Down-Conversion for each channel with a

unique phase of the same NCO frequency prior to

summing the eight channels as shown in

Figure 4-24.

• After down-conversion by the DDC, the resulting

signal can then be decimated to achieve very high

SNR in a narrow bandwidth.

ICH n



ADC COS 2

f

NCOt

 n





QCH n

ADC SIN 2

f

NCOt

 n





IICH n





QQCH n





 n



360

 CH(n)_NCO_PHASE<15:0>

-----------------------------------------------------------------------



0.005493164

 CH(n)_NCO_PHASE<15:0>



Where:

(n) = NCO phase offset of channel n

ADC = the output of the ADC block

MCP37D11-80E/TE Datasheet(PDF) 62 Page - Microchip Technology

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