AD9276-65EBZ Analog Devices Inc, AD9276-65EBZ Datasheet - Page 27

• Manufacturer Part Number: AD9276-65EBZ
• Description: 65MSPS ADC Converter Evaluation Board
• Manufacturer: Analog Devices Inc

Specifications of AD9276-65EBZ

• Silicon Manufacturer: Analog Devices
• Application Sub Type: ADC
• Kit Application Type: Data Converter
• Silicon Core Number: AD9276
• Number Of Adc's: 1
• Number Of Bits: 12
• Sampling Rate (per Second): 65M
• Data Interface: Serial, SPI™
• Inputs Per Adc: 1 Differential
• Input Range: *
• Power (typ) @ Conditions: 195mW @ 40MSPS
• Voltage Supply Source: Analog and Digital
• Operating Temperature: -40°C ~ 85°C
• Utilized Ic / Part: AD9276
• Development Tool Type: Hardware - Eval/Demo Board
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

CHANNEL A
CHANNEL H
Phase Compensation and Analog Beamforming
Beamforming, as applied to medical ultrasound, is defined as
the phase alignment and summation of signals generated from a
common source but received at different times by a multielement
ultrasound transducer. Beamforming has two functions: it imparts
directivity to the transducer, enhancing its gain, and it defines a
focal point within the body from which the location of the return-
ing echo is derived. The primary application for the AD9276 I/Q
demodulators is in analog beamforming circuits for ultrasound
CW Doppler.
Modern ultrasound machines used for medical applications
employ an array of receivers for beamforming, with typical CW
Doppler array sizes of up to 64 receiver channels that are phase
shifted and summed together to extract coherent information.
When used in multiples, the desired signals from each of the
channels can be summed to yield a larger signal (increased by a
factor N, where N is the number of channels), whereas the noise
is increased by the square root of the number of channels. This
technique enhances the signal-to-noise performance of the
machine. The critical elements in a beamformer design are the
means to align the incoming signals in the time domain and the
means to sum the individual signals into a composite whole.
LNA
LNA
Figure 53. Typical Connection Interface for I/Q Outputs in CW Mode
GENERATION
4
LO
Rev. 0 | Page 27 of 48
In traditional analog beamformers incorporating Doppler, a
V-to-I converter per channel and a crosspoint switch precede
passive delay lines used as a combined phase shifter and
summing circuit. The system operates at the carrier frequency
(RF) through the delay line, which also sums the signals from
the various channels, and then the combined signal is down-
converted by an I/Q demodulator. The dynamic range of the
demodulator can limit the achievable dynamic range.
The resultant I and Q signals are filtered and then sampled by
two high resolution analog-to-digital converters. The sampled
signals are processed to extract the relevant Doppler information.
Alternatively, the RF signal can be processed by downconversion
on each channel individually, phase shifting the downconverted
signal and then combining all channels. Because the dynamic
range expansion from beamforming occurs after demodulation,
the demodulator dynamic range has little effect on the output
dynamic range. The AD9276 implements this architecture. The
downconversion is done by an I/Q demodulator on each channel,
and the summed current output is the same as in the delay line
approach. The subsequent filters after the I-to-V conversion
and the ADCs are similar.
CWI+
CWI–
CWQ+
CWQ–
AD9276s
OTHER
1.5V
1.5V
1.5V
1.5V
AD8021
AD8021
AD8021
AD8021
C
R
R
C
C
R
R
C
FILT
FILT
FILT
FILT
FILT
FILT
FILT
FILT
Q
I
AD9276
18-BIT ADC
18-BIT ADC