Octal Ultrasound Receiver with Digital I/Q Demodulator and Decimation Filter Reduces Processor Overhead in Ultrasound Systems

The AD9670 also integrates a low-noise amplifier, variable gain amplifier, anti-aliasing filter, and a 14-bit, A/D converter with the industry’s highest sample rate (125 MSPS) and best SNR performance (75 dB) for enhanced ultrasound image quality. The new octal receiver is the latest addition to Analog Devices’ award winning ultrasound receiver portfolio and is designed for mid- to high-end portable and cart-based ultrasound systems.

The integrated digital I/Q demodulator, programmable-oscillator and 16-tap FIR decimation filter of the AD9670 reduce the FPGA’s data bandwidth requirements, allowing designers to use less expensive processors or reallocate processing bandwidth to other system functions. The new receiver also provides a continuous wave processing path with an analog I/Q demodulator that has harmonic rejection to the 13th order, which allows designers to reduce the number of filter components to lower system cost, reduce design complexity, and improve signal sensitivity. The CW-mode output dynamic range is more than 160 dBc/ √Hz per channel.

Additionally, the AD9670 octal receiver’s 30-MHz anti-aliasing filter frequency and 125-MSPS A/D converter sample rate combine to yield SNR performance that is 3-dB higher than competing devices. The 14-bit A/D converter also features a programmable clock, data alignment, and programmable digital test pattern generation, including built-in fixed and pseudo random patterns and custom user-defined test patterns, entered via a serial port interface. Total power is 130-mW per channel, while an eight-channel low-noise amplifier reduces input-referred noise to just 0.78 nV/√Hz typical at 5 MHz (gain = 21.3 dB).

“By introducing the first octal ultrasound receiver with digital demodulation and decimation filtering, we are able to minimise the data I/O and throughput rates and place less stress on the system processor,” said Pat O’Doherty, vice president, healthcare segment, Analog Devices. “At the same time, by extending the anti-aliasing filter frequency range and maintaining a high A/D converter sample rate, we are continuing to help medical and industrial ultrasound equipment manufacturers meet the trend toward higher frequency probes and superior image quality.”

AD9670 Octal Ultrasound Receiver Key Features:

• Digital I/Q demodulator with programmable oscillator
• FIR decimation filter
o 16 taps per decimation factor
o Maximum decimation of 32
• 14-bit, 125-MSPS A/D converter
o SNR: 75 dB
• 8-channel LNA, VGA, AAF, ADC
• Low power:
o 130-mW/channel @ 40 MSPS in TGC mode
o 55 mW/channel in CW mode
• Noise: 0.78 nV/√Hz typical at 5 MHz (gain = 21.3 dB)
• Harmonic rejection to 13th order on CW-Doppler signals

The AD9670 octal receiver with integrated digital demodulation and decimation filtering is pin-similar to ADI’s AD9278 and AD9279 octal receivers, allowing designers to upgrade cart-based and portable ultrasound equipment designs using a common PCB board layout.

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