Eight-channel Ultrasound Receivers Enable High-quality Continuous Wave Doppler Processing

Ultrasound equipment uses CW Doppler processing to measure the speed and direction of blood flow. This provides physicians with a measurement technique that more accurately diagnoses vascular conditions, such as faulty valves and arteries in the heart. ADI's new octal ultrasound receivers allow system designers to provide CW Doppler capabilities while reducing system size, complexity, and power consumption for mid- and high-end cart-based ultrasound systems.

The AD9276 and AD9277 octal ultrasound receivers consume only 90 mW per channel when processing signals in CW Doppler mode and require 80 percent less board space than competing ultrasound receiver subsystems.

CW Doppler differs from other medical sonographic techniques in that it measures the Doppler shift, which is the change in frequency and phase of the reflected ultrasound signal, to determine the direction and rate of blood flow in blood vessels, veins, and arteries, said Patrick O'Doherty, healthcare segment director, Analog Devices. ADI's octal ultrasound receivers enable medical equipment designers to provide physicians with an effective tool to assess various cardiac and vascular conditions.

The AD9276 octal ultrasound receiver combines an eight-channel VGA (variable-gain amplifier) with a LNA (low-noise preamplifier), anti-aliasing filters, and a 12-bit 80-MSPS (million samples per second) ADC (analogue-to-digital converter). The AD9277 octal ultrasound receiver features the same level of integration but incorporates a 14-bit 50-MSPS ADC. These two octal receivers provide the industry's lowest input-referred noise (0.75 nV/rt-Hz @ 5 MHz typical) when operating under real-world conditions, and 6 dB/rt-Hz better input dynamic range than competing devices. The AD9276 dissipates 190 mW per channel at 12 bits and 40 MSPS, while the AD9277 dissipates 190mW per channel at 14 bits and 40 MSPS.

The AD9276 and AD9277 octal ultrasound receivers include an integrated I/Q (in-phase/quadrature) demodulator with programmable phase rotation on each channel, which reduces size and power consumption while improving the performance of the CW Doppler signal path. Each LNA output drives a I/Q demodulator to produce an output dynamic range that typically exceeds 160 dB/rt-Hz.

Both the AD9276 and AD9277 octal ultrasound receivers feature a variable gain range of up to 42 dB and a selection of anti-aliasing filter options. The new receivers also feature a SPI (Serial Port Interface ) that allows designers to further customise the noise and power performance for any given imaging mode, probe, or power requirement. In CW Doppler mode, each demodulator has independently programmable phase rotation through the SPI with 16 phase settings. By writing to the SPI registers, designers can optimise an ultrasound signal processing architecture for the best possible noise performance. An easy-to-use software tool simplifies each configuration.

Complementary components for the AD9276 and AD9277 octal ultrasound receivers include the ADA4899-1 ultralow noise and distortion unity-gain stable voltage feedback op amp; AD7982 18-bit, 1 MSPS PulSAR® analogue-to-digital converter; and ADR433 3.0-V ultra-low-noise voltage reference.