Low Power Continuous Wave (CW) Doppler for Portable Ultrasound Systems
Portable ultrasound equipment with CW doppler requires blood flow data where only extremely faint signals are present. Detection of limited level signal input due to low blood volume or distance between the target and the transducer (as in the case of fetal monitoring or obesity) requires an extremely large dynamic range in the receiver signal chain. The continuous wave in-phase and quadrature modulated receiver and data converter must fit within an increasingly smaller board area while maintaining low power consumption.
In portable ultrasound front ends, analog signal processing components are key elements in determining overall system performance and limits. For increased channel density, ADI has a number of key integrated and low power solutions that provide unmatched performance in the smallest area.
The AD8339 quad I/Q demodulator and phase shifter reduces board space as much as 75% compared to competing devices by replacing the large crosspoint-switch matrices and analog delay lines typically used in phased-array beamforming. The AD8339 consumes just 73 mW per channel, suitable for portable ultrasound equipment. The power savings of the device enables designers to increase the channel density of cart-based ultrasound systems, which often use hundreds of phase shifters per unit. The AD8339 is available in a 40-lead LFCSP.
The low power AD7980 16-bit PulSAR® analog-to-digital converter sums and samples the AD8339 I/Q channels at rates of up to 1 MSPS. The device consumes minimal power and board space as well as provides an uncompromised signal-to-noise ratio of 91.5 dB @ 1 MSPS. It dissipates only 7 mW at the full 1 MSPS rate and contains no pipeline delay in its conversion process. The digital output I/Q data is available via a serial SPI bus™further minimizing board layout complexity within the portable ultrasound system. The AD7980 is available in ultrasmall 10-lead MSOP or QFN packaging.
