Analog Devices announced an integrated circuit that simplifies the development of continuous wave (CW) Doppler imaging in stationary and portable ultrasound systems. The AD8333 is a dual-channel I/Q demodulator and phase-shifter for CW Doppler ultrasound. The monolithic Doppler phase-shifter IC achieves a dynamic range of 161 dB/Hz.

CW Doppler ultrasound systems require analog beam forming (ABF) because the large dynamic range cannot be processed digitally.  Historically, an ABF front-end consisted of multiple low-noise amplifiers, analog delay lines, and numerous cross-point switch matrices. The dual-channel AD8333 significantly alters this approach by replacing it with a programmable phase-shifting technique with an I/Q demodulator for each input channel, eliminating the need for multiple analog delay lines and cross-point switches. The reduction in board space and low power allow for an increase in continuous wave functionality compared to the delay line approach.

The AD8333 is designed with 22.5 degree phase steps, allowing for accurate time alignment of multiple channels in continuous wave beam forming applications. The amplifier offers parallel 4-bit digital control of phase states, and provides accurate channel matching through a common LO interface.  Analog Devices offers a suite of products to complement the AD8333 and help customers complete the design of their medical ultrasound systems, including the AD8332 dual variable gain amplifier (VGA) or the AD8335 quad VGA, the AD9510 clock IC, the AD8021 high-speed amp and AD8016 line driver, and either the AD7665, AD7679, or AD7685 members of ADI’s PulSAR family of analog-to-digital converters.

Applications

The AD8333 is usefull for the development of advanced CW Doppler ultrasound equipment for both fixed and portable medical environments, the combination of I/Q demodulation and phase shifting also suits the AD8333 to other applications where measurement of phase shifts are required, including weather radar, adaptive antenna arrays, and automotive collision avoidance systems. 

Availability and Pricing

The AD8333 monolithic Doppler phase-shifter is currently sampling and will be in full production in August 2005.  The device is offered in a 5 mm × 5 mm LFCSP (lead-frame chip scale package) and is priced at $8.95 each in 1,000-unit quantities.