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Chip enables portable CW Doppler ultrasound

Posted: 02 Feb 2007 ?? ?Print Version ?Bookmark and Share

Keywords:demodulator? phase shifter? Doppler? ADI? ultrasound?

AD8339 quad programmable I&Q demodulator from ADI

Analog Devices Inc. has announced the AD8339, a quad programmable I&Q demodulator with phase shifter that's suited for medical ultrasound systems. In ultrasonic beam-forming applications like continuous wave (CW) Doppler ultrasound, this device reduces board space by as much as 75 percent compared to competing devices by replacing the large crosspoint-switch matrices and analog delay lines typically used in phased-array beam forming.

Power savings
The AD8339 consumes 73mW/channel, which is 30 percent less than competitive solutions, allowing medical instrument manufacturers to provide CW Doppler capabilities in portable and battery-powered equipment. Alternately, the power savings of the new device enables designers to increase the channel density of cart-based ultrasound systems, which often use hundreds of phase shifters per unit.

When transmitting and receiving Doppler ultrasound signals, variables such as tissue density, fluid viscosity and rate of fluid movement create signals with exceptional dynamic range requirements. The AD8339 achieves a large dynamic range of 158dB/Hz and features 22.5 phase steps, which compensates for signal latency caused by physiological variables to ensure accurate, time-aligned ultrasound images.

Digital control
The AD8339 features a simple three-wire SPI for digital control of channel selection and phase states by system computer commands. A single synchronized common local oscillator (LO) input for all channels enables precise phase locking to the system clock. The new device features a quadrature phase error of 0.5, and I&Q amplitude imbalance of 0.25dB. The LO frequency range is 100MHz and the basic RF input frequency range is 25MHz.

The new phase shifter works well with the company's AD8332, AD8334 and AD8335 VGAs, the AD8021 high-speed voltage-feedback amplifier, the AD7686 and AD7693 PulSAR ADCs and the AD9510 clock distribution IC.

The AD8339 quad-programmable I&Q demodulator and phase shifter is sampling today and will be available in full production quantities in June 2007. The device is priced at $11.95 in 1,000-piece quantities. The AD8339 is available in a 40-lead LFCSP.

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Related Datasheets
Part Number Description Category
? AD8339 DC to 50 MHz, Quad I/Q Demodulator and Phase Shifter ICs, Power Management



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