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¡¡¡¡The AD9671 is designed for low cost£¬ low power£¬ small size£¬ and ease of use for medical ultrasound applications. It contains eight channels of a VGA with an LNA£¬ a CW harmonic rejection I/Q demodulator with programmable phase rotation£¬ an AAF£¬ an ADC£¬ and a digital demodulator and decimator for data processing and bandwidth reduction. Each channel features a maximum gain of up to 52 dB£¬ a fully differential signal path£¬ and an active input preamplifier termination. The channel is optimized for high dynamic performance and low power in applications where a small package size is critical. The LNA has a single-ended to differential gain that is selectable through the serial port interface £¨SPI£©¡£ Assuming a 15 MHz noise bandwidth £¨NBW£© and a 21.6 dB LNA gain£¬ the LNA input SNR is 94 dB. In CW Doppler mode£¬ each LNA output drives an I/Q demodulator that has independently programmable phase rotation with 16 phase settings. Power-down of individual channels is supported to increase battery life for portable applications. Standby mode allows quick power-up for power cycling. In CW Doppler operation£¬ the VGA£¬ AAF£¬ and ADC are powered down. The ADC contains several features designed to maximize flexibility and minimize system cost£¬ such as a programmable clock£¬ data alignment£¬ and programmable digital test pattern generation. The digital test patterns include built-in fixed patterns£¬ built-in pseudorandom patterns£¬ and custom user defined test patterns entered via the SPI.