AD9279八进制的低噪声放大器VGA/AAF/ADC连续解调器

　　The AD9279 is designed for low cost， low power， small size， and ease of use for medical ultrasound and automotive radar. It contains eight channels of a variable gain amplifier （VGA） with a low noise preamplifier （LNA）， an antialiasing filter （AAF）， an analog-to-digital converter （ADC）， and an I/Q demodulator with programmable phase rotation. Each channel features a variable gain range of 45 dB， a fully differential signal path， an active input preamplifier termination， and a maximum gain of up to 52 dB. 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 SPI. Assuming a 15 MHz noise bandwidth （NBW） and a 21.3 dB LNA gain， the LNA input SNR is roughly 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 pseudo random patterns， and custom user-defined test patterns entered via the serial port interface.