IF diversity receivers maximize sensitivity

The AD6649 and AD6643 IF diversity receivers maximize receiver sensitivity and dynamic range for 3G and 4G cellular basestations. The AD6649 is able to monitor the incoming signal power and adjust the VGA gain setting directly without the need for a microprocessor. This part integrates an ultra-low-latency peak detector, an rms signal power monitor, and a digital down converter that includes a 32-bit NCO, a decimating half-band filter, and an output FIR filter. Specs include an SNR of 73.0 dBFS (95 MHz BW at 185 MHz AIN and 245.76 MSPS), a SFDR of 85 dBc at 185 MHz AIN and 250 Msamples/s, a noise density of –151,2 dBFS/Hz input at 185 MHz (–dBFS AIN and 250 Msamples/s).

The AD6643 integrates two high performance A/D converters and noise shaping requantizer (NSR) digital blocks. With the NSR feature enabled, the outputs of the A/D converters are processed such that the AD6643 supports enhanced SNR performance within a limited portion of the Nyquist bandwidth while maintaining 11-bit output resolution. The NSR block can be programmed to provide a bandwidth of either 22% or 33% of the sample clock. Performance with NSR enabled includes an SNR of 76.1 dBFS in a 40-MHz band to 90 MHz at 185 MSPS and with NSR disabled, an SNR of 66.5 dBFS up to 90 MHz at 185 MSPS and an SFDR of 88 dBc up to 185 MHz at 185 MSPS. (Ea/1,000: AD6649, 250Msamples/s, $83.30; AD6643, 200 Msamples/s, $63.92 and 170 Msamples/s, $72.49 — available now.)

By Christina Nickolas

Analog Devices , Wilmington , MA
Sales 800-262-5643
www.analog.com