Analog Devices’ AD6649 and AD6643 IF diversity receivers and AD9643 and AD9613 high-speed A/D converters complement other receive chain components to simplify control loops and maximize base station receiver sensitivity and dynamic range. When paired with ADI’s dual-channel ADL5202 VGA (variable gain amplifier), the AD6649 IF receiver ensures that both weak and strong incoming cell phone call signals are effectively received and processed. The VGA is directly controlled by the AD6649 which can use the 1-dB gain step resolution in a simplified AGC (automatic gain control) loop.
The AD6649 is the industry’s first IF diversity receiver able to monitor the incoming signal power and adjust the VGA gain setting directly without the need for a microprocessor. It integrates many of the functions required for a diversity receive path in a single device, including an ultra-low-latency peak detector and a rms signal power monitor. There is also an integrated DDC (digital down converter) that includes a 32-bit NCO (numerically-controlled oscillator), a decimating half-band filter and an output FIR (finite-impulse response) filter that provides an effective band-pass filtering function and reduces the output rate.
The AD6643 is an IF diversity receiver for cost-sensitive applications that integrates two high performance A/D converters and noise shaping requantiser (NSR) digital blocks. The integrated NSR circuitry allows for improved SNR (signal-to-noise ratio) performance in a smaller frequency band within the Nyquist bandwidth. 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 percent or 33 percent of the sample clock.
For wideband, multi-carrier wireless communications applications that require only a dual A/D converter function without DDC functionality due to cost or size constraints, ADI introduced the AD9643 14-bit A/D converter with sampling speeds up to 250 MSPS. The AD9643