27 May 2011
High speed data converters and IF diversity receivers
Analog Devices has launched four high speed data converter products designed to support signal sampling rates necessary to accommodate multi carrier radio platform requirements for 3G and 4G cellular infrastructure communication standards. These include CDMA2000, UMTS/LTE, TD-SCDMA and TD-LTE.
The 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 maximise base station receiver sensitivity and dynamic range.
When paired with ADI's dual channel ADL5202 variable gain amplifier (VGA), the AD6649 IF receiver is designed to ensure 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 automatic gain control (AGC) loop.
According to ADI, 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 an rms signal power monitor. There is also an integrated digital down converter (DDC) that includes a 32bit numerically controlled oscillator (NCO), a decimating half band filter and an output 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 signal to noise ratio (SNR) 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 11bit output resolution. The NSR block can be programmed to provide a bandwidth of either 22 or 33% of the sample clock.
For wideband, multicarrier wireless communications applications that require only a dual a/d converter function without DDC functionality due to cost or size constraints, ADI has introduced the AD9643 14bit a/d converter. Ir features a multistage, differential pipelined architecture with integrated output error correction logic. Wide bandwidth inputs support a variety of user selectable input ranges, while an integrated voltage reference eases design considerations. Programming for setup and control are handled using a three-wire SPI compatible serial interface.