IF-to-baseband diversity

Analog Devices has introduced an integrated IF-to-baseband diversity receiver for GSM/EDGE wireless base stations.

The AD6650 chip is a member of the company’s MxFE family and is based on the company’s ‘smart partitioning’ methodology – a mixed-signal design technique that partitions the signal path according to performance-enhancing, rather than analog/digital, boundaries.

As such, the device replaces five active components and two SAW filters in existing solutions, reducing both board size and test costs. The new chip integrates a digitally controlled VGA (variable-gain amplifier) that acts as part of an on-board automatic gain control loop, an IF-to-baseband I&Q demodulator, analog low-pass filtering, and dual analog-to-digital converters (ADC).

An on-chip synthesiser with an integrated VCO (voltage-controlled oscillator) drives the I&Q demodulator. The part also integrates digital decimation filters, which generate serial output data streams and remove unwanted signals and noise outside the channel of interest.

The AD6650 can accommodate IF input frequencies from 70 MHz to 300 MHz and features a linear signal range of more than 106 dB and a dynamic range of more than 110 dB; thus requiring only one external SAW filter for the entire Rx signal path to meet GSM/EDGE blocking requirements.

The AD6650 is sampling now and will be in full production in the autumn. It is available in 121-pin plastic ball-grid array (BGA) packaging. It is priced at $20.00 per unit in 1,000-piece quantities.

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