COMPLEX FILTERING/AGC RADIO RECEIVER ARCHITECTURE FOR LOW-IF OR ZERO-IF

摘要

A low power IF strip architecture suitable for Zero-IF (ZIF) or low-IF (LIF)radioreceivers for filtering and amplifying a received signal. The apparatusincludes aplurality of sequentially connected complex filter/amplifier stages. Eachstage includesa complex filter having one or more poles and an automatic gain controlledamplifier(AGC). Each AGC may be feedback or feedforward with fixed minimum and maximumgains. Each stage further includes a control circuit that produces a gaincontrol signal forcontrolling the amplifier gain within the fixed minimum and maximum gains as afunction of a projected amplitude level. The received signal passes throughmultiplestages of filtering and controlled amplification to attenuate the interferingsignal andamplify the desired signal. This is done at a restricted level in each stagesuch that thecircuits in the stages operate at efficient power saving levels. Theindividual gain controlsignals from each stage are summed in a received signal strength indicator toprovide theoverall gain of the apparatus. The overall gain when taken with the amplitudeof theapparatus output signal determines the original strength of the desiredreceived signal.