Dynamic gain assignment in analog basebband circuits

Abstract

A system and method is provided for filtering and amplifying a signal where amplification can be distributed between stages of a filter and gain can be assigned throughout the filter to optimize system performance. Such a system can be implemented in the baseband section of RF receivers. VGAs can be implemented between filter stages, such as biquads, or VGAs can be incorporated in filter stages. Substantially linear VGAs comprising a parallel resistor array can be incorporated in the circuitry of the filter stages to reduce distortion. Gain can be assigned dynamically in the amplification stages to improve noise and/or linearity performance. For example, gain assignments can be implemented so that high power undesired signal components are filtered out before amplification to prevent component saturation, and low power signals are amplified before they are filtered to improve noise performance.

What is claimed is: 
     
         1 . An apparatus for amplifying and filtering a signal in the baseband portion of a receiver comprising:
 a series of stages, which series of stages contains one of:   two or more variable gain amplifier (VGA) stages and a filter stage located between the two or more VGA stages;   two or more Combination stages;   a Combination stage and a VGA stage;   a Combination stage, a VGA stage, and a filter stage located between the Combination stage and the VGA stage;   where a Combination stage combines a VGA stage and a filter stage in one stage; and   a Gain Control Unit that varies gain assignment in the amplification stages according to measured signal strength by distributing a total amount of gain among the amplification stages, where the VGA stages and the Combination stages are amplification stages.