Constant-phase, gain-controlled amplification circuit

Abstract

An amplification circuit () is used in a radio receiver () to achieve both constant phase shift over the gain range and low intermodulation. A gain-controlled amplifier () is desirably optimized for good fidelity, even if at the expense of poor phase linearity. A phase shift compensator () compensates for phase non-linearity by imposing a delay of variable duration downstream of the gain-controlled amplifier (). The delay duration is determined in response to a gain-control signal () generated by an AGC circuit (). The gain-control signal () is translated through a look-up table () into delay values which control a programmable delay element (). The programmable delay element () generates an adjusted clock signal () that drives a digitizer (). The digitizer () both digitizes and delays an amplified signal () produced by gain-controlled amplifier ().