Communications receiver with integrated if filter and method therefor

Abstract

A receiver () includes an IF filter () and a nearby process-variant circuit () formed on a common semiconductor substrate (). The actual center frequency of the IF filter () is determined by resistors () and capacitors () exhibiting imprecise values and is unlikely to equal a nominal center frequency. The process-variant circuit () includes a test resistor () and test capacitor () formed using the same resistor-forming and capacitor-forming processes used to form the IF filter resistors (70, 74) and capacitors (). In response a test signal () from the process-variant circuit () and a reference signal () from a process-invariant circuit (), a tuning parameter for a tunable local oscillator () is determined so that a local oscillation signal () will exhibit a frequency which, when mixed with an RF signal () yields an IF signal () at the actual center frequency of the IF filter ().