Patent ID: 7039385

Claim:
A radio having a tunable bandpass filter wherein said tunable bandpass filter is tuned by apparatus within said radio said apparatus comprising: a reference generator for generating a reference signal to tune said tunable bandpass filter to a desired center frequency; the tunable bandpass filter for receiving the reference signal and providing a filter output signal; and a digital signal processing and control processor connected to the tunable bandpass filter to receive the filter output signal, to provide a phase error metric from the filter output signal, and to tune said tunable bandpass filter to provide a desired phase error metric thereby tuning said tunable bandpass filter to the desired center frequency said digital signal processing and control processor further comprising: a low-frequency quadrature down converter tuned to a frequency below the desired center frequency to down convert the filter output signal into low-frequency in-phase and quadrature outputs; a high frequency quadrature down converter tuned to a frequency above the desired center frequency to down convert the filter output signal into high-frequency in-phase and quadrature outputs; a low-frequency phase measurement block connected to the low-frequency quadrature down converter to provide a low frequency phase angle from the low-frequency in-phase and quadrature outputs; a high-frequency phase measurement block connected to the high-frequency quadrature down converter to provide a high-frequency phase angle from the high-frequency in-phase and quadrature outputs; a summing circuit for comparing the low-frequency phase angle and the high-frequency phase angle and providing a difference angle; an absolute value function for removing a negative sign from the difference angle; and an integrate and dump circuit for integrating and dumping the difference angle value thereby providing the desired phase error metric.