Method and apparatus for automatic tuning calibration of electrically tuned filters

An automatic tuning calibrator for tuning electronically tuned filters in a radio receiver, the automatic tuning calibrator comprising:

• synthesizer means for producing a calibration frequency signal;
• mixer means coupled to the synthesizer means for receiving the calibration frequency signal;
• bias switch means for enabling the mixer means, the bias switch means coupled to the mixer means;
• first filter means for producing a filtered calibration frequency signal from the calibration frequency signal, the first filter means coupled to the mixer means;
• detector means for producing a detector voltage from the filtered calibration frequency signal, the detector means coupled to the first filter means;
• processor means for enabling the bias switch means for calibration, for producing a stepped filter tuning voltage and for storing the detector voltage in response to the stepped filter tuning voltage, the processor means coupled to the bias switch means, to the detector means and to the synthesizer means;
• and
• converter means for receiving the stepped filter tuning voltage and for providing digital-to-analog conversion of the stepped filter tuning voltage for input to the filter means, the converter means coupled to the processor means and to the filter means;
• and
• radio receiver means for receiving an operating frequency signal, the radio receiver means coupled to the first filter means, to the detector means, and to the converter means.

A method for automatic tuning calibration of electronically tuned filters comprising the steps of:

• producing a calibration frequency signal in a programmable frequency generator including:
• enabling a bias switch with a microprocessor;
• producing a fixed frequency signal in a synthesizer;
• and
• enabling the mixer with the bias switch during calibration;
• producing a filtered calibration frequency signal from the calibration frequency signal in a first filter;
• producing a detector voltage in a detector from the filtered calibration frequency signal;
• producing a stepped filter tuning voltage in a processor;
• storing the detector voltage in response to the stepped filter tuning voltage in the processor;
• calculating a filter tuning voltage from the detector voltage in the processor;
• converting the stepped filter tuning voltage to a filter tuning voltage in a converter;
• providing a radio receiver filter substantially identical in performance to the first filter;
• and
• calibrating the radio receiver filter with the filter tuning voltage.