System and method for on-chip filter tuning

An integrated circuit tuner comprising:

• an on-chip crystal having a reference frequency;
• means for generating a first oscillator output at the reference frequency;
• a first adjustable on-chip filter having a first plurality of selectable capacitors that determine its center frequency;
• a second adjustable on-chip filter having a second plurality of selectable capacitors that determine its center frequency;
• means for selecting a number of the first plurality of capacitors to adjust the first filter to the reference frequency;
• and
• means for transferring the selection of the first plurality of capacitors to the second plurality of capacitors to adjust the second filter to a frequency proportional to the reference frequency.

A method for on-chip filter tuning comprising:

• stimulating a dummy filter with a frequency available in the receiver by utilizing the frequency as the filter stimulus;
• tuning the dummy filter to its designed center frequency by switching in capacitors to shift the filter response curve down in frequency;
• calculating the capacitor values required to center the response of the actual filter to its designed center frequency;
• adding the calculated capacitance to the actual filter so that its response curve is centered about its designed center frequency;
• and
• removing the tuning circuitry from the signal path.

Electronic tuning circuitry for tuning a filter comprising:

• a first switchable capacitor that is part of a tunable filter that is capable of being tuned to a first characteristic frequency;
• a dummy filter capable of being tuned to a second characteristic frequency;
• a second switchable capacitor that is part of the tunable dummy filter;
• a signal generator producing the second characteristic frequency and applying it to the dummy filter;
• a first phase detector that compares the phase of the dummy filter input to the dummy filter output;
• a comparator that produces an output signal indicative of the dummy filter being tuned to the second characteristic frequency;
• and
• a counter that continues to switch in first and second switchable capacitors simultaneously until disabled by the comparator circuit.

Electronic tuning circuitry for tuning a filter comprising:

• a dummy filter means for producing a tuned response at a frequency of a locally available frequency generator;
• a filter means for filtering unwanted signals from a desired signal;
• a phase detector means for detecting a phase difference across a set of dummy filter terminals with minimal DC off set;
• a low pass filter means for removing AC signals from the phase detector output;
• a comparator means for indicating that a desired phase difference has been achieved;
• and
• a counter means for tuning a filter until disabled by the comparator means.

Electronic tuning circuitry for tuning a filter comprising:

• a substrate upon which the electronic tuning circuitry is disposed;
• a first switchable capacitor that is part of a tunable filter that is capable of being tuned to a first characteristic frequency;
• a dummy filter capable of being tuned to a second characteristic frequency;
• a second switchable capacitor that is part of the tunable dummy filter;
• a signal generator producing the second characteristic frequency and applying it to the dummy filter;
• a first phase detector that compares the phase of the dummy filter input to the dummy filter output;
• a comparator that produces an output signal indicative of the dummy filter being tuned to the second characteristic frequency;
• and
• a counter that continues to switch in first and second switchable capacitors simultaneously until disabled by the comparator circuit.