Patent ID: 7702306

Claim:
In a receiver having a first mixer, a second mixer, and a bandpass filter coupled between said first mixer and said second mixer, said first mixer responsive to a first local oscillator signal that is coupled to said first mixer and said second mixer responsive to a second local oscillator signal, a method of compensating for passband variation of said bandpass filter, comprising: disabling an RF input signal applied to an RF port of said first mixer so that said RF port receives no signal input during a calibration mode; injecting said first local oscillator signal into an LO port of said first mixer; leaking said first local oscillator signal from the LO port of said first mixer to an IF port of said first mixer that is coupled to an input port of said bandpass filter; determining an actual passband of said bandpass filter responsive to said first local oscillator signal; enabling said RF input signal applied to said RF port of said first mixer; mixing an RF input signal having plurality of channels with said first local oscillator signal after said step of determining to generate a first IF signal, including said step of adjusting a frequency of said first local oscillator signal based upon a selected channel of said plurality of channels and based upon said actual passband of said bandpass filter.