Patent ID: 7610034

Claim:
A double conversion tuner, comprising: an input for a source of a plurality of RF channels, the plurality ranging from a lowest frequency channel signal to a highest frequency channel signal; a synthesizer to generate a first and second local oscillator signal, the synthesizer capable of generating signals having frequencies within a first range; a first mixer to mix a selected channel signal with the first local oscillator signal to generate a high intermediate frequency; a first filter to filter the high intermediate frequency; a second mixer to mix the high intermediate frequency with the second local oscillator signal to generate a low intermediate frequency; a second filter to filter the low intermediate frequency; and a processor, responsive to sources of interference signals in a second frequency range, configured to adjust the frequency of the first local oscillator signal to avoid interference between the first local oscillator signal, or its harmonics, and the interference signals, wherein the sources of interference signals in the second frequency range span from a low-frequency interference signal to a high-frequency interference signal, and wherein the processor is configured to: a. calculate values of potential first local oscillator signals that are at least one-half the frequency of any of the interference signals in the second frequency range; b. determine if the values of potential first local oscillator signals are all within the first range; c. if the values of potential first local oscillator signals are all within the first range, then: i. choose a high intermediate frequency by dividing the high-frequency interference signal by two and subtracting the frequency of the lowest frequency channel signal, and choosing a value greater than or equal to the result; ii. validate the selection of the high intermediate frequency for the second local oscillator; iii. if the selection of the high intermediate frequency cannot be validated for the second local oscillator, adjust the value of the high intermediate frequency until the value of the high intermediate frequency is validated for the second local oscillator; and iv. calculate the range of first local oscillator frequencies based on the high intermediate frequency.