Patent ID: 7274919

Claim:
A signal processing apparatus comprising: radiowave receiving means which convert an electromagnetic wave into a first signal, a first mixer which converts the first signal into a second signal by a fixed frequency transposition, a filtering means which converts the second signal into a third signal by selecting part of the spectrum of the said second signal, a second mixer which converts the third signal into a fourth signal by frequency transposition by means of a transposition signal coming from a frequency synthesizer, wherein the filtering means comprises a first bandpass filter for passing frequencies within a first frequency range, a second bandpass filter for passing frequencies within a second frequency range, wherein said first frequency range and said second frequency range are separated by a third frequency range, wherein said filtering means is provided with switching means which make it possible to select either said first bandpass filter or said second bandpass filter, wherein the frequency synthesizer generates a transposition signal at a frequency determined in response the frequency range of the selected bandpass filter and the third frequency range.