Patent ID: 7272370

Claim:
Apparatus for processing an input signal having a carrier frequency that defines a desired band and at least a side band having a side band frequency that is higher than the carrier frequency, the apparatus comprising a main input for receiving said input signal, a first mixer having a first mixer input, a first local oscillator input, and a first mixer output, the first mixer input being connectable to the main input and the first local oscillator input being connectable to a source providing a first local oscillator signal having a frequency close to or equal to the carrier frequency, the first mixer performing a multiplication of said input signal and said first local oscillator signal to provide a first output signal at the, first mixer output, the apparatus further comprising at least a second mixer having a second mixer input, a second local oscillator input, and a second mixer output, the second mixer input being connectable to the main input and the second local oscillator input being connectable to a source providing a second local oscillator signal having the sideband frequency, the second mixer performing a multiplication of said input signal and said second local oscillator signal to provide a second output signal at the second mixer output, means for performing a superpositioning of the first output signal and the second output signal-whereby an undesired component of the first output signal is partially or wholly cancelled, the first local oscillator signal and the second local oscillator signal being square wave signals.