Patent ID: 6675004
Filing Date: 2004-01-06
Classification: H04B

Abstract:
A noise suppression apparatus for use in a receiver, comprising:an input terminal adapted to receive an inbound signal comprising a desirable signal component and an internal noise component; a channel splitter coupled to the input terminal and configured to split the inbound signal into a substantially identical first signal and second signal; a first mixer coupled to the channel splitter and configured to receive the first signal, and a second mixer coupled to the channel splitter and configured to receive the second signal; a first local oscillator coupled to the first mixer and configured to generate a first LO frequency signal, and a second local oscillator coupled to the second mixer and configured to generate a second LO frequency signal, where the first LO frequency signal and second LO frequency signal differ from one another by an offset in frequency; wherein the first mixer is coupled to the first local oscillator and configured to mix the first signal with the first LO frequency signal to create a first mixed signal, and the second mixer is coupled to the second local oscillator and configured to mix the second signal with the second LO frequency signal to create a second mixed signal; a first bandpass filter coupled to the first mixer having a first passband frequency range and configured to generate a first filtered signal; a second bandpass filter coupled to the second mixer having a second passband frequency range and configured to generate a second filtered signal; wherein said first LO frequency signal, said second LO frequency signal, and said first and second passband frequency ranges are selected such that said first filtered signal comprises said desirable signal component and said second filtered signal consists essentially of said internal noise component; a first phase shifting structure coupled to the second bandpass filter and configured to shift the phase of the second filtered signal approximately 180 degrees from the phase of the second filtered signal to create a phase-shifted second filtered signal; a second phase shifting structure coupled to the first bandpass filter and configured to shift the phase of the first filtered signal to create a phase-shifted first filtered signal that corrects for the offset in frequency; and a combiner coupled to the first filter and the second filter and configured to combine the phase-shifted first filtered signal with the phase-shifted second filtered signal to generate a noise suppressed output signal having said desirable signal component and wherein said internal noise component is substantially suppressed