Patent ID: 7904047

Claim:
A method for filtering a radio frequency (RF) signal, comprising: amplifying a first RF communication signal in a first signal path; filtering the first RF communication signal in a second signal path, said filtering the first RF communication signal in the second signal path including down-converting the first RF communication signal to a down-converted signal, high pass filtering the down-converted signal, and up-converting the high pass filtered down-converted signal to a second RF communication signal; adjusting a signal phase in the second signal path; and subtracting the second RF communication signal from the amplified first RF communication signal to generate a third RF communication signal; wherein said down-converting the first RF communication signal to a down-converted signal comprises down-converting the first RF communication signal to a first I-phase down-converted signal, down-converting the first RF communication signal to a first Q-phase down-converted signal, down-converting the first RF communication signal to a second I-phase down-converted signal, and down-converting the first RF communication signal to a second Q-phase down-converted signal; wherein said high pass filtering the down-converted signal comprises high pass filtering the first I-phase down-converted signal, high pass filtering the first Q-phase down-converted signal, high pass filtering the second I-phase down-converted signal, and high pass filtering the second Q-phase down-converted signal; wherein said adjusting a signal phase in the second signal path comprises scaling the high pass filtered first I-phase down-converted signal according to a first scale factor, scaling the high pass filtered first Q-phase down-converted signal according to a second scale factor, combining the scaled high pass filtered first I-phase down-converted signal and the scaled high pass filtered first Q-phase down-converted signal to generate a first combined signal, scaling the high pass filtered second I-phase down-converted signal according to an inverted version of the second scale factor, scaling the high pass filtered second Q-phase down-converted signal according to the first scale factor, and combining the scaled high pass filtered second I-phase down-converted signal and the scaled high pass filtered second Q-phase down-converted signal to generate a second combined signal; and wherein said up-converting the high pass filtered down-converted signal to a second RF communication signal comprises up-converting the first combined signal to an I-phase RF communication signal, up-converting the second combined signal to a Q-phase RF communication signal, and combining the I-phase RF communication signal and the Q-phase RF communication signal to generate the second RF communication signal.