Patent ID: 7436249

Claim:
A circuit for filtering a radio frequency signal, wherein said circuit comprises: a circuit input terminal; an active AC shunt circuit including a first input terminal, a second input terminal and an output terminal, wherein the first input terminal of said active AC shunt circuit is connected to said circuit input terminal; and a filter device connected between said circuit input terminal and the second input terminal of said active AC shunt circuit, wherein the filter device is configured to attenuate the radio frequency signal at a first frequency to the second input terminal of said active AC shunt circuit, the filter device comprising at least one of a resonant circuit or a notch filter configured to block the radio frequency signal at the first frequency; wherein said active AC shunt circuit is configured to shunt a signal at a second frequency contained in said radio frequency signal other than said first frequency to ground, and is further configured to output the radio frequency signal as filtered at said output terminal.