Patent ID: 8005448

Claim:
A radio frequency (RF) duplex filter comprising: an integrated circuit die including a series impedance circuit and a series resonant circuit, wherein: the series impedance circuit: includes at least one series impedance element coupled to the series resonant circuit to form at least one RF output that provides at least one RF output signal, and adapted to receive an RF input signal; and the series resonant circuit includes a parallel resonant circuit having a parallel resonant frequency that is approximately equal to a receive frequency, wherein the at least one series parallel resonant circuit includes a switched capacitor bank in parallel with a first parallel resonant capacitive element, a parallel resonant inductive element, and a negative transconductance circuit; and at least one series resonant element coupled in series with the parallel resonant circuit; and wherein the series resonant circuit has a series resonant frequency that is approximately equal to a transmit frequency, and wherein the at least one RF output signal is based on the at least one RF input signal and filtering characteristics provided by the series impedance circuit and the series resonant circuit.