Patent ID: 9154178
Filing Date: 2015-10-06
Classification: H01P,H03H,H04B

Abstract:
1. A system comprising: a transmit filter in a transmit path of a duplexer configured to be coupled to an antenna, the transmit filter configured to pass signals in a transmit band; a receive filter in a receive path of the duplexer, the receive filter configured to be coupled to the antenna and to the transmit filter, and configured to pass signals in a receive band different from the transmit band; a quarter wave transformer tuned to a substantially open circuit impedance in the transmit band, the quarter wave transformer configured to couple the receive filter to the antenna and transmit filter; a frequency-variable impedance coupled to the receive path to provide isolation between signals in the transmit and receive bands on the receive path by attenuating signals in the transmit band; and a pair of couplers forming a phase shift path, wherein wherein each coupler of the pair of couplers is coupled to the other coupler of the pair, the pair of couplers to provide a corresponding magnitude control to effectively cancel signals leaking from the transmit path into the receive path at substantially the point at which the pair is tapped into the transmit path and the receive path.