Patent ID: 8364092

Claim:
A circuit for improving isolation between a transmitter and a receiver, said circuit comprising: a first branch between the transmitter and the receiver, the first branch having a main duplexer with a port operatively connected to an antenna and adapted to generate a first duplexer signal, a first hybrid coupler with a 90° phase shift between signals operatively connected to an input of the main duplexer and an output of the transmitter for receiving a signal from the transmitter and producing two signals therefrom, and a second hybrid coupler with a 90° phase shift between signals operatively connected to an output of the main duplexer and an input of the receiver for receiving the first duplexer signal and a second duplexer signal and combining them into a single corrected signal, the single corrected signal to be injected into the receiver; a second branch between the first hybrid coupler and the second hybrid coupler, the second branch comprising a cancellation duplexer having characteristics similar to the main duplexer and receiving one of the two signals, and the cancellation duplexer adapted to generate the second duplexer signal and transmit the second duplexer signal to the second coupler such that it be combined with the first duplexer signal to form the corrected signal; and a third hybrid coupler with a 90° phase shift between signals connected to a port of the antenna, to a port of the main duplexer, and to a port of the canceling duplexer.