Patent ID: 7373115

Claim:
A transmit-receive switch for coupling a radio frequency (RF) transceiver capable of time-division duplex operation to an antenna, said transmit-receive switch comprising: a first circulator having a first port for receiving a transmit signal from a transmit path of said RF transceiver during transmit mode, a second port for sending said transmit signal to said antenna during transmit mode and receiving a received signal from said antenna during receive mode, and a third port for sending said received signal towards a receive path of said RF transceiver during receive mode; a second circulator having a first port for receiving said received signal from said third port of said first circulator during receive mode and a second port for sending said received signal towards said RF transceiver during receive mode; and a tunable filter and a quarter-wave transmission line coupled in series between said second port of said second circulator and said receive path of said RF transceiver, wherein said quarter-wave transmission line appears as a high impedance during transmit mode and reflects a reflected RF signal back to said second circulator during transmit mode.