On chip transmit and receive filtering

摘要

This application relates to transmit/receive switching in an integrated circuit chip for a transceiver. The chip includes a chip pin 201 suitable for connection to a common antenna 803. A signal path from the chip pin 206 divides into a receive signal path 207 coupled to an input unit 202 and a transmit signal path 208 coupled to an output unit 203. A first filter 204 is provided on the receive path and a second filter 205 on the transmit path. The transmit and receive paths also have respective switches 210, 212, which selectively couple the respective paths to ground. The switches are controllable so as to isolate the input unit from the output unit when the integrated circuit chip is transmitting a radio frequency signal, and to isolate the output unit from the input unit when the integrated circuit chip is receiving a radio frequency signal. The first and second filters are preferably LC circuits, and may include variable capacitors which can be configured so that each of the filters presents a different impedance when the chip is receiving than when it is transmitting.