Patent ID: 8412261

Claim:
A transceiver comprising a transmitting unit, a receiving unit, and a coupling apparatus for dividing a radio frequency (RF) transmitting signal and an RF receiving signal in the transceiver with the transmitting unit and the receiving unit sharing an antenna, comprising: a four-port circuit having port 1 , port 2 , port 3 , and port 4 , a through path being formed between the port 1 and the port 2 , a first signal input to the port 1 being coupled to the port 4 , a second signal input to the port 2 being coupled to the port 3 , and an isolation path being formed between the port 1 and the port 3 and between the port 2 and the port 4 ; and an attenuator attenuating and outputting a signal output from the port 4 of the four-port circuit, wherein the RF transmitting signal is input to the port 1 of the four-port circuit, the RF receiving signal is input to the port 2 of the four-port circuit, and outputs of the attenuator and the port 3 of the four-port circuit are provided the receiving unit; wherein the attenuator is a variable attenuator operable to control variably an attenuation value, and the receiving unit includes: a low-noise amplifier subtracting and amplifying an output signal of the attenuator from an output signal of the port 3 of the four-port circuit; a received signal strength indicator (RSSI) measuring unit measuring an RSSI of a transmission leakage signal based on an output of the low-noise amplifier; and a control unit controlling an attenuation value of the attenuator based on the measured RSSI.