Patent attributes
In a Frequency Duplex Division (FDD) radio, the transmit and receive signals are separated by frequency. In a wireless application, the power of the transmitted signal is typically much larger than the power of the received signal. A duplexer is used to separate the transmit and receive signals. Despite the operation of the duplexer, a residual transmit signal, or echo, can be present at the receiver input as a result of finite attenuation in the duplexer and other sources of transmit to receive crosstalk. With a relatively linear low-noise amplifier (LNA) and output limited mixer linearity, the echo can be cancelled in analog baseband directly at the mixer output using an out-of-channel signal indicator as the error signal for an echo control loop.
