Patent ID: 7062235

Claim:
A method for testing the radio transceiver in a system where the transmission signal pass band, limited by the transmission branch filter of a duplex filter, and the reception signal pass band, limited by the reception branch filter, are adjacent so that the frequency response curves of said filters partially overlap at the stop band between the pass bands, comprising the steps of: arranging a test loop between the transmission branch and the reception branch, wherein the test loop includes a TX coupling, a band pass filter, and a RX coupling, the test loop having essentially less attenuation on the test frequency than the duplex filter and thus a test signal proceeds via the test loop from the transmitter to the receiver, adjusting a transmitter local oscillator of the transmitter for tuning the transmitter's transmission frequency away from the transmission signal pass band to a test frequency that falls into the stop band of the transmission branch filter frequency response curve and the reception branch filter frequency response curve, adjusting a receiver local oscillator of the receiver for tuning the receiver reception frequency to the test frequency, transmitting the test signal, and receiving the test signal which has been attenuated while passing through the test loop.