Testing of a radio transceiver

The objective of this invention is to provide a test procedure that enables testing of not only the transceiver but also of the cable connecting the transmitters and receivers to the duplex filter and the duplex filter itself. The invention is based on the idea of utilizing the fact that the frequency response of the filter in the duplex filter transmission branch and that of the filter in the reception branch partially overlap in the stop band. This makes it possible to use the same stop band frequency in test transmission and test reception. On the transmitter, the test signal frequency (fTEST) is adjusted so as to fall in between the system reception band (RX) and the transmission band (TX). The receiver reception frequency is shifted to the same frequency between the reception and transmission frequency bands to which the transmitter has been adjusted. This will provide a test signal that is sufficiently weak to satisfy the antenna interface requirements, but still strong enough to remain above the sensitivity threshold of the receiver despite the attenuation in the TX filter section of the duplex filter (A dB) and the attenuation in the RX filter section of the duplex filter. In this way, it is possible to have the receiver receive the test signal transmitted by the transmitter without any additional components being required.