A transmitter-receiver includes an electronic chip a mixer for mixing the frequency of a received radio frequency signal with that of an oscillating signal supplied by a first frequency synthesizer in, a switch having two inputs connected to an output of the mixer and to an auxiliary input terminal, a filter and gain stage connected to the output of the switch, and a modulator-demodulator connected to the output of the filter and gain stage. The first frequency synthesizer is connected between the output of the modulator-demodulator and radio frequency input and output terminal, and configured to supply a frequency-modulated signal to the radio frequency input and output terminal. The electronic chip further includes a second frequency synthesizer connected between the output of the modulator-demodulator and an auxiliary output terminal, and configured to synthesize a modulated low-frequency signal supplied by the auxiliary output terminal, whereby the center value of the low frequency is equal to the value of the intermediate frequency.