Abstract: There is described an FM receiver (29) including; an antenna (2) able to receive a high frequency signal from a transmitter; a high frequency stage (3); an oscillator (5); a mixer unit (30) able to provide a signal (S6) at an intermediate frequency (fIF); an FM demodulation stage (8); and an automatic frequency control stage (36) able to control the oscillator, so as to keep said intermediate frequency (fIF) of said signal (S6) constant. This receiver further includes a locked loop (32) arranged to enslave said intermediate frequency (fIF) from a pilot frequency (fp) present in the demodulated signal. One advantage of such a locked loop is that the intermediate frequency is enslaved so that the aliasing phenomenon does not prevent demodulation of the signals containing the RDS data.

Abstract: The correction circuit comprises a first quadrature phase comparator intended to receive as input two signals which are desired to be in quadrature and to have equal amplitudes. Phase adjustment means are firstly intended to correct the phase of at least one of the signal to re-establish a phase difference of 90.degree. therebetween. The correction circuit further comprises means to effectuate the sum and the difference of the signals which it receives as input and to supply the sum and the difference to a second quadrature phase comparator intended to supply as output a second error signal representative of the difference of the effective phase shift of these calculated signals and 90.degree.. The second error signal is finally supplied to amplitude adjustment means intended to correct the amplitude of at least one of said signals.

Abstract: A modulator is adapted for use in a transmitter of an information transmission signal in which the information is in the form of a frequency shift keyed code. The signal is centered on a fictional carrier frequency fc, on either side of which are emitted two actual frequencies separated from the frequency fc by .DELTA.f, according to whether the binary information has a high value (+1) or a low value (-1). A first generator (1) creates carrier signals in the form of sin(2.pi.f.sub.c t) and cos(2.pi.f.sub.c t). A second generator (6) creates, as a function of the information, modulation signals of the form sin(2.pi..DELTA.ft) and cos(2.pi..DELTA.ft) which are mixed with the carrier signals. At each transition of the information, first phase shifting means (8,14) modify by k.pi. the phase of one of the modulation signals.