Abstract: A PLL circuit (1) is regulated by means of a digital modulation signal (28) at a first frequency, and is then regulated at a second frequency, by deactivation of the digital modulation signal (28). A difference signal (32), which is characteristic of the voltage change in a control signal (22) for the VCO (7) which is produced by deactivation of the digital modulation signal (28) is compared with an analog modulation signal (34). The analog modulation signal (34) is changed so as to correct any discrepancy determined during the comparison.

Abstract: The quadricorrelator for a demodulator for frequency-modulated signals has a first input receiving an in-phase component of the signal and a second input receiving a quadrature component of the signal. The first and second inputs are followed by respective first and second multiplier units. The output of the first multiplier unit is connected with a positive sign, and the output of the second multiplier unit is connected with a negative sign to the output adder unit. The in-phase component is supplied via a first transfer function to the second multiplier unit, and the quadrature component is supplied via a second transfer function to the first multiplier unit. A demodulator characteristic formed between the input and output of the quadricorrelator cuts the frequency axis at a point where the frequency is nonzero and runs essentially linearly in a sufficiently wide frequency band which surrounds or is adjacent to the intersection point.