Abstract: A demodulator which is arranged to demodulate a first signal with the aid of a second signal, comprises a first bandpass (30) filter arranged to recover the first signal (36) from a received signal (10) and a second bandpass filter (32) arranged to recover the second signal (30) from the received signal (10). Wherein the passband of the second bandpass filter (32) is substantially narrower than the passband of the first bandpass filter (30).

Abstract: A receiver having, arranged in this order, an input section, an FM demodulator, to which a frequency-modulated input signal is applied, and an LF section, which FM demodulator includes a pulse shaper and a low-pass filter, the pulse shaper comprising a series arrangement of at least a load and a capacitance, the base-emitter junction of a transistor being arranged across the capacitance, and further including a switching device for charging and discharging the capacitance. The pulse shaper generates a low-noise pulse in that charging of a capacitance is started upon an edge of the input signal. The capacitance voltage is measured by a single transistor and when the transistor is turned on, the charging current of the capacitance is diverted via the transistor, so that the capacitance voltage is limited. The capacitance is discharged upon a second edge, after which the cycle is repeated. The output signal of the pulse shaper is a signal which varies with the current through the capacitance.

Abstract: An electric circuit including a local oscillator circuit and which is adapted to prevent voltage transients. The oscillator circuit comprises two voltage sources which are alternately connected to respective electrodes of a capacitor. The capacitor electrodes are also connected, via respective load circuits, to a common reference node of the voltage sources. Thus, the respective voltage sources alternately generate mutually opposed currents in the capacitor, which currents charge and discharge the capacitor 20 to threshold levels, after which a switching control circuit interchanges the coupling of the voltage sources. In order to prevent a transient in the voltage level at the first capacitor electrode upon switching, a voltage control circuit provides a voltage difference between the voltages supplied by the voltage sources, which voltage difference corresponds to the charge voltage built up across the capacitor.

Abstract: A signal receiving device is kept tuned by a tuning signal, which supplied to a tuning input of a tunable circuit in the signal receiving device. The tuning signal is supplied from a memory. The signal receiving device has an operating state and a calibrating state. The calibrating state serves to determine the tuning signal and to store it in the memory. In the calibrating state, a broadband signal source supplies a broadband signal to a band-pass filter. The band-pass filter is tuned to and passes a reference signal to the tunable circuit which provides the signal receiving device with selectivity in the operating state. The response of the tunable circuit to the reference signal is monitored and a tuning signal is selected for which it is measured that the tunable circuit is tuned to the reference signal which is passed by the band-pass filter.