U.S. Philips Corporation

Wolfgang Nolde

Winfried B Jansen

Wolfdietrich G Kasperkovitz

Dieter J Janta

Winfrid B Jansen

Detlef Gottlieb

An FM stereo receiver has a loop having a negative loop gain for the pilot signal contained in the input signal in the form of a frequency modulation. As a result thereof the frequency modulation of the input signal is reduced or suppressed by the pilot signal, so that the interference introduced by this pilot signal is also reduced or suppressed.

FM stereo receiver

In an FM-stereo receiver the demodulated stereo-difference signal is mixed with a non-sinusoidal signal of the sub-carrier frequency and the mixing product is used to modulate the frequency of an oscillator by means of which the aerial signal is converted to the intermediate frequency range. Interference in the reception is avoided because of the fact that the signal used for modulating the oscillator is free from third and fifth harmonics of the sub-carrier frequency.

FM-stereo receiver

An approximately sinusoidal signal is generated by superimposing a first signal, which has a half cycle duration and corresponds to a triangular signal which is suppressed during every second half cycle, on a second triangular signal, every second waveform of the superimposed signal thus obtained being inverted.

Method of generating an approximately sinusoidal signal and circuit

The invention relates to a receiver circuit comprising a loop in which the oscillator frequency is controlled by the useful signal. The loop gain in the useful tuning range is negative and greater than unity. An attenuator is provided which is controlled by a control circuit so that larger deviations of the intermediate frequency loop from a target value result in the loop gain being reduced, improving the receiver tuning behaviour.

Circuit for improving the tuning behavior of a receiver frequency

An FM receiver for demodulating an RF carrier signal containing a pilot frequency signal is provided. The receiver includes first and second frequency control loops. The first frequency control loop selects the local oscillator signal frequency. The reference signal oscillator in the first frequency control loop forms a part of a second frequency control loop. The second frequency control loop locks the phase of the reference signal oscillator with a detected pilot signal. In this way, the tuning signal of the local oscillator is kept phase locked to the detected pilot signal. Additional provisions are provided for changing the divisor of the second phase lock loop such that the time for establishing phase lock is reduced.

Receiver circuit comprising two phase control loops

The invention relates to a circuit for an FM-receiver having a very low intermediate frequency and a tuning frequency-independent amplitude of the LF output signal. The oscillator frequency is controlled in such a way by a reactance circuit that frequency swing reduction occurs. In addition, a reactance circuit is described by means of which a constant fine tuning slope can be obtained during the capacitive tuning of the oscillator circuit.

Oscillator control circuit in an F.M. receiver

A demodulator circuit for demodulating a signal which varies substantially sinusoidally with time, such as a stereo signal having a carrier frequency, comprises a mixer circuit having a first input with a linear transfer characteristic which receives the stereo multiplex signal u.sub.m to be demodulated and having a second input with a substantially hyperbolic tangent transfer characteristic, the second input receiving a signal u.sub.d. The signal u.sub.d is a voltage having a triangular wave shape superimposed with the triangular wave shape having the carrier frequency. A stereo output signal L and R is produced having minimal third and fifth harmonics of the carrier frequency is produced from a matrix circuit as a result of the triangular shape and amplitude of the signal u.sub.d.

Demodulation circuit having triangular wave for blocking harmonics

An amplifier comprising means for eliminating direct-voltage transients on the amplifier output includes a controllable voltage source, coupled to the output or to a point in the amplifier such that the output voltage gradually increases to the steady-state value. The magnitude of the output voltage of said source, which conducts current in one direction only, can be controlled by means of a control voltage which is continuously variable during the turn-on period and which is applied to its input. The voltage source is connected to the amplifier so that as the amplifier output voltage rises, it is cut off by the resulting potential changes.

Amplifier comprising means for eliminating direct voltage transients on

A receiver for AM signals, in which the carrier is amplitude modulated with a first signal (L+R) and phase modulated with a second signal (L-R), includes a circuit for reducing distortion in the output signal due to amplitude overmodulation. This circuit includes an overmodulation detector for controlling a switch in a phase demodulation signal channel, which switch, coupled between a demodulator and an integrator in this signal channel, effectively short-circuits the input to the integrator causing the output thereof to remain constant for the duration of the overmodulation.

Growing community of inventors

Hamburg, Germany

Wolfgang Nolde