Abstract: A signal receiver and a method for separating a RDS signal component from a received signal is described. After the received signal has been downconverted to the baseband, the baseband signal is split up into a first baseband signal for a first signal path and a second baseband signal for a second signal path. The first baseband signal is highpass filtered and forwarded to a frequency synchronization unit that generates a frequency synchronization carrier. The second baseband signal is modified in accordance with the frequency synchronization carrier provided by the first signal path, and a synchronized baseband signal is obtained that still comprises the full range of the RDS signal's spectral components.

Abstract: The noise in a frequency demodulated audio signal is detected on the basis of the characteristics of the stereo-multiplex signal to obtain a very reliable information that can be used for the sliding stereo-mono transition, noise blanking and a de-noising of the stereo difference signal. A noise (vd,q(t)) is calculated by performing a coherent amplitude demodulation of the frequency demodulated stereo-multiplex signal with the second harmonic of the pilot carrier that is quadrature to the pilot carrier and as a direct measure for the quality of the signal generating the variance (&sgr;2vd,q) of the noise signal by squaring and thereafter averaging the noise signal.

Abstract: A receiver and a method for receiving a digital signal and an analogue signal is described, whereby both signals transmit the same audio program. In dependence of the reception situation, the receiver switches or slides from said digital signal to said analogue signal and back. Each time the receiver switches between the digital signal, which has an audio bandwidth of about 12 kHz, and the analogue signal, which has an audio bandwidth of only 4.5 kHz, the sound of the received audio output signal changes from a rich sound to a rather flat sound, or vice versa. To avoid this, the audio bandwidth of the digital signal is reduced in dependence of the reception situation. In case of frequent occurrence of switching, or in case of a bad reception of the digital signal, the bandwidth of the digital signal is reduced.

Abstract: A reduced peak simulcast signal generator and a method for generating a stable peak-attenuated simulcast signal, which combines a digital broadcast signal and an analogue broadcast signal, are described. The simulcast signal generator comprises at least one attenuation stage for attenuating the digital and/or the analogue broadcast signal in order to obtain a stable simulcast signal. Each attenuation stage comprises a simulcast signal generator for generating an error signal, and attenuation means which attenuate, in dependence of said first error signal, at least one of the analogue and the digital broadcast signal.

Abstract: The noise in a frequency demodulated audio signal is detected on basis of the characteristics of the stereo-multiplex signal to obtain a very reliable information that can be used for the sliding stereo-mono transition, noise blanking and a de-noising of the stereo-difference signal. A noise signal (vd,l(t)−vd,u(t) or vd,u(t)−vd,l(t)) is calculated by subtracting one sideband of the stereo-difference signal from the other sideband of the stereo-difference signal and as a direct measure for the quality of the signal generating the variance (&sgr;2vd) of the noise signal by squaring and thereafter averaging the noise signal.

Abstract: A receiver for simulcast signals and a method for receiving a simulcast signal transmitted via a distorted channel is described. By means of a bandpass filter, an initial digital signal is separated from the simulcast signal. This initial digital signal is subtracted from said simulcast signal, and as a result of the subtraction, an intermediate analogue signal is obtained. With respect to the initial digital signal, a channel estimation and equalization is performed. Thus, it is possible to estimate the channel's frequency response, to remove channel impairments due to frequency selective fading and/or to non-symmetric receiver input filter, and to generate a corrected digital signal. Said corrected digital signal, or a signal derived therefrom, is added to said intermediate analogue signal, in order to obtain the simulcast signal's analogue signal part.

Abstract: A receiver for broadcast signals, e.g. DAB, FM, DVB, and digital or analog short-wave RF broadcast signals according to the present invention includes a polyfunctional circuit (5) that can be switched into three modes and performs the digital frequency demodulation which is needed for the reception of a frequency modulated signal in a first mode A, a digital frequency adjustment of the receiver in case of the reception of a digital or analog modulated broadcast signal like DAB, DVB, DRM or AM in a second mode B and the digital frequency adjustment and the digital gain control of the receiver which is needed in case of the reception of a digitally modulated broadcast signal like DAB, DVB, DRM in a third mode C. Depending on the needed functionality not all of these modes need to be realized. Nevertheless, the same hardware will be used for different purposes although the circuit is realized with an optimized amount of hardware to realize an efficient receiver.

Abstract: The bandwidth of a first variable IF filter (5) for a neighbour channel suppression of a currently received channel, which first variable IF filter (5) is arranged in a first reception path of a broadcast receiver additionally comprising at least one second reception path is controlled by obtaining at least one first quality signal corresponding to a received broadcast signal on basis of a first filtering of the received and eventually pre-processed broadcast signal with said first variable IF filter (5) set to a predetermined bandwidth, obtaining at least one second quality signal corresponding to said received broadcast signal on basis of at least one second filtering of the received and eventually pre-processed broadcast signal with a second variable IF filter (13) arranged in said at least one second reception path with a bandwidth different to the first variable IF filter (5) bandwidth and/or with a different filter characteristic, and controlling the bandwidth of the first variable IF filter (5) on basi

Abstract: An automatic gain control loop for a radio receiver, comprising a switchable lowpass filter (21) to reduce distortions in an analogue gain control signal (6) by switching said switchable lowpass filter (21) to a low time constant in case a change of a gain control signal (6) of the automatic gain control loop lies above a predetermined threshold, which low time constant is lower than a normally used time constant, comprises a hold unit (24) which affects that said switchable lowpass filter (21) uses said low time constant a predetermined time after a change of the gain control signal (6) of the automatic gain control loop lies below said predetermined threshold.

Abstract: A digital filter realization is proposed that consists of only one multiplier, i. e. which operates with a higher clock rate and changes coefficient at the multiplier each clock cycle, but in which the clock rate of the multiplier is reduced in comparison to prior art filters by considering equal filter coefficients, e. g. based on the symmetry of FIR filter coefficients. According to the present invention preferably the samples belonging to equal filter coefficients are added in advance in order to reduce the number of multiplications, which concludes in a reduced clock rate for the filter, a reduced needed calculation power, and therefore a reduced power consumption.

Abstract: In an automatic gain control unit, the gain of a voltage-controlled amplifier (VCA) (25) is regulated with a closed-loop control circuit. The time constant of the control circuit is varied dependent on the magnitude (31) of the VCA output signal. As long as the magnitude (31) of the VCA output signal is small, the gain is slowly adjusted. In case the magnitude (31) of the VCA becomes so large that saturation of the analog-digital converter (28) might occur, the time constant of the control circuit is decreased, in order to allow for a quick adjustment of the amplifier's gain.

Abstract: A FM broadcast compander system is combined with a conventional denoising system suited for FM receiver, wherein a noise indicator is determined by a subtraction of the conventionally transmitted difference signal Ud(z) from the additionally transmitted difference signal (Uc(z)) which is additionally transmitted according to the companding system. This system gives a noise reduction of 20 dB in a stereo FM broadcast receiver.

Abstract: A compander for noise reduction of a FM-signal is described, wherein a linear phase compression and/or expansion is performed.

Abstract: A compander for noise reduction of a FM signal is described, wherein a group delay (&tgr;) linked to the generation of the compressor gain (cc(t)) is equalised during generation of the multiplex signal (m(t)), and a group delay (&tgr;) linked to the generation of the expander gain (ce(t)) is equalised during generation of the sum signal (us(t)) and the expanded difference signal (ue(t)). Alternatively or additionally the compressor gain and/or the expander gain is controlled by an auxiliary signal on the basis of a combination of sum signal and difference signal of the FM signal. Such companders avoid overmodulation in the transmitter.

Abstract: A method to denoise a stereo signal which comprises a stereo sum signal (Us(z)) and a stereo difference signal (Ud(z)), wherein a stereo to mono blending on basis of an attenuation of the stereo difference signal (Ud(z)) is performed, determines an attenuation of the stereo difference signal (Ud(z)) under consideration of the difference signal amplitude. Therefore, a stereo signal noise reducer which performs a stereo to mono blending on basis of an attenuation of the stereo difference signal, comprises an attenuation factor determination unit which determines an attenuation factor (Hatt) under consideration of the difference signal amplitude.

Abstract: An alternative frequency of e. g. a digital shortwave signal like a DRM signal can easily and satisfactorily be checked whether or not the same service is transmitted before a fast seamless switching to this alternative frequency can be performed. The inventive method to perform such a checking is characterized by a respective correlation of at least two sets of samples taken from the signal transmitted on the alternative frequency having a predetermined time relationship (&Dgr;tcorr) and a comparison of said respective correlation results, i.e. comparison of the time (t1) of occurance of a correlation peak included in a first correlation result with the time (t2) of occurance of a correlation peak included in a respective further correlation result, to verify that both services are the same when the time relationship (|t2 l -t1|) between said correlation peaks is the same as said predetermined time relationship (&Dgr;tcorr) of the at least two sets of samples.

Abstract: An AM simulcast broadcast signal combining a digital transmission signal and an analogue transmission signal in one transmission channel. The digital transmission signal is modulated to one sideband of a carrier of the transmission channel and a correcting signal (C) is modulated to the other sideband of the carrier of the transmission channel, which correcting signal (C) is determined so that the envelope demodulation of the transmission channel represents the analogue transmission signal.

Abstract: Noise and multipath distortions in a broadcast receiver are reduced by an optimal antenna/frequency diversity concept in which the distortions in the audio signal are evaluated to choose a different antenna and/or a different frequency for at least signal parts.

Abstract: A stereo demultiplexer is proposed which can be calculation power efficiently implemented in a DSP. Modern digital FM receivers exploit the information content in the in quadrature component of the modulated difference signal for a noise reduction. The proposed stereo demultiplexer derives the in phase component and the in quadrature component of the difference signal with a minimized number of sinus and cosinus calculations by first downconverting the modulated difference signal to a not synchronized complex baseband signal on basis of a fixed frequency, thereafter a complex sampling rate decimation unit sampling rate decimates the not synchronized complex baseband signal with a factor N and a second complex mixer synchronizes and coherent demodulates the sampling rate decimated not synchronized baseband signal on basis of a first complex carrier signal derived on basis of the pilot carrier signal and the fixed frequency.

Abstract: A broadcast receiver designed according to a two tuner concept for alternative broadcast frequency or system switching comprises a delay unit (3) receiving an output signal of the first tuner (1) and an output signal of the second tuner (2) to compensate a time delay between said both output signals. Preferrably, an additional amplitude adaptation unit (4) connected after said delay unit (3) compensates an amplitude difference between said both time delay compensated output signals.