Abstract: A system for decoding a stereo multiplex signal, including one or more devices operable to convert the stereo multiplex signal into a sum signal (L+R) and a difference signal (L?R). The sum signal and the difference signal may be derived from a left stereo signal (L) and right stereo signal (R). The system may also be operable to determine a first transfer function HL(f) and a second transfer function (HR(f)) from the sum signal (L+R) and the difference signal (L?R). Further, the system may be operable to filter the sum signal (L+R) according to the first transfer function to provide the left stereo signal (L), and filter the sum signal (L+R) according to the second transfer function to provide the right stereo signal (R).

Abstract: A system for decoding a stereo multiplex signal, including one or more devices operable to convert the stereo multiplex signal into a sum signal (L+R) and a difference signal (L?R). The sum signal and the difference signal may be derived from a left stereo signal (L) and right stereo signal (R). The system may also be operable to determine a first transfer function HL(f) and a second transfer function (HR(f)) from the sum signal (L+R) and the difference signal (L?R). Further, the system may be operable to filter the sum signal (L+R) according to the first transfer function to provide the left stereo signal (L), and filter the sum signal (L+R) according to the second transfer function to provide the right stereo signal (R).

Abstract: A processing front-end for FM radio signals includes a receiver, a filter, and a mixer. The receiver obtains an FM radio signal including data content centered at a data frequency and programming content. The filter is coupled to the receiver and removes the programming content from the FM radio signal. The mixer accepts the filtered FM radio signal and shifts the center frequency of the data content to a lower frequency than the first frequency. The lower frequency is selected according to a sampling rate available in an analog-to-digital converter present in a subsequent processing stage, typically a low cost digital signal processor.

Abstract: In order to suppress as much noise as possible in a hands-free device in a motor vehicle, for example, two microphones (M1, M2) are spaced a certain distance apart, the output signals (MS1, MS2) of which are added in an adder (AD) and subtracted in a subtracter (SU). The sum signal (S) of the adder (AD) undergoes a Fourier transform in a first Fourier transformer (F1), and the difference signal (D) of the subtracter (SU) undergoes a Fourier transform in a second Fourier transformer (F2). From the two Fourier transforms R(f) and D(f), a speech pause detector (P) detects speech pauses, during which a third arithmetic unit (R) calculates the transfer function HT of an adaptive transformation filter (TF). The transfer function of a spectral subtraction filter (SF), at the input of which the Fourier transform R(f) of the sum signal (S) is applied, is generated from the spectral power density Srr of the sum signal (S) and from the interference power density Snn generated by the adaptive transformation filter (TF).

Abstract: The sound reproduction of a multichannel sound reproduction system with a plurality of speakers which is connected to the output of an FM stereo receiver is controlled by a control signal derived from the reception quality. Preferably, the control signal from the FM stereo receiver for controlling the stereo and mono components is also employed to control the multichannel sound reproduction system. For example, stereo, pseudo-stereo or mono reproduction are provided in the multichannel sound reproduction system in response to the stereo component within the output signal.

Abstract: A method and apparatus for operating a radio reception system, which comprises a plurality of receivers assigned to a common output device, in which one of the receivers is designated as audio receiver and is tuned to a frequency of a radio transmitter, and outputs a signal received from the transmitter to the output device. At least one second receiver is designated as search receiver, and continuously searches its own reception frequency band for a frequency of the same transmitter. The system changes to a frequency of this transmitter, which was found by the search receiver, if the quality of the signal received by the audio receiver falls below a certain limit.

Abstract: This invention provides a signal synchronizer that is capable of minimizing the effects of multi-path reception. The signal synchronizer provides signal samples from a first signal source and a second signal source for generating an output signal. The signal synchronizer includes a memory for storing signal samples obtained from a first signal source and for storing signal samples obtained from a second signal source. Circuitry in the synchronizer determines a signal transit time difference between the first signal source and the second signal source. A readout controller then determines a memory offset from the signal transit time difference. The memory offset specifies a location in the memory from which to begin reading the signal samples obtained from the second signal source.

Abstract: In order to suppress as much noise as possible in a hands-free device in a motor vehicle, for example, two microphones (M1, M2) are spaced a certain distance apart, the output signals (MS1, MS2) of which are added in an adder (AD) and subtracted in a subtracter (SU). The sum signal (S) of the adder (AD) undergoes a Fourier transform in a first Fourier transformer (F1), and the difference signal (D) of the subtracter (SU) undergoes a Fourier transform in a second Fourier transformer (F2). From the two Fourier transforms R(f) and D(f), a speech pause detector (P) detects speech pauses, during which a third arithmetic unit (R) calculates the transfer function HT of an adaptive transformation filter (TF). The transfer function of a spectral subtraction filter (SF), at the input of which the Fourier transform R(f) of the sum signal (S) is applied, is generated from the spectral power density Srr of the sum signal (S) and from the interference power density Snn generated by the adaptive transformation filter (TF).

Abstract: In order to suppress as much noise as possible in a hands-free device in a motor vehicle, for example, two microphones (M1, M2) are spaced a certain distance apart, the output signals (MS1, MS2) of which are added in an adder (AD) and subtracted in a subtracter (SU). The sum signal (S) of the adder (AD) undergoes a Fourier transform in a first Fourier transformer (F1), and the difference signal (D) of the subtracter (SU) undergoes a Fourier transform in a second Fourier transformer (F2). From the two Fourier transforms R(f) and D(f), a speech pause detector (P) detects speech pauses, during which a third arithmetic unit (R) calculates the transfer function HT of an adaptive transformation filter (TF). The transfer function of a spectral subtraction filter (SF), at the input of which the Fourier transform R(f) of the sum signal (S) is applied, is generated from the spectral power density Srr of the sum signal (S) and from the interference power density Snn generated by the adaptive transformation filter (TF).

Abstract: A motor vehicle entertainment system includes a radio receiver and a control unit. The control unit receives a first status signal indicative of whether or not a motor vehicle door has been unlocked and initiates the application of power to the radio receiver upon the first status signal indicating that the door has been unlocked. Upon the application of power to the radio receiver, the radio receiver scans through a selected frequency spectrum to identify valid frequencies and their associated broadcast identifying information and stores a list of the valid frequencies and their associated broadcast identifying information in a memory device associated with the radio receiver. The radio receiver acquires and records information on a plurality of transmitters initially in a standby mode before it switches over to an operating mode. The radio receiver has a device for receiving an ON command from the user and switches from the standby mode to the operating mode when the ON command is received.

Abstract: An apparatus determines an optimal antenna and frequency combination by selecting the optimal antenna from among a plurality, N, of antennas associated with a receiver and also selects the optimal frequency from among a plurality, M, of alternative receiving frequencies transmitted from a transmitter. This is achieved by determining all N×M possible antenna/frequency combinations, by determining the received signal quality at each combination, by comparing the N×M received signal qualities, and by selecting the one antenna/frequency combination having the optimal received signal quality.

Abstract: To ensure that a phase-locked loop locks quickly to the pilot tone of the stereo-multiplex signal when a new transmitter is tuned in, the stereo-multiplex signal is multiplied in a multiplier M by the quadrature component of the pilot tone generated by a digital oscillator, is low-pass-filtered in a low-pass filter, and is fed as a control signal to the oscillator which is composed of a table of length N and a counter for addressing the table entries. The zero phase angle ?0 is set by a counter offset n0 by incrementing or decrementing the counter. It is advantageous to employ a virtual table of length N+ which is larger than the length N of the real table. To access the real table, however, only the corresponding MSBs of the actual count n(k) are used which match the address space of the real table of length N.

Abstract: A system for decoding data, such as travel and traffic information, configured in data blocks embedded in an electromagnetic signal, such as a broadcasted radio signal, has been developed. The system includes a method and receiver for decoding the data with a background tuner in a manner that does not impair the ability of the background tuner to demodulate other signals. While a main tuner is tuned to demodulate a first electromagnetic signal to produce a data stream, the background tuner is switched to decode the data blocks only when the data blocks are expected to be received. In the remaining time, the background tuner is free to demodulate other signals to support a diversity or other function. If a data block is not received, or not received when expected, the background tuner returns to demodulating one or more other frequencies after a predetermined time interval has elapsed.

Abstract: For the purpose of largely suppressing the noise pulses caused in a stereo radio receiver in the reception signal, particularly by the ignition system of a motor vehicle, a digital field strength signal representing the analog field strength signal is produced for example by digitizing the analog field strength signal. The scanning values of the digital audio signal, for example of the (L+R) signal, are produced by interpolation for at least as long as the digital field strength signal is outside a presettable tolerance range.

Abstract: A method and apparatus for operating a radio reception system, which comprises a plurality of receivers assigned to a common output device, in which one of the receivers is designated as audio receiver and is tuned to a frequency of a radio transmitter, and outputs a signal received from the transmitter to the output device. At least one second receiver is designated as search receiver, and continuously searches its own reception frequency band for a frequency of the same transmitter. The system changes to a frequency of this transmitter, which was found by the search receiver, if the quality of the signal received by the audio receiver falls below a certain limit.

Abstract: A phase-locked loop locks relatively quickly to a pilot tone of the stereo-multiplex signal when a new transmitter is tuned in. The stereo-multiplex signal may be multiplied in a multiplier by the quadrature component of the pilot tone generated by a digital oscillator. The result is a control signal that is provided to a low-pass filter, and the low-pass filtered control signal is provided as a control signal to an oscillator which may include a table of length N and a counter for addressing the table entries. The zero phase angle ?0 may be set by a counter offset n0 by incrementing or decrementing the counter. A table may be utilized having a virtual length N+ which is larger than the length N of the real table. To access the real table, however, the corresponding MSBs of the actual count n(k) are used which match the address space of the real table of length N.

Abstract: The sound reproduction of a multichannel sound reproduction system with a plurality of speakers which is connected to the output of an FM stereo receiver is controlled by a control signal derived from the reception quality. Preferably, the control signal from the FM stereo receiver for controlling the stereo and mono components is also employed to control the multichannel sound reproduction system. For example, stereo, pseudo-stereo or mono reproduction are provided in the multichannel sound reproduction system in response to the stereo component within the output signal.

Abstract: A method and apparatus for operating a radio reception system, which comprises a plurality of receivers assigned to a common output device, in which one of the receivers is designated as audio receiver and is tuned to a frequency of a radio transmitter, and outputs a signal received from the transmitter to the output device. At least one second receiver is designated as search receiver, and continuously searches its own reception frequency band for a frequency of the same transmitter. The system changes to a frequency of this transmitter, which was found by the search receiver, if the quality of the signal received by the audio receiver falls below a certain limit.

Abstract: The sound reproduction of a multichannel sound reproduction system with a plurality of speakers which is connected to the output of an FM stereo receiver is controlled by a control signal derived from the reception quality. Preferably, the control signal from the FM stereo receiver for controlling the stereo and mono components is also employed to control the multichannel sound reproduction system. For example, stereo, pseudo-stereo or mono reproduction are provided in the multichannel sound reproduction system in response to the stereo component within the output signal.

Abstract: According to the invention, a precise criterion for evaluating the reception quality is derived in a stereo radio set from the signal energy or power of the upper and lower sideband (OS, US) of the L?R signal (L?R) of the stereo multiplex signal (MPX). To achieve this, the upper sideband (OS) is filtered out of the L?R signal (L?R) using a first bandpass filter (BP1) and is mixed with an auxiliary carrier (H) of 38 KHz in a first mixer (M1) and shifted to the baseband. Similarly, the lower sideband (US) is filtered out of the L?R signal (L?R) using a second bandpass filter (BP2) and is mixed in a second mixer (M2) with an auxiliary carrier (H) of KHz and shifted to the baseband. The output signal of the first mixer (M1) is filtered in a first lowpass filter (TP1), whilst the output signal of the second mixer (M2) is filtered in a second lowpass filter (TP2).