Abstract: An audio receiver may include a mono/stereo detector that causes the audio receiver to output either a monophonic or a stereophonic signal based on a difference between a pilot energy signal and a filtered pilot energy signal. The audio receiver includes a filter that filters the pilot energy signal to generate a filtered pilot energy signal, wherein a variable leakage factor associated with the filter is used to minimize a noise level of the filtered pilot energy signal and to reduce a response time of the audio receiver.

Abstract: Disclosed herein are systems and methods for accurate removal of I/Q mismatch in received signals of an analog FM receiver. The analog FM receiver includes a down-converter, a calibration circuit that estimates I/Q mismatch values, and a compensation circuit that uses the estimated mismatch values to reduce the effects of I/Q mismatch. In one aspect, the calibration circuit uses an adaptive dual-parameter compensation scheme to iteratively correct the received signals by approximating a coefficient value and an amplitude value that minimize the signals' amplitude variation from the amplitude value. In another aspect, phase and amplitude mismatch parameters can be determined using the coefficient value.

Abstract: Methods and apparatus are provided for receiving a first signal and generating an output signal indicative of radio data system (“RDS”) information. A receiver circuit of the invention can include mixer circuitry, lowpass filter circuitry, downsampler circuitry, and decoder circuitry. Advantageously, the receiver circuit can operate entirely within the digital domain, promoting interoperability with digital frequency modulation (“FM”) demodulator circuitry.

Abstract: Disclosed herein are systems and methods for recovering a sub-carrier signal from a multiplexed signal having an embedded pilot tone signal. The recovery system includes circuitry for recovering a pilot signal from the received multiplexed signal, for generating a frequency-doubled signal from the recovered pilot signal, and for phase-shifting the frequency-doubled signal by a pre-determined phase difference from the embedded pilot tone signal. Another recovery system includes circuitry for recovering a pilot signal from the received multiplexed signal, for phase-shifting the pilot signal by a pre-determined phase difference from the embedded pilot tone signal, and for generating a frequency-doubled signal from the phase-shifted signal.

Abstract: Methods and apparatus are provided for receiving a first signal and generating an output signal indicative of radio data system (“RDS”) information. A receiver circuit of the invention can include mixer circuitry, lowpass filter circuitry, downsampler circuitry, and decoder circuitry. Advantageously, the receiver circuit can operate entirely within the digital domain, promoting interoperability with digital frequency modulation (“FM”) demodulator circuitry.

Abstract: An FM audio receiver can include a mono/stereo detector that causes the audio receiver to output either a monophonic or a stereophonic signal based on a received pilot tone energy. An accurate operation of the receiver, including but not limited to correct decoding of monophonic/stereophonic reception, can be based on the receiver operating with the same rated maximum system deviation (RMSD) as the received signal itself. Aspects of the disclosure describe a system and method of detecting and matching a receiver's RMSD to that of a received signal by demodulating a carrier bearing a an input signal over a first bandwidth, extracting a pilot energy signal from the input signal, and demodulating the carrier bearing the input signal over a second bandwidth if the pilot energy signal is within a pilot energy range for a first predetermined amount of time.

Abstract: Disclosed herein are systems and methods for recovering a sub-carrier signal from a multiplexed signal having an embedded pilot tone signal. The recovery system includes circuitry for recovering a pilot signal from the received multiplexed signal, for generating a frequency-doubled signal from the recovered pilot signal, and for phase-shifting the frequency-doubled signal by a pre-determined phase difference from the embedded pilot tone signal. Another recovery system includes circuitry for recovering a pilot signal from the received multiplexed signal, for phase-shifting the pilot signal by a pre-determined phase difference from the embedded pilot tone signal, and for generating a frequency-doubled signal from the phase-shifted signal.

Abstract: A receiver may estimate a channel condition based on a difference between a pilot energy signal and a filtered pilot energy signal. The receiver may further switch to a stereophonic mode when both the difference and an energy level of the pilot energy signal satisfy a predetermined requirement of the receiver, and switch to a monophonic mode when either the difference or the energy level of the pilot energy signal fail to satisfy the predetermined requirement of the receiver.

Abstract: A system and method for switching a mode of a receiver between a monophonic and stereophonic mode is disclosed. The method can include generating a residual signal indicative of a noise level associated with a pilot energy signal, calculating a residual block energy level of the residual signal over an observation interval, generating a monitor signal based on a number of times the pilot energy signal is less than a pilot energy threshold during the observation interval and switching the mode of the receiver based on the residual block energy level and the monitor signal.

Abstract: Methods and apparatus are provided for receiving a first signal and generating an output signal indicative of radio data system (“RDS”) information. A receiver circuit of the invention can include mixer circuitry, lowpass filter circuitry, downsampler circuitry, and decoder circuitry. Advantageously, the receiver circuit can operate entirely within the digital domain, promoting interoperability with digital frequency modulation (“FM”) demodulator circuitry.

Abstract: An audio receiver may include a mono/stereo detector that causes the audio receiver to output either a monophonic or a stereophonic signal based on a difference between a pilot energy signal and a filtered pilot energy signal. The audio receiver includes a filter that filters the pilot energy signal to generate a filtered pilot energy signal, wherein a variable leakage factor associated with the filter is used to minimize a noise level of the filtered pilot energy signal and to reduce a response time of the audio receiver.

Abstract: A constant modulus indicator (CMI) measure is calculated for a received signal having a constant modulus component C and a noise component N. The CMI measure indicates a ratio of an energy of C to an energy of N. A determination of whether to attenuate a derived signal is made based on the CMI measure, wherein the derived signal is generated from the received signal. The derived signal is attenuated based on the determination.

Abstract: Disclosed herein are systems and methods for accurate removal of I/Q mismatch in received signals of an analog FM receiver. The analog FM receiver includes a down-converter, a calibration circuit that estimates I/Q mismatch values, and a compensation circuit that uses the estimated mismatch values to reduce the effects of I/Q mismatch. In one aspect, the calibration circuit uses an adaptive dual-parameter compensation scheme to iteratively correct the received signals by approximating a coefficient value and an amplitude value that minimize the signals' amplitude variation from the amplitude value. In another aspect, phase and amplitude mismatch parameters can be determined using the coefficient value.

Abstract: In a method for synchronizing to a signal encoded as a group of blocks, a data symbol is received and stored with previously received data symbols as a current potential group. Errors, if any, are detected in the current potential group, and a level of errors associated with the current potential group is deter mined. The current potential group is determined to be an actual group if the current potential group is without errors. Also, the current potential group is determined to be an actual group if a set of potential groups including the current potential group and at least one previous potential group has an acceptable level of errors.

Abstract: In a technique for detecting single or multiple channels in a broadcast RF signal, a receiver determines a constant modulus indication value for each frequency of the receiver's local oscillator, as that oscillator is tuned across a range of possible channel frequencies. The receiver may determine this constant modulus indication value by determining the magnitudes of a constant modulus signal and a noise signal, for a signal output from a digital front end, that signal representing a mixing of the local oscillator frequency signal with the broadcast RF signal and a channelization thereof. As the local oscillator frequency signal is tuned through the range of possible channel frequencies, the receiver evaluates the constant modulus indication value course and or fine frequency increments to determine if the constant modulus indication value at any frequency rises above a threshold value, thereby indicating that the local oscillator frequency signal has locked onto an RF channel in the original RF signal.

Abstract: A method and apparatus for performing multiple descriptive source coding in which a plurality of homogeneous encoders are advantageously employed in combination with a corresponding plurality of advantageously substantially identical decoders. In particular, diversity is provided to the multiple encoders by modifying the quantization process in at least one of the encoders such that the modified quantization process is based at least on a quantization error resulting from the quantization process of another one of the encoders. In this manner, diversity among the multiple bit streams is obtained, and in particular, the quality of a reconstructed signal based on a combination of multiple decoded bit streams at the receiver is advantageously superior to that based on any one of the decoded bit streams. In accordance with a first illustrative embodiment of the present invention, two Pulse Code Modulation (PCM) coders are employed.

Abstract: In an apparatus, method, and system for reducing interference with an input signal to an FM receiver, a plurality of inputs are filtered by a first stage of filters. The outputs are received by an interference detector and further processed by a second filtering stage, an energy calculation stage, and a comparator stage. A switch, responsive to the outputs of the comparator stage, may output one of the first stage filter outputs based on a first set of comparator outputs and may output an interpolated value determined by the first stage filter outputs and based on a second set of comparator outputs.

Abstract: In an apparatus for generating a synchronized sub-carrier signal based on a pilot signal, a zero-crossing detector may detect a pilot signal zero-crossing in response to consecutive pilot signal samples. In response to the zero-crossing detector, a sub-carrier signal phase sampler generates a sequence of sub-carrier phase samples at a sampling frequency, inclining a first sub-carrier signal phase sample and additional sub-carrier signal phase samples at predetermined phase sample intervals. A phase sample counter counts the number of phase samples obtained by the sub-carrier signal phase sampler. A sub-carrier signal generator generates a synchronized sub-carrier signal in response to the sub-carrier signal phase samples.

Abstract: Disclosed herein are systems and methods for recovering a sub-carrier signal from a multiplexed signal having an embedded pilot tone signal. The recovery system includes circuitry for recovering a pilot signal from the received multiplexed signal, for generating a frequency-doubled signal from the recovered pilot signal, and for phase-shifting the frequency-doubled signal by a pre-determined phase difference from the embedded pilot tone signal. Another recovery system includes circuitry for recovering a pilot signal from the received multiplexed signal, for phase-shifting the pilot signal by a pre-determined phase difference from the embedded pilot tone signal, and for generating a frequency-doubled signal from the phase-shifted signal.

Abstract: Methods and apparatus are provided for receiving a first signal and generating an output signal indicative of radio data system (“RDS”) information. A receiver circuit of the invention can include mixer circuitry, lowpass filter circuitry, downsampler circuitry, and decoder circuitry. Advantageously, the receiver circuit can operate entirely within the digital domain, promoting interoperability with digital frequency modulation (“FM”) demodulator circuitry.