Abstract: Aspects of this disclosure relate to determining a spectrum mode of a Convergent Digital Radio signal. The Convergent Digital Radio signal can be filtered by a plurality of filters. Correlation coefficients can be generated from filtered signals, in which each correlation coefficient corresponds to a particular spectrum mode. The spectrum mode can be selected based on the correlation coefficients.

Abstract: Aspects of this disclosure relate to canceling a tone in a radio signal. A location of an interfering tone can be estimated in an orthogonal frequency division multiplexing symbol (OFDM). An interfering tone can be detected in a subsequent OFDM symbol based on the estimate of the location of the interfering tone in the OFDM using closed loop tone detection. The interfering tone in the subsequent OFDM can be canceled. Tone cancellation can be performed using digital signal processing circuitry. Tone cancellation can be performed in radio systems.

Abstract: Systems and methods for asynchronous data flow in digital radios are provided. In one aspect, a demodulator circuit includes a receiver circuit configured to receive: a plurality of samples of a radio frequency signal received from a tuner, a clock, and a target size value, the receiver circuit further configured to output the samples at a first rate based on the target size value. The demodulator circuit also includes a sample rate converter configured to receive the samples from the receiver circuit and output the samples at a second rate based on a rate offset value, and a buffer configured to receive the samples from the sample rate converter and output the samples. The demodulator circuit further includes a digital demodulator configured to receive the samples from the buffer and demodulate the samples, and a control loop configured to generate the target size value.

Abstract: Systems and methods for synchronizing with and decoding radio frequency signals are provided. In one aspect, a radio receiver includes an antenna configured to receive a radio frequency signal and digital signal processing circuitry configured to receive the radio frequency signal from the antenna and perform a first synchronization algorithm and a second synchronization algorithm on the radio frequency signal in parallel. The digital signal processing circuitry is further configured to determine which of the first synchronization algorithm and the second synchronization algorithm completes first and begin playback on the radio frequency signal based on synchronization with the radio frequency signal based on the determination of which of the first synchronization algorithm and the second synchronization algorithm completed first.

Abstract: Aspects of this disclosure relate to determining a transmission mode and a spectrum mode of a Convergent Digital Radio signal. The Convergent Digital Radio signal can be filtered by a plurality of filters. Correlation coefficients can be generated from the filtered signals, in which each correlation coefficient corresponds to a particular transmission mode and at least one particular spectrum mode. The transmission mode and the spectrum mode can be selected based on the correlation coefficients.

Abstract: Systems and methods for estimating noise variance are provided. In one aspect, an apparatus includes a front end circuit configured to receive a radio frequency signal and process the radio frequency signal into a plurality of samples and a transform engine configured to convert at least one of the samples into a plurality of frequency carriers. The apparatus further includes a detector configured to determine a channel estimate for a subset of the frequency carriers located within an evaluation window, select one of the carriers within the evaluation window, determine differences between the channel estimate of the selected carrier and the channel estimates of other carriers within the evaluation window, and estimate the noise variance for a symbol including the at least one of the samples based on the differences between the channel estimate of the selected carrier and the channel estimates of other frequency carriers within the evaluation window.

Abstract: In one aspect, an apparatus includes: a fast Fourier transform (FFT) engine to receive and convert a plurality of orthogonal frequency division multiplexing (OFDM) samples into a plurality of frequency carriers; a detector coupled to the FFT engine to determine a channel estimate for a first frequency carrier using a first channel estimate for the first frequency carrier and a plurality of other channel estimates, each of the plurality of other channel estimates for one of a plurality of neighboring frequency carriers within an evaluation window, and determine a log likelihood ratio (LLR) for the first frequency carrier using the channel estimate for the first frequency carrier; and a decoder coupled to the detector to decode a first OFDM symbol comprising the first frequency carrier using the LLR for the first frequency carrier.

Abstract: A receiver has a sample rate converter that outputs samples of orthogonal frequency division multiplexing symbols. The receiver includes a fast Fourier transform engine that receives the samples and converts them into a plurality of frequency domain sub-carriers. A timing control circuit generates a timing error and controls the sample rate converter to adjust a sample rate of the orthogonal frequency division multiplexing symbols based at least in part on the timing error.

Abstract: In one aspect, an apparatus includes: a front end circuit to receive and process incoming radio frequency (RF) signals into orthogonal frequency division multiplexing (OFDM) samples; a fast Fourier transform (FFT) engine to receive and convert the OFDM samples into frequency domain sub-carriers; a demodulator to demodulate the frequency domain sub-carriers; a channel estimator to: compute a first pilot channel estimate for a first channel condition comprising a flat channel condition and a second pilot channel estimate for a second channel condition comprising a selective channel condition based on a first set of pilot sub-carriers of the frequency domain sub-carriers; and select one of the first and second pilot channel estimates using the first and second pilot channel estimate; and a control circuit to configure at least the demodulator based at least in part on the selected first or second pilot channel estimate.

Abstract: In one aspect, an apparatus includes: a fast Fourier transform (FFT) engine to receive and convert a plurality of orthogonal frequency division multiplexing (OFDM) samples into a plurality of frequency carriers; a detector coupled to the FFT engine to determine a channel estimate for a first frequency carrier using a first channel estimate for the first frequency carrier and a plurality of other channel estimates, each of the plurality of other channel estimates for one of a plurality of neighboring frequency carriers within an evaluation window, and determine a log likelihood ratio (LLR) for the first frequency carrier using the channel estimate for the first frequency carrier; and a decoder coupled to the detector to decode a first OFDM symbol comprising the first frequency carrier using the LLR for the first frequency carrier.

Abstract: Aspects of this disclosure relate to determining a spectrum mode of a Convergent Digital Radio signal. The Convergent Digital Radio signal can be filtered by a plurality of filters. Correlation coefficients can be generated from filtered signals, in which each correlation coefficient corresponds to a particular spectrum mode. The spectrum mode can be selected based on the correlation coefficients.

Abstract: Aspects of this disclosure relate to frequency offset compensation in a radio receiver. In embodiments of the disclosure, a carrier frequency offset can be compensated for in a time domain orthogonal frequency-division multiplexing signal, a frequency domain signal can be generated from the time domain orthogonal frequency-division multiplexing signal, and a phase error offset can be compensated for in the frequency domain signal. Such offset compensation can be performed using two offset compensation loops. Related radio receivers and radio systems are disclosed.

Abstract: Systems and methods for asynchronous data flow in digital radios are provided. In one aspect, a demodulator circuit includes a receiver circuit configured to receive: a plurality of samples of a radio frequency signal received from a tuner, a clock, and a target size value, the receiver circuit further configured to output the samples at a first rate based on the target size value. The demodulator circuit also includes a sample rate converter configured to receive the samples from the receiver circuit and output the samples at a second rate based on a rate offset value, and a buffer configured to receive the samples from the sample rate converter and output the samples. The demodulator circuit further includes a digital demodulator configured to receive the samples from the buffer and demodulate the samples, and a control loop configured to generate the target size value.

Abstract: Aspects of this disclosure relate to frequency offset compensation in a radio receiver. In embodiments of the disclosure, a frequency domain orthogonal frequency-division multiplexing signal can be received, and a phase error offset in individual frequency segments of the frequency domain orthogonal frequency-division multiplexing signal can be compensated for based on estimates of the phase error offset for the individual frequency segments. Related radio receivers and radio systems are disclosed.

Abstract: Aspects of this disclosure relate to canceling a tone in a radio signal. A location of an interfering tone can be estimated in an orthogonal frequency division multiplexing symbol (OFDM). An interfering tone can be detected in a subsequent OFDM symbol based on the estimate of the location of the interfering tone in the OFDM using closed loop tone detection. The interfering tone in the subsequent ODFM can be canceled. Tone cancellation can be performed using digital signal processing circuitry. Tone cancellation can be performed in radio systems.

Abstract: Aspects of this disclosure relate to determining a transmission mode and a spectrum mode of a Convergent Digital Radio signal. The Convergent Digital Radio signal can be filtered by a plurality of filters. Correlation coefficients can be generated from the filtered signals, in which each correlation coefficient corresponds to a particular transmission mode and at least one particular spectrum mode. The transmission mode and the spectrum mode can be selected based on the correlation coefficients.

Abstract: A receiver has a sample rate converter that outputs samples of orthogonal frequency division multiplexing symbols. The receiver includes a fast Fourier transform engine that receives the samples and converts them into a plurality of frequency domain sub-carriers. A timing control circuit generates a timing error and controls the sample rate converter to adjust a sample rate of the orthogonal frequency division multiplexing symbols based at least in part on the timing error.

Abstract: In one aspect, an apparatus includes: a fast Fourier transform (FFT) engine to receive and convert a plurality of orthogonal frequency division multiplexing (OFDM) samples into a plurality of frequency carriers; a detector coupled to the FFT engine to determine a channel estimate for a first frequency carrier using a first channel estimate for the first frequency carrier and a plurality of other channel estimates, each of the plurality of other channel estimates for one of a plurality of neighboring frequency carriers within an evaluation window, and determine a log likelihood ratio (LLR) for the first frequency carrier using the channel estimate for the first frequency carrier; and a decoder coupled to the detector to decode a first OFDM symbol comprising the first frequency carrier using the LLR for the first frequency carrier.

Abstract: In one aspect, an apparatus includes: a fast Fourier transform (FFT) engine to receive and convert a plurality of orthogonal frequency division multiplexing (OFDM) samples into a plurality of frequency carriers; a detector coupled to the FFT engine to determine a channel estimate for a first frequency carrier using a first channel estimate for the first frequency carrier and a plurality of other channel estimates, each of the plurality of other channel estimates for one of a plurality of neighboring frequency carriers within an evaluation window, and determine a log likelihood ratio (LLR) for the first frequency carrier using the channel estimate for the first frequency carrier; and a decoder coupled to the detector to decode a first OFDM symbol comprising the first frequency carrier using the LLR for the first frequency carrier.

Abstract: In one aspect, an apparatus includes: a front end circuit to receive and process incoming radio frequency (RF) signals into orthogonal frequency division multiplexing (OFDM) samples; a fast Fourier transform (FFT) engine to receive and convert the OFDM samples into frequency domain sub-carriers; a demodulator to demodulate the frequency domain sub-carriers; a channel estimator to: compute a first pilot channel estimate for a first channel condition comprising a flat channel condition and a second pilot channel estimate for a second channel condition comprising a selective channel condition based on a first set of pilot sub-carriers of the frequency domain sub-carriers; and select one of the first and second pilot channel estimates using the first and second pilot channel estimate; and a control circuit to configure at least the demodulator based at least in part on the selected first or second pilot channel estimate.