Abstract: A method includes: receiving an FM radio signal including an analog-modulated portion; digitally sampling an analog-modulated portion of the radio signal to produce a plurality of samples; using a ratio between an average magnitude and an RMS magnitude of a block of the samples to compute a signal quality metric; detecting sum and difference components of the baseband multiplex signal content; using the baseband content to produce an output signal; and blending the output signal from stereo to monaural as the signal quality metric falls below a threshold value.

Abstract: A method for detecting the digital quality of a radio signal includes: receiving a radio signal including an analog modulated portion; digitally sampling an analog modulated portion of the radio signal to produce a plurality of samples; using a ratio between an average magnitude and an RMS magnitude of a block of the samples to compute an analog signal quality metric. Receivers that implement the method are also provided.

Abstract: A method includes: constructing complementary low density parity check codewords by generating a first codeword having a first code rate; and partitioning the first codeword by assigning groups of bits of the first codeword to four quarter-partitions, wherein each of the quarter partitions includes bits in one half of one of four independently decodable semi-codewords each having a second code rate that is larger than the first code rate. Receivers that receive signals produced by the method are also disclosed.

Abstract: A method for detecting the digital quality of a radio signal includes: receiving a radio signal including a digital portion modulated by a series of symbols each including a plurality of samples; computing correlation points between endpoint samples in cyclic prefix regions of adjacent symbols; and using the correlation points to produce a digital signal quality metric. Receivers that implement the method are also provided.

Abstract: A method includes: receiving an FM radio signal including an analog-modulated portion; digitally sampling an analog-modulated portion of the radio signal to produce a plurality of samples; using a ratio between an average magnitude and an RMS magnitude of a block of the samples to compute a signal quality metric; detecting sum and difference components of the baseband multiplex signal content; using the baseband content to produce an output signal; and blending the output signal from stereo to monaural as the signal quality metric falls below a threshold value.

Abstract: A method for processing a radio signal includes: receiving an FM in-band on-channel radio signal including a plurality of digitally modulated subcarriers in upper and lower sidebands; sampling the FM in-band on-channel radio signal to produce an input signal including complex digital samples of a combination of a desired one the upper and lower sidebands and an FM interferer; removing FM interferer components from the first signal by notch filtering to produce a notch-filtered signal; weighting the notch-filtered signal to produce a weighted notch-filtered signal; using a parametric filter to filter the input signal to produce a parametric-filtered input signal; and combining the weighted notch-filtered signal and the parametric-filtered input signal to produce an output signal. A radio receiver that implements the method is also included.

Abstract: A peak-to-average power reduction method includes: (a) quadrature amplitude modulating a signal including a set of subcarriers with a set of data to produce an OFDM modulated symbol vector; (b) limiting the magnitude of the modulated symbol vector to produce a first limited OFDM modulated symbol; (c) demodulating the first limited OFDM modulated symbol to recover distorted QAM constellations; (d) constraining points in the distorted QAM constellations recovered from the first limited OFDM modulated symbol to produce constrained QAM constellations; (e) modulating an OFDM symbol vector with the constrained QAM constellations to produce a modified modulated OFDM symbol; and (f) output the modified modulated OFDM symbol. A transmitter that implements the method is also provided.

Abstract: A method for processing a radio signal includes: receiving an FM in-band on-channel radio signal including a plurality of digitally modulated subcarriers in upper and lower sidebands; sampling the FM in-band on-channel radio signal to produce an input signal including complex digital samples of a combination of a desired one the upper and lower sidebands and an FM interferer; removing FM interferer components from the first signal by notch filtering to produce a notch-filtered signal; weighting the notch-filtered signal to produce a weighted notch-filtered signal; using a parametric filter to filter the input signal to produce a parametric-filtered input signal; and combining the weighted notch-filtered signal and the parametric-filtered input signal to produce an output signal. A radio receiver that implements the method is also included.

Abstract: A method of transmitting digital information includes: receiving a plurality of information bits representing audio information and/or data; encoding the information bits using complementary low density parity check coding to produce a composite codeword and a plurality of independently decodable semi-codewords; modulating at least one carrier signal with the forward error corrected bits; and transmitting the carrier signal(s). Transmitters that implement the method, and receivers that receive signals produced by the method, are also provided.

Abstract: A method is provided for estimating channel state information in an in-band on-channel radio signal including a plurality of digitally modulated reference subcarriers. The method includes: receiving symbols transmitted on the reference subcarriers; combining the reference subcarrier symbols with a known reference sequence conjugate to produce a plurality of samples; median filtering the samples to produce filtered samples; smoothing the samples for each of the reference subcarriers over the plurality of reference subcarriers to produce a complex channel gain estimate for each of the subcarriers; and using a bias correction function to compensate for estimation bias error in the complex channel gain estimate due to the median filtering. Receivers that implement the method are also provided.

Abstract: A method for processing a radio signal includes: receiving a signal on two antennas; demodulating the signal using first and second independent signal paths that are synchronized by symbol number; maximum ratio combining branch metrics from the two receiver paths; and using the combined branch metrics to produce an output, wherein the receiver paths include an arbitration scheme. A receiver that implements the method is also provided.

Abstract: A method is provided for equalizing OFDM symbol vectors received on AM in-band on-channel radio signal including a main carrier and first and second BPSK modulated subcarriers. The method comprises: computing a BPSK magnitude signal; filtering the BPSK magnitude signal; filtering complex samples received on the main carrier; using the filtered BPSK magnitude signal and the filtered complex samples received on the main carrier to compute a plurality of flat fade equalization coefficients; and multiplying the OFDM symbol vectors by the flat fade equalization coefficients. A receiver that includes an equalizer, which operates in accordance with the method is also provided.

Abstract: A method for processing a radio signal includes: receiving a signal on two antennas; demodulating the signal using first and second independent signal paths that are synchronized by symbol number; maximum ratio combining branch metrics from the two receiver paths; and using the combined branch metrics to produce an output, wherein the receiver paths include an arbitration scheme. A receiver that implements the method is also provided.

Abstract: A method for processing a digital signal includes: receiving a plurality of protocol data units, each having a header including a plurality of control word bits; and a plurality of audio frames, each including a cyclic redundancy check code; decoding the protocol data units using an iterative decoding technique, wherein the iterative decoding technique uses a soft output decoding algorithm for iterations after the first iteration; and using decoded cyclic redundancy check codes to flag the audio frames containing errors. A receiver that implements the method is also provided.

Abstract: A method of transmitting digital information includes: receiving a plurality of information bits representing audio information and/or data; encoding the information bits using complementary low density parity check coding to produce a composite codeword and a plurality of independently decodable semi-codewords; modulating at least one carrier signal with the forward error corrected bits; and transmitting the carrier signal(s). Transmitters that implement the method, and receivers that receive signals produced by the method, are also provided.

Abstract: A method for detecting the digital quality of a radio signal includes: receiving a radio signal including a digital portion modulated by a series of symbols each including a plurality of samples; computing correlation points between endpoint samples in cyclic prefix regions of adjacent symbols; and using the correlation points to produce a digital signal quality metric. Receivers that implement the method are also provided.

Abstract: A radio receiver includes a first signal path including a first tuner configured to receive a first signal from a first antenna, and a first demodulator configured to demodulate symbols from an output of the first tuner to produce first branch metrics derived from the demodulated symbols; a second signal path including a second tuner configured to receive a second signal from a second antenna, and a second demodulator configured to demodulate symbols from an output of the second tuner to produce second branch metrics derived from the demodulated symbols; a combiner for maximum ratio combining the first branch metrics and the second branch metrics; and processing circuitry to process the combined first and second branch metrics to produce an output signal.

Abstract: A method for detecting the digital quality of a radio signal includes: receiving a radio signal including a digital portion modulated by a series of symbols each including a plurality of samples; computing correlation points between endpoint samples in cyclic prefix regions of adjacent symbols; and using the correlation points to produce a digital signal quality metric. Receivers that implement the method are also provided.

Abstract: A method includes: (a) modulating a set of subcarriers with a set of data to produce a modulated OFDM symbol vector; (b) modulating a FM carrier signal with the set of data to produce a modulated FM symbol; (c) combining the modulated OFDM symbol and the modulated FM symbol to produce a modulated hybrid symbol; (d) limiting the magnitude of the modulated hybrid symbol to produce a first limited modulated hybrid symbol; (e) demodulating the first limited modulated hybrid symbol to recover distorted QPSK constellations; (f) constraining the distorted QPSK constellations to values greater than or equal to a minimum threshold value to produce constrained QPSK constellations; (g) demodulating the modulated hybrid symbol to produce a demodulated hybrid symbol vector; (h) subtracting the demodulated FM symbol vector from the Hybrid symbol vector to produce modified OFDM symbol vector; (i) applying a mask to inactive subcarriers in the plurality of subcarriers of the OFDM symbol vector; (j) modulating an OFDM symbol

Abstract: A radio receiver includes a first signal path including a first tuner configured to receive a first signal from a first antenna, and a first demodulator configured to demodulate symbols from an output of the first tuner to produce first branch metrics derived from the demodulated symbols; a second signal path including a second tuner configured to receive a second signal from a second antenna, and a second demodulator configured to demodulate symbols from an output of the second tuner to produce second branch metrics derived from the demodulated symbols; a combiner for maximum ratio combining the first branch metrics and the second branch metrics; and processing circuitry to process the combined first and second branch metrics to produce an output signal.