Abstract: A method comprises receiving an approximate location of a rover platform based on satellite signals for a Global Navigation Satellite System (GNSS), and receiving for the GNSS a differential correction map (DCM) representing a non-planar surface of differential corrections that varies across a geographical area represented by the DCM. The differential corrections are based on a reference station constellation of GNSS reference stations having respective locations spanning the geographical area. The method further comprises deriving DCM-based differential corrections for the satellite signals at the approximate location based on the DCM, correcting the satellite signals using the DCM-based differential corrections, and determining a location of the rover platform using the corrected satellite signals.

Abstract: A method comprises generating for a Global Navigation Satellite System (GNSS) a differential correction map (DCM) representing a non-planar surface of differential corrections that varies across a geographical area represented by the DCM, the differential corrections being based on a reference station constellation of GNSS reference stations having respective locations spanning the geographical area, the GNSS reference stations including physical or virtual reference stations.

Abstract: A method comprises generating for a Global Navigation Satellite System (GNSS) a differential correction map (DCM) representing a non-planar surface of differential corrections that varies across a geographical area represented by the DCM, the differential corrections being based on a reference station constellation of GNSS reference stations having respective locations spanning the geographical area, the GNSS reference stations including physical or virtual reference stations.

Abstract: A method comprises receiving an approximate location of a rover platform based on satellite signals for a Global Navigation Satellite System (GNSS), and receiving for the GNSS a differential correction map (DCM) representing a non-planar surface of differential corrections that varies across a geographical area represented by the DCM. The differential corrections are based on a reference station constellation of GNSS reference stations having respective locations spanning the geographical area. The method further comprises deriving DCM-based differential corrections for the satellite signals at the approximate location based on the DCM, correcting the satellite signals using the DCM-based differential corrections, and determining a location of the rover platform using the corrected satellite signals.

Abstract: A method for symbol tracking in AM in-band on-channel radio receivers comprises the steps of: receiving a stream of time domain samples; assembling a set of the time domain samples equal to a symbol time plus a half symbol delay in response to a symbol timing adjustment value for each symbol period; interpolating the time domain samples; partitioning the interpolated time domain samples into a first group of samples representing half-off symbols and a second group of samples representing on-time symbols; processing the first and second groups of samples to produce the symbol timing adjustment value; and outputting the second group of samples representing on-time symbols at a symbol rate. An apparatus that performs the method is also included.

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 the steps of: 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 carrier tracking in AM in-band on-channel radio receivers comprises the steps of receiving an input signal, generating a local oscillator signal in response to an oscillator control signal, mixing the input signal with a local oscillator signal to produce a first signal, filtering the first signal to produce a filtered first signal at a decimated sample rate, detecting the phase error and frequency error of the filtered first signal normalized to mitigate effects of signal fades, and using an adaptive loop filter to produce the oscillator control signal in response to the phase error and frequency error of the filtered first signal. An apparatus that performs the method is also provided.

Abstract: This invention provides a method of detecting time alignment of an analog audio signal and a digital audio signal in a hybrid radio system. The method comprises the steps of filtering the analog audio signal to produce a filtered analog audio signal, filtering the digital audio signal to produce a filtered digital audio signal, and using the filtered analog audio signal and the filtered digital audio signal to calculate a plurality of correlation coefficients, wherein the correlation coefficients are representative of time alignment between the analog audio signal and the digital audio signal. An apparatus for performing the method is also provided.

Abstract: A method for synchronizing an exciter clock with a modem frame clock in a broadcasting system comprises the steps of receiving a plurality of modem frame pulses that are representative of the start of modem frames of audio signals and data signals, wherein timing of the modem frame pulses is controlled by a modem frame clock, producing an exciter clock signal, counting pulses representative of the exciter clock signal to produce a count representative of timing error of each incoming modem frame pulse, and controlling the exciter clock signal in response to the count. An apparatus that performs the method is also provided.

Abstract: A method of processing a baseband multiplex signal comprises the steps of frequency modulating the baseband multiplex signal to produce a first modulated signal, filtering the first modulated signal to produce a first filtered signal, demodulating the filtered signal to produce a demodulated baseband multiplex signal, correcting the demodulated baseband multiplex signal to reduce or eliminate distortion in a predetermined frequency range of the demodulated baseband multiplex signal to produce a corrected signal, and frequency modulating the corrected signal to produce a second modulated signal. An apparatus that operates in accordance with the method is also provided.

Abstract: A method for processing a composite digital audio broadcast signal to mitigate intermittent interruptions in the reception of the digital audio broadcast signal, the method comprising the steps of separating an analog audio portion of the digital audio broadcast signal from a digital audio portion of the digital audio broadcast signal, detecting errors in the digital audio portion of the digital audio broadcast signal, adjusting the digital audio portion of the digital audio broadcast signal in response to errors in the digital audio portion of the digital audio broadcast signal to produce an adjusted digital audio portion, and blending the analog audio portion with the adjusted digital audio portion to produce an audio output. A receiver that performs the method is also included.

Abstract: A method of reducing peak-to-average power ratio in an OFDM signal comprises the steps of modulating a set of subcarriers with a set of data symbol vectors to produce a first modulated signal, limiting the magnitude of the first modulated signal to produce a first limited modulated signal, demodulating the first limited modulated signal to recover distorted input symbol vectors, constraining the distorted input symbol vectors to values greater than or equal to a minimum threshold value to produce constrained data symbol vectors, constraining out-of-band spectral components to lie within a predetermined mask, and remodulating the constrained data symbol vectors. A transmitter that performs the method is also included.

Abstract: An AM compatible digital audio broadcasting signal comprises an analog modulated carrier signal centrally positioned in a radio channel, wherein the analog modulated carrier signal is modulated by an analog signal, and a plurality of digitally modulated subcarrier signals in the radio channel, wherein the digitally modulated subcarrier signals are modulated using complementary pattern-mapped trellis code modulation including a code mapped to overlapping partitions. Time diversity can be included between the analog modulated carrier signal and the plurality of digitally modulated subcarrier signals, and/or between groups of the digitally modulated subcarrier signals. A broadcasting method, and transmitters and receivers and that utilize the signal are also provided.

Abstract: A method for coherently tracking a radio signal including at least one digitally modulated reference carrier is provided, wherein the method comprises the steps of demodulating the reference carrier to produce complex coherent reference gains, detecting a transient that affects the complex coherent reference gains, and adjusting the complex coherent reference gains in the vicinity of the transient to produce adjusted complex coherent reference gains. The transient can be caused by switching among the antenna elements or impulsive noise. Receivers that process signals in accordance with the method, and a method of estimating noise variance of symbols in a radio signal are also provided.

Abstract: A method is provided for coherently tracking a radio signal including a plurality of digitally modulated reference subcarriers. The method comprises the steps of 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, and smoothing the samples for each of the reference subcarriers over the plurality of reference subcarriers to produce a coherent reference signal estimate for each of the subcarriers. A receiver for coherently tracking a radio signal including at least one digitally modulated reference carrier is also provided.