Abstract: A method of digital audio broadcasting comprises the steps of providing a plurality of bits of digital information to be transmitted, forward error correcting the bits of digital information using a combination of pragmatic trellis code modulation and complementary punctured code, and transmitting the bits of digital information. The step of forward error correcting the bits of digital information can comprise the steps of representing the bits as independently coded in-phase and quadrature signals, applying a first error correcting code to the in-phase signals, and applying a second error correcting code to the quadrature signals. The bits of digital information can be arranged in a plurality of partitions of code, wherein first and second ones of the partitions do not overlap, a third one of the partitions overlaps a first portion of the first and second partitions, and a fourth one of the partitions overlaps a second portion of the first and second partitions.

Abstract: A method for detecting a digital radio signal includes the steps of receiving the digital radio signal, developing a correlation waveform having a peak that corresponds to a symbol boundary, normalizing the correlation waveform, calculating a peak value of the normalized correlation waveform, and dwelling on the received digital radio signal when the peak value exceeds a predetermined threshold. A receiver that performs the method is also provided.

Abstract: A method for detecting a digital radio signal includes the steps of receiving the digital radio signal including a series of symbols, developing a correlation waveform having a peak that corresponds to a symbol boundary, normalizing the correlation waveform, and calculating a peak value of the normalized correlation waveform, wherein the peak value represents the quality of the received digital radio signal. A receiver that performs the method is also provided.

Abstract: A method of broadcasting an AM compatible digital audio broadcasting signal includes: producing an analog modulated carrier signal centrally positioned in a radio channel, wherein the analog modulated carrier signal is modulated by an analog signal, producing 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 (CPTCM) including a code mapped to overlapping partitions including an upper main partition, a lower main partition, an upper backup partition and a lower backup partition, and a non-overlapping tertiary partition, and transmitting the analog modulated carrier signal and the plurality of digitally modulated subcarrier signals. Transmitters that broadcast the signal and receivers that receive the signal, and the reception method are also included.

Abstract: A transmitter for broadcasting an AM compatible digital audio broadcasting signal includes an analog modulator for producing 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 digital modulator for producing 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. In a first operating mode the analog modulated carrier signal and the plurality of digitally modulated subcarrier signals are in a 20 kHz channel and in a second operating mode the analog modulated carrier signal and the plurality of digitally modulated subcarrier signals are in a 30 kHz channel.

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 of receiving an FM digital audio broadcasting signal including a first plurality of subcarriers in an upper sideband of a radio channel and a second plurality of subcarriers in a lower sideband of the radio channel comprises the steps of mixing the digital audio broadcasting signal with a local oscillator signal to produce an intermediate frequency signal, passing the intermediate frequency signal through a bandpass filter to produce a filtered signal, determining if one of the upper and lower sidebands of the digital audio broadcasting signal is corrupted, and adjusting the local frequency oscillator signal to change the frequency of the intermediate frequency signal such that the bandpass filter removes the subcarriers in the upper or lower sideband that has been corrupted. A receiver that processes a digital audio broadcasting signal in accordance with the method is also provided.

Abstract: A method of receiving an AM radio signal comprises the steps of: receiving the AM radio signal using a first loop antenna to produce a first received signal, receiving the AM radio signal using a second loop antenna to produce a second received signal, adjusting the relative gains of the first and second received signals to produce adjusted first and second signals, combining the adjusted first and second signals, demodulating the combined adjusted first and second signals, and producing an output signal in response to the demodulated combined adjusted first and second signals. A receiver that operates in accordance with the method is also provided.

Abstract: A method of processing an AM radio signal comprises the step of receiving an AM radio signal including an upper sideband portion and a lower sideband portion, demodulating the upper sideband portion and the lower sideband portion to produce a demodulated upper sideband signal and a demodulated lower sideband signal, weighting the demodulated upper sideband signal and the demodulated lower sideband signal in response to noise power to produce a weighted demodulated upper sideband signal and a weighted demodulated lower sideband signal, and combining the weighted demodulated upper sideband signal and the weighted demodulated lower sideband signal to produce an output signal. Demodulators which process AM radio signals in accordance with the method, and receivers incorporating the demodulators, are also included.

Abstract: A method of transmitting digital information comprises the steps of forward error correction encoding a plurality of bits of digital information using complementary pattern-mapped convolutional codes, modulating a plurality of carrier signals with the forward error corrected bits, and transmitting the carrier signals. The modulation can include the step of independently amplitude shift keying in-phase and quadrature components of the QAM constellation using Gray code constellation points corresponding to amplitude levels. Transmitters that transmit signals in accordance with the method and receivers that receive such signals are also included.

Abstract: A transmitter for transmitting data in a digital audio broadcasting system includes a signal generator for providing a plurality of orthogonal frequency division multiplexed sub-carriers, with the sub-carriers including data sub-carriers and reference sub-carriers, and a modulator for modulating the data sub-carriers with a digital signal representative of information to be transmitted. The reference sub-carriers are modulated with a sequence of timing bits, wherein the sequence of timing bits includes an unambiguous block synchronization word, and the number of bits comprising the block synchronization word is less than one half of the number of bits in said timing sequence. The orthogonal frequency division multiplexed sub-carriers are transmitted to receivers that differentially detect the block synchronization word and use the block synchronization word to coherently detect the digital signal representative of information to be transmitted are also included.

Abstract: A method of in-band on-channel (IBOC) digital audio broadcasting (DAB) comprises the steps of providing an analog modulated carrier signal in a central frequency band of an AM radio channel, providing a first plurality of subcarriers in an upper sideband of the AM radio channel, providing a second plurality of subcarriers in a lower sideband of the AM radio channel, providing a third plurality of subcarriers in the central frequency band of the AM radio channel, modulating the first, second and third plurality of subcarriers with one or more digitally encoded signals, and transmitting the analog modulated signal and the first, second and third plurality of subcarriers, wherein the subcarriers in the third plurality of subcarriers that are positioned closest to the center of the channel are transmitted at higher power spectral densities than the subcarriers in the third plurality of subcarriers that are positioned farther from the center of the channel.

Abstract: A method for weighting orthogonal frequency division multiplexed soft symbols is provided, including the steps of receiving a plurality of sub-carriers modulated by digital information and filtering the sub-carriers to produce complex soft decision outputs. The magnitudes of the soft decision outputs are used to creating a first sequence of data. The differences between successive samples in the first sequence are used to create a second sequence of data. The first and second sequences are used to determine a plurality of weights and the weights are applied to the complex soft decision outputs. A receiver which incorporates the method is also disclosed.

Abstract: A method for pre-compensating an analog signal in a composite digital audio broadcasting signal including the analog signal and a plurality of digitally modulated sub-carrier signals, the method comprising the steps of sampling the analog signal to obtain successive blocks of samples, demodulating each of the blocks of samples to obtain a plurality of demodulator outputs, remodulating the demodulator outputs that correspond to the predetermined ones of the digitally modulated sub-carrier signals to produce an error signal, subtracting the error signal from the one of the blocks of samples to produce a pre-compensated block of samples, and combining the pre-compensated block of samples with a plurality of OFDM pulses to produce a compensated composite signal. An apparatus for performing the method is also included.

Abstract: A method of processing an AM radio signal comprises the step of receiving an AM radio signal including an upper sideband portion and a lower sideband portion, demodulating the upper sideband portion and the lower sideband portion to produce a demodulated upper sideband signal and a demodulated lower sideband signal, weighting the demodulated upper sideband signal and the demodulated lower sideband signal in response to noise power to produce a weighted demodulated upper sideband signal and a weighted demodulated lower sideband signal, and combining the weighted demodulated upper sideband signal and the weighted demodulated lower sideband signal to produce an output signal. Demodulators which process AM radio signals in accordance with the method, and receivers incorporating the demodulators, are also included.

Abstract: A method of in-band on-channel (IBOC) digital audio broadcasting (DAB) comprises the steps of providing an analog modulated carrier signal in a central frequency band of an AM radio channel, providing a first plurality of subcarriers in an upper sideband of the AM radio channel, providing a second plurality of subcarriers in a lower sideband of the AM radio channel, providing a third plurality of subcarriers in the central frequency band of the AM radio channel, modulating the first, second and third plurality of subcarriers with one or more digitally encoded signals, and transmitting the analog modulated signal and the first, second and third plurality of subcarriers, wherein the subcarriers in the third plurality of subcarriers that are positioned closest to the center of the channel are transmitted at higher power spectral densities than the subcarriers in the third plurality of subcarriers that are positioned farther from the center of the channel.

Abstract: A method is provided for transmitting a composite digital audio broadcast signal having an analog portion and a digital portion to mitigate intermittent interruptions in the reception of said digital audio broadcast signal. The method comprises the steps of arranging symbols representative of the digital portion of the digital audio broadcast signal into a plurality of audio frames, producing a plurality of modem frames, each of the modem frames including a group of the audio frames, and adding a frame synchronization signal to each of the modem frames. The modem frames are then transmitted along with the analog portion of the digital audio broadcast signal, with the analog portion being delayed by a time delay corresponding to an integral number of the modem frames. The invention also encompasses radio receivers and transmitters which process signals according to the above methods.

Abstract: A method for transmission of compressed data for a digital audio broadcasting system comprises the steps of producing digital information representative of an audio signal; estimating the number of bits to be allocated to the digital information in a modem frame; encoding the digital information within the estimated number of bits to produce encoded data; removing selected bits from the encoded data; adding bits corresponding to digital messages to the encoded information to form a composite modem frame; formatting the composite modem frame bits to produce formatted composite modem frame bits; and transmitting the formatted composite modem frame bits. The invention also encompasses transmitters that perform the method.

Abstract: A method of transmitting digital audio broadcasting signals comprises the steps of generating a plurality of output frames of information to be transmitted, wherein each of the output frames includes a plurality of blocks of data and each of the output frames is synchronized with an absolute time reference, and transmitting the output frames to a plurality of receivers. The information to be transmitted can identify the location of a transmitter. Transmitters that broadcast in accordance with the method and receivers that receive the transmitted signal are also disclosed.