56 results about "In-band on-channel" patented technology

An interleaving method and apparatus is disclosed for an in-band on-channel (IBOC) digital audio broadcasting (DAB) system. The disclosed interleaver method and apparatus utilize a convolutional interleaver having a row size equal to one OFDM symbol and a time span of arbitrary size. A structured memory block is utilized in the de-interleaver at the receiver having a row size of one OFDM symbol (the number of active sub-carriers in the applicable sub-band of the IBOC system). The self-synchronizing nature of the present invention permits a receiver in an OFDM-based IBOC system to sort the scrambled blocks and descramble the received symbols according to its own frame count, without regard to the frame count of the transmitter. The disclosed interleaver method and apparatus does not require interleaver synchronization between the transmitter and receiver. In one implementation, separate convolutional encoders and convolutional interleavers are applied to each sub-band in a multi-stream structure to provide independent error spreading for each sub-band.

A method and system are provided for the transmission and reception of an In-band On-channel (IBOC) FM-band digital audio broadcast (DAB) signal. The IBOC DAB signal is generated in the transmitter to substantially occupy the upper and lower sideband frequency regions in the RF emission mask for the conventional broadcast analog FM-band. Redundant source bit information is transmitted in both the upper and lower sidebands so that the loss of information in either one but not both sidebands due to large amounts of interference or distortion, caused by, for example, first-adjacent interference, does not deleteriously affect the IBOC DAB receiver performance. The system exhibits both frequency-diversity and time-diversity. The receiver determines which codeword bit estimate, corresponding to either upper or lower sideband signals, is less likely to be erroneous. The receiver system selects between decoded estimates for each pair of demodulated ECC codewords or combines both ECC codeword estimates prior to decoding in certain embodiments.

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.

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.

A phase shift is defined as a point in frequency at which the phase is changed from 0 degrees to 180 degrees. A device is provided for combining analog and digital in-band-on-channel (IBOC) signals to feed a common antenna utilizing phase shifting allpass filter modules to provide a 180 degree phase shift to specific IBOC channels within a constant impedance dual-hybrid circuit. The IBOC Allpass combiner includes one input 90 degree 3 dB quadrature hybrid coupler, one output 90 degree 3 dB quadrature hybrid coupler, a load resistor, and two phase shifting allpass filter modules. Each phase shifting allpass filter module is comprised of a two coaxial cavity resonators coupled to a 90 degree 3 dB quadrature hybrid coupler. Components and modules are coupled using mating transmission lines. The four coaxial cavity resonators are used as devices to produce two distinct phase shifts at isolated upper and lower IBOC side band frequencies. The circuit is designed for one center analog frequency and two sideband IBOC OFDM carrier frequencies, such that all frequencies will combine in phase at the common antenna input with minimal loss and minimal group delay. Out of phase and spurious emissions are ported to the load resistor.

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.

An FM broadcast transmitter transmits a broadcast signal having a carrier at a broadcast frequency and sidebands, able to be transmitted at full power, within a transmission band-width around the carrier. It includes a source of a modulated FM stereo signal having a carrier at the broadcast frequency and having sidebands with a bandwidth less than the transmission bandwidth representing a stereo signal. It also includes a source of a modulated IBOC signal, having carrier pulses spaced relative to each other to represent the IBOC digital data signal encoded as a variable pulse width encoded signal, and a bandwidth within the transmission bandwidth not overlapping the FM stereo signal sidebands. A signal combiner combines the modulated FM stereo signal and the modulated IBOC signal to form the broadcast signal. An FM broadcast receiver receives a broadcast signal including a first modulated signal representing an FM stereo signal, and a second modulated signal, having carrier pulses spaced relative to each other to represent an in-band-on-channel (IBOC) digital data signal encoded as a variable pulse width encoded signal. It includes a signal separator for generating a first separated signal representing the FM stereo signal and a second separated signal representing the IBOC digital data signal. An FM signal processor generates a stereo audio signal represented by the FM stereo signal. An IBOC signal processor generates a digital data signal represented by the IBOC digital data signal.

A method for processing a digital audio broadcast signal includes: separating an analog audio portion and a digital audio portion of the digital audio broadcast signal; determining the loudness of the analog audio portion and the digital audio portion over a first short time interval; using the loudness of the analog and digital audio portions to calculate a short term average gain; determining a long term average gain; converting one of the long term average gain or the short term average gain to dB; if an output has been blended to digital, adjusting a digital gain parameter by a preselected increment to produce a digital gain parameter; if an output has not been blended to digital, setting the digital gain parameter to the short term average gain; providing the digital gain parameter to an audio processor; and repeating the above steps using a second short time interval.

The invention discloses a dynamic spectrum access method based on an HD Radio system. The HD Radio system achieves the aim of in-band common-frequency transmission of analog signals and digital signals. According to the in-band common-frequency transmission mode, the digital signals are fixedly arranged at the position deviating from the carrier frequency by 130-200KHZ and are coupled with the FM analog signals through a fixed combination mode; however, as the spectral bandwidth of the FM analog signals changes along with program signals, the bandwidth is large in change range. An ITU-R BS. 1387-1 psychological acoustics model serves as a support, the access position of a spectrum of the digital signals is changed dynamically on the time dimension, the analog audio quality after signal modulation is analyzed, the bandwidth which can be saved by signal transmission on the premise of not affecting the quality of audio signals is counted and obtained, and supporting is provided for improving the transmission capacity of the digital signals in the HD Radio system.

The invention relates to a segmented in-band modulation method for FM (frequency modulation) radio band digital analog mixed signals, in which analog sound broadcasting signals and digital sound broadcasting signals are combined to digital analog mixed signals which share an FM band. The FM band includes a plurality of sub-bands. For the digital sound broadcasting signals, sub-carriers are set to zero in an intermediate sub-band, or only synchronization symbol sub-carriers are retained; modulation modes in different orders are used in other sub-bands, and the distribution of sub-carriers of the sub-bands forms mirror symmetry to the center of the sub-bands, that is, the higher the modulation order is, the farther the distance is to the center. The synchronization symbol sub-carriers of the digital sound broadcasting signals are equally spaced and are modulated in an order lower than 24. Sound data symbol sub-carriers of the digital sound broadcasting signals are modulated in an order lower than 24 in a sub-band where the potential of analog signals is higher than 3.5 mu V. On the contrary, the sound data symbol sub-carriers of the digital sound broadcasting signals are modulated in an order higher than or equal to 24. The segmented in-band modulation method for FM radio band digital analog mixed signals has the advantages that the demodulation signal-to-noise ratio and the distortion index of analog signals of an FM digital analog mixed system are obviously improved, and the interference of digital analog signals in band same-frequency broadcasting signals is effectively eliminated.

The invention discloses a digital spectrum detection method for an in-band on-channel (IBOC) system based on ear perception. By a high-definition (HD)-Radio system, in-band same-frequency transmission of an analog signal and a digital signal is realized; by the in-band same-frequency transmission mode, the digital signal is fixedly arranged at a position deviated from a carrier frequency of 130 to 200 KHZ; by a fixed combination mode, the digital signal is coupled with a frequency modulation (FM) analog signal; and the spectrum bandwidth of the FM analog signal is changed along with a program signal, so that the bandwidth change range is wide. Analog audio quality subjected to signal modulation under spectrum positions of different digital signals according to an international telecommunications union-radiocommunication (ITU-R) base station (BS).1387-1 psychological acoustics model, so that on the premise that the audio signal quality is not influenced, bandwidth which can be saved by signal transmission is counted; and the transmission capacity of the digital signals in the HD-Radio system can be improved.

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.

The invention provides a method for reducing radio frequency interference in an FM in-band co-frequency digital audio broadcasting receiver. The method comprises the steps of: receiving a composite signal comprising a useful signal and an interference signal, demodulating the composite signal to generate a first demodulated signal, calculating a first binary soft decision from the first demodulated signal, processing the composite signal to generate a processed signal, demodulating the processed signal to generate a second demodulated signal, computing a second binary soft decision from the second demodulated signal, and combining the first and second binary soft decisions meta soft decision to generate an output signal. Also included is a radio receiver utilizing the method described above.

A method for processing a digital audio broadcast signal in a radio receiver includes: receiving a digital audio broadcast signal; demodulating the digital audio broadcast signal to produce an analog audio stream and a digital audio stream; determining a digital signal quality value for the digital audio stream; blending an output of the radio receiver from the analog audio stream to the digital audio stream when the digital signal quality value exceeds an adaptive analog-to-digital threshold value; and blending the output of the radio receiver from the digital audio stream to the analog audio stream when the digital signal quality value falls below an adaptive digital-to-analog threshold value, wherein the adaptive digital-to-analog threshold value is lower than the adaptive analog-to-digital threshold value.

The invention relates to an improved method for generating in-band on-channel digital-analog audio broadcasting signals. The method comprises a step of obtaining and digitalizing analog audio broadcasting signals and transmitting the obtained digitalized analog audio broadcasting signals in the same broadcasting channel, and a step of duplicating digital signals of another path in adjacent signal frames. Time domain hybrid is carried out on an analog signal and a digital signal, an analog audio broadcasting signal x2m plus a corresponding digital broadcasting signal dm equals x2m+dm, an analog audio broadcasting signal x2m+1 plus the corresponding digital broadcasting signal equals x2m+1+dm, wherein the analog broadcasting signal x2m and the analog broadcasting signal x2m+1 are in adjacent signal frames, and a digital mixed signal is transmitted in the same broadcasting channel. A digital-analog hybrid signal j*x2m+dm is obtained by a manner that the x2m multiplies a nonzero integer j, and a digital-analog hybrid signal k*x2m+dm is obtained by a manner that the x2m+1 multiplies a nonzero integer k, or the digital signal dm recurs after an interval of L digital signals to be mixed with the analog signal in an add-subtract or add-add mode. The digital-analog hybrid signal with frequency spectrums completely overlapped is obtained, frequency bands are saved, much energy can be accumulated in a preset bandwidth, leakage out of a band is small, and signal energy loss is reduced.

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.