Abstract:
A network datacast system includes a plurality of transmission facilities. Each transmission facility receives primary programs from one or more media studios. Each transmission facility also receives ancillary data programs from a network datacast center. Each transmission facility broadcasts a wireless signal that includes a primary channel and at least one ancillary data channel. The transmission facilities contemporaneously transmit the ancillary programs on the ancillary data channels. A network datacast receiver contemporaneously receives the wireless signals and extracts the datacast programs from each datacast signal. The extracted datacast programs are stored in the receiver for subsequent output to the user.
Abstract:
A method for transmission of data in a digital audio broadcasting system includes the steps of providing a plurality of orthogonal frequency division multiplexed sub-carriers, with the sub-carriers including data sub-carriers and reference sub-carriers, and 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. Then the orthogonal frequency division multiplexed sub-carriers are transmitted. 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 and apparatus are disclosed for estimating the power of the first adjacent FM interference and for using the estimated power to identify the number of OFDM bins that are at least partially corrupted by the first adjacent FM interference. The number of corrupted bins, Ncorr, is obtained based on measurements of the power of each of the first adjacent FM analog interference, Ik, and the power of the background noise, Nk, of the digital side bands. The power measurements, together with the known slope of the first adjacent FM analog interference, is used to identify when the power of the measured background level equals the prorated power of the slope. All of the bins that fall below a threshold value are determined to be at least partially corrupted. The FFT output provides the power of the first adjacent FM analog interference, Ik, measured, for example, at ±200 kHz, and the power of the background noise, Nk, of each of the digital side bands, measured, for example, at 130 kHz and −130 kHz. In a hard-masking implementation, the corrupted bins are discarded (set to zero) and in a soft-masking implementation, the partially corrupted bins are scaled according to the interference slope before further processing, for example, by the Viterbi decoder.
Abstract:
A system (100) for mitigating intermittent interruptions in an audio radio broadcast system is provided wherein a primary radio signal and a redundant radio signal are transmitted from a transmitter subsystem (120) and received by a receiver subsystem (140). The output (112) of an audio source (110) is coupled to a modulator (160) for modulating a radio frequency signal (162) for coupling to a transmit antenna (172). A second output (114) of audio source (110) is coupled to a delay circuit (116), for adding a predetermined time delay thereto. The delayed audio source signal is coupled to modulator (164) for modulating a second radio frequency signal (166) that is also coupled to the transmit antenna (172). The receiver subsystem (140) receives both the primary radio signal and the delayed redundant radio signal and couples each to a respective demodulator (180, 182). At least demodulator (180) includes a circuit (181) for determining the degradation in the primary radio signal and provides a quality measurement output signal (186) to a blend control circuit (190). The recovered primary audio signal from demodulator (180) is coupled to a second delay circuit (184), the time delay of second delay circuit (184) being substantially equal to the time delay of delay circuit (116). The audio output from delay circuit (184) and the redundant audio output from demodulator (182) are coupled to a blending subsystem (135), wherein each is combined with a weighting factor and then combined together to form a composite audio signal for coupling to the audio output circuit (150).
Abstract:
In a system for simulcasting digitally modulated and analog FM signals over the same FM frequency band, the effect of the analog FM signal on the digitally modulated signal in the simulcast is calculated and canceled from the latter signal before its transmission. As a result, the digital transmission is free from interference from the analog FM signal. Moreover, the digital transmission is designed in such a manner that the interference caused thereby to the analog FM signal is kept at a minimal level.
Abstract:
A system and method for transmitting digital information through a medium such as atmospheric free-space includes a transmitter which generates a signal based on a basis set of mutually orthogonal, spectrally-shaped, sequences of substantially equal length and having predetermined autocorrelation values. The sequences may resemble noise in at least some of their characteristics. The orthogonality or cross-correlation characteristics, the autocorrelation characteristics and the resemblance to noise are due to features derived from sequences of pseudo-random numbers which themselves resemble noise in at least some of their characteristics. The waveform set based on the sequences is modulated digitally. The modulated set may be summed together along with a wideband reference signal of reduced amplitude and optionally an FM analog signal to form a composite signal which is broadcast typically through free space to at least one receiver. The receiver separates the analog FM signal from the digital signal and thereafter demodulates the digital data-carrying waveforms and outputs a stream of digital data. It has been determined to be resistant to multipath degradation.
Abstract:
An apparatus (10) for the simultaneous broadcast of an analog and digital radio signals, used in the frequency band of the FM (Frequency Modulation) signal, comprising a block or electronic card (12) to which one, two or more analog and/or digital audio and/or radio signals are inputted, consisting of a plurality of blocks or units for handling and processing analog audio signals, a possible RDS (Radio Digital System) and/or DARC (Data Radio Channel) signal, and a digital DRM (Digital Radio Mondiale) signal.
Abstract:
A network datacast system (200) includes a plurality of transmission facilities (210,212). Each transmission facility (210,212) receives primary programs (206,208) from one or more media studios (202,204). Each transmission facility (210,212) also receives ancillary data programs (226,228) from a network datacast center (220). Each transmission facility (210,212) broadcasts a wireless signal (234,236) that includes a primary channel and at least one ancillary data channel. The transmission facilities (210,212) contemporaneously transmit the ancillary programs (226,228) on the ancillary data channels. A network datacast receiver (250) contemporaneously receives the wireless signals (234,236) and extracts the datacast programs from each datacast signal. The extracted datacast programs are stored in the receiver (250) for subsequent output to the user.
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.