Abstract: An apparatus for demodulating digital video broadcast signals comprising data modulated on a plurality of spaced carrier frequencies, comprising a transform circuit and a timing synchronization circuit. The transform circuit may be configured to analyze digital sample values. The timing synchronization circuit may be configured to synchronize the transform circuit with symbol periods of the broadcast signal. The timing synchronization circuit may be further configured to operate in (i) a first mode for analyzing the digital sample values over a relatively wide timing range to establish synchronization and (ii) a second mode for analyzing the digital sample values over a relatively narrow range about a synchronization point.

Abstract: A demodulator suitable for implementation in a single chip for demodulating digital video broadcast signals comprising data modulated on a multiplicity of spaced carrier frequencies, wherein an input broadcast signal is converted to a frequency sufficiently low to enable analog digital conversion of the signal, the demodulator comprising analog to digital conversion means (20) for converting the broadcast signal to a series of digital samples, real to complex conversion means (22) for converting each digital sample to a complex number value, Fourier transform means (24) for analyzing the complex number values to provide a series of signal values for each carrier frequency, frequency control means (9, 38), comprising means responsive to the output of said Fourier Transform means for producing a signal for controlling the frequency of the signal formed by said complex number values, and signal processing means for receiving the signal values and providing an output for decoding, the signal processing means incl

Abstract: Apparatus for demodulating digital video broadcast signals with an improved automatic frequency control comprises data modulated on a multiplicity of spaced carrier frequencies, including: analog to digital conversion device for providing a series of digital samples of the broadcast signal, Fourier Transform for analysing the samples to provide a series of data signal values for each carrier frequency signal processing devices for processing the series of data signal values including the phase-error-correcting, and automatic frequency control device for controlling the frequency of the signals input to the Fourier Transform Processor, wherein the automatic frequency control device includes coarse frequency control unit for controlling the frequency in terms of increments of the carrier spacing frequency, and fine frequency control unit for controlling the frequency for values less than a single carrier spacing frequency interval, wherein the coarse frequency unit includes recursive of filtering for assessing

Abstract: In order to correct for common phase error in demodulated digital video broadcast signals which comprise data modulated on a multiplicity of spaced carrier frequencies, a demodulator includes analog to digital conversion means (20) for providing a series of digital samples of the broadcast signal, real to complex conversion means (22) for converting each digital sample to a complex number value, Fourier Transform means (24) for analysing the complex number values to provide a series of data signal values in complex number format for each carrier frequency, and signal processing means for processing the series of data signal values including phase error correcting means (30), the phase error correcting means including means for converting the data signal values from a complex number format to a phase angle format, means for determining a common phase error by assessing the phase of continual pilot signals in the broadcast signals and determining the variation in phase of the continual pilot signals between c

Abstract: An apparatus for demodulating a digital video broadcast signal comprising data modulated on a multiplicity of spaced carrier frequencies. A transform device may analyze the digital broadcast signal to provide a series of symbol values for each of the multiplicity of carrier frequencies. An automatic frequency control device may control the frequency of the series of symbol values in dependence on a common phase error signal from the series of symbol values. First and second common phase error correction (CPE) devices may receive common phase error signals, for correcting the signal values from the transform device. A channel equalization device may compensate for communication channel impairments for receiving directly the phase error corrected signals from the first CPE device.

Abstract: A demodulator suitable for implementation in a single chip for demodulating digital video broadcast signals including data modulated on a multiplicity of spaced carrier frequencies, wherein an input broadcast signal is converted to a frequency sufficiently low to enable analog to digital conversion of the signal, converter for converting the broadcast signal to a series of digital samples in complex format, transformer for analyzing the digital sample values to provide a series of data symbol values for each carrier frequency and signal processor including channel equalizer for receiving the signal values and providing an output for decoding, automatic frequency controller for controlling the frequencies of the digital sampling signals applied to the transformer, and timing synchronizer for synchronizing the transformer with the symbol periods of the broadcast signal, including correlator for receiving the digital signal values and including a delay having a time period equal to the active symbol period, and

Abstract: A demodulator suitable for implementation in a single chip for demodulating digital video broadcast signals including data modulated on a multiplicity of spaced carrier frequencies, wherein an input broadcast signal is converted to a frequency sufficiently low to enable analog digital conversion of the signal. The demodulator includes an analog to digital converter for converting the broadcast signal to a series of digital samples; a real to complex converter for converting each digital sample to a complex number value; Fourier transformer for analyzing the complex number values to provide a series of data symbol values for each carrier frequency; a signal processor for receiving the data symbol values and providing an output for decoding; and a timing synchronizer for synchronizing the Fourier transformer with the symbol periods of the broadcast signal.

Abstract: Apparatus for demodulating digital video broadcast signals with an improved mechanism for automatic frequency control including data modulated on a multiplicity of spaced carrier frequencies. The apparatus includes an analog to digital converter for providing a series of digital samples of the broadcast signal, a Fourier Transformer for analyzing the samples to provide a series of data signal values for each carrier frequency, signal processor for processing the series of data signal values including the phase-error-correcter, and automatic frequency controller for controlling the frequency of the signals input to the Fourier Transformer. The automatic frequency controller includes coarse frequency controller for controlling the frequency in terms of increments of the carrier spacing frequency, and fine frequency controller for controlling the frequency for values less than a single carrier spacing frequency interval.

Abstract: A go-back-N automatic repeat request method for use on a duplex installation having noisy return channels. When an acknowledge signal (ACK) is not correctly received, it is assumed to be positive until the Nth successive incorrectly received acknowledgement, which is treated as a negative acknowledgement, thereby ensuring that blocks are repeated even if acknowledgements are degraded by jamming.

Abstract: A method and apparatus for coherent demodulation for phase shift keyed signals including:a phase estimation stage based on a sequence of reference symbols transmitted at the start of each block of data anda second order phase-locked loop stage.

Abstract: Enough room is provided in a transmitted frame to receive a plurality (n) of useful information blocks, thereby making it possible to catch up any excessive lateness (r) which may arise due to successive repeats. The decoder (2) provides a confidence flag (3) to the controlling microprocessor (5). The command block (COM) from the decoder includes an indication of the number of useful blocks that are transmitted in the frame. This block is advantageously applied to an HDLC component (8).

Abstract: A method of detecting a disturbing signal for demodulating digital data, wherein, on the modulated signal transposed into baseband, the disturbing signal is detected by periodically inserting known signals by means of a fixed guard time delay ((R+I)T.sub.s) applied to the received signal prior to demodulation, and wherein said method includes: a step of estimating the square of the modulus of the cross-correlation of the received referenced signal and of the expected signal at a determined instant when the reference signal is assumed to be present; a step of estimating the square of the correlation of the received signal at the same instant, of multiplying by a coefficient which represents the square of the threshold for the estimated correlation coefficient, and of multiplying by the number of reference symbols used in a reference burst; and a step of comparing with each other the two quantities obtained simultaneously during the preceding two steps.

Abstract: In a circuit for decoding convolutional codes for executing the survivor path storage and reverse scanning stage of a Viterbi algorithm, decoding consists in reverse scanning a plurality of paths of a trellis representing a diagram of the possible transitions resulting from encoding by an encoder comprising .nu. flip-flops, each node of the trellis being represented by a word on N=2.sup..nu. bits. The circuit selects from a plurality of possible survivor paths that which has the lowest metric, so as to reconstitute the trellis path actually determined by the encoding process and to recover the sequence of information bits that caused this path to be adopted. The circuit comprises a memory storing a plurality of said words of N=2.sup..nu. bits and, connected to the output of said memory, a cascade of .nu. groups of 2-in-1 multiplexers progressively combining the 2.sup..nu. outputs of the memory into a single output, a D flip-flop being provided at the output of each multiplexer.

Abstract: A method of establishing an inverse pilot sequence for deinterleaving as used in digital transmission, with the interleaving being performed by means of a transmit register and a pilot sequence. Each portion (2 5 1 4 3 6) of the inverse pilot sequence is obtained from the preceding portion (3 1 6 5 4 2) of the inverse pilot sequence and from the two corresponding portions (2 6 1 5 4 3, 4 1 3 6 5 2) of the pilot sequence, with the k-th element of the N-th portion of the inverse pilot sequence being determined by observing the rank of the k-th element in the (N-1)-th portion of the pilot sequence in the N-th portion of the pilot sequence, and then in selecting the element to be found at this rank in the (N-1)-th portion of the inverse pilot sequence.

Abstract: A psuedo-random interleaving method suitable for use in transmitting digital data. A pseudo-random pilot sequence is used for simultaneously reading from and writing to a vector of size Tv.gtoreq.Tc.times.Lm, the pilot sequence satisfying a minimum distance law Lm, except when blocking occurs. Deinterleaving is performed symmetrically by means of an inverse pilot sequence suitable for reconstituting successive code words.

Abstract: A method of detecting erasures in a digital radio link conveying a signal which is encoded prior to modulation and transmission of the signal by means of an error correcting code having a low covering radius which signal is demodulated and decoded, after which a flag signal is generated whenever the error correcting capacity of said decoding is exceeded, and said capacity-exceeded flag signal is integrated in order to obtain an erasure flag signal.