Lsi Logic Corporation

British Broadcasting Corporation

Other

Adrian Paul Robinson

Oliver Paul Haffenden

Philippe Roger Sadot

Justin David Mitchell

Jean-Marc Guyot

Jonathan Highton Stott

Lauret Regis

Christopher Keith Perry Clarke

Christopher K Clarke

Regis Lauret

Jonathan Highton Scott

Jonathan Hghton Stott

Christopher Keith Perry Clark

Christopher K P Clarke

Andrew J Bower

A DVB-T receiver includes a channel equalizer, a metric assignment and demapping circuit, a Viterbi decoder and an outer Reed-Solomon decoder. The metric assignment and demapping circuit includes a soft-decision quantising arrangement which provides confidence values for the Viterbi decoder. The quantising arrangement receives a control input from channel state indication (CSI) measurement circuitry. A further channel state indication is obtained on a symbol-by-symbol basis. This is compared an average obtained over a few symbols, to detect impulsive interference, and applied as part of the control for the soft-decision quantiser. A signal derived from the further channel state indication is also applied to the erasures input of the Reed-Solomon decoder.

Decoders for many-carrier signals, in particular in DVB-T receivers

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.

Demodulating digital video broadcast signals

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 (,) for converting the broadcast signal to a series of digital samples, real to complex conversion means (,) for converting each digital sample to a complex number value, Fourier transform means (,) for analyzing the complex number values to provide a series of signal values for each carrier frequency, frequency control means (,), 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 including channel equalization means (,) and channel state information generating means (,).

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 a predetermined number (N) of carrier signals on either side of the nominal position of a predetermined continual pilot signal, wherein the outputs of the filter are provided to respective memory locations of a memory, the memory being divided into a plurality of sections, first device for determining within each section a first signal best representing the continual pilot signal, and device means for determining from among the first signals from the plurality of sections, a second signal which best represents the continual pilot signal.

Improved synchronization of OFDM signals is achieved. A controlled oscillator (,) provides clock pulses to derive complex samples of an input signal which are applied both to a fast Fourier transform (,) for data recovery and to a synchronization unit (,). The synchronization unit generates the complex product XY* of the input and the delayed input, which is applied to a high-pass filter (,) to suppress frequencies below the symbol frequency. The filter output is applied through a symbol comb filter (,) to an adaptive slicer (,) which determines the larger magnitude of the real and imaginary components of the signal. A pulse processor (,) generates a single pulse at the leading edge of the symbol pulse which is applied to a symbol counter (,). The symbol counter includes two count stages arranged to lock in quickly and yet be variable to accomodate different guard intervals in the OFDM signal.

OFDM symbol synchronization

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.

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 a multiplier for receiving the digital signal values and a version thereof delayed by the delay, to form a complex product signal, and a processor for processing the complex product signal to derive timing synchronization pulses, wherein the timing synchronizer is operable in an initial hunt mode for analyzing the digital sample values over a relatively wide timing range to establish synchronization, and then operable in a zoom mode for analyzing the digital sample values over a relatively narrow range about the synchronization point.

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. The synchronizer includes a correlation for receiving the data sample values and including a delay having a time period delay equal to the active symbol period, and a multiplier for receiving the data symbol values and a version thereof delayed by the delay, to form a complex product signal, and a filter for filtering the complex product signal. The timing synchronizer includes a coarse synchronizer employing a subset of the data sample values for providing a course timing synchronization, and a fine synchronizer for providing a fine synchronization within a time period determined by the coarse synchronization.

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. The coarse frequency controller includes a recursive filter for assessing a predetermined number (N) of carrier signals on either side of the nominal position of a predetermined continual pilot signal, to determine which signal best represents the continual pilot signal, whereby to determine the coarse frequency error.

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London, United Kingdom

Adrian Paul Robinson