Lsi Logic Corporation

British Broadcasting Corporation

Jonathan Highton Stott

Oliver Paul Haffenden

Adrian Paul Robinson

Philippe Roger Sadot

Jean-Marc Guyot

Justin David Mitchell

Lauret Regis

Christopher Keith Perry Clarke

Nicholas Dominic Wells

Christopher K Clarke

Regis Lauret

Peter Neil Moss

Christopher K P Clarke

Christopher Ryan Nokes

An RF active deflector is described for use with orthogonal frequency division multiplex signals. An input antenna receives an RF input signal and an output antenna transmits an RF signal on substantially the same frequency as the input signal. An amplification path between the input antenna and the output antenna provides substantially linear processing and includes a delay. Means responsive to the signal in the amplification path produce a plurality of control coefficients. A transversal filter receives the signal in the amplification path and, under control by the control coefficient, provides a modified signal. A combiner is provided for combining the modified signal with the signal in said amplification path so as to reduce the effect of the feedback.

Method and apparatus for reduction of unwanted feedback

A diversity receiver for receiving digital signals has a soft-decision decoder in each of its receiving sections, to provide confidence values for the received decoded digital values, and combines the values from the receiving sections in dependence upon the confidence values. The receiver is especially suitable for use with COFDM, and has two sections, the outputs of which are applied to a soft-decision combiner which combines the signals in dependence upon confidence values received from the demodulators. The output is then applied to a Viterbi decoder. The combining can simply involve switching but preferably involves averaging. Synchronisation and squelching can be provided. The system can be used with frequency diversity, spatial or polarisation diversity, or with antenna pattern diversity, in which case it can constitute an automatic rotator. The system automatically switches between different types of diversity reception, e.g. frequency and spatial diversity, in dependence upon the received signal quality.

Diversity reception method and diversity 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

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.

The feedback caused between the output and the input of an amplification path is reduced by providing a delay in the amplification path, passing through the amplification path a signal having an auto-correlation function which is substantially a delta function, correlating the said signal before being delayed in the delay with the signal after being delayed in the delay to produce a plurality of correlation coefficients, modifying the signal in the amplification path to provide a modified signal, the modification being provided by a transversal filter controlled by the said plurality of correlation coefficients, and combining the modified signal with the signal in the amplification path so as to reduce the effect of the feedback. The signal having an auto-correlation function which is substantially a delta function may be an added noise signal or may be constituted by the signal being processed itself The system can be used to reduce &ldquo;howl-around&rdquo; in audio situations or feedback in simultaneous coherent re-broadcast transceivers.

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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Tadworth, United Kingdom

Jonathan Highton Stott