Mitsubishi Electric Corporation

Mitsubishi Denki Kabushiki Kaisha

Jun Ido

Mitsuru Takeuchi

Naosuke Ito

Eiji Arita

Takashi Fujiwara

Naoki Hayashi

Shuji Murakami

Kazuya Yamanaka

Hiroyuki Nagahama

Tsutomu Asahina

Masakazu Morita

Daisuke Shimbo

Hiroshi Kayashima

Naotoshi Maeda

Ryuichiro Kono

Tadashi Sakaguchi

Akio Sasai

Kenji Urasaki

Ryosuke Umeno

Akiko Maeno

The present invention is provided with: a CIR generating unit which generates an channel impulse response from a received signal; a CIR variation detection unit which uses a plurality of channel impulse responses generated from a plurality of different sections of the received signal by the CIR generating unit to detect an amount of variation in the channel impulse response; an equivalent width control unit which determines an equivalent width corresponding to a signal length used in equalization of the received signal such that the equivalent width is shortened as the amount of variation in the channel impulse response increases; and a waveform equalization unit which uses the channel impulse response generated by the CIR generating unit to equalize the received signal over the equivalent width determined by the equivalent width control unit and generate a demodulated signal.

Equalizer device, receiver device and equalization method

A reception device includes signal receiving units that generate received signals from signals obtained by receiving a transmitted signal at antennas, signal processing units that perform processes of generating received frequency domain signals by transforming the received signals to signals in the frequency domain, calculating channel impulse responses of the received signals, calculating estimated received signals from the channel impulse responses, and calculating residual error weights with values that decrease with increasing differences between the received signals and the estimated received signals, a combining ratio calculation unit that calculates combining ratios for the received frequency domain signals such that the ratios decrease as the residual error weights decrease, a diversity combining unit that combines the received frequency domain signals according to the combining ratios to generate a diversity combined signal, and an inverse Fourier transform unit that transforms the diversity combined signal to a time domain signal.

Reception device and reception method

This equalization device and method, while preventing an expansion of circuit size, enable high-speed detection of a CIR in order to effectively achieve frequency domain equalization even when the phase of the received signal is significantly different from the phase of the known signal, and when the transmission channel has large temporal variations. A reference signal extraction unit () extracts both a real part component and an imaginary part component from the portion of the received signal including the known signal. A CIR detection filter unit () filters the known signal to generate a first processed signal and a second processed signal, detects real part filter coefficients by updating a first filter coefficient used in filtering the known signal in such a way that the first processed signal converges to the real part component, and detects imaginary part filter coefficients by filtering the known signal in such a way that the second processed signal converges to the imaginary part component. A CIR output unit () uses either the real part filter coefficients or the imaginary part filter coefficients to identify the channel impulse response.

Equalization device, reception device and equalization method

Provided are a transmission channel estimating device, a transmission channel estimating method, and a receiving apparatus. A transversal filter unit generates an estimated reception signal on the basis of a stored known signal sequence and tap coefficients, generates an error signal on the basis of a difference between a reception signal and the estimated reception signal, generates updated tap coefficients on the basis of the known signal sequence, the tap coefficients and the error signal, designates an effective section formed by a predetermined number of taps out of a plurality of taps in the transversal filter unit, and designates a first section and a second section set so as to include a center tap, wherein the generation of the estimated reception signal and the updated tap coefficients is performed by generating an estimated reception signal and updated tap coefficients for the first section and generating an estimated reception signal and updated tap coefficients for the second section.

Transmission channel estimating device, transmission channel estimating method and receiving apparatus

In a reception device and a reception method for a multivalue VSB, QPSK, or mutlivalue QAM modulated signal, reliability information (R) is generated () on the basis of estimation results for the received signal transmission channel, and Viterbi decoding is performed on the basis of the reliability information (R). It may be so arranged that the smaller the absolute value of the difference between the maximum gain and the minimum gain within the transmission frequency band of the output of a transmission channel estimation means () is, the higher the reliability indicated by the output reliability information will be. Error correction capabilities can be improved in various transmission channel environments, and errors in transmitted data recovered at the receiving end can be reduced.

Reception device and method

A channel characteristic obtained from a pilot signal is stored for a prescribed number of symbols and a Fourier transform is performed (), the power of each Doppler frequency component is calculated (), filtering is performed in the time direction for each Doppler frequency component (), noise components are masked (), power changes between mutually adjacent Doppler frequency components are emphasized (), and motion information is generated by comparison with a predetermined decision threshold (). Velocity detection that detects velocity of motion from a received signal with high precision in order to improve mobile reception performance by optimizing demodulation operations according to velocity of motion thereby becomes possible.

Reception device and method of determining the velocity of the device based on a received pilot signal

The steps and corresponding structures include: extracting at least K+N pieces of data corresponding to one symbol including a guard interval from a frequency-transformed received signal to generate 2N pieces of data, as expanded time axis data, by adding zero before and after the extracted data; shaping, by utilizing a window shaping part, a waveform by multiplying the expanded time axis data by a window coefficient; performing DFT (discrete Fourier transform), by utilizing a DFT part, with respect to output of the window shaping part; performing a demodulation of a sub-carrier by extracting a sub-carrier component; calculating an inter-carrier interference component from output of the DFT part; and selecting a window coefficient based on the inter-carrier interference component to output to the window shaping part.

Receiving apparatus and receiving method

A diversity receiver includes: a plurality of demodulating means for demodulating inputted OFDM signals, to output their demodulated signals; noise component calculating means provided for each demodulating means, for calculating noise components included in the demodulated signals outputted from corresponding demodulating means; channel profile calculating means provided for each demodulating means, for calculating channel profiles based upon the demodulated signals outputted from corresponding demodulating means; transmission channel decision means for determining transmission channel based upon the channel profiles; reliability information generating means for generating reliability information indicating reliability of the demodulated signals outputted from each demodulating means, based upon the noise components and the results of the determinations by the transmission channel decision means; a weighting factor calculating means for calculating, depending on the reliability information, weighting factors used in combining the demodulated signals outputted from each demodulating means; and a combining means for combining, depending on the weighting factors, the demodulated signals outputted from each demodulating means.

Demodulator, diversity receiver, and demodulation method

A digital broadcasting receiving apparatus is characterized in that the digital broadcasting receiving apparatus is provided with an antenna combination determination processing unit for selecting at least two antennas from among a plurality of antennas which have directivities in different directions and each of which receives a digital broadcasting wave transmitted from outside the digital broadcasting receiving apparatus, and for providing an instruction for switching among the above-mentioned plurality of antennas on the basis of a state of reception of the digital broadcasting waves received by the selected antennas, and switches for switching among the above-mentioned plurality of antennas according to the instruction from the above-mentioned combination determination processing unit.

Digital broadcasting receiving apparatus

The value of a pilot signal extracted from the received signal is divided by the known value (s) of the pilot signal to obtain a channel characteristic value (), changes in the timing of the Fourier transform are detected (), and on the basis of the detected result, interpolated data are generated () by selection or interpolation in the time direction, using the channel characteristic values as the original data. The decoding error rate after equalization when the timing of the Fourier transform changes is lowered, and receiving performance is improved.

Apparatus and method for receiving an orthogonal frequency division multiplexed signal

A diversity receiver is provided with antennas () and () in a first branch and antennas () and () in a second branch each of which antenna gains is controlled so that the offset between the directions of directional radiation patterns for the first and second branches becomes approximately &#x3c0;/2. Thereby, the diversity receiver can obtain a sufficient diversity gain even when it is incorporated into an indoor television with the antennas being built thereinto in close vicinity to one another.

Diversity receiver

A delay profile generating circuitgenerates a delay profile signal. Concerning the delay profile signal, a ghost decision circuitmakes a decision as to the presence or absence of ghosts that will appear during traveling of a mobile vehicle in response to a transmission mode signal fed from a changeover switch. The delay profile signal and the decision signal about the presence/absence of the ghosts are delivered to a window control circuitvia an accumulator. The window control circuitsets and controls the FFT window position of an FFT circuitin response to a guard correlation signal fed from a guard correlation signal generating circuitand a signal fed from the accumulator

Digital broadcasting receiving apparatus with channel estimation function

The present invention relates to a OFDM signal receiver device that performs weighting for branch metrics based on average noise power or signal-to-noise power ratio and conducts Viterbi decoding based on the result of the weighting. In the present invention, based on a demodulated signal, electric power corresponding to a noise component contained in the demodulated signal is calculated. A noise power signal corresponding to the result of the calculation is output from a noise power-calculating unit. Based on the noise power signal and a transmission channel characteristic corresponding to a subcarrier component that is output from an interpolation filter unit, a weighing factor for a branch metric is calculated by a weighting factor-calculating unit, and based on the weighting factor, the demodulated signal is decoded by decoding unit

OFDM signal receiver device and OFDM signal receiving method

The present invention relates to a demodulation device and a demodulation method, and its object is to demodulate subcarrier components utilizing estimated delay profiles to control the timing for performing a Fourier transform and the pass band of an interpolation filter used in interpolating transmission channel characteristics along a frequency axis so as to suppress unnecessary noise components, whereby an error rate after the demodulation is reduced. To achieve the object, in a demodulation device according to the present invention, a Fourier transform unitperforms a Fourier transform according to a timing signal and an interpolation filter unitsets a pass band of a frequency interpolation filter used for interpolation along the frequency axis based on a signal corresponding to a maximum delay time, whereby the frequency band of a transmission channel characteristic corresponding to a subcarrier component is restricted when it is output.

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Tokyo, Japan

Jun Ido