Kabushiki Kaisha Toshiba

Hidehiro Matsuoka

Hiroki Shoki

Hideo Kasami

Yasushi Murakami

Makoto Tsuruta

Ichiro Seto

Akihiro Tsujimura

Osamu Shibata

Yong Sun

Tatsuhisa Furukawa

Kazumi Sato

Tsuguhide Aoki

Shuichi Obayashi

Masami Aizawa

Hisao Iwasaki

The channel estimator includes a plurality of correlating sections configured to calculate a plurality of time correlation values between the signal and a plurality of known pattern signals having different code lengths, an analyzing section configured to output a control signal representing a selected period for extracting a preferable correlation output from the output from each of the plurality of correlating sections, and a delay profile generating section configured to output a delay profile obtained by adaptively selecting or combining parts of the outputs from the plurality of correlating sections based on the output from the analyzing section.

Channel estimator

A frequency error detecting circuit includes: an oscillator; a frequency converting unit for a received signal on the basis of the oscillation output and output the received signal; a time-to-frequency converting unit configured to convert the output of the frequency converting unit into a frequency domain signal; a frequency shift determining unit configured to determine presence or absence of a frequency shift between an output frequency of the frequency converting unit and a predetermined carrier frequency; and a control unit configured to repeat frequency conversion processing and time-to-frequency conversion processing while controlling an oscillation frequency of the oscillator on the basis of a determination result of the frequency shift determining unit and cause the output frequency of the frequency converting unit to converge on a predetermined value to thereby detect a frequency error between the frequency of the received signal and the predetermined carrier frequency.

Frequency error detecting circuit, frequency error detecting method, and frequency correcting circuit

An OFDM receiver apparatus mounted on a movable object for receiving an OFDM signal, includes a plurality of directional antennas which receive an OFDM signal, an estimator to estimate a center frequency of a spectrum of a Doppler component from one of the received signals or a multiplexed signal obtained by multiplexing the received signals, a shift quantity calculator to calculate a shift quantity from the estimated center frequency of the estimator and directivity information representing directivity directions of the directional antennas, a plurality of frequency shifters to subject the received signals to frequency shift according to the shift quantity to compensate for Doppler shift, a combining unit to diversity-combine frequency shifted signals of the frequency shifters, and a demodulator/decoder to demodulate and decode combining diversity signals of the combining unit.

Orthogonal frequency division multiplexing (OFDM) receiver

An OFDM demodulator that demodulates an OFDM signal includes an antenna that receives a signal including delayed signals, an estimation circuit that estimates the channel response of the received signal, and a control circuit that controls a length of a retention time interval based on the estimated channel response. The retention time interval includes a time period from the head of a delayed signal having a maximum delay time in the delayed signals to the tail of a preceding signal in the delayed signals based on the estimated channel response. The OFDM demodulator also includes a retention memory that retains a portion of the received signal corresponding to the retention time period, and a selection circuit that selects an OFDM symbol based on a calculation of a maximum likelihood that the retained received signal is equivalent to a signal replica based on the channel response.

Orthogonal frequency division demodulator, method and computer program product

Orthogonal frequency division multiplexing demodulation apparatus includes: antenna to receive signal including holding period including part of period ranging from leading portion of delayed wave of maximum-delay time to trailing portion of preceding wave, unit estimating channel response of signal received by antenna, unit holding, based on channel response, first-signal component contained in holding period, first-signal component including second-signal component which is contained in period of preset length which is included in holding period, unit acquiring filter-bank outputs by subjecting second-signal component to frequency conversion, unit generating replicas for each of filter-bank outputs, based on estimated-channel response, frequency response of each of filter-bank outputs, and candidates for modulation signal corresponding to subcarrier included in each of filter-bank outputs, unit selecting one of replicas which minimizes quantity corresponding to differences between components of each of filter-bank outputs and components of replicas, and unit determining modulation signal based on selected replica.

OFDM demodulation apparatus, method and computer readable medium

There is disclosed a radio communication system in which a constitution of a base station and further a control station can be simplified. A radio communication system according to the present invention converts a received signal received by a plurality of antenna elements in a base station to a signal of different frequency band, and then conflates the converted signal in order to generate sub-carrier wave multiplex signal. The signal is converted to an optical signal, and then the optical signal is transmitted to a control station via an optical fiber. Or the control station performs weighting to phase of the transmitted signal transmitted from a plurality of antennas of a base station, and then performs frequency conversion to different frequency band, and then conflates the converted signal in order to generate the sub-carrier wave multiplex signal. The signal is converted to an optical signal, and then an optical signal is transmitted to the base station side via the optical fiber. The control station and the base station divides the received sub-carrier wave multiplex signal by each frequency band, and then the frequency of the divided signals are converted to the same frequency band in order to generate the transmitted/received signal of each antenna element. By such a constitution, it is possible to reduce constituent of the optical transmission components to the minimum and to simplify the constitution of the base station. Furthermore, it is possible to maintain the relative phase difference and the relative intensity of the transmitted/received signal of each antenna element. Because of this, it is possible to estimate an arrival direction of the received signal and to control radiation beam pattern of the transmitted signal.

Radio communication system

A received signal selector for a received signal, the received signal including a set of carriers, the received signal selector being configured for use with an antenna system including a plurality of antenna elements. The received signal selector includes a plurality of received signal inputs for receiving signals from the plurality of antenna elements, an interference detector for each of the received signals inputs, coupled to the received signal inputs to receive, from each input, a version of the received signal, and configured to provide an interference output for the set of carriers from each input, a selection controller configured to receive the interference output for each input and having a control output, and a selector coupled to the received signal inputs and responsive to the control output to select one or more of the versions of the received signal for output. The invention provides a simplified technique for mitigating the effects of co-channel interference and severe multipath distortion.

Signal selection systems

A receiver comprising: an antenna which receives a radio signal including N possible symbols {c, c, . . . c, c}, an N correlation units which are provided corresponding to the N possible symbols, respectively, each correlation unit detecting the degree of correlation with the radio signal received by the antenna, and a symbol determination unit which determines the symbol included in the radio signal received by the antenna based on the degree of correlation detected by the N correlation units. The N correlation units detect the degree of correlation between the radio signal received by the antenna and the N possible symbols represented by M chips {&#x3b1;c, &#x3b1;c+&#x3b1;c, . . . , &#x3b1;c+&#x3b1;c, &#x3b1;c+&#x3b1;c}.

Receiver and wireless LAN apparatus in which a received signal is correlated to a reference symbol

Antenna techniques particularly for orthogonal frequency division multiplexed (OFDM) communications systems. A signal processing system determines weights for an adaptive antenna, the antenna including plural antenna elements each receiving a signal including plural subcarriers. The system includes plural inputs for receiving signals from the antenna elements, a time-to-frequency domain transformer for each input for transforming the signal from each input to a plurality of subcarrier signals, a first weight determiner coupled to the inputs, before the time-to-frequency domain transformer in the signal path, and configured to determine a first set of weights, one for each input, and a second weight determiner coupled to the first weight determiner and configured to determine, from the determination of the first set of weights, at least one second set of weights including a frequency-domain weight for a subcarrier signal derived from each of the inputs.

Antenna signal processing systems

A beam formation circuit and an apparatus and a method of receiving radio frequency signals making use of a smart antenna are described in which the amount of computation tasks required for the weight calculation is significantly reduced. In realizing the directivity of the smart antenna, the output signals corresponding to a plurality of sub-carriers are weighted with a common antenna weight for each of the antenna elements.

Use of smart antenna in beam formation circuit

In a radio communication apparatus, delay profiles of a desired wave and delay waves thereof are estimated by plural delay profile estimation sections for each of received signals from directional antennas constituting an array antenna. Received signals from the antennas selected by a reception antenna selector on the basis of the delay profile are subjected to a temporal/spatial equalization processing by an adaptive signal processing section and a path diversity combining section, thereby obtaining a reception output. An arrival angle range of the desired wave is estimated by a DOA estimation section from the delay profile estimated by the delay profile estimation section. Based on the arrival angle range, the antenna for transmission is selected by a transmission antenna selection section, and transmission signals are sent out.

Radio communication apparatus using adaptive antenna

A patch having a circular shape for instance is formed on the main surface of a substrate in the shape of, for example, an equilateral triangle. The center of the main surface of the patch is at a position different from the center of the substrate. A grounding conductor is disposed on the backside of the substrate. Power is supplied to the patch through, for example, a microstrip line, triplate line, coplanar waveguide, slot line or the like. An antenna configured as described above has the center of the patch at a position different from the center of the triangle substrate, so that beams can be tilted in a desired direction by a single patch and a single feeder circuit.

Antenna capable of tilting beams in a desired direction by a single

An adaptive antenna is disclosed, that comprises a plurality of antenna elements 1.sub.1, 1.sub.2, . . . , and 1.sub.N with different directivity, delay profile measuring units 2.sub.1, 2.sub.2, . . . , and 2.sub.N for estimating states of received signals of the antenna elements for each of delay times that have been designated, antenna selecting units 3.sub.1, 3.sub.2, . . . , and 3.sub.L for selecting a part of the antenna elements for each of the delay times corresponding to the estimated result, adaptive signal processing portions 4.sub.1, 4.sub.2, . . . , and 4.sub.L for determining the received signals of the part of the antenna elements that have been selected and multiplying the received signals to which relevant weights have been determined for each of the delay time and summing the weighted signals, delaying circuits 5.sub.2 and 5.sub.3 for compensating the time lag, or delay of each of the received signals for each of the delay times, and a combining unit 6 for combining the weighted signals that have been compensated for the delay times.

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Yokohama, Japan

Hidehiro Matsuoka