Mitsubishi Denki Kabushiki Kaisha

Toshiharu Kojima

Seiji Okubo

Tatsuya Uchiki

Akinori Fujimura

Takashi Asahara

Makoto Miyake

Mari Matsunaga

Hiroyasu Sano

Nobuhisa Kataoka

Akinori Fujimora

A demodulator in a receiver has a multiple symbol differential phase detector which calculates phase differences between a received signal and received signals of 1, 2, . . . , N (Where N is an integer greater than 2) before so as to output the calculated results as N symbol differential phase detected signals. Further, a soft decision sequence estimating unit in this demodulator estimates a transmitted differential phase sequence according to the 1, 2, . . . , N symbol differential phase detected signals using a trellis diagram representing transitions of differential phase states of a transmitted signal and Viterbi algorithm and estimates soft decision demodulated data according to estimated transmitted differential phase sequence and the survival path metrics that transit into each state on the trellis diagram.

Demodulator, receiver, and communication system

A spread spectrum transmitter provides delays having different magnitudes to spread spectrum (SS) signals for a plurality of channels, and multiplexes the SS signals to generate transmission multiplex SS signal. A spread spectrum receiver calculates a partial correlation value between the transmission multiplex SS signal and spreading codes multiplied to the SS signals, multiplies the partial correlation values by a prescribed matrix prepared based on each orthogonal code sequence to calculate a plurality of orthogonal correlation values. The receiver identifies for a respective channel each parallel data sequence related in advance to an orthogonal code sequence whose orthogonal correlation value is a maximum, corrects delay differences of the parallel data sequences, and then performs sampling and parallel-serial conversion to obtain a serial demodulated data sequence.

Spread spectrum transmitter and spread spectrum receiver

The demodulator of the invention includes a DSP. The DSP determines the distortion amount of the transmission channel based on known signals included in a radio receiving signal, and estimates the frequency of the direct wave based on the distortion amount. Furthermore, the DSP rotates the phase of the distortion amount based on the phase amount corresponding to the estimated frequency of the direct wave. Next, the DSP estimates the center frequency of the Doppler spread based on the distortion amount after the phase is rotated. Furthermore, the DSP synthesizes the phase amount corresponding to the estimated center frequency of the Doppler spread and the phase amount corresponding to the frequency of the direct wave to estimate the last frequency offset. Thereafter, the DSP eliminates frequency offset of the radio receiving signal based on the estimated frequency offset. Thereby, a sufficient frequency offset compensating range can be secured, and excellent BER characteristics can be realized.

Method and apparatus for automatic frequency control and demodulator

A spread spectrum transmission apparatus includes, a chip clock generation section which outputs a chip clock in one frame formed of M+L&#x2212;1 chips, a frame clock generation section which outputs a frame clock synchronized to frame occurrence timing, SS-PPM signal generation sections each of which inserts a pseudonoise code sequence corresponding to one period from some of M chips located at a head of a frame based on K-bit transmission data and generates an SS-PPM signal, delay sections which respectively delay N SS-PPM signals respectively by determined delay quantities, and a multiplexing section which adds up all of outputs respectively of the delay units and generates a multiplexed SS-PPM signal.

Spread spectrum transmission apparatus, spread spectrum reception apparatus, and spread spectrum communication system

A base band signal is sampled, based on an asynchronous sampling clocking, to output two sampled data series. A transmission side complex symbol frequency generator generates a complex transmission symbol frequency component combining an envelope value and an amplitude change amount value, which are each calculated from the two sampled data series. The transmission side complex symbol frequency component is provided to a correlation value calculator that outputs a correlation data series correlated to the complex symbol frequency and the symbol frequency generated by a cosine wave generator. The correlation data series is converted a timing error by an inverse tangent calculator. By the above configuration, a timing reproducing unit, which includes the above components, determines the timing error at a sampling speed of twice the symbol rate.

Method and apparatus for reproducing timing, and a demodulating apparatus that uses the method and apparatus for reproducing timing

There are provided a spread code generating section generates a spread code list from the input parallel information, spread modulating sections generate a plurality of parallel spectrum spread signals corresponding to the parallel information list by multiplying each of the parallel information list and the spread code list respectively, phase shifting sections shift the phase of the parallel spectrum spread signals, delay sections delay the parallel spectrum spread signals. A multiplexing section generates a multiplexed spectrum spread signal by adding the delayed parallel spectrum spread signals. The multiplexed spectrum spread signal are converted into a radio frequency signal, amplified and then transmitted.

Spread spectrum communication system and method for the same

In-phase and orthogonal components of a base band signal having a preamble symbol are squared to obtain squared in-phase orthogonal components. Amount of correlation is obtained between the squared in-phase component and a symbol frequency component output from a VCO or an oscillator, and amount of correlation is obtained between the squared orthogonal component and the symbol frequency component. Finally, a phase control signal for carrying out a phase control is generated by using the obtained amount of correlations.

Timing reproducing device and demodulator

A timing recovery device and demodulator. An adding device adds together an in-phase component and a quadrature component of a base band signal. A subtracting device subtracts the in-phase component and the quadrature component of the base band signal from each other. Then, the correlation between the added signal and a &frac12; symbol frequency component generated at the receiver side and the correlation between the subtracted value and the &frac12; symbol frequency component are calculated. A vector selector compares the added value correlation signal and the subtracted value correlation signal, and selects the larger one of the correlation signals. A timing phase difference calculator then calculates a timing phase difference, using the vector angle indicated by the selected correlation signal.

Timing reproducer and demodulator comprising this

A transmitting side periodically inserts a known signal consisting of successive N symbols into an information signal consisting of (N &minus;N ) symbols and transmits the N symbol signal. The receiving side receives the N symbol signal, and automatically controls a frequency by estimating a frequency deviation from the incoming signal. More specifically, the receiving side outputs I and Q-channel analog baseband signals from the received incoming signal as well as from a sinusoidal signal outputted from an oscillator, and converts the analog baseband signals to the digital baseband signals. Then a phase difference for one symbol cycle is estimated from the digital baseband signals, integration processing is executed by iterative addition of the estimated values, and the frequency deviation is eliminated from the digital baseband signals using a result of the processing for integration.

Automatic frequency control apparatus

A typical Viterbi decoder having a coherent detection function suffers from degraded performance under certain fading-induced phase shift conditions when used in a time diversity system. This problem is resolved by providing a demodulator for demodulating a data sequence multiplexed by multiplexing a plurality of data sequences of a same content with a time difference inserted therebetween for a time diversity system, which comprises: a phase correction unit for phase correcting the multiplexed data sequence; a diversity combiner for demultiplexing the multiplexed data sequence output from the phase correction unit into a plurality of data sequences, removing the time difference inserted between data sequences, and combining the data sequences; and a Viterbi decoding unit for Viterbi decoding the diversity combined signal from the diversity combiner.

Demodulator and communications system

In a DLL, in-phase correlation signal and orthogonal correlation signal are squared and adder to generate correlation power. Delays are provided so that the peaks of N number of divided correlation power portions to have coincided timing with each other. Composite correlation power is generated from the respective correlation power portions. A composite error signal of a sample clock is generated by subtracting the composite correlation power from the composite correlation power that has been delayed. A data clock is generated by frequency-dividing the sample clock based upon an acquisition pulse. A sample clock is finally generated based upon the composite error signal that has been latched and noise-removed therefrom in synchronized timing with the data clock that has been delayed.

Delay lock loop, receiver, and spectrum spreading communication system

An adaptive array communication system includes an adaptive control unit ( ) which performs a weighting process by multiplying received signals from a plurality of antennas by complex weights which are different from each other for respective states to combine the received signals, a decoding unit ( ) which calculates a metric corresponding to a transition to a desired state, and an error vector calculation circuit ( ) which calculates an error vector for calculating complex weights which are different from each other for the respective states.

Adaptive array communication system and receiver

In a communication system using the time diversity transmission scheme, the communication system provided with the stable automatic frequency control circuit with the wide frequency pull-in range and under low CN ratio transmission is achieved by removing the modulation phase from the received data through the application of the data correlation of the time diversity. The frequency offset in the received signal is compensated as the phase rotator rotates the phase of the received signal, the phase converter converts the phase rotator output into a phase, the serial-to-parallel converter converts the phase converter outputs into serial-to-parallel sequence, the delay units gives a delay to the serial-to-parallel converter output, the phase adder adds the serial-to-parallel converter output to the delay unit output, the multiplier multiplies the phase adder output by a certain value, the integrator integrates the multiplier output, another integrator integrates the integrator output, and the phase rotator controls the phase of the received signal based on the other integrator output.

Automatic frequency control communication system

In the present invention, the amplitude subtracting type of phase detector of the timing recovery section outputs a difference &ggr; of a synthesized amplitude deviation at &frac12; of a symbol time. The averaging section computes an average value of this difference &ggr; and outputs a phase control signal V corresponding to the average value to the phase controller. The phase controller controls a timing phase of the sampling clock according to this phase control signal V . Dichotomizer generates a recovered symbol clock by dichotomizing the sampling clock that has been timing phase controlled. Removal of DC offset from and demodulation of the sampled baseband signal is executed in parallel to the above processing using the recovered symbol clock with the Nyquist data extracting section, the offset detector, the offset correcting section, and the data determining section.

Phase detector, timing recovery device using the same, and a demodulator using the timing recovery device

An automatic frequency controller includes a frequency offset estimating section that calculates phase distortion quantities and the average thereof from known signals contained in a received signal. The frequency offset estimating section obtains, from the average distortion quantity, signal powers corresponding to a plurality of candidate frequency offsets set at frequency offset estimation accuracy intervals in a frequency offset estimation range. The frequency offset estimating section looks at the signal powers through a frequency window with a frequency width corresponding to a transmission path state. This makes it possible to maximize the signal power of a frequency of a radio wave or radio waves corresponding to the transmission path state, and to place the radio wave or radio waves corresponding to the transmission path state as a frequency controlled object. This can improve demodulation accuracy. Fine adjustment of the candidate frequency offsets can improve the estimation accuracy of the frequency offset without changing the frequency offset estimation range.

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Tokyo, Japan

Toshiharu Kojima