Nec Corporation

Shinichi Koike

Tetsu Koyama

Seiichi Noda

Tomohiro Miyazaki

A modulation and demodulation system capable of minimizing a bit error rate in a six-phase phase modulation method. A senary signal phase-modulated and outputted by a modulator is received and phase-modulated by a destination demodulator to a binary signal before conversion by the modulator. The modulator assigns (0, 0), (0, 1), (0, 2), (1, 2), (1, 1) and (1, 0) which are senary signals (b, t) to first to sixth phases respectively. The demodulator performs a conversion process from the senary signals to the binary signals, for instance, by storing transmitted senary signals and sequentially converting every senary signal of length m to binary signal of length b so as to output them. The process of the demodulator assigns the first to sixth phases as the senary signals (b, t) to (0, 0), (0, 1), (0, 2), (1, 2), (1, 1) and (1, 0) respectively.

Modulation and demodulation system, modulator, demodulator and phase modulation method and phase demodulation method used therefor

An adaptive filter, employing an adaptively controlled forgetting factor, includes a first circuit for determining a gradient of an error signal and a second circuit for determining a value of the forgetting factor. The value of the forgetting factor is updated based on comparing the gradient of the error signal to the forgetting factor. Equations to update the forgetting factor may be solved using a recursive least squares algorithm. Comparing the gradient of the error signal to the forgetting factor may include, for example, dividing the error signal gradient by a compliment of the forgetting factor. A method for updating the forgetting factor includes determining the gradient of the error signal, determining a value of the forgetting factor, and updating the value of the forgetting factor based on comparing the gradient of the error signal to the forgetting factor. The forgetting factor may be stored in the adaptive filter.

Adaptive filter employing adaptively controlled forgetting factor and adaptively controlling method of forgetting factor

An adaptive filter, a control method of the adaptive filter, and a storage medium storing therein a program for executing the control method thereof enable a tap weight control method to be provided in order to realize high speed convergence of an adaptive filter using sign-sign algorithm. The adaptive filter having a non-recursive filter obtains a correlation value in such a way that a sum between an error signal and an additive noise is multiplied by a value in every respective taps of input signal. The correlation value undergoes operation of a correlation non-linear processor to obtain a value. Such the value is multiplied by a step gain. An obtained product is utilized for updating above described respective tap weight coefficients. It causes a power-number of a power function to be controlled according to an estimated value of an electric power of the error signal while taking the non-linear function of the correlation non-linear processor to be the power function of the correlation value. The estimated value is obtained in such a way that it causes average value of the correlation value to be calculated by a leakage accumulator before squaring the average value.

Adaptive filter, control method of adaptive filter and storage medium storing therein program thereof

A FSK code with reduced high frequency content is generated. First through fourth waveforms are provided to a selector which selects one of the four waveforms in accordance with a control signal which, in turn, is generated in accordance with a state indication signal identifying the presently selected one of the four waveforms. A D/A converter converts the selected digital waveform data to an analog waveform signal. First and second of the digital waveform data represent +sin .theta. and -sin .theta., and third and fourth of the digital waveform data represent +f(.theta.) and -f(.theta., respectively, where ##EQU1## wherein 0.ltoreq..theta..ltoreq.2.pi. and a, b and c are nonzero coefficients.

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Tokyo, Japan

Shinichi Koike