Kokusai Denshin Denwa Kabushiki Kaisha

Kokusai Denshin Denwa Co., Ltd.

Hidetaka Yanagidaira

Michitoshi Tamori

Katsuhiko Furuya

Sotokichi Shintani

Kazuo Kawai

Hideo Kobayashi

Hiroshi Sakaki

Hisakichi Michishita

An automatic amplitude and phase equalization system in an FM communication circuit, in which a pilot signal included in a baseband signal of a transmitted FM signal demodulated by an FM demodulator is extracted and frequency-multiplied, a high harmonic wave of the pilot signal generated in the baseband signal is phase-detected using the frequency-multiplied output as a reference signal, an amplitude equalizer provided before the FM demodulator is driven by a component included in the phase detected output and of the same phase as the reference signal, and a phase equalizer provided before the FM demodulator is driven by a component included in the phase detected output and orthogonal to the reference signal, whereby amplitude and phase characteristics of a transmission path of the FM signal are automatically equalized.

Automatic equalization system in FM communication circuit

A smear filter and/or a de-smear filter having the characteristics that the delay time is proportional to the frequency comprising (a) a transversal filter having a plurality of delay elements connected in series with one another, the delay time (T) of each delay element being the same as the sampling interval of the input signal, the first delay element being connected to the input terminal, a plurality of potentiometers each connected to the junction points of said delay elements and the output of the last delay element providing the tap weight to each of the tap output, and an adder for providing the sum of the outputs of said potentiometers to provide an output of the present delay circuit, (b) a digital memory storing the precalculated value for each desired delay characteristics for providing the tap weights of said potentiometers, and (c) means for providing the content of said digital memory selectively to the potentiometers according to the desired delay characteristics.

Delay circuit

A transversal type automatic equalizer comprises a transversal filter having a plurality of taps separated by time delay intervals, said transversal filter receiving input signals from a transmission line, a plurality of potentiometers being connected to each of said taps to provide a tap weight and the outputs of the potentiometers being summed up to provide an equalized output signal, and said potentiometers being adjusted by an equalization arithmetic unit. The potentiometers and thereby the tap weights are adjusted according to the output of the arithmetic unit whereby an equalized output with a suppressed ripple characteristic is produced.

Transversal type automatic equalizer

A Bessel function type automatic delay equalizer comprising a plurality of transversal filters each of which has an independent delay cosine equalization component having a predetermined period, and the superposition of those filters providing the desired characteristics, characterized in that, said equalizer further comprises a Bessel function generator for controlling the tap gain of said transversal filters.

Bessel function type automatic delay equalizer

A system for demodulating digital phase-modulated wave having signal elements of constant length by detecting in a detector the signal wave elements during every period of substantially the constant length, in which a combining circuit is further provided for estimating digital information content of the signal wave elements by the use of a combined output of detected results obtained by sequentially detecting, the information content of successive two of each signal wave element of the detected output of the detector, so that a demodulated output is obtained by selecting one of the outputs of the detector or the combining circuit.

System for demodulating a digital modulated wave

A system for detecting the signal quality of a phase-modulated wave, in which the phase positions of the signal elements of the digital phase-modulated wave are each detected with respect to a reference phase carrier by a phase detector for developing digital output signals composed of higher digits representing the ideal quantized phase positions of the phase-modulated wave signal elements and at least one lower digit representative of the direction of phase deviation of the signal elements from the ideal quantized phase positions so that the lower digit is taken out as signal quality information of the phase-modulated wave.

Growing community of inventors

Omiya, Japan

Hidetaka Yanagidaira