Kokusai Denshin Denwa Co., Ltd.

Kokusai Denshin Denwa Kabushiki Kaisha

Michitoshi Tamori

Hidetaka Yanagidaira

Sotokichi Shintani

Kazuo Kawai

Hideo Kobayashi

Katsuhiko Furuya

Hiroshi Sakaki

Hidemi Kuroda

Nobuo Nagai

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

In a sampling function type equalizer having a transversal filter with a plurality of potentiometers, the tap weights of the transversal filter are adjusted according to the desired values of the amplitude-frequency characteristics A.sub.p (n), and the delay-frequency characteristics .tau..sub.p (n). The first multiplication of A.sub.p (n) and the predetermined discrete function in addition to the second multiplication of said .tau..sub.p (n) and said predetermined discrete function, are performed. Also, the Bessel function is provided according to the product of the second multiplication. The first convolution integration is performed for the product of the first multiplication, the second convolution integration is performed for the output of the Bessel function, and the third convolution integration is performed between the results of said first and the second convolution integrations. The result of the third convolution integration provides the tap weights of the potentiometers of the transversal filter.

Sampling function type equalizer

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

In a delay equalizer having a plurality of quadratic all pass networks for equalizing the delay characteristics of a circuit, the automatic adjustment of the value of Q of each quadratic all pass network when calculated through the asymptotic formula ##EQU1## CAN PROVIDE PERFECT DELAY EQUALIZATION, WHERE Q.sub.i.sup.k is the value of Q of the i'th quadratic all pass network, and .alpha..sub.i is the step size parameter of i'th quadratic all pass network. Before applying said formula, the delay of the circuit to be equalized at the center frequency of each quadratic all pass network is measured, and said formula is calculated according to the result of the measurement.

Method for automatically equalizing the delay characteristics of a

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

An equalizer having improved amplitude characteristics and phase characteristics of more than several hundred MHz has been found by using a four port directional coupler. The equalizer consists of coupled lines, and two far end ports of the directional coupler are grounded through two resistances R.sub.1, respectively; while interconnecting the two far end ports through a resistance r, an input port is formed at one of the near end ports of the directional coupler, and an output port is formed at the other end thereof, said resistances substantially satisfying the relation of

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Tokyo, Japan

Michitoshi Tamori