Nec Corporation

Nec Electronics Corporation

Shigeki Wada

Yasuyuki Suzuki

Yasuhiro Watanabe

Kenichi Hosoya

An equalization filter is provided for solving the problem in which there is a limited range in which compensated for distortion of a transmission signal can be made. Measuring instrumentmeasures a distortion quantity which characterizes distortion of the transmission signal. Comparatorgenerates a differential signal which indicates the difference between the transmission signal and a compensation signal. Delay devicedelays the differential signal based on the distortion quantity measured by measurement instrumentand generates the compensation signal.

Equalization filter and distortion compensating method

An equalizing filter circuit includes a first transmission line in which a plurality of first delay devicesare connected in cascade to input terminal, a second transmission line in which a plurality of second delay devicesare connected in cascade to output terminal, a plurality of weighting circuitsconnected in parallel between the first transmission line and the second transmission line and having a gain which is adjustable by setting coefficients, and variable adjusting circuitarranged at the output side of at least one of weighting circuitsfor correcting a fluctuation of the output characteristics of the weighting circuits.

Equalizing filter circuit

A clock and data recovery circuit including a phase synchronization loop including an oscillator, the oscillation frequency of which is variably controlled, the phase synchronization loop performing phase-synchronization of a clock signal output from the oscillator with an input data signal. The circuit also includes a discriminator circuit, responsive to a clock signal for discrimination, for discriminating the input data signal and outputting the discriminated signal. The circuit further includes a phase detector circuit for detecting the phase difference between an output data signal, discriminated and output by the discriminator circuit, and the input data signal. The circuit also includes a phase shift circuit for shifting the phase of the clock signal, output from the oscillator, based on a comparison result output from the phase detector circuit. The clock signal, which is output from the phase shift circuit, is supplied as the clock signal for discrimination to the discriminator circuit.

Clock and data recovery circuit

In an equalizing filter circuit having an input terminal, an output terminal, delay devicesconnected in multi-stage to the input terminal, and a plurality of weighting circuitswhich are branched from and connected to the plurality of delay devices to thereby combine respective output signals of the weighting circuits, gain adjustment of the weighting circuits is performed to determine a coefficient of the equalizing filter circuit without depending on a load connected to the output terminal. Thus, an amount of compensation for a distorted waveform may be enhanced. To this end, an impedance converting circuitis connected between at least one weighting circuit and the output terminal.

A voltage controlled oscillator of the present invention includes power supply terminal (), control terminal () for controlling an output frequency, output terminals (), cross-coupled transistors (), capacitances (), LC tanks (), resistor (), grounding capacitance () and center frequency control circuit (). Center frequency control circuit () includes resistors (), grounding capacitance (), center frequency control terminal () for controlling a center frequency of the output frequency, and voltage-divider circuit (). Resistors () are connected to the base terminals of cross-coupled transistors (), the other ends of resistors () are connected to each other, and, to this connecting point, one end of grounding capacitance () and one end of voltage-divider circuit () are connected. The other end of voltage-divider circuit () is connected to center frequency control terminal ().

Voltage controlled oscillator and frequency control method of the voltage controlled oscillator

A separation circuit part is used to separate an amplified signal path from a feedback signal path. An amplifier circuit part comprises a resistor-loaded common-source FET, a level adjustment diode and a source-follower circuit. The separation circuit part comprises a source-follower circuit, an output part of which is connected to a feedback circuit part comprising a resistor, thereby forming a feedback signal path to an input terminal of the amplifier circuit part. The signal separation circuit is used to separate the amplified signal path from the feedback signal path, thereby reducing the loads of the signal paths. In this way, the loads of the amplified signal and feedback signal paths are reduced. The delay time to be added in the separation circuit part is adjusted to cause the frequency range where the feedback changes from a negative feedback to a positive feedback to be coincident with the frequency range where the gain of the negative feedback amplifier part decreases, thereby realizing a wide band of gain.

Feedback amplifier having amplified signal path and feedback signal path separated

Method for manufacturing semiconductor device capable of improving etching rate ratio of insulator to refractory metal

In a method for manufacturing a semiconductor device, an insulating layer is formed on a semiconductor substrate, and a refractory metal is formed layer on the insulating layer. Then, a first opening is perforated in the refractory metal layer, and a part of the insulating layer is etched by using the refractory metal as a mask. Then, a second opening is perforated in the refractory metal layer. The second opening is superposed onto the first opening and is larger than the first opening. Then, the insulating layer is again etched by using the refractory metal layer as a mask, so that a T-shaped opening is perforated in the insulating layer. Finally, a modified T-shaped gate metal electrode is formed on the insulating layer having the T-shaped opening.

Method for manufacturing modified T-shaped gate electrode

In a method for manufacturing a semiconductor device, an insulating layer is formed on a refractory metal layer, and a contact hole in the insulating layer by a dry etching process using an etching gas includes one of: a mixture gas of fluorocarbon and hydrogen; a mixture gas of hydrofluorocarbon and hydrogen; a gas of hydrofluorocarbon; and a fluorocarbon gas except for CF.sub.4.

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Tokyo, Japan

Shigeki Wada