Abstract: A frequency converter includes a multiplying circuit, a load circuit, and an output buffer circuit. The multiplying circuit is arranged to multiply an RF signal and an LO signal and output a difference frequency signal with a frequency, which is the difference between the frequencies of the two signals, from its output terminal. The load circuit is arranged to connect the output terminal of the multiplying circuit to a power supply. The output buffer circuit is arranged to have an input terminal connected to the output terminal of the multiplying circuit, and an output terminal for outputting a signal to the next stage. A notch circuit for removing an undesired signal frequency component is combined in the load circuit. The notch circuit has an impedance characteristic in which the impedance is abruptly reduced to provide a valley point at the undesired signal frequency.

Abstract: A surface-treated steel sheet includes a steel sheet, an Al—Zn-base alloy plating layer formed on the steel sheet, a chemical conversion film provided on the alloy plating layer, and a concentric layer of a Cr compound that is formed on the alloy plating layer of the chemical conversion film. The surface-treated steel sheet may include a steel sheet, an zinc-base plating layer formed on the steel sheet, and a film that contains chromium and calcium and that is formed on the zinc-base plating layer.

Abstract: A variable gain amplifier comprises a main amplifier circuit whose gain is controllable and which amplifies a difference signal between an input signal and a feedback signal, a feedback amplifier circuit whose gain is controllable and which amplifies an output signal of the main amplifier circuit, and a gain control circuit which complementarily control the gain of the main amplifier circuit and the gain of the feedback amplifier circuit.

Abstract: In a master block, the exponential conversion characteristic is determined on the basis of a common mode reference voltage and a reference voltage. In a slave block, the exponential conversion characteristic determined with the master block is used to create a control voltage and a gain control signal on the basis of a common mode reference voltage and a reference voltage. For example, a gain of the variable gain amplifier is controlled by using this gain control signal.

Abstract: A variable gain amplifier device controlled by a first gain control signal comprises a gain controlled amplifier having a gain and including a differential pair of first and second MOS type transistors configured to operate in a weak inversion region; and a control signal converter configured to convert the first gain control signal into a second gain control signal, and supply the second gain control signal to the gain controlled amplifier to exponentially vary the gain with respect to the first gain control signal.

Abstract: A frequency converter including a mixer circuit which inputs a local oscillation signal and a radio-frequency input signal modulated for communication of information, and performs frequency conversion. A buffer amplifier is higher than a desired signal frequency band, and has a low-pass passage characteristic of cut-off frequency lower than an adjacent channel carrier frequency.

Abstract: A variable gain amplifier comprises a main amplifier circuit whose gain is controllable and which amplifies a difference signal between an input signal and a feedback signal, a feedback amplifier circuit whose gain is controllable and which amplifies an output signal of the main amplifier circuit, and a gain control circuit which complementarily control the gain of the main amplifier circuit and the gain of the feedback amplifier circuit.

Abstract: An active array antenna system comprises a plurality of element antennas and radio frequency circuits connected to the element antennas. The radio frequency circuits comprises first frequency converters provided to correspond to the element antenna and converts the frequency between a carrier-wave frequency and a first intermediate-frequency by using a carrier-wave frequency band local signal, second frequency converters provided to correspond to the element antenna and converts the frequency between the first intermediate-frequency signal and a second intermediate-frequency which is lower than the first intermediate frequency by using an intermediate-frequency band local signal, and a variable phase shifter circuit for individually controlling the phases of the intermediate-frequency local signals which are supplied to the second frequency converters.

Abstract: By disposing the first filter circuit and the second filter circuit whose connection structures are the same and whose element values are different on an integrated circuit, a phase shifter with output signals whose frequency characteristics and errors of phase shift characteristics equally vary can be accomplished.

Abstract: A frequency converter includes: a signal synthesizer element for inputting first and second input signals to synthesize these signals and for outputting a synthesized signal, from which noises even times as large as the frequency of the second input signal are removed; an amplitude limitation amplifier element, composed of a differential amplifier circuit, for amplifying the synthesized signal outputted from the signal synthesizer element to output an amplified signal having a constant amplitude; and a filter for inputting the amplified signal outputted from the amplitude limitation amplifier element, to remove an unnecessary signal component to produce an output a baseband signal including only a desired signal component.

Abstract: A variable-gain amplifier circuit has an offset correcting function by which the fluctuation of offset due to the switching of a gain is decreased. In an offset detection mode, an input offset voltage of the variable-gain amplifier circuit is inputted to an offset retaining section, and in a signal amplifying mode, the offset is corrected by subtracting the output of the offset retaining section from an input signal by means of an input section of the variable-gain amplifier circuit. In addition, the variable-gain amplifier circuit can be applied to a radio receiver. The offset produced in a baseband section of a receiver is corrected by the offset correcting function of the variable-gain amplifier circuit, so as to prevent the quality of communication from being deteriorated.

Abstract: An A/D converter apparatus comprising a negative feedback loop having a main signal line supplied with an input signal of a predetermined frequency and a feedback signal line passing through a feedback signal, a A/D converter connected to the main signal line for frequency-converting the input signal to a signal having a frequency different from that of the input signal to output a converted signal, a D/A converter connected to the feedback signal line for frequency-converting the feedback signal to a signal having a frequency substantially equal to that of the input signal, and a subtracter for subtracting the feedback signal from the D/A converter from the input signal to supply a subtraction result signal to the A/D converter.

Abstract: In a modulator, a linear converter inputs modulation signals and feed-back signals as an input vector and linearly converts the input vector. An encoder vector-quantizes the linearly converted vector and outputs the resultant signals as selection signals. A vector decoder decodes the encoded output into the plurality of feed-back signals. A selector selects and outputs one of signals with the same frequency and different phase or amplitude according to the selection signals.

Abstract: In an amplitude modulator, a delta sigma modulator converts a digital or analog modulation signal into a binary signal. The binary signal and a carrier signal are sent to a multiplication circuit. The phase of the carrier signal is changed to normal phase or opposite phase. The resultant carrier signal is output as an amplitude modulation wave. An orthogonal modulator sends a local oscillation signal to a phase shifter. The phase shifter outputs two carrier signals with phases which differ by 90.degree. each other. The modulation signal and carrier signals are sent to the amplitude modulator. The amplitude modulator outputs an amplitude modulation signal. These signals are sent to an analog signal composing unit. The analog signal composing unit composes the input signals and outputs an amplitude and phase modulation signal.

Abstract: A frequency converter includes a high-frequency signal input circuit for forming a high-frequency signal with bias voltage or current to output a bias-added high-frequency signal; a local oscillation signal input circuit having a first element for forming a local oscillation signal with bias voltage or current and an element for suppressing a noise component having a frequency near a frequency of multiple of even number of a local oscillation frequency to output a bias-added and noise suppressed local oscillation signal; and a multiplication circuit for multiplying the bias-added high-frequency signal and the bias-added and noise suppressed local oscillation signal.

Abstract: In an amplitude modulator, a delta sigma modulator converts a digital or analog modulation signal into a binary signal. The binary signal and a carrier signal are sent to a multiplication circuit. The phase of the carrier signal is changed to normal phase or opposite phase. The resultant carrier signal is output as an amplitude modulation wave. An orthogonal modulator sends a local oscillation signal to a phase shifter. The phase shifter outputs two carrier signals with phases which differ by 90.degree. each other. The modulation signal and carrier signals are sent to the amplitude modulator. The amplitude modulator outputs an amplitude modulation signal. These signals are sent to an analog signal composing unit. The analog signal composing unit composes the input signals and outputs an amplitude and phase modulation signal.

Abstract: A multiplying circuit in which a pair of common-base transistors each having a small emitter area are inserted between the common emitter terminals of first and second differential amplifiers, which amplify a signal input to an input terminal pair and are connected in such a way as to cancel out their outputs which correspond to the input signal, and the output terminal pairs of multiple third differential amplifiers, which amplify a signal input to another input terminal pair and have a predetermined DC offset characteristic.

Abstract: A lubricant composition effectively enhancing the press-formability, and corrosion-resistance of a zinc-plated steel material and providing a superior, anti-powdering property and degreasing comprises (A) 70 -97% by weight of a lubricant component comprising the sub-components of (a) a succinate of a C.sub.12-18 aliphatic alcohol, (b) a paraffin wax with a melting point of 45.degree. C. -55.degree. C. and (c) a C.sub.12-18 fatty acid ester of C.sub.6-10 aliphatic alcohol and/or a mineral oil, the weight ratio ((a)+(b))/(c) being 1/3 to 1/1 and the weight ratio (a)/(b) being 1/3 to 4/1, and (B) 3 to 30% by weight of a rust-inhibiting component comprising a sulfonates with C.sub.16 or more, a carboxylic acid with C.sub.12 or more and/or a salt of the carboxylic acid, and has a melting point of 25.degree. C. to 40.degree. C. and an acid value of less than 2.0.