Abstract: A digital signal transmission system including a transmitter and a receiver and capable of transmitting highly efficiently compressed/coded digital video signals and receiving the video signals so that the text of emergency information or the like can be displayed together with video images without once expanding/decoding the digital video signals on the transmitter side. In this system, the multiplexer of the transmitter multiplexes digital video signals and digital audio signals with a digital information signal of text which is produced and has N-level priority information added by the information stream generator, and transmits the multiplex signal to the receiver.

Abstract: A sync signal generator of a television receiver for use in a vehicle has a phase reset detector for gradually absorbing a phase fluctuation of an input sync signal which occurs due to a ghost phenomenon or a fading phenomenon and reducing a phase fluctuation. The sync signal generator provides a sync signal synchronized with an output signal of the phase reset signal detector. Thus, a stable sync signal without a sudden change in phase can be obtained although it is synchronized with the input sync signal.

Abstract: A diversity reception apparatus which has a plurality of antennas and in which one of the antennas having the best receiving condition is automatically selected and connected to a broadcasting signal receiver. The diversity reception apparatus has a feature in that after demodulated signals, obtained by the receiver respectively corresponding to the plurality of antennas, are converted into digital signals by an A/D converter, the best demodulated signal and the antenna corresponding thereto are selected by comparing the digital signals with each other, and that the width of a switch driving pulse from a switch driving pulse generator is made not more than 3 .mu.s.

Abstract: A transmission distortion elimination device for eliminating from a transmitted TV signal, for example, signal distortion such as ghost under fuzzy inferenced control based on an iterative correction method with the capabilities of fast control settling, and a flexible and stable distortion removal operation. The device comprises a filter section for suppressing such transmission distortion as ghost, a controller for controlling the tap coefficients of the filter section, and a fuzzy inference section for receiving distortion information obtained by the controller. The fuzzy inference section iteratively infers and evaluates a correction value of tap coefficients of the filter section. The tap coefficient correction value is determined through fuzzy inference, and the control method for counteracting disturbance coefficients to the control system is described in rules of IF-THEN form based on fuzzy levels, which facilitates the organization of the control algorithm.

Abstract: A ghost elimination device equipped in a television receiver extracts a reference signal from the television signal, the reference signal being inserted in the television signal in a certain sequence or at random with the intention of ghost elimination, implements the sequence decoding process and noise elimination process for the reference signal, and controls the characteristics of the ghost eliminating transversal filter which suppresses the transmission distortion. The device includes a sequence decoding circuit for decoding the transmission sequence of the reference signal, a transversal filter for suppressing the distortion of transmission path disposed in a rear stage of sequence decoding circuit, and a controller which introduces the reference signal provided by the filter to control the characteristics of the filter or apply the output of the sequence decoding circuit to the transversal filter through a noise elimination filter.

Abstract: A sync generator which generates a reference horizontal synchronizing signal, a time difference detector which detects the time difference between the reference horizontal synchronizing signal and a horizontal synchronizing signal within a received television signal, and a variable delay circuit which responds to an output signal of the time difference detector to control the delay time and delay the received television signal are installed in a television receiver. When a plurality of horizontal synchronizing signals exist in one horizontal scanning period of the received television signal, the time difference between the horizontal synchronizing signal with the maximum amplitude and the reference horizontal synchronizing signal is detected, and the delay time of the received television signal is controlled in the variable delay circuit according to this time difference.

Abstract: A frequency converter which is capable of rejecting unnecessary signals generated by image signals. The frequency converter has first and second local oscillation circuits which generate local oscillation signals whose frequencies are the same and whose phases are different by 90 degrees from each other. The converter further includes two mixer circuits, and a hybrid coupler. The mixer circuits generate two unnecessary signals whose phases are different by 90 degrees from each other. The hybrid coupler delays one unnecessary signal by a quarter of a wavelength to generate two unnecessary signals whose phases are different by 180 degrees from each other, so that they are cancelled by each other.

Abstract: A frequency converter circuit for converting a high-frequency signal into an intermediate-frequency signal includes a local oscillation with a first transistor having first, second and third terminals. A first terminal of the first transistor is grounded through a first inductance and a first capacitor, while a second capacitor is inserted between the other two terminals. A resonance circuit including variable-capacity diodes and a second inductance is connected to the second terminal through a third capacitor. The frequency converter circuit further includes a mixer formed with a second transistor having a base thereof connected to the grounded terminal of the first transistor and an emitter thereof grounded through impedances offering substantially no resistance to the intermediate-frequency signal. The emitter of this second transistor is connected to a high-frequency input terminal supplied with a high-frequency signal.

Abstract: A phase locked loop circuit for use in a heterodyne receiver for stably demodulating a carrier-suppressed double-sideband signal such as a 2-phase or 4-phase PSK signal. The phase locked loop circuit comprises a reference oscillator oscillating at a frequency corresponding to an intermediate frequency, and the frequency difference between the reference frequency and the input frequency is detected by a Costas loop, a signal indicative of the frequency difference being fed back to a local oscillator through a loop filter thereby stabilizing the intermediate frequency.

Abstract: In an FM demodulator of the phase locked loop system wherein a closed loop is formed by a phase detector, an amplifier, a loop filter, and a voltage controlled oscillator, a part of the amplifier is formed by a differential amplifying circuit which has a constant current source and is driven by a constant current. The center frequency of the frequency demodulation slope of the constant current source is changed by changing the current from the constant current source in response to the signal which was frequency demodulated by the phase locked loop. Further, a low-pass filter having the pass band of the frequency band of the signal to be modulated is provided in the path of the system from the differential amplifying circuit to the constant current source.

Abstract: A receiving circuit for receiving an FM-modulated television signal with an energy dispersal signal superposed thereon is used for a television receiver for receiving the FM-modulated television signal. The receiving circuit is provided with a triangle wave signal generator for generating a triangle wave signal in synchronism with a vertical synchronizing signal. The energy dispersal signal superposed on the FM-modulated television signal is suppressed by frequency modulating an oscillation signal of a local oscillator by the triangle wave signal obtained.

Abstract: A matching circuit for a pre-amplifier of an SHF band television signal receiver is disclosed. The matching circuit comprises a stub line arranged near a gate terminal of an FET, and a pair of stub lines connected to a transmission line, one being a stub line exhibiting a short circuit impedance at a lower frequency than operating frequencies of the matching circuit and the other being a stub line arranged oppositely to the stub line and exhibiting a short circuit at a higher frequency than the operating frequencies. A distance between the stub line and the pair of stub lines is selected to be approximately equal to 1/4 wavelength of a center frequency of the desired signal band.

Abstract: A microwave oscillator circuit with an FET, a dielectric resonator and a micro-strip line has a capacitive reactance element connected between the source terminal of the FET and ground or between the source and drain terminals of the FET, so that the oscillation frequency fluctuations due to the power supply voltage fluctuations or the ambient temperature variations can be suppressed.

Abstract: A receiving circuit for a television receiver for receiving an FM-modulated television signal is disclosed, in which the oscillation frequency of a local oscillator circuit is fine adjusted by a voltage of a sync signal of the FM-modulated television signal thereby to receive the television signal properly.

Abstract: A microwave oscillator circuit comprises a micro-strip line having a substrate of a dielectric material, a semiconductor such as a Gunn diode or an FET, and a dielectric resonator connected to the micro-strip line as a resonator circuit. A hole is formed in the substrate beside the micro-strip line, or the substrate is cut off to provide a recess. Through this hole or recess, as the case may be, the dielectric resonator is directly secured to the metal casing supporting the micro-strip line on the opposite side thereof or to the grounding conductor of the micro-strip line.

Abstract: A mixer circuit formed of a micro strip line for converting an input signal in SHF band into an intermediate frequency signal in UHF band is disclosed which includes an arch-shaped half-wavelength line having a length equal to one half of the wavelength of the input signal and a series circuit of two diodes connected between both ends of the half-wavelength line, and in which the input signal and a local oscillation signal are applied respectively to the junction point of the diodes and one end of the half-wavelength line, and the intermediate frequency signal is delivered from a given point on the half-wavelength line.

Abstract: A self-oscillating mixer circuit to operate mainly at SHF band comprises a single-gate FET and a micro strip line. The gate or source terminal of the FET is connected to a radio frequency signal input line. A feedback path is provided between the drain terminal and the gate or source terminal. An intermediate frequency output line is connected to the drain electrode of the FET. A dielectric resonator is coupled to the radio frequency signal input line to improve the stability of an oscillator frequency and to suppress leakage of a local oscillator signal.

Abstract: A mixer circuit employing a distributed constant circuit using a strip line includes a strip line for applying a high frequency signal and a local oscillation signal to a diode. The strip line is provided with a filter for exclusively blocking the local oscillation signal and a filter for exclusively blocking the high frequency signal. The strip line further includes a line which acts as a shortcircuit for an intermediate frequency signal and as an open impedance for the high frequency signal and the local oscillation signal.

Abstract: An SHF band oscillation circuit using a field effect transistor (FET) having a feedback path between gate and drain or source and a resonator connected to the gate. Impedances connected to the respective terminals of the FET comprise microstrip lines. A gate bias circuit includes a temperature-sensitive semiconductor device so that a gate bias is changed with the change in ambient temperature. In this manner, the change of oscillation frequency which would otherwise occur by the change of the ambient temperature is compensated. The resonator connected to the gate comprises a dielectric resonator to further stabilize the oscillation frequency.

Abstract: A microwave oscillator circuit with an FET, a dielectric resonator and a micro-strip line has a capacitive reactance element connected between the source terminal of the FET and ground or between the source and drain terminals of the FET, so that the oscillation frequency fluctuations due to the power supply voltage fluctuations or the ambient temperature variations can be suppressed.