Abstract: A digital broadcast receiver for receiving a digital modulation signal of the present invention includes channel selection means inputting a digital modulation signal of a radio frequency band and frequency converting a desired digital modulation signal into a designated intermediate frequency signal; oscillation means for generating a local oscillation signal used for frequency conversion at the channel selection means; oscillation frequency control means for controlling a frequency of the local oscillation signal at the oscillation means; phase noise characteristic control means for improving a phase noise characteristic of the local oscillation signal generated at the oscillation means; filter means for extracting the intermediate frequency signal selected at channel selection means; orthogonal detection means for orthogonally detecting the intermediate frequency signal extracted at the filter means; A/D converter means for converting the analog output of the orthogonal detection means into a digital signa

Abstract: A receiving apparatus is presented, in which a channel frequency can be selected over a wide band with an increased attenuation at an image frequency and/or at a local oscillation frequency by including a tunable filter having a following construction. Microstrip lines are connected between either one of the input or the output terminal or both of the input and output terminals of the tunable filter; a plurality of resonant circuits are formed by each of a plurality of coils and a plurality of variable capacitance diodes; and the coils are electromagnetically coupled and where a voltage applied to each cathode of each of a plurality of variable capacitance diodes through each of a plurality of resistors is controlled to tune a frequency to be received.

Abstract: A frequency modulation signal demodulator receives an intermediate frequency signal to demodulate a FM signal. The frequency modulation signal demodulator includes a voltage-controlled oscillator having variable capacitance diodes. The voltage-controlled oscillator varies the oscillating frequency of a signal by controlling a voltage across the variable capacitance diodes using a DC voltage. Also included is a phase comparator which produces a phase difference by comparing the phase of the intermediate frequency signal to the phase of the signal from the voltage-controlled oscillator and provides a direct current voltage signal corresponding to the phase difference. Also included is a differential amplifier which has an adjustable reference voltage source. The differential amplifier amplifies the direct current voltage signal to produce a demodulated signal. The demodulated signal is negatively fed back to the voltage-controlled oscillator as the direct current signal.

Abstract: The present invention relates to a satellite television broadcasting receiver which receives waves from a satellite, selects a broadcasting channel and obtains an FM demodulated video signal by passing a selected signal through the band-pass filter. In this satellite television broadcasting receiver, the video signal superposed with a large energy dispersion signal is inputted to the first clamping circuit at a low level, to eliminate the energy dispersion signal. Thus, a room is provided in the dynamic range of the amplifier at the later stage and the DG and DP of the amplifier at the later stage are maintained at a satisfactory level by the second clamping circuit.

Abstract: A diode type mixer includes a diode circuit and a balun transformer, and is used in a frequency convertor which converts a 1-GHz primary intermediate frequency signal to a secondary intermediate frequency signal in a satellite broadcast receiver. The balun transformer (5) is fixed to a support block (10), and the terminals of the balun transformer (5) are connected to the stems (11) of the support block (10). Hollow coils (12 and 13) are connected between the ground terminal and the balanced terminals of the support block (10). The high frequency characteristics of the mixer can be improved, and productivity in mass production can be enhanced.

Abstract: A frequency modulator is provided, in which, for instance, a video signal is used as a modulation signal. A differential amplifier is formed by first and second transistors. First and second load resistors are connected between respective collectors of the first and second transistors and a power supply terminal (A). A series circuit of first and second feedback capacitors is inserted between the collector of the first transistor and a base of the second transistor. A series circuit of third and fourth feedback capacitors is inserted between the collector of the second transistor and a base of the first transistor. The respective same electrodes of first and second variable capacitance diodes are connected with each other and the other electrodes thereof are connected respectively to a junction point of the first and second feedback capacitors and to a junction point of the third and fourth feedback capacitors.

Abstract: An AFC apparatus effectively used for a satellite broadcasting receiver and making up a tuning circuit of frequency synthesizer system using a phase-locked loop (PLL) is disclosed, in which a frequency error detector for detecting an error of an output signal of a demodulator from the central frequency comprises first and second comparators supplied with an output of the demodulator and reference voltages, a first latch circuit for latching an output of the first comparator by a key pulse, and a second latch circuit for latching an output of the second compartor by a key pulse. A demodulation output is thus accurately held to realize an accurate data comparison even against a key pulse of a large duty factor.

Abstract: By the extraction of the noise component from the FM demodulated output and the detection thereof, the output proportional to the noise power is obtained, and it is indicated as the CN ratio of the received signal. This quality indication of the received signal makes the antenna pointing angle adjustment easier than before, and also realizes the picture quality indication for a satellite broadcasting receiver.

Abstract: A first and a second transistors coupled in series by connecting the collector of the first one to the emitter of the second one are connected at the collector of the second transistor through a resistor to a first power source of a voltage as high as about two times the breakdown voltage of these transistors, a third transistor is coupled at the collector to the base of the second transistor and a second power source of the lower voltage than the first power source through a load resistor, and the base of the third transistor is connected to the base of the first transistor; whereby an output voltage of the second transistor is divided into the respective collector-emitter voltages of the first and second transistors, and the output voltage exceeding the breakdown voltage of the transistor is obtainable.

Abstract: A satellite TV receiver for receiving a satellite broadcasting, wherein neighboring televison signals are vertical and horizontal polarized waves, and wherein a polarizer for the satellite receiver controls an antenna so that the polarization plane of the antenna is adapted to the polarization plane of television signal to be received. The receiver further includes a narrow band-pass filter for rejecting terrestrial interference so that the desired polarization plane can be more easily determined.

Abstract: An A.F.C. control system for reception of wide-band F.M. transmission such as satellite transmissions, in which a center frequency of an F.M. I.F. signal is repetitively and alternately compared with an upper and a lower frequency limit value so long as the center frequency lies between these values, with the results of the comparisons being respectively stored in two latch memories, whose contents thereby indicate any error of the center frequency relative to the frequency limits. Any departure of the center frequency from between the limits is corrected by successive frequency shifts of the local oscillator frequency, with the results of correction being indicated by the latch memory contents and with the number of frequency shifts being determined accordingly.