Abstract: A frequency synthesized receiver utilizes, as a local oscillator, a phase-locked circuit formed of a reference signal oscillator, a voltage controlled oscillator, a programmable divider, a phase comparator, and a low-pass filter. For tuning to a desired frequency, the dividing ratio of the programmable divider is controlled by an up/down counter connected in parallel with a shift register. The latter is supplied with a clock pulse signal and a binary coded selecting signal furnished from a micro computer. The selecting signal corresponds to a desired broadcast frequency. The up/down counter is caused by the micro computer to count up or down from the count value stored in the shift register, thereby causing the received frequency to rapidly sweep, at predetermined steps of, for example, 100 KHz.

Abstract: A high frequency wide band resonant circuit is formed of a lump capacitor, a lump inductor and a voltage controlled variable capacitor. The resonant circuit is suitable to be used in a receiving circuit which selectively receives a signal in the UHF band.

Abstract: A varactor device comprised of plural varactor elements disposed in a semiconductor body, each varactor element includes first and second semiconductor regions defining a PN junction therebetween. Any two of the varactor elements in the semiconductor body are separated from each other by semiconductor material of one conductivity type. Electrodes are provided on the semiconductor material of one conductivity type and on the plural varactor elements. Individual conductors are provided on the respective electrodes. In accordance with this construction, the electrodes on the semiconductor material are adapted to be supplied with a predetermined potential to substantially shield the varactor elements and minimize stray capacitance therebetween.In one preferred application of the varactor device, it is used with a tuner, such as a UHF tuner, such that the variable capacitance of the varactor device changes the frequency to which the tuner is tuned.