Hitachi Denshi Kabushiki Kaisha

Fumihito Tomaru

Makoto Ohnishi

Norio Hikasa

Hirotake Wakai

A fractional-N system frequency synthesizer and a field pickup unit which uses the synthesizer and adapts to a plurality of different channel frequencies in a microwave band. The synthesizer is made up of a fractional control unit which in turn is made up of a modulo-m counter which counts signals of a predetermined frequency fed from a reference oscillator, a channel setting unit for setting a required channel frequency in a predetermined frequency band and for outputting data on the set channel frequency, a memory which stores information on a dividing ratio at an address determined by the count of signals counted by the modulo-m counter and the data on the set channel frequency outputted by the channel setting unit, wherein switching pulses each for selecting a dividing ratio in a dual modulus prescaler are dispersively arranged at equal intervals in the counting period of the modulo-m counter. The field pickup unit is made up of a transmitter and a receiver. A transmission high-frequency unit of the transmitter and a reception high-frequency unit of the receiver each have a fractional-N system frequency synthesizer which frequency-converts an intermediate frequency signal of 1.5 GHz to a signal in a transmission/reception microwave frequency band.

Fractional-N system frequency synthesizer and synthesizing method and field pickup unit using the method

An amplifier includes an amplifying section for simultaneously amplifying a plurality of input signals having different frequency bands, a distortion extracting section for separating and extracting at every different frequency bands a distortion component from a plurality of signals having the different frequency bands outputted from the amplifying section, a distortion compensation section for adjusting independently at every different frequency bands the phase and the amplitude of the distortion component separated and extracted at every different frequency bands and a distortion eliminating section for canceling and outputting a distortion component from a plurality of signals having the different frequency bands outputted from the amplifying section based on the distortion component adjusted at every different frequency bands. The above distortion compensation section adjusts independently at every different frequency bands the phase and the amplitude of the distortion component separated and extracted at every different frequency bands in such a manner that the above-mentioned phase and amplitude agree with the phases and the amplitudes of the distortion components contained in a plurality of signals having the different frequency bands outputted from the amplifying section.

Amplifier and amplifying method for amplifying a plurality of signals

A digital demodulator which demodulates an analog signal obtained through a quadrature amplitude modulation to produce a digital demodulated signal includes a converter to convert the analog signal into a digital signal and a signal processor to quadrature-demodulating the digital signal from the converter. Assuming that the analog signal has a carrier frequency of f.sub.IF and the signal conversion is accomplished with the sampling frequency fs, the demodulator is set to satisfy fs=4.multidot.f.sub.IF /(2n+1), where n denotes a positive integer. The signal processing section conducts the quadrature demodulation according to a quadrature local oscillation signal having a frequency fc satisfying fc=fs/4.

Growing community of inventors

Higashikurume, Japan

Fumihito Tomaru