Abstract: A digital portable telephone device includes a receiver section which receives a signal within one of an analog receiving frequency band and a digital receiving frequency band. A received signal is converted into one of a digital-band first intermediate-frequency signal and an analog-band first intermediate-frequency signal by using a first local signal. A transmitter section transmits a signal within one of an analog transmitting frequency band and a digital transmitting frequency band, wherein a modulation signal is generated by using the first local signal. A radio-frequency local signal generating section generates the first local signal within one of a digital local signal frequency band and an analog local signal frequency band, and supplies the first local signal to one of the receiver section and the transmitter section.

Abstract: A digital portable telephone device includes a receiver section which receives a signal within one of an analog receiving frequency band and a digital receiving frequency band. A received signal is converted into one of a digital-band first intermediate-frequency signal and an analog-band first intermediate-frequency signal by using a first local signal. A transmitter section transmits a signal within one of an analog transmitting frequency band and a digital transmitting frequency band, wherein a modulation signal is generated by using the first local signal. A radio-frequency local signal generating section generates the first local signal within one of a digital local signal frequency band and an analog local signal frequency band, and supplies the first local signal to one of the receiver section and the transmitter section.

Abstract: A digital portable telephone device includes a receiver section which receives a signal within one of an analog receiving frequency band and a digital receiving frequency band. A received signal is converted into one of a digital-band first intermediate-frequency signal and an analog-band first intermediate-frequency signal by using a first local signal. A transmitter section transmits a signal within one of an analog transmitting frequency band and a digital transmitting frequency band, wherein a modulation signal is generated by using the first local signal. A radio-frequency local signal generating section generates the first local signal within one of a digital local signal frequency band and an analog local signal frequency band, and supplies the first local signal to one of the receiver section and the transmitter section.

Abstract: A mobile telephone system includes: a portable telephone set, an adaptor on a vehicle for the portable telephone set to rest thereon, a remote controller unit for dialing and voice talking, and a transceiver unit for modulating/demodulating voice signal and control signals, and transmitting/receiving radio frequency signals. The portable telephone set has apparatus for electrically connecting to the adaptor when the portable telephone set is rested thereon, and a first control circuit for transferring identification numbers of the portable telephone set to the transceiver unit and then disabling a predetermined part of functions of the portable telephone set except charging a battery of the portable telephone set from the adaptor.

Abstract: A transmission power control circuit comprises a control data table in which digital data of a monitor voltage depending on a transmission power level for a plurality of values of transmission frequency and a plurality of values of transmission power are stored. A D/A converter converts selected values of the digital data to an analog signal as a reference voltage. The transmission power is controlled so that the monitor voltage becomes equal to the reference voltage.

Abstract: A variable transmission power type transmitter comprises a transmission amplifier, a detecting circuit for detection of a transmission wave signal from the transmission amplifier, an automatic power control circuit for automatic control of the transmission power of the transmitter amplifier depending on the difference between a set value and a detected output of the detecting circuit, a set point providing circuit for generating set values and for selecting one of the set values to be supplied to the automatic power control circuit, and a transmission interruption detecting circuit for detecting existence or absence of the transmission wave signal by comparing the detected output of the detecting circuit with a reference value. The reference value is automatically generated from one of the set values in the set point providing circuit. Therefore, a variable resistor for adjusting the reference value and a adjustment process of the reference value are not required.

Abstract: A frequency synthesizer, including a phase-locked loop. The phase locked loop effects phase comparison between a comparison signal based on an output from a voltage-controlled oscillator and a reference signal based on an output from a reference oscillator. The resultant phase difference signal is submitted to a loop filter whose output serves as a control signal of the voltage-controlled oscillator. The frequency synthesizer includes a preset circuit for switching the output of the voltage-controlled oscillator by quickly charging or discharging a capacitor of the loop filter and a modifying circuit for modifying the time constant of the loop filter. The phase-locked loop is brought to phase lock at a high speed by decreasing the time constant of the loop filter when switching the output frequency.

Abstract: A frequency converter circuit which includes a first frequency conversion unit which mixes a received signal and a first local oscillation signal to produce a first intermediate frequency signal and a second frequency conversion unit which mixes the first intermediate frequency signal and a second local oscillation signal to produce a second intermediate frequency signal. Here, the first frequency deviation included in the first local oscillation signal and the second frequency deviation included in the second local oscillation signal are combined and applied to the reference oscillation unit. The oscillation frequency of the reference oscillation unit is subjected to feedback control so that the combined frequency deviation becomes zero. This feedback is formed so that a first and second local oscillation signals are produced based on reference signals obtained by dividing a reference signal having the oscillation frequency by a first dividing ratio and a second dividing ratio.

Abstract: A .pi./4 shift QPSK modulator includes a pre-processing part for subjecting an input transmitting code sequece to a pre-processing, a modulator part for selectively subjecting the transmitting code sequence received via the pre-processing part to a modulation in conformance with QPSK and a modulation in conformance with a .pi./4 shift QPSK, and an output part for outputting a modulated signal having a burst form based on an output of the modulator part depending on a burst signal having leading and trailing edges, where the pre-processing part carries out the pre-processing so that I-axis and Q-axis data supplied to the modulator part have the same symbol in succession at parts corresponding to the leading and trailing edges of the burst signal, so as to suppress generation of unwanted waves in the output part.

Abstract: A base-band delayed detector has an operation circuit for performing a delayed detecting operation with respect to an input signal, the operation circuit outputting an altered signal having a predetermined symbol rate. The base-band delayed detector includes a clock generator for generating a clock signal having a frequency twice as large as the symbol rate, the clock signal being used as a timing signal in the operation circuit, a synchronizing circuit for synchronizing the clock signal with the altered signal output from the operation circuit and a data determination circuit for obtaining output data from the altered signal at a predetermined timing based on the clock signal synchronized with the altered signal.

Abstract: A power amplifier device includes m power amplifier units provided in parallel where m is an integer, a distributor for distributing an input signal to the m power amplifier units, and a combining device for combining m amplified input signals output by the m power amplifier to generate an amplified output signal. The power amplifier device includes a group of switches for gradually disconnecting the m power amplifier units from the distributor and the combining device and for gradually connecting the m power amplifier units to the distributor and the combining device.

Abstract: An amplifier system includes a power amplifier which generates undesired distortion in its main output signal, and a distortion detecting circuit for detecting distortion spectrums included in the main output signal so as to output a distortion level indicating signal by attaining a difference of a main input signal having no distortion and a monitor signal representing the main output signal while the main input signal and the monitor signal are kept in phase and equal in level. The amplifier system also includes compensation circuit, provided at the input of the amplifier, for adding a compensation signal, to the main input signal which is to be equivalent generated equivalently to the distortion in the main output signal. The amplifier system further includes and a control circuit for precisely adjusting phase and level of the compensation signal so as to keep the distortion level indicating signals minimum.

Abstract: In a mobile radio communication system, a mobile station constantly monitors a quality of a radio line between the mobile station and a first base station with which the mobile station is presently communicating, detects a deterioration of the quality of the radio line between the mobile station and the first base station outside a tolerable range, successively detects field intensities of signals received from the base stations neighboring the first base station using a free time slot which is unused by the mobile station for communication to determine a maximum field intensity, supplies to the first base station predetermined information related to a second base station from which the signal with the maximum field intensity is received so as to make a handover request, and ends the communication with the first base station in response to a handover message.