Abstract: A wireless communication method for a wireless communication apparatus to communicate wirelessly with a corresponding wireless communication apparatus with adaptively selecting a modulation scheme from a plurality of modulation schemes, comprising: a step of grasping a quality of a received signal; a step of selecting a first modulation scheme based on the grasped quality of the received signal; a step of calculating a retransmission rate of received signals in the first modulation scheme; a step of determining an estimated throughput from the calculated retransmission rate based on relations between throughput and retransmission rate; a step of comparing the estimated throughput with a throughput in a second modulation scheme having a smaller multi-value number than that in the first modulation scheme; and a step of performing wireless communication in either the first modulation scheme or the second modulation scheme depending on the comparison result.

Abstract: A diversity receiving apparatus having a plurality of antennas, antenna feeders each being associated with respective one of the antennas, and a single diversity receiving section to which the antennas are connected via the associated antenna feeders. A breakage detecting circuit is included in the apparatus for detecting the breakage of any one of the antenna feeders. The detecting circuit uses an antenna whose radiation element is connected to ground and, by applying a predetermined DC potential to the hot line of the antenna feeder via a resistor, constantly monitors the potential. On the breakage of the antenna feeder, the detecting circuit produces an alarm in response to the resultant change in the potential. The apparatus is capable of readily detecting that the diversity reception effect has been lost and the receiving ability has been degraded due to the breakage of the antenna feeder.

Abstract: A diversity reception of signals involves first and second mobile receivers which recover first and second baseband signals. The first and second receivers have first and second wave detectors, respectively, for generating output voltages corresponding to the strength of an FM modulated signal. When the difference in output voltages between the first and second detectors exceeds a predetermined value, a comparator gives an output detection signal. An adder circuit combines the first and second recovered baseband signals. First and second switching circuits selectively cut off the lower level one of the first or second recovered signal, which is then being supplied to the adder circuit. A third switching circuit adjusts the gain of the adder circuit. When the comparator does not give an output detection signal, the first and second switching circuits feed both the first and second recovered baseband signals to the adder circuit.

Abstract: A phase locked loop frequency synthesizer comprises a voltage-controlled oscillator (VCO) for generating a signal having a frequency which varies in response to a control voltage. A variable frequency divider divides the output frequency of the VCO in a ratio which is determined by a control signal. A reference oscillator supplies a reference signal having a predetermined frequency. A fixed frequency divider divides the frequency of the reference signal in a fixed ratio. A phase comparator compares the phases of the outputs of the fixed frequency divider and variable frequency divider to provide a control pulse corresponding to a phase difference between these outputs. A charge pump has a power supply terminal for generating a charge/discharge voltage in response to the control pulse. A loop filter includes a first capacitor which is supplied with the charge/discharge voltage for supplying a control voltage to the VCO which corresponds to the charge/discharge voltage. A power supply circuit generates a D.C.

Abstract: In an improved phase-locked loop frequency synthesizer, a voltage is continuously applied from a power source to a fixed divider and a programmable divider respectively composed of such lower electric power consuming means as C-MOS circuitry such that the fixed and programmable dividers preserve the counting value thereof when their inputs are interrupted at the time of changing from a phase-locked loop to an open loop so that phase lock is achieved in a short time with less consumption of electric power.

Abstract: A temperature-compensated oscillator avoids noise heretofore caused by unduly high signal level changes of a control voltage resulting from sensed temperature changes. This is done by reducing the high level changes into a plurality of relatively low level changes which produce a cumulative effect comparable to the high level effect. The many low level changes do not produce reactions which are abrupt enough to cause noise, especially a phase modulation or frequency modulation noise.

Abstract: In a radio transmitter/receiver comprising a transmitter, a superheterodyne receiver, and a local oscillator for supplying a local oscillation signal to the superheterodyne receiver, the intermediate frequency f.sub.if of the superheterodyne receiver is set to have a value expressed byf.sub.if =(2K-1).times.f.sub.ch /2where f.sub.ch represents a frequency spacing between radio frequencies assigned to a communication and K represents a natural number.

Abstract: A frequency modulation transmitter has a frequency synthesizer comprised of a voltage controlled oscillator for operating a transmitter section of the modulation transmitter. The output center frequency of the voltage controlled oscillator is determined by channel designation information. The level of a modulation input signal applied to the voltage controlled oscillator for modulating the center frequency is changed in accordance with the channel designation information.