Abstract: A communication apparatus includes a phase-locked loop circuit which receives a first signal having a frequency and converts it into an output signal having a transmission frequency and includes a current output type phase comparator which converts a phase difference between the first signal and a second signal into a current signal, a low pass filter which filters the current signal of the current output type phase comparator to produce an output signal a voltage controlled oscillator which produces an output signal having a transmission frequency corresponding to the output signal of the low pass filter the output signal of the voltage controlled oscillator constituting the output signal of the phase-locked loop circuit, a frequency converter which frequency-converts the output signal of the voltage controlled oscillator to produce the second signal, and a current source which supplies a current to an input of the low pass filter.

Abstract: A communication apparatus includes a phase-locked loop circuit which receives a first signal having a frequency and converts it into an output signal having a transmission frequency, and includes a current output type phase comparator which converts a phase difference between the first signal and a second signal into a current signal, a low pass filter which filters the current signal of the current output type phase comparator to produce an output signal, a voltage controlled oscillator which produces an output signal having a transmission frequency corresponding to the output signal of the low pass filter, the output signal of the voltage controlled oscillator constituting the output signal of the phase-locked loop circuit, a frequency converter which frequency-converts the output signal of the voltage controlled oscillator to produce the second signal, and a current source which supplies a current to an input of the low pass filter.

Abstract: In a PLL circuit, the number of LPFs is reduced to one to reduce mounting area and pin number, and to simplify design. In one embodiment, the PLL circuit includes a variable-gain phase comparator, a mixer, an LPF, VCOs, couplers, and a control circuit to controlling the on/off operation of the VCOs. The variable-gain phase comparator is capable of varying a phase difference gain. The on/off of the operation of the VCOs is controlled by the control circuit so that one of the VCOs is turned off. The phase difference conversion gain is varied in accordance with the sensitivity of the VCOs so the number of LPFs required for the PLL circuit can be reduced to only one.

Abstract: A communication apparatus includes a phase-locked loop circuit which receives a first signal having a frequency and converts it into an output signal having a transmission frequency, and includes a current output type phase comparator which converts a phase difference between the first signal and a second signal into a current signal, a low pass filter which filters the current signal of the current output type phase comparator to produce an output signal, a voltage controlled oscillator which produces an output signal having a transmission frequency corresponding to the output signal of the low pass filter, the output signal of the voltage controlled oscillator constituting the output signal of the phase-locked loop circuit, a frequency converter which frequency-converts the output signal of the voltage controlled oscillator to produce the second signal, and a current source which supplies a current to an input of the low pass filter.

Abstract: A communication apparatus includes a phase-locked loop circuit which receives a first signal having a frequency and converts the first signal into an output signal having a transmission frequency. The phase-locked loop circuit includes a current output type phase comparator which converts a phase difference between the first signal and a second signal into a current signal, a low pass filter which filters the current signal of the current output type phase comparator to produce an output signal, a voltage controlled oscillator which produces an output signal having a transmission frequency corresponding to the output signal of the low pass filter, the output signal of the voltage controlled oscillator constituting the output signal of the phase-locked loop circuit, and a frequency converter which frequency-converts the output signal of the voltage controlled oscillator to produce the second signal.

Abstract: A communication apparatus includes a phase-locked loop circuit which receives a first signal having a frequency and converts the first signal into an output signal having a transmission frequency. The phase-locked loop circuit includes a current output type phase comparator which converts a phase difference between the first signal and a second signal into a current signal, a low pass filter which filters the current signal of the current output type phase comparator to produce an output signal, a voltage controlled oscillator which produces an output signal having a transmission frequency corresponding to the output signal of the low pass filter, the output signal of the voltage controlled oscillator constituting the output signal of the phase-locked loop circuit, and a frequency converter which frequency-converts the output signal of the voltage controlled oscillator to produce the second signal.

Abstract: A phase-locked loop circuit includes a current output type phase comparator for converting a phase difference between a first signal and a second signal into a current signal to be outputted, a low pass filter for filtering the current signal of the current output type phase comparator to produce an output signal, a voltage controlled oscillator for producing an output signal having a frequency corresponding to the output signal of the low pass filter, a current source for supplying a current to an input of the low pass filter, a reset switch for applying to the voltage controlled oscillator a reset voltage for canceling a phase-locked state of the phase-locked loop, and a frequency converter for frequency-converting the output signal of the voltage controlled oscillator to produce the second signal.