SYSTEM AND METHOD FOR GENERATING FILTERED SIGNAL HAVING PRESCRIBED FREQUENCY, AND RADIO TRANSMITTER FOR PERFORMING TRANSMISSION AT FREQUENCY SET BY VARIABLE FREQUENCY OSCILLATOR

摘要

PROBLEM TO BE SOLVED: To provide a system for generating a signal filtered at a prescribed frequency by providing a filter capable of being tuned to the prescribed frequency, and changing the frequency of the filter corresponding to an oscillation frequency control signal.;SOLUTION: This system is provided with a filter capable of tuning to a prescribed frequency and the frequency of the filter can be changed corresponding to the oscillation frequency control signal. For example, a transmitter 100 is provided with a variable frequency oscillator 10, on the basis of a phase-locked loop, equipped with a voltage controlled oscillator 20, a programmable divider 22, a phase comparator 24 and a low-pass filter 26. This transmitter 100 is provided with a variable frequency filtering step to be controlled by a control signal Vref for similarly controlling the frequency of an oscillator 10 as well. Therefore, a central frequency in the signal passing band of a filter 60 is dynamically changed so as to be tuned to a transmission frequency to be changed corresponding to a transmission channel under using at all the time.;COPYRIGHT: (C)2001,JPO