Phase locked loop synthesizer

A PLL synthesizer comprising a reference signal oscillator;

• a programmable counter means;
• a phase detector which detects a phase difference between the output frequencies from said counter means and said signal oscillator and obtains a d.c. voltage in accordance with said phase difference;
• a voltage controlled oscillator whose oscillation frequency is controlled by the d.c. voltage from said phase detector;
• a local oscillator;
• a mixer which mixes the output frequencies of said local oscillator and said voltage controlled oscillator;
• a tuning means having a tuning coil and a variable capacitance diode for tuning to the difference frequency of the output of said mixer, an amplifier for amplifying the output having said funed frequency and leading it to said programmable counter means;
• a digital-analog converter which detects a part of the frequency division ratio setting digital input data from said programmable counter means and converts it to an analog d.c. voltage signal in accordance with the level of said detected d.c. voltage signal;
• and a means for controlling the capacitance of said variable capacitance diode to tune the frequency of said tuning means to the mixed difference frequency of said mixer.

A PLL synthesizer comprising a reference signal oscillator;

• a programmable counter means;
• a phase detector which detects a phase difference between the output frequencies from said counter means and said signal oscillator and obtains a d.c. voltage in accordance with said phase difference;
• a voltage controlled oscillator whose oscillation frequency is controlled by the d.c. voltage from said phase detector;
• a local oscillator;
• a mixer which mixes the output frequencies of said local oscillator and said voltage controlled oscillator;
• a tuning means having a plurality of tuning coils and a tuning capacitor for tuning to a prescribed frequency of the output of said mixer, an amplifier for amplifying the tuned frequency output of said tuning means and leading it to said programmable counter means;
• and a plurality of switching transistors for detecting the presence or absence of the frequency division ratio setting digital input data from said programmable counter means, switching on or off in accordance with the presence or absence of said data to shortcircuit selectively said tuning coils, and controlling to tune the frequency of said tuning means in said frequency mixing and extracting means to the mixed difference frequency of said mixer in accordance with said frequency division setting digial input data.

In a PLL synthesizer comprising a voltage controlled oscillator for generating an output having a prescribed frequency in accordance with a value of an applied controlled voltage;

• a local oscillator which generates an output having a frequency to be mixed with the frequency of the output of said voltage controlled oscillator;
• a mixer which mixes the outputs of said both oscillators;
• a means for receiving the outputs of said mixer and extracting therefrom a component having a difference frequency between the frequencies of said both oscillators;
• a programmable counter means for frequency dividing the output of said frequency extracting means in accordance with a prescribed program;
• a reference signal oscillator whose output is compared with the output having its frequency divided by said counter means, a phase detector which detects, a phase difference between the outputs of said reference signal oscillator and said counter means, generates a d.c. voltage corresponding to the phase difference and applies it to said voltage controlled oscillator as a control signal;
• an improvement wherein said programmable counter means sets the frequency division ratio by the application of a plurality of digital inputs, and said frequency extracting means comprises a resonance circuit of inductors and capacitors and a means for controlling said resonance circuit by varying at least inductances of said inductors and capacitances of said capacitors in accordance with said digital inputs, and varies a resonance frequency of said resonance circuit in accordance with a change of frequency division ratio setting by said programmable counter means thereby to tune the resonance frequency to the difference frequency of the output of said mixer.