Afc system for microwave energy sources

Claim 2

An automatic frequency control system for an output oscillator which develops an output signal having a first frequency, including in combination, reference oscillator means for developing a reference signAl having a second frequency and including modulator means, generation means for developing a modulation signal coupled to said modulator means, said modulator means being responsive to said modulation signal whereby said reference signal is modulated by said modulation signal, mixer means coupled to said output oscillator and said reference oscillator means and responsive to said output signal and reference signal to develop a difference signal according to the difference in frequency therebetween with said difference signal being modulated by said modulation signal, a low pass filter circuit having an input thereof coupled to said mixer means and further having an output for passing frequencies from zero to a predetermined maximum value, demodulation means coupled to said output of said low pass filter circuit for developing a demodulated signal having the same frequency as said modulation signal, phase discriminator means coupled to said generation means and said demodulation means and responsive to the phase difference between said demodulated signal and said modulation signal to develop a control signal, said phase discriminator means further being coupled to said output oscillator for applying said control signal thereto to control the frequency of said output signal.

Claim 3

The automatic frequency control system of claim 1 wherein, said reference oscillator means includes a crystal oscillator.

Claim 4

The automatic frequency control system of claim 2 wherein, said modulator means acts to FM modulate said reference signal.

Claim 5

The automatic frequency control system of claim 3 wherein, the frequency developed by said crystal oscillator is 1/n times said second frequency, said reference oscillator means further including frequency multiplier means for multiplying the frequency of the signal from said crystal oscillator n times to develop said reference signal having said second frequency.

Claim 6

The automatic frequency control system of claim 4, and further including band-pass filter means coupling said output oscillator means to said mixer means, said band-pass filter means acting to reject signals having frequencies (n+1) and greater times the frequency of said signal from said crystal oscillator, said band-pass filter further acting to reject signals having frequencies (n-1) and less times the frequency of said signal from said crystal oscillator.

Claim 7

The automatic frequency control system of claim 5 wherein, said demodulator means includes low pass filter means coupled to said mixer means and detector means coupling said low pass filter means to said phase discriminator means, said low pass filter means acting to change the FM modulation of said difference signal to AM modulation for detection by said detector means.

Claim 8

An automatic frequency control system for an output oscillator which develops an output signal having a first frequency, including in combination, reference oscillator means for developing a reference signal having a second frequency and including modulator means, said reference oscillator means including a crystal oscillator and a frequency multiplier for multiplying the frequency of the crystal oscillator n times to produce said reference signal of said second frequency, generation means for developing a modulation signal coupled to said modulator means, said modulator means being responsive to said modulation signal whereby said reference signal is modulated by said modulation signal, mixer means coupled to said output oscillator and said reference oscillator means and responsive to said output signal and said reference signal to develop a difference signal according to the difference in frequency therebetween, with said difference signal being modulated by said modulation signal, demodulation means coupled to said mixer means for developing a demodulated signal having the same frequency as said modulation signal, phase discriminator means coupled to said generation means and said demodulation meanS and responsive to the phase difference between said demodulated signal and said modulation signal to develop a control signal, said phase discriminator means further being coupled to said output oscillator for applying said control signal thereto to control the frequency of said output oscillator, and band-pass filter means coupling said output oscillator to said mixer means, said band-pass filter means acting to reject signals having frequencies (n+1) and greater times the frequency of said signal from said crystal oscillator, said band-pass filter further acting to reject signals having frequencies (n-1) and less times the frequency of said signal from said crystal oscillator.

Claim 9

An automatic frequency control system for an output oscillator which develops an output signal having a first frequency, including in combination, reference oscillator means for developing a reference signal having a second frequency and including modulator means, said reference oscillator means including a crystal oscillator and a frequency multiplier for multiplying the frequency of the crystal oscillator n times to produce said reference signal of said second frequency, generation means for developing a modulation signal coupled to said modulator means, said modulator means being responsive to said modulation signal whereby said reference signal is modulated by said modulation signal, mixer means coupled to said output oscillator and said reference oscillator means and responsive to said output signal and said reference signal to develop a difference signal according to the difference in frequency therebetween, with said difference signal being modulated by said modulation signal, demodulation means coupled to said mixer means for developing a demodulated signal having the same frequency as said modulation signal, phase discriminator means coupled to said generation means and said demodulation meanS and responsive to the phase difference between said demodulated signal and said modulation signal to develop a control signal, said phase discriminator means further being coupled to said output oscillator for applying said control signal thereto to control the frequency of said output oscillator, and band-pass filter means coupling said output oscillator to said mixer means, said band-pass filter means acting to reject signals having frequencies (n+1) and greater times the frequency of said signal from said crystal oscillator, said band-pass filter further acting to reject signals having frequencies (n-1) and less times the frequency of said signal from said crystal oscillator.