Differential frequency meter

Claim 2

Apparatus for measuring the frequency difference ( Delta F) between two signals at frequencies F1 and F2, said apparatus comprising; a first signal channel including: a first signal generator for generating a reference signal at a frequency fR1 different than F1; a first mixer connected so as to receive the signals at frequencies fR1 and F1, combine them, and generate a signal having a plurality of frequency components; and, a first low pass filter connected to the output of said first mixer for selecting and passing only the lowest frequency component, fR1-F1, of the signal generated by said first mixer; a second signal channel including: a second signal generator for generating a reference signal at a frequency fR2 different than fR1 and different than F2; a second mixer connected so as to receive the signals at frequencies fR2 and F2, combine them, and generate a signal having a plurality of frequency components; and, a second low pass filter connected to the output of said Second mixer for selecting and passing only the lowest frequency component, fR2-F2, of the signal generated by said second mixer; a common signal channel including: a third mixer connected to said first and second low-pass filters so as to receive the signals at frequencies fR1-F1 and fR2-F2, combine them, and generate a signal that includes a frequency component (fR1-F1)-(fR2-F2); and, a third-low pass filter connected to the output of said third mixer for selecting and passing only the frequency component (fR1-F1)-(fR2-F2) of the signal generated by said third mixer; measuring means connected to the output of said third low pass filter means for measuring the frequency of said frequency component (fR1-F1)-(fR2-F2).

Claim 3

Apparatus according to claim 1 wherein said measuring means comprises: a rectangular pulse generator that generates pulses having a predetermined amplitude and time duration, said generator being connected to the output of said third low pass filter and being triggered each time the amplitude of said (fR1-F1)-(fR2-F2) signal component becomes zero; and, an integrator connected to the output of said rectangular pulse generator for integrating the rectangular pulses generated by said rectangular pulse generator each time it is triggered.

Claim 4

Apparatus according to claim 2 wherein said rectangular pulse generator comprises: a stabilized clock oscillator; and, a flip-flop circuit connected to the output of said stabilized clock oscillator, said flip-flop circuit delivering pulses of time duration at a multiple of the oscillation period of said stabilized clock oscillator.

Claim 5

Apparatus according to claim 1 wherein the signals fR1 and fR2 generated by said first and second signal generators are successive multiples of the same frequency.

Claim 6

Apparatus according to claim 4 wherein said first and second signal generators generate successive harmonics of a fundamental frequency fR generated by a stabilized oscillator.

Claim 7

Apparatus for measuring the frequency difference ( Delta F) between two signals at frequencies F1 and F2, said apparatus comprising: a first signal channel including: a first signal generator for generating a reference signal at a frequency fR1 higher than F1; a first multiplier connected so as to receive the signals at frequencies fR1 and F1, multiply them, and generate a signal having a plurality of frequency components; and, a first low pass filter connected to the output of said first multiplier for selecting and passing only the lowest frequency component, fR1-F1, of the signal generated by said first multiplier; a second signal channel including: a second signal generator for generating a reference signal at a frequency fR2 different than fR1 and higher than F2; a second multiplier connected so as to receive the signals at frequencies fR2 and F2, multiply them, and generate a signal having a plurality of frequency components; and a second low pass filter connected to the output of said second multiplier for selecting and passing only the lowest frequency component, fR2-F2, of the signal generated by said second multiplier; a common signal channel including: a third multiplier connected to said first and second low pass filters so as to receive the signals at frequencies fR1-F1 and fR2-F2, multiply them, and generate a signal that includes a frequency component (fR1-F1)-(fR2-F2); and, a third low pass filter connected to the output of said third multiplIer for selecting and passing only the frequency component (fR1-F1)-(fR2-F2) of the signal generated by said third multiplier; and, measuring means connected to the output of said third low pass filter means for measuring the frequency of said frequency component (fR1-F1)-(fR2-F2).

Claim 8

Apparatus for measuring the frequency difference ( Delta F) between two signals at frequencies F1 and F2, said apparatus comprising: a first signal channel including: a first signal generator for generating a reference signal at a frequency fR1 higher than F1; a first multiplier connected so as to receive the signals at frequencies fR1 and F1, multiply them, and generate a signal having a plurality of frequency components; and, a first low pass filter connected to the output of said first multiplier for selecting and passing only the lowest frequency component, fR1-F1, of the signal generated by said first multiplier; a second signal channel including: a second signal generator for generating a reference signal at a frequency fR2 different than fR1 and higher than F2; a second multiplier connected so as to receive the signals at frequencies fR2 and F2, multiply them, and generate a signal having a plurality of frequency components; and a second low pass filter connected to the output of said second multiplier for selecting and passing only the lowest frequency component, fR2-F2, of the signal generated by said second multiplier; a common signal channel including: a third multiplier connected to said first and second low pass filters so as to receive the signals at frequencies fR1-F1 and fR2-F2, multiply them, and generate a signal that includes a frequency component (fR1-F1)-(fR2-F2); and, a third low pass filter connected to the output of said third multiplIer for selecting and passing only the frequency component (fR1-F1)-(fR2-F2) of the signal generated by said third multiplier; and, measuring means connected to the output of said third low pass filter means for measuring the frequency of said frequency component (fR1-F1)-(fR2-F2).