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Frequency deviation measuring and adjusting system

  • US 4,122,391 A
  • Filed: 09/19/1977
  • Issued: 10/24/1978
  • Est. Priority Date: 09/19/1977
  • Status: Expired due to Term
First Claim
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1. Apparatus for checking the frequency deviation Δ

  • f of a carrier frequency fc in a frequency modulation system comprising;

    frequency modulator means, including an adjustable modulation amplifier for adjusting the modulation sensitivity and a voltage controlled frequency modulated oscillator operating at the carrier frequency fc, said frequency modulator means having a modulation frequency input path, an oscillator frequency control input and having an output, whereby frequency deviation of the carrier fc is obtained at said output when a modulation frequency is applied to the modulation frequency input;

    means for applying to said modulation frequency input path a calibrated modulation frequency fs having an amplitude such that a predetermined peak frequency deviation Δ

    f will be obtained at the output of said frequency modulator means if the modulation sensitivity is properly adjusted;

    means for changing the frequency of the frequency deviated signal said predetermined amount, but in the opposite direction so that the original diviation will be effectively cancelled if the modulation sensitivity is properly adjusted, said changing means having an input connected to the output of said frequency modulator means and having an output;

    means for automatically controlling the frequency of the voltage controlled oscillator by supplying from an output a control signal to the oscillator frequency control input of the frequency modulator means, said controlling means having an input connected to the output of said changing means; and

    measuring means having an input connected to the output of said automatic controlling means, for providing an indication of the frequency diviation.

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