Apparatus and method for frequency modulation

• US 6,057,798 A
• Filed: 01/18/1985
• Issued: 05/02/2000
• Est. Priority Date: 10/19/1981
• Status: Expired due to Term

• Current Assignee: Raytheon Company (Rtx Corporation)
• Original Assignee: Raytheon Company (Rtx Corporation)
• Inventors: Burrier, Richard W., Hanson, James T.
• Primary Examiner(s): Sotomayor, John B.
• Application Number:
  US06/719,021
• Time in Patent Office: 5,583 Days
• Field of Search: 343/17, 343/5, 328/133, 328/134, 328/155, 342/199, 342/200, 327/5, 327/100, 331/2, 331/11
• US Class Current: 342/200
• CPC Class Codes: G01S 13/34 using transmission of continuous, frequency-modulated waves while heterodyning the received signal, or a signal derived therefrom, with a locally-generated signal related to the contemporaneously transmitted signal
• CPC Class Codes: G01S 13/342 using sinusoidal modulation
• CPC Class Codes: G01S 7/35 Details of non-pulse systems

Abstract

A method and apparatus for frequency modulating a continuous wave signal is shown to comprise a voltage-controlled oscillator (VCO) having a first and a second control loop to maintain the carrier frequency of such VCO at a frequency determined by a crystal-controlled oscillator and to maintain the peak deviation of the FM modulation on such carrier frequency at a value equal to the deviation of the first Bessel null from the carrier frequency.

Claims

1. An improved ranging standard generator for generating a frequency modulated waveform having a precise frequency deviation, such generator comprising:

(a) a voltage controlled oscillator;

(b) a divide-by-M frequency divider for dividing the output signal from the voltage-controlled oscillator;

(c) a crystal-controlled reference oscillator;

(d) a pair of divide-by-N frequency dividers for dividing the output signals from the divide-by-M frequency divider and the crystal-controlled reference oscillator;

(e) an oscillator tuned to the modulating frequency;

(f) means, responsive to the output signals from the oscillator tuned to the modulating frequency and the pair of divide-by-N frequency dividers, for frequency modulating the voltage-controlled oscillator; and

(g) means, responsive to the undivided output signal from the crystal-controlled reference oscillator and the output signal from the divide-by-M frequency divider, for controlling the deviation of the frequency modulated output signal from the voltage-controlled oscillator.

2. The improved ranging standard generator as in claim 1 wherein the means for frequency modulating the voltage-controlled oscillator comprises a phase lock loop including an Armstrong phase modulator for combining the divided-by-N output signal from the crystal-controlled reference oscillator and the output signal from the oscillator tuned to the modulation frequency.

3. The improved ranging standard generator as in claim 2 wherein the means for controlling the deviation of the frequency modulated output signal from the voltage controlled oscillator comprises a Bessel nulling loop including a phase sensitive amplitude detector for generating a bipolar D.C. signal for controlling the level of the modulating signal to the voltage controlled oscillator.