PHASE LOCKED LOOP

• US 3,683,279 A
• Filed: 12/17/1969
• Issued: 08/08/1972
• Est. Priority Date: 12/17/1969
• Status: Expired due to Term

• Current Assignee: ITT Corporation (ITT, Inc.)
• Original Assignee: Irving A. Krause, Murray Weinberg
• Inventors: Weinberg, Murray, Irving, A. Krause
• Primary Examiner(s): Robert L. Griffin
• Assistant Examiner(s): Kenneth W. Weinstein
• Application Number:
  US04/885,775
• Time in Patent Office: 965 Days
• Field of Search: 325/3-11,17,58,63,346,349,419,421,423 343/6.8
• US Class Current: 455/13.2
• CPC Class Codes: H03L 7/06 using a reference signal applied to a frequency- or phase-locked loop

Abstract

An oscillator in a spacecraft transponder or repeater is frequency stabilized by a phase locked loop with reference signal therefor having a frequency (N/M) F being received in the repeater from a ground station. The reference signal is processed in the repeater and returned to the ground station where it is monitored to detect when the pull-in range of the loop is exceeded. When this condition is detected, the frequency of the reference signal is swept in the ground station until the frequency of the reference signal and frequency of the signal of the oscillator in the repeater is within said pull-in range. The oscillator frequency F is divided by M and the phase comparator includes a first tuned input circuit to respond to a frequency (N/M) F, a second turned input circuit to respond to the nth harmonic of the frequency F/M and a phase error detecting circuit to produce a control signal used to stabilize the frequency of the oscillator.

Claims

1. In an information transmission system having at least two spaced stations in communication with each other, a phase locked loop to stabilize the frequency of an oscillator disposed in one of said stations comprising:

said oscillator having an output frequency F;

a source of reference signal having a frequency (N/M) F, where N and M are different integers greater than one such that (N/M) is a fractional number, said source being disposed in the other of said stations;

first means disposed in said one of said stations coupled to perform the combined function of multiplying said frequency F by a factor (N/M) and comparing the phase relation between said multiplied frequency F and said reference signal received from said other of said stations to produce a phase control signal;

second means disposed in said one of said stations to couple said control signal to said oscillator for frequency stabilization thereof;

third means disposed in said other of said stations coupled to said source to sweep the frequency of said reference signal when the pull-in range of said loop is exceeded, said pull-in range being that range of frequency differences between the frequency of said reference signal and said output frequency of said oscillator where said loop is effective to perform the desired frequency stabilization; and

fourth means disposed in said other of said stations coupled to respond to said reference signal received from said one of said stations to activate said third means when said reference signal has an amplitude less than a given threshold value indicating that said pull-in range is exceeded.

2. A phase locked loop according to claim 1, wherein said first means includes fifth means coupled to the output of said oscillator to divide said frequency F by M, sixth means tuned to frequency (N/M) F to respond to said reference signal received from said other of said stations, seventh means tuned to respond to the Nth harmonic of the frequency F/M at the output of said first means, and eighth means coupled to said sixth and seventh means to produce said control signal.

3. A phase locked loop according to claim 2, wherein said second means includes a filter network coupled between the output of said first means and the frequency control input of said oscillator, and an operational amplifier coupled in parallel with said filter network.

4. A phase locked loop according to claim 1, wherein said second means includes a filter network coupled between the output of said first means and the frequency control input of said oscillator, and an operational amplifier coupled in parallel with said filter network.

5. In an information transmission system having at least two spaced stations in communication with each other, a phase locked loop to stabilize the frequency of an oscillator disposed in one of said stations comprising:

said oscillator having an output signal F;

a source of reference signal having a frequency (N/M) F, where N and M are different integers greater than 1, said source being disposed in the other of said stations;

first means disposed in said one of said stations coupled to perform the combined function of multiplying said frequency F by a factor (N/M) and comparing the phase relation between said multiplied frequency F and said reference signal received from said other of said stations to produce a phase control signal;

second means disposed in said one of said stations to couple said control signal to said oscillator for frequency stabilization thereof;

third means disposed in said other of said stations coupled to said source to sweep the frequency of said reference signal when the pull-in range of said loop is exceeded, said pull-in range being that range of frequency differences between the frequency of said reference signal and said output frequency of said oscillator where said loop is effective to perform the desired frequency stabilization; and

fourth means disposed in said other of said stations coupled to respond to said reference signal received from said one of said stations to activate said third means when said reference signal has an amplitude less than a given threshold value indicating that said pull-in range is exceeded.

6. A phase locked loop according to claim 5, wherein said first means includes fifth means coupled to the output of said oscillator to divide said frequency F by M, sixth means tuned to frequency (N/M) F to respond to said reference signal received from said other of said stations, seventh means tuned to respond to the Nth harmonic of the frequency F/M at the output of said first means, and eighth means coupled to said sixth and seventh means to produce said control signal.

7. A phase locked loop according to claim 6, wherein said second means includes a filter network coupled between the output of said first means and the frequency control input of said oscillator, and an operational amplifier coupled in parallel with said filter network.

8. A phase locked loop according to claim 5, wherein said second means includes a filter network coupled between the output of said first means and the frequency control input of said oscillator, and an operational amplifier coupled in parallel with said filter network.