Programmable digital phase control apparatus

• US 4,013,969 A
• Filed: 03/18/1976
• Issued: 03/22/1977
• Est. Priority Date: 03/18/1976
• Status: Expired due to Term

• Current Assignee: Rockwell International Corporation
• Original Assignee: Rockwell International Corporation
• Inventors: Dennison, Charles M.
• Primary Examiner(s): Heyman, John S.
• Application Number:
  US05/668,105
• Time in Patent Office: 369 Days
• Field of Search: 307/232, 307/233 R, 307/233 B, 328/133, 328/134, 328/110, 328/155, 328/55, 328/63, 328/48
• US Class Current: 327/241
• CPC Class Codes: H03H 11/20 Two-port phase shifters providing an adjustable phase shift
• CPC Class Codes: H03L 7/081 provided with an additional controlled phase shifter H03L7/0998 takes precedence

Abstract

A phase lock loop incorporating a novel feedback arrangement to provide an output of the same frequency as an input reference and phase shifted therefrom by a settable amount. The feedback portion of the phase lock loop from the output of the voltage controlled oscillator to the second input of a phase detector comprises a cycling digital counter and a coincidence detector which detects coincidence between the count of the counter and a set or programmable input. Whenever coincidence occurs, an output signal is provided to the phase detector such that the VCO is adjusted to provide the proper phase relationship between the input and the output signal.

Claims

1. Phase shifting apparatus comprising in combination:

phase detector and variable frequency oscillator means including first and second input means and an output means for providing an output signal which changes in frequency in accordance with difference in phase of signals applied to said input means thereof;

means for supplying a reference frequency signal to said first input means;

counter means connected to said output means of said oscillator means for providing a repetitive series of digital word outputs of the number of cycles generated;

variable count detection means, connected between said second input means and to said counter means for providing a signal to said phase detector whenever the count of said counter means coincides with a predeterminable count set in said count detection means; and

apparatus output means, connected to said counter means, for providing an output signal phase shifted from, but of the said frequency as, the reference frequency.

2. The method of generating a signal of a given frequency, phase shifted with respect to a reference signal of the same frequency comprising, the steps of:

generating a first signal whose frequency changes as a function of phase difference between a reference frequency signal and a feedback signal;

generating a cycling digital word output signal indicative of the number of cycles of said first signal wherein the most significant bit of said output signal has the same frequency as, but is phase shifted with respect to, the reference frequency signal; and

comparing the digital word output signal with a predetermined count for generating a feedback signal upon detection of coincidence.

3. Phase lock loop apparatus for generating a signal of a given frequency wherein the phase of the signal is shifted with respect to the phase of a reference signal of the same frequency comprising, in combination:

first means for supplying a reference signal having a first phase and a first frequency;

second means, connected to said first means, for generating a second signal whose frequency is higher than the frequency of said reference signal and whose frequency changes as a function of a phase difference between said reference frequency signal and a feedback signal;

third means, connected to said second means, for generating a repeating series of digital word output signals which are successively indicative of individual cycles of said second signals wherein the most significant bit of the digital word output signal has the same frequency as, but is phase shiftable with respect to, the reference frequency signal; and

fourth means, connected to said third means, for comparing the digital word output signal with a predetermined count for generating a feedback signal to be supplied to said second means upon detection of coincidence.