US3983501A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Hybrid tracking loop for detecting phase shift keyed signals
Assignee: United States Department of the Navy
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Filing: 1975-09-29
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Granted: 1976-09-28
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Expires: 1995-09-29
Abstract
Abstract A hybrid tracking loop detector system that accurately demodulates phase ft keyed acoustic telemetry signals. The system internally determines the received carrier frequency and detects phase shifts that denote the digital format depicted by the phase shift keyed signals. The system is particularly useful for operating at low signal to noise ratios and with relatively short messages. The detector includes a phase lock loop comprising a phase comparator, an amplifier, an adjustable filter and a voltage controlled oscillator. The phase and frequency of the oscillator are divided and are locked to the carrier frequency of the received signal and are used as a reference for the phase comparison detection. The system has two sequented modes of operation, a direct acquisition mode and a holding mode. The detector switches automatically from the direct acquisition mode to the holding mode. The filter is initially broadband to allow detection of doppler shifted carrier signals and after locking onto the carrier signal it is switched to a narrow bandwidth to permit detection of low signal to noise ratio signals. A switching circuit is also provided to eliminate cycle slipping or loss of lock during periods when there is a phase shift in the received signals.
Inventors
- 👤 Alan L. Lindstrum
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 03:12
CPC Classifications
H; H03; H03D; H03D3/00; H03D3/02; H03D3/24; H03D3/241; H04; H04L; H04L27/00; H04L27/18; H04L27/22; H04L27/227; H04L27/2271; H04L27/2272; Y; Y10; Y10S; Y10S331/00; Y10S331/02
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
114 words
A detector for detecting phase shift keyed signals including a carrier signal having a frequency f c comprising: a. receiver means for receiving said phase shift keyed signals; b. a phase locked loop means for locking onto said carrier signal; c. the output of said receiver means connected to the input of said phase locked loop means; d. control means; e. said control means operably connected to said receiver means and said phase locked loop means for selecting one or more of a plurality of input signals to be applied to said phase locked loop means in response to the output of said receiver means and the output of said phase locked loop means.
Claim 2
Dependent Claim
114 words
A detector for detecting phase shift keyed signals including a carrier signal having a frequency f c comprising: a. receiver means for receiving said phase shift keyed signals; b. a phase locked loop means for locking onto said carrier signal; c. the output of said receiver means connected to the input of said phase locked loop means; d. control means; e. said control means operably connected to said receiver means and said phase locked loop means for selecting one or more of a plurality of input signals to be applied to said phase locked loop means in response to the output of said receiver means and the output of said phase locked loop means.
Claim 3
Dependent Claim
73 words
The detector of claim 1 wherein: a. during the search mode of operation where said carrier signal has not been received and locked upon by said phase locked loop means said control means selects a first control position that applies the incoming carrier signal directly to one input of said phase locked loop means and the output of said phase locked loop means to the other input of said phase locked loop means.
Claim 4
Dependent Claim
58 words
The detector of claim 2 wherein: a. during said search mode of operation said first control position of said control means selects a broadband filter means in said phase locked loop means for processing said incoming carrier signal prior to and until said carrier signal is being received and is locked upon by said phase locked loop means.
Claim 5
Dependent Claim
85 words
The detector of claim 2 wherein: a. after said phase locked loop means has locked upon said carrier frequency and is in the locked mode of operation said control means selects a second control position that applies an integer multiple of the frequency of said incoming carrier signal to said one input of said phase locked loop means and an even integer multiple of the frequency of said output of said phase locked loop means to the other input of said phase locked loop means.
Claim 6
Dependent Claim
39 words
The detector of claim 4 wherein: a. during said locked mode of operation said second control position of said control means selects a narrow band filter means in said phase locked loop means for processing said incoming carrier signal.
Claim 7
Dependent Claim
121 words
The detector of claim 4 wherein: a. after said phase locked loop means has locked upon said carrier frequency and said control means is in said second control position and there is a phase shift in said phase shift keyed signal, said control means detects said phase shift and selects a third control position that applies said even integer multiple of the frequency of said output of said phase locked looped means to said other input of said phase locked loop means and a 90° phase shifted signal of said even integer multiple of the frequency of said output of said phase locked looped means to said one input of said phase locked loop means for a predetermined period of time.
Claim 8
Dependent Claim
70 words
The detector of claim 1 wherein: a. said receiver means includes a band pass filter and a frequency multiplier connected in series; b. said phase locked loop means includes a first phase comparator, an amplifier, an adjustable filter, a voltage controlled oscillator and a divide circuit connected in series; wherein: c. said frequency multiplier has an integer multiplier that is the same as the integer divider of said divide circuit.
Claim 9
Dependent Claim
85 words
The detector of claim 7 wherein: a. said control means includes a 90° phase shifter, a second phase comparator, a lock sense circuit and a plurality of switching elements; b. the output of said voltage controlled oscillator being connected to the input of said 90° phase shifter, the output of which is connected to the input of said second phase comparator and a first of said switching elements, and the output of said second phase comparator connected to the input of said lock sense circuit.
Claim 10
Dependent Claim
138 words
The detector of claim 8 wherein: a. said plurality of switching elements including first, second, third, fourth, fifth and sixth switching elements; b. the outputs of said first, second, and third switching elements being connected to a first input of said first phase comparator and the outputs of said fourth, fifth and sixth switching elements being connected to a second input of said first phase comparator; c. said lock sense circuit including first means for detecting when said second phase comparator provides no output signal and second means for detecting when said second phase comparator provides an output signal; d. the output of said first means connected to the gate inputs of said third and sixth switching elements; and e. the output of said second means connected to the gate inputs of said second and fifth switching elements.
Claim 11
Dependent Claim
45 words
The detector of claim 9 wherein: a. said lock sense circuit includes third means for detecting when said phase shift keyed signal shifts in phase; and b. the output of said third means connected to the gate inputs of said first and fourth switching elements.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1979-09-28 | 1980-03-29 | 1980-09-28 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1983-09-28 | 1984-03-29 | 1984-09-28 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1987-09-28 | 1988-03-29 | 1988-09-28 | $7700.00 | Window Closed / Lapsed |