US4255810A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Jam resistant frequency modulation system
Assignee: United States Department of the Navy
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Filing: 1965-01-13
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Granted: 1981-03-10
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Expires: 1985-01-13
Abstract
Abstract 1. An interference proof FM video communication system comprising: means for frequency modulating a carrier frequency by a video signal; means for bi-phase modulating the output of said frequency modulating meansn accordance with a binary code, said phases being 180° apart; means for transmitting the output signal of said bi-phase modulator; means remote from said transmitter for receiving said output signal; means associated with said receiving means for mixing said received signal with a beat frequency signal bi-phase modulated by a generated code substantially identical to said binary code; means for synchronizing said generated code with said binary code by comparing a filtered and an unfiltered value of the output of said mixing means; means for holding said generated code in synchronization with said binary code by correlating said received signal bi-phase modulated according to said generated code with said received signal bi-phase modulated according to a time-delayed version of said generated code; and means for detecting said video signal from the output of said mixing means.
Inventors
- 👤 Karl Solomon
- 👤 George C. Hennessy
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 22:14
CPC Classifications
H; H04; H04K; H04K3/00; H04K3/20; H04K3/22; H04K3/224; H04K3/228; H04K2203/00; H04K2203/10; H04K2203/14
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
167 words
An interference proof FM video communication system comprising: means for frequency modulating a carrier frequency by a video signal; means for bi-phase modulating the output of said frequency modulating means in accordance with a binary code, said phases being 180° apart; means for transmitting the output signal of said bi-phase modulator; means remote from said transmitter for receiving said output signal; means associated with said receiving means for mixing said received signal with a beat frequency signal bi-phase modulated by a generated code substantially identical to said binary code; means for synchronizing said generated code with said binary code by comparing a filtered and an unfiltered value of the output of said mixing means; means for holding said generated code in synchronization with said binary code by correlating said received signal bi-phase modulated according to said generated code with said received signal bi-phase modulated according to a time-delayed version of said generated code; and means for detecting said video signal from the output of said mixing means.
Claim 2
Dependent Claim
167 words
An interference proof FM video communication system comprising: means for frequency modulating a carrier frequency by a video signal; means for bi-phase modulating the output of said frequency modulating means in accordance with a binary code, said phases being 180° apart; means for transmitting the output signal of said bi-phase modulator; means remote from said transmitter for receiving said output signal; means associated with said receiving means for mixing said received signal with a beat frequency signal bi-phase modulated by a generated code substantially identical to said binary code; means for synchronizing said generated code with said binary code by comparing a filtered and an unfiltered value of the output of said mixing means; means for holding said generated code in synchronization with said binary code by correlating said received signal bi-phase modulated according to said generated code with said received signal bi-phase modulated according to a time-delayed version of said generated code; and means for detecting said video signal from the output of said mixing means.
Claim 3
Dependent Claim
32 words
An interference proof FM video communication system as recited in claim 1 further comprising: means to control said beat frequency by detection of non-video signals in the output of said detecting means.
Claim 4
Dependent Claim
75 words
A video communication system as recited in claim 1 wherein said means for synchronizing comprises: means for filtering the output of said mixing means; first means for detecting the average root mean square value of the filtered signal; second means for detecting the average root mean square value of the unfiltered output of said mixing means; and means for comparing said unfiltered RMS value with said filtered RMS value and having an output indicating synchronization.
Claim 5
Dependent Claim
67 words
A video communication system as recited in claim 3 wherein said means for comparing comprises: a first amplifier for raising the filtered value by a predetermined amount; a second amplifier for raising the unfiltered value by an amount greater than the first amplifier by a predetermined amount; and means for detecting when the output of said first amplifier is greater than the output of said second amplifier.
Claim 6
Dependent Claim
86 words
A video communication system as recited in claim 4 further comprising: a variable clock issuing a series of bits at a rate near the rate of said codes, the bit rate of said clock varying periodically; a code generator in said receiver, the rate of which is controlled by said clock bit rate; and means for switching said code generator from said variable clock to said holding means upon detection that the output of said first amplifier is greater than the output of said second amplifier.
Claim 7
Dependent Claim
57 words
A video communication system as recited in claim 5 wherein said switching means comprises: a relay responding to a signal from said means for detecting when the output of said first amplifier is greater than the output of said second amplifier; and a switch operable by said relay selectively connecting said variable clock or said holding means.
Claim 8
Dependent Claim
115 words
A video communication system as recited in claim 1 wherein said holding means comprises: means associated with said receiver to compare the received signal with a generated signal which is a combination of a code one-half bit early and a code one-half bit late with respect to said generated code supplied to said mixing means; means for detecting correlation of said received signal with the code one-half bit early or one-half bit late; and oscillator means controlling the rate of said generated code and controlled by said correlation detection means, adapted to change the bit rate in accordance with correlation detection to return the generated code to the midpoint between the early and late codes.
Claim 9
Dependent Claim
143 words
A video communication system as recited in claim 7 wherein said means associated with said receiving means for mixing said received signal comprises: a first means to mix the received signal with a beat frequency bi-phase modulated by a generated code; and said communication system further comprises: first means to remove the phase switch components from the output of said first mixing means; second means to mix the received signal with a beat frequency modulated by a code which is a combination of a generated code one-half bit early and a generated code one-half bit late and reversed in polarity; second means to remove phase switch components from the output of said second mixing means; and said means to compare the received signal with a generated signal comprises: means to compare the phases of the outputs of said first and second removing means.
Claim 10
Dependent Claim
162 words
A video communication system as recited in claim 8 wherein said oscillator controlling the bit rate is controlled by said phase comparing means and further comprising: a code generator controlled by said oscillator, issuing said generated code; a first delay line adapted to delay the output of said code generator by one-half bit; a beat frequency oscillator; first means for bi-phase modulating said beat frequency by the output of said first delay line, the output of said first bi-phase modulating means passing to said first mixing means; a second delay line adapted to delay the output of said first delay line by one-half bit; means to reverse the polarity of the output of said second delay line; an adder to combine the outputs of said code generator and said reversing means; and second means for bi-phase modulating said beat frequency by the output of said adder means, the outputs of said second bi-phase modulating means being passed to said second mising means.
Claim 11
Dependent Claim
97 words
A video communication system as recited in claim 8 wherein: the outputs of said first and second removing means are intermediate frequencies in phases respectively corresponding to the majority phases of the inputs of said first and second removing means, and of amplitude proportional to the ratio between said majority and minority phases; and said output of said phase comparing means is a voltage proportional to the amplitudes of the inputs to said phase comparing means and of a polarity selected according to the match of said inputs; and said oscillator means is a voltage controlled oscillator.
References Cited (Backward Citations)
US3706933A
Cited
US3475558A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1984-03-09 | 1984-09-08 | 1985-03-10 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1988-03-09 | 1988-09-08 | 1989-03-10 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1992-03-09 | 1992-09-08 | 1993-03-10 | $7700.00 | Window Closed / Lapsed |