Coded phase modulation communications system

• US 6,313,782 B1
• Filed: 11/16/1960
• Issued: 11/06/2001
• Est. Priority Date: 11/16/1960
• Status: Expired due to Term

• Current Assignee: The United States Of America As Represented By The Secretary Of The Army
• Original Assignee: The United States Of America As Represented By The Secretary Of The Army
• Inventors: Rechtin, Eberhardt, Victor, Walter K., Lehan, Frank W.
• Primary Examiner(s): Sotomayor, John B.
• Application Number:
  US04/069,775
• Time in Patent Office: 14,965 Days
• Field of Search: 250/6.6, 250/1.12, 250/2, 250/22, 331/78, 244/14, 178/22, 342/13, 342/16, 342/17, 342/18, 342/19, 342/159, 342/162, 342/202, 342/203
• US Class Current: 342/16
• CPC Class Codes: G01S 13/288 phase modulated
• CPC Class Codes: G01S 7/35 Details of non-pulse systems
• CPC Class Codes: H04B 1/71 the interference being narrowband interference

Abstract

A coded phase modulation communications system which relates to communications systems in which undesired detectability of the radiated signal is materially reduced, and wherein the vulnerability of the system to interfering signals, such as, intentional jamming signals, is substantially reduced. In the system, a radio frequency communications signal is phase modulated by a random or random appearing, but repeatable pattern of noise signal. The received signal is modulated by an identical noise signal, which when synchronized with the original noise modulation results in erasing the noise, and thereby recreating the original, continuous, communications signal. The noise source of the system is a pseudo noise generator that may be readily synchronized with an identical noise source or sources. The pseudo noise generator provides an apparently orderless noise-like sequence that may be exactly reproduced at the same or at a remote location or locations.

Claims

1. In combination, means for developing a continuous-wave alternating current output generator means for providing a sequence of encoding pulses occurring in a pseudo-random pattern, means for modulating the phase of the continuous wave output signal in accordance with the occurrence of the pseudo-random encoding pulses, means for radiating the phase-modulated output signal toward a target and for receiving a phase-modulated output signal from the target corresponding to the radiated phase modulated signal resonant means responsive to pass only the signals received in a selected frequency range, phase-demodulating means interposed between said resonant means and said receiving means means including a second pseudo-random pulse-generator for controlling the operation of the phase-demodulating means in accordance with the occurrence of pulses in the pseudo-random pattern to convert the signal received from the target to a signal of invariable phase, and means including time delay means included in said controlling means and adjustable in accordance with the range between the target and the radiating and receiving means to cause the control of the phase-demodulating means to coincide with phase modulations in the received signals for the passage of a signal of substantially invariable phase in the selected frequency range to the resonant means for the production of indications as to parameters of the target relative to the radiating and receiving means in accordance with the adjustment in the time delay means.

2. In combination, means for providing an intelligence modulated signal, first and second synchronistical electronics, pseudo-noise generating means for providing identical pseudo-random patterns, means for synchronizing said generating means, modulating means coupled to said signal means and said first generating means for modulating said signal by inverting the phase of said signal in accordance with said random pattern, means responsive to said modulating means for transmitting the inversion modulated signal, means for receiving said transmitted signal, first demodulating means responsive to the received signal and said second generating means for reproducing said intelligence modulated signal, and second demodulation means responsive to the reproduced intelligence modulated signal for obtaining the intelligence modulation.

3. In combination, a signal carrier circuit, an encoder, a subcarrier circuit and a control signal generating means, said subcarrier circuit comprising a subcarrier generator and first modulation means responsive to said control signal generating means for phase modulating the subcarrier by control signals, said encoder comprising a synchronized pseudo-noise generator and multiplier means, said pseudo-noise generator being synchronized by the modulated subcarrier, the output of said pseudo-noise generator being multiplied by said modulated subcarrier in said multiplier means, said signal carrier circuit comprising a carrier generator, a carrier phase modulator and means for transmitting the output of said carrier phase modulator, said carrier phase modulator modulating the output of said carrier generator responsive to the output of said multiplier means.

4. The combination set forth in claim 3 further comprising means for receiving said transmitted output means for decoding the received signal and detecting means for detecting the subcarrier and control signal modulation, decoding means for comprising a synchronistical pseudo-noise generator and decoder multiplying means responsive to said last named generator and received signal for producing sidebands corresponding to said subcarrier about a suppressed intermediate frequency, a first local oscillator of a frequency corresponding to said suppressed intermediate frequency and a first detector responsive to said first local oscillator and said decoding means for reproducing said modulated subcarrier, a second local oscillator corresponding in frequency to said subcarrier, a first 90°

phase shifter, a first phase detector responsive to the output of said first detector and output of said second local oscillator supplied thru said first phase shifter for reproducing said control signals, first control means responsive to the direct current component of said first phase detector for locking the frequency of said second local oscillator to the frequency of said subcarrier, an output of sad second local oscillator being connected to said synchronistical pseudo-noise generator to synchronize said last named generator with the frequency of said subcarrier, frequency control means for maintaining the frequency of said first local oscillator at a frequency corresponding to said suppressed carrier, said frequency control means comprising single sideband filter means responsive to said decoder multiplying means for passing one of said sidebands, a second 90°

phase shifter, a second detector responsive at one input to the output of said filter means and at a second input to the output of said first local oscillator supplied thru said second phase shifter for producing the difference of said inputs, second phase detector means for comparing the phase of the output of said second local oscillator and the output of said second detector, and means responsive to the output of said second phase detector for controlling the frequency of said first local oscillator.

5. In combination, means for providing an intelligence modulated signal, first and second synchronistical electronic pseudo-noise generating means for providing identical pseudo random patterns, said first and second generating means each comprising a delay circuit having an input, a total delay output and an intermediate delay output, a half adder, an amplifier, a clock oscillator and a gating circuit, said outputs of said delay circuit being coupled to and combined in said half adder, amplified in said amplifier and coupled to the input of said delay circuit, the half adder output being coupled thru said gating circuit, and said gating circuit being controlled responsive to the output of said clock oscillator, means for synchronizing said generating means, modulating means coupled to said signal means and said first generating means for modulating said signal by inverting the phase of said signal in accordance with said random pattern, means responsive to said modulating means for transmitting the inversion modulated signal, means for receiving said transmitted signal, first demodulating means responsive to the received signal and said second generating means for reproducing said intelligence modulated signal, and second demodulation means responsive to the reproduced intelligence modulated signal for obtaining the intelligence modulation.

6. The combination set forth in claim 5 wherein said means for synchronizing comprises an “

or”

circuit having first and second inputs and an output one of said “

or”

inputs and said “

or”

output being connected in series between the output of said half adder and the input of said delay circuit of said second generating means, an output of said first generating means being connectable, at least instantaneously, to said second input of said “

or”

circuit, means responsive to said clock oscillator of said first and second generating means for controlling the frequency of said second generating means clock oscillator to conform with the frequency of said first generating means clock oscillator.