US3654473A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Phase modulation laser communication system
Assignee: Raytheon Co
•
Filing: 1969-04-28
•
Granted: 1972-04-04
•
Expires: 1989-04-28
Abstract
Abstract In the disclosed laser communication system, at a transmitter a linearly polarized laser carrier beam is phase modulated with an informational signal such that when the resultant beam is resolved into two linearly polarized component beams in mutually perpendicular planes the respective component beams are shifted forwardly and backwardly in phase by an amount proportional to the informational signal. In a receiver the received phase modulated beam is combined with a local oscillator laser beam which is linearly polarized in a plane parallel to the plane of polarization of the carrier beam, and the resultant beam is separated into a pair of linearly polarized laser beams in respective planes parallel to the planes of the aforementioned transmitter component beams. These linearly polarized laser beams are converted into respective intermediate frequency electrical signals, and a reproduction of the informational signal is obtained by phase comparing these electrical signals.
Inventors
- 👤 Thomas A Nussmeier
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-22 17:19
CPC Classifications
H; H03; H03C; H03C3/00; H03C3/36; H04; H04B; H04B10/00; H04B10/50; H04B10/516; H04B10/548; H04B10/60; H04B10/66; H04B10/67; H04B10/671
Claims Analysis
Total Claims: 5
Claim 1
Independent Claim
224 words
A phase modulation laser communication system comprising: a transmitter including means for generating a laser carrier beam at a predetermined carrier frequency and linearly polarized in a predetermined plane, means for phase modulating said laser carrier beam with an informational signal such that when the resultant beam is resolved into two linearly polarized component beams in mutually perpendicular planes the respective component beams are shifted forwardly and backwardly in phase relative to said laser carrier beam, and means for directing the phase modulated laser beam toward a receiver; and a receiver including means for Receiving said phase modulated laser beam, means for generating a second laser beam at a frequency equal to the difference between said carrier frequency and a preselected intermediate frequency and linearly polarized in a plane parallel to said predetermined plane, means for combining the received phase modulated laser beam and said second laser beam and for separating the resultant beam into a pair of linearly polarized laser beams in respective planes perpendicular to one another, transducer means for converting each of said pair of linearly polarized laser beams into an electrical signal at essentially said preselected intermediate frequency, and means for comparing the instantaneous phase of the said electrical signals and producing an electrical output signal corresponding to the phase difference therebetween, said output signal essentially reproducing said informational signal.
Claim 2
Dependent Claim
224 words
A phase modulation laser communication system comprising: a transmitter including means for generating a laser carrier beam at a predetermined carrier frequency and linearly polarized in a predetermined plane, means for phase modulating said laser carrier beam with an informational signal such that when the resultant beam is resolved into two linearly polarized component beams in mutually perpendicular planes the respective component beams are shifted forwardly and backwardly in phase relative to said laser carrier beam, and means for directing the phase modulated laser beam toward a receiver; and a receiver including means for Receiving said phase modulated laser beam, means for generating a second laser beam at a frequency equal to the difference between said carrier frequency and a preselected intermediate frequency and linearly polarized in a plane parallel to said predetermined plane, means for combining the received phase modulated laser beam and said second laser beam and for separating the resultant beam into a pair of linearly polarized laser beams in respective planes perpendicular to one another, transducer means for converting each of said pair of linearly polarized laser beams into an electrical signal at essentially said preselected intermediate frequency, and means for comparing the instantaneous phase of the said electrical signals and producing an electrical output signal corresponding to the phase difference therebetween, said output signal essentially reproducing said informational signal.
Claim 3
Dependent Claim
66 words
A phase modulation laser communication system according to claim 1 wherein the beam combining and separating means of the receiver includes a beam splitter disposed so as to transmit a portion of the energy in the received phase modulated laser beam and to reflect a portion of the energy in said second laser beam along the same path, and a polarizing prism disposed in said path.
Claim 4
Dependent Claim
63 words
A phase modulation laser communication system according to claim 2 wherein said means for phase modulating said laser carrier beam includes an electro-optic device having mutually perpendicular induced axes of birefringence oriented at an angle of 45* with respect to said predetermined plane, and said polarizing prism has a polarizing axis disposed at an angle of 45* with respect to said predetermined plane.
Claim 5
Dependent Claim
63 words
A phase modulation laser communication system according to claim 1 wherein said receiver further includes control means coupled to said transducer means for deriving a signal indicative of the frequency of at least one of said electrical signals and for controlling the frequency of said means for generating a second laser beam to maintain said preselected intermediate frequency at an essentially constant value.
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) | 1975-04-04 | 1975-10-04 | 1976-04-04 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-04-04 | 1979-10-04 | 1980-04-04 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-04-04 | 1983-10-04 | 1984-04-04 | $7700.00 | Window Closed / Lapsed |