Precise RF timing signal distribution to remote stations
OwnerRobert A. Administrator of the National Aeronautics and Space Administration, with respect to an invention of Frosch, Georg F. Lutes, Jr.inventors
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Abstract
This invention relates to a method and apparatus for distributing a stable reference frequency from a hydrogen maser frequency standard, or similar RF source, to remote stations over great distances with very good phase stability, and with constant amplitude, at each distribution point, using a light beam carrier, and more particularly to a technique for providing automatic gain control at an optical receiver with phase stability in the RF reference.
Claims6
A method of distributing a precise RF frequeny signal from a source to a plurality of remotely located stations for use at said stations in processing of data comprising,
- generating a light beam,
- modulating the amplitude of said light beam with said RF timing signal from said source,
- dividing said modulated beam into a plurality of split beams,
- transmitting each split beam to a different station over an optical fiber, and at each station
- detecting the amplitude modulation of the split beam with an optical detector to produce an RF electrical signal that conforms in frequency with said RF reference signal from said source for use at the station,
- detecting the average amplitude of said RF electrical signal to produce an automatic gain control signal, and
- controlling an optical attenuator at the input of said optical detector for automatic gain control of said RF electrical signal without introducing any appreciable phase shift.
In a system for transmitting an RF signal amplitude modulated on a light beam to a remote station, an optical receiver comprising
- means for detecting said light beam and producing an RF electrical signal proportional to the amplitude thereof,
- means responsive to said RF electrical signal for producing an automatic gain control signal proportional to the average amplitude of said electrical signal, and
- voltage variable means for attenuating said light received for detection by said detecting means in response to said automatic gain control signal, whereby automatic gain control is achieved for said RF electrical signal with phase stability.
Dependencies are inferred from the claim text.