Pulse or digital communications – Receivers
Reexamination Certificate
1998-04-01
2001-10-23
Chin, Stephen (Department: 2634)
Pulse or digital communications
Receivers
C375S130000, C359S305000, C356S450000, C324S076370
Reexamination Certificate
active
06307895
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a system that performs the measurement of complex Fourier coefficients of RF signals. More particularly, the present invention relates to a system that performs complex Fourier coefficient measurements of RF signals using optical processing techniques, specifically, a technique that improves on the Bragg cell optical technique so as to yield the phase parameters along with the frequency coefficient amplitude parameters of the RF signals being characterized.
2. Description of the Prior Art
Digital signal processing techniques are currently employed to provide complex Fourier coefficient measurements of RF signals so as to classify such RF signals. The digital signal processing techniques begin with the digitizing of the RF signal and then electronically calculating the Fourier transform which, in turn, yields the Fourier coefficients. The existing techniques that calculate complex Fourier coefficients take in the order of 300 microseconds which is relatively slow for many applications and are especially slow for dense signal environments made up of many RF signals. It is desired that the measurement of the Fourier coefficient be accomplished by faster means than digital signal processing techniques, more particularly, by optical processing techniques based on Bragg cell spectrum analysis techniques.
OBJECTS OF THE INVENTION
It is a primary object of the present invention to provide an electronic/optical hybrid system that provides complex spectrum analysis of the signal modulation that yields Fourier coefficients and which builds on known Bragg cell spectrum analysis techniques.
It is another object of the present invention to provide for optical processing techniques that yield the determination of the Fourier coefficients, especially the phase parameter thereof.
It is another object of the present invention to provide for a system that yields the determination of complex Fourier coefficients, especially the phase parameter, with minimum processing time by employing speed of light and parallel signal processing techniques.
Further still, it is an object of the present invention to provide for various embodiments of optical processing techniques each yielding the accurate determination of the Fourier coefficients, including the phase parameter thereof.
Further, it is an object of the present invention to reduce, in certain cases, the amount of sampling of an unknown RF signal that is needed to determine the Fourier coefficients, for example, when the intensity of the unknown RF signal is a known quantity.
SUMMARY OF THE INVENTION
The present invention is directed to an apparatus for extracting Fourier coefficients from an RF signal of interest so as to characterize the RF signal. The RF signal has a fundamental frequency and harmonics thereof along with a leading edge and a carrier frequency which is modulated. The apparatus is adapted to permit interference between beams of the same frequency launched from two different Bragg cells and preferably extracts the Fourier coefficient by using parallel and optical processing techniques so as to provide a rapid determination thereof.
The apparatus comprises a generator, first and second Bragg cells, and means for receiving the outputs of the Bragg cells. The generator generates a signal having a predetermined spectrum that includes one of the fundamental and harmonic frequencies of the RF signal of interest. The first Bragg cell has means for receiving the RF signal and providing a representative output thereof. The second Bragg cell has means for receiving the signal generated by the generator and providing a representative output thereof. The means for receiving the outputs of the first and second Bragg cells allows for the outputs of the Bragg cells to interact with each other to produce an interference pattern that contains amplitude and relative phase information representative of the Fourier coefficients of the RF signal of interest. In one embodiment, the generator provides a frequency spectrum containing a frequency that corresponds to one of the fundamental and harmonic frequencies of the RF signal of interest.
REFERENCES:
patent: 4225938 (1980-09-01), Turpin
patent: 4365310 (1982-12-01), Green
patent: 4414583 (1983-11-01), Hooker, III
patent: 4467276 (1984-08-01), Marten et al.
patent: 4558925 (1985-12-01), Casseday et al.
patent: 4644267 (1987-02-01), Tsui et al.
patent: 4696061 (1987-09-01), Labrum
patent: 4699513 (1987-10-01), Brooks et al.
patent: 4725774 (1988-02-01), Davis et al.
patent: 4735476 (1988-04-01), Heffner et al.
patent: 4802149 (1989-01-01), Moore
patent: 4909627 (1990-03-01), Brousseau
patent: 4951061 (1990-08-01), Lee
patent: 4962382 (1990-10-01), Lee
patent: 5090795 (1992-02-01), O'Meara et al.
patent: 5267188 (1993-11-01), Pape et al.
patent: 5327142 (1994-07-01), Tsui et al.
patent: 5682238 (1997-10-01), Levitt et al.
patent: 5923460 (1999-07-01), Stewart et al.
patent: 6061135 (2000-05-01), Levitt et al.
Alexander Edward
Krantz Brian
Levitt Hal
Spezio Anthony
Chin Stephen
Fan Chieh M.
Karasek John J.
Legg L. George
The United States of America as represented by the Secretary of
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