Edward R Alexander

US Patent:

7024120, Apr 4, 2006

Filed:

Mar 29, 2002

Appl. No.:

10/113653

Inventors:

Timothy N. Reynolds - Lanham MD, US
Edward M. Alexander - Falls Church VA, US
Anthony E. Spezio - Laurel MD, US

Assignee:

The United States of America as represented by the Secretary of the Navy - Washington DC

International Classification:

H04B 10/00

US Classification:

398116, 398 91, 398115

Abstract:

A phase tracking multichannel apparatus includes a plurality of optical transmitters, an optical multiplexer, a common optical link, and a user electronics. RF signals having different phases are received and are output on separate RF channels, each of which is coupled to an optical transmitter. RF-modulated optical output signals are then output to the optical multiplexer to produce a multiplexed output signal. The multiplexed signal is applied to a common optical link that at its output substantially maintains the phase separation of RF modulation components on optical carriers as received at its input. The optical output of the common optical link is then applied to an optical signal receiving system, such as an optical demultiplexer and a plurality of photodetectors. By multiplexing all of the optical signals onto the common optical fiber, all signals transmit the same path and, therefore, have the same time and phase delay. The phase tracking is preserved because all of the signals experience the same optical or expansive properties of the common optical fiber.

US Patent:

H17027, Jan 6, 1998

Filed:

Jan 6, 1995

Appl. No.:

8/369437

Inventors:

Ronald D. Esman - Burke VA
Lew Goldberg - Fairfax VA
Edward Alexander - Falls Church VA
Keith J. Williams - Accokeek MD

International Classification:

H04B 1002
H04B 1004
H04B 1006

US Classification:

359154

Abstract:

In the transmission electrical signals using an optical carrier the signal power carried by an optical carrier is proportional to the optical power. High optical power levels are desired for optical carriers that are modulated by weak electrical signals, however, significant unmodulated power is left in the original carrier after processing. To maximize the radio frequency (RF) signal power generated by a given (maximized) photodetector current (for a given input power), in this invention, the optical carrier power is reduced. This is accomplished by the addition of a narrowband optical filter, such as a Fabry-Perot filter, to reduce the average optical carrier power without reducing the modulation sidebands, which results in an increased modulation depth. Therefore, greater RF and microwave power is generated by a photodetector with the same photocurrent. With a laser source exhibiting a beam whose linewidth is narrow compared to the filter bandwidth, the filter is tuned, or frequency locked, to match the filtering resonance with the optical carrier wavelength.

US Patent:

63078953, Oct 23, 2001

Filed:

Apr 1, 1998

Appl. No.:

9/052676

Inventors:

Edward Alexander - Falls Church VA
Anthony Spezio - Laurel MD
Hal Levitt - Baltimore MD
Brian Krantz - Gaithersburg MD

Assignee:

The United States of America as represented by the Secretary of the Navy - Washington DC

International Classification:

H03K 900

US Classification:

375316

Abstract:

A system for extracting the complex Fourier coefficients from an unknown RF signal to classify the RF signal is disclosed. The extraction system utilizes optical signal processing in combination with the generation of electronic timing and control signals. The system employs an optical processor comprising a Bragg cell to yield the Fourier coefficients including the amplitude, phase and frequency parameters thereof. The system further includes a parallel arrangement that provide for parallel processing to reduce the computational time needed to determine the complex Fourier coefficients including the amplitude, phase and frequency parameters thereof.

US Patent:

53231260, Jun 21, 1994

Filed:

Jun 30, 1993

Appl. No.:

8/083776

Inventors:

Anthony E. Spezio - Laurel MD
Saurabh Dalal - Lanham MD
Edward M. Alexander - Falls Church VA
Hal L. Levitt - Baltimore MD

Assignee:

The United States of America as represented by the Secretary of the Navy - Washington DC

International Classification:

H01P 518

US Classification:

333109

Abstract:

A circuit link, and method for using link, for self initializing any device peratively connected to the link. An input signal is split into two portions, one of which is delayed so that the undelayed signal can transverse the circuit link before the delayed signal. A pair of quadrature splitters are operatively connected to one another to split and combine the undelayed and delayed signals in their turns, and recombine them in their turns, in a manner effective to cause one of the circuit link's outputs to be nonzero responsive to the delayed signal, and zero responsive to the undelayed signal, with the opposite result on the other circuit output. The undelayed signal is thus available to initialize any device requiring initialization, and the delayed signal, unperturbed by any such device, is thus available for use as the circuit link's ultimate output. The circuit is especially useful with frequency selective limiters (FSL's), which are commonly used as channelizers in multichannel communication systems, and which are ineffective before initialization.

US Patent:

55878296, Dec 24, 1996

Filed:

Aug 29, 1994

Appl. No.:

8/296883

Inventors:

Edward M. Alexander - Falls Church VA
Anthony E. Spezio - Laurel MD

Assignee:

The United States of America as represented by the Secretary of the Navy - Washington DC

International Classification:

G02F 111

US Classification:

359287

Abstract:

A signal filter, and method of signal filtering, in which an optical signal s spatially dispersed according to frequency, and undesired frequencies blocked out. In an embodiment, a Bragg cell receives a (typically microwave) signal, and transduces it to an acoustic signal. A light source, e. g. a laser diode, directs light through the acoustic signal in a known manner so as to produce an optical output which is spatially dispersed according to frequency. A programmable spatial light modulator blocks out unwanted frequency components. Upon removal of the optical carrier, e. g. by heterodyning the spatial light modulator's output with a reference signal from the light source, the components can be recombined into a resultant filtered signal. The invention can be used as a repeater, a military electronic countermeasure, in environments which have large amounts of electromagnetic clutter but in which one does not want the clutter repeated. The spatial light modulator can be programmed to pass only frequency components in which one is interested, thus blocking the clutter from the repeated signal.

US Patent:

58221115, Oct 13, 1998

Filed:

May 3, 1995

Appl. No.:

8/492270

Inventors:

Edward M. Alexander - Falls Church VA
John N. Lee - Silver Spring MD
Anthony E. Spezio - Laurel MD

Assignee:

The United States of America as represented by the Secretary of the Navy - Washington DC

International Classification:

G02F 133

US Classification:

359306

Abstract:

A apparatus and method for coherently stretching or compressing signals of nterest, i. e. without loss of information. A first, or tapping, Bragg cell has an acoustic signal launched in it which is modulated onto a laser carrier. The signal of interest is launched into a second, or signal, Bragg cell, and is similarly modulated onto the carrier exiting the first Bragg cell. Upon demodulation, the resultant signal, is the convolution of the two acoustic signals in the respective Bragg cells, but whose duration is either stretched or compressed according to the relative velocity between the acoustic signals in the two Bragg cells, and by the magnification of optics between the two cells. If the signal in the first Bragg cell is of such a short duration that it is effectively an impulse, the resultant signal is a coherently stretched or compressed replica of the signal launched into the second Bragg cell, i. e. the signal of interest.