The Army MICOM Weapons Sciences Directorate, with assistance from Martin Marietta Corp, has provided support to the ARPA TOPS Program by generating training video imagery to be used by the TOPS contractors and any other agencies which have need for the data. The data include 1448 tank, APC, and M60-A2 tank recorded using four TV FOV's. Targets were mounted on a turntable below a 300 ft tower, and viewed through all azimuth/elevations behind sun screen and in direct sun. Additional video recorded target drive—around past trees and shadows. Helicopter captive carry TV data, using a gimballed seeker flying a simulated FOG-M flight path, were collected of an M60-A2 tank surrounded by four false targets. Mid and far IR FLIR data include tower/turntable and drive-around, with targets with various thermal states. Video tapes have annotations of turntable az—el positions and sun angle relative to the target. Captive carry includes range data. Representative TV and FLIR video, documentary coverage, and some typical optical correlator results using these data are presented.
Martin Marietta is conducting a TOPS optical correlation program in which several algorithms and four optical correlators involving two spatial light modulator technologies will be developed and tested. The program will culminate in 1994 with an automatic target recognition flight demonstration using a UH-1 helicopter flying a Fiber Optic Guide Missile (FOG-M) mission profile. The flight demonstration will be conducted by US Army Missile Command (MICOM) and Martin Marietta and will involve detecting, locating and tracking a M60A2 tank positioned among an array of five vehicle types. Current status of the TOPS program will be given.
A review of concept designs for the Transition of Optical Processing to Systems (TOPS) correlator program are examined. The different concepts are different combination available SLMs and lens designs which are completed. A concept is chosen and described.
The technical approach and recent experimental results for the acousto-optic time- and space- integrating real-time SAR image formation processor program are reported. The concept overcomes the size and power consumption limitations of electronic approaches by using compact, rugged, and low-power analog optical signal processing techniques for the most computationally taxing portions of the SAR imaging problem. Flexibility and performance are maintained by the use of digital electronics for the critical low-complexity filter generation and output image processing functions. The results include a demonstration of the processor's ability to perform high-resolution spotlight-mode SAR imaging by simultaneously compensating for range migration and range/azimuth coupling in the analog optical domain, thereby avoiding a highly power-consuming digital interpolation or reformatting operation usually required in all-electronic approaches.
The Acousto-Optic Precision Direction Finding (AOPDF) system is a demonstration EW receiver in development at the Naval Research Laboratory as a DARPA sponsored activity. A two-dimensional Acousto-Optic processing element extracts frequency, angle of arrival (AOA), and time of arrival (TOA) on a pulse-by-pulse basis. Performance advantages achieved through use of Acousto-Optic technology include a wide instantaneous RF bandwidth, multiple simultaneous signal capture, and accurate AOA measurement over a quadrant field of view. This paper describes the conceptual design, system development, and evaluation of a demonstration unit based on the AOPDF concept.
A need for very high probability of detection in modern passive Electronic Combat (EC) systems has stimulated development of ever-wider receiver bandwidths. As the receiver bandwidths increase, some portions of the RF spectrum will begin to have a probability of signal overlap approaching unity. Wideband receivers, when operating in these environments with increasing signal threat densities and new modern modulation techniques, must incorporate computationally intensive algorithms within the receiver architecture to ensure reliable performance. Acousto-optic processing subsystems offer a real-time solution to several of the computationally intensive signal processing functions required in wideband EW systems. Two such acousto-optic subsystems that are being developed by DARPA through the Naval Research Laboratory will be discussed in this paper: Channelization and Direction Finding.
An acousto-optic (AO) correlator is being constructed that offers a small, lightweight solution to detecting and analyzing wide-bandwidth, spread-spectrum signals. The processor is being inserted into an existing electronic support measure (ESM) test-bed under the Defense Advanced Research Projects Agency (DARPA) Transition of Optical Processors into Systems (TOPS) program. The correlator has a processing bandwidth of 500 MHz and will be used to detect direct-sequence, phase-modulated signals, frequency-hopped signals, chirps, and impulses. A description of the processor is provided along with experimental results obtained from an interim developmental breadboard. Subsequent digital processing, which includes nonlinear detection and Fourier transformation, is used to determine center frequencies, bandwidths, and band shape. Theoretical descriptions of the post-processing are provided and simulations results are discussed.
An acousto-optic (AO) range-Doppler processor is interfaced to an advanced ground-based radar system developed by the U.S. Army Missile Command (MICOM). Demonstration of this optical processor in the MICOM radar is the primary objective of this program, part of the DARPA-sponsored Transition of Optical Processors into Systems (TOPS) program. This paper reviews the MICOM radar system, describes the design of the AO range-Doppler processor, and details the digital electronic interfaces required to achieve real-time operation in the MICOM radar. Experimental results for the AO processor are also provided.
The Acousto-Optic Null Steering Processor (AONSP) is an acousto-electro-optic implementation of a radar multiple sidelobe canceler (MSLC) addressing wideband jamming and multipath. The flowdown of requirements from adaptive canceler performance to hardware configuration is the subject of this paper. The development program is sponsored by DARPA and Rome Laboratory.
This system provides rapid location of free form text retrieved from an optical disk by content addressing. A highly parallel, spatial intensity integrating correlator has been breadboarded using commercially available off-the-shelf components for proof of concept and identification of key component characteristics. Performance is found to be sensitive to light source coherence, optics modulation transfer function, media bit placement and contrast uniformity. Simplified processing algorithms extendable to on-chip implementation are evaluated with simulated and experimental results.
Under the Optical Control of Phased Arrays program a fully functional L-band two- dimensional conformal array is being developed. The scope of work includes the development of a wideband radiating element, T/R modules, and a 5-bit photonic time-shift network for beam steering. The photonic time-shifter uses a combination of RF switching, laser switching, fiber starcoupling and photodetector switching to provide the selection of 32 possible delay combinations.
An optical time delay network (OTDN) for time delay steering of arrays of various sizes is being developed which features passive waveguides and micromechanical switches monolithically fabricated on silicon. Separately packaged directly modulated lasers and optical envelope detectors perform the RF and optical conversions. Recent developments in the areas of phosphosilicate glass (PSG) waveguides and micromechanical switches are presented. Broadband reactive matching circuits for commercially available directly modulated lasers and optical detectors are described which demonstrate VSWRs of less than 1.5:1 and improvement of 16 dB in overall RF/optical/RF conversion efficiency for an octave bandwidth. Finally, plans for demonstrating the operation of the time delay network in a 4 by 16 element phased array with an operating band of 2 to 4 GHz are presented.
We describe and present experimental results for two optical control techniques for phased array antennas. The first technique is based on interferometric heterodyning of two narrow- linewidth YAG lasers for the generation of required microwave signal and for simultaneous steering of the radiated beam. The constructed system is simple and well-suited for narrowband applications, and it may be built without any active mechanical components. The measured radiated antenna patterns are in close agreement with the predicted ones. The second technique is a novel and elegant method for implementing a true time-delay function for optical control. It relies on using a wavelength-tunable laser to provide the optical carrier for the microwave signal and a fiber-optic prism--a set of equal delay fibers with differing net dispersion. The relative interelement time-delay (beam angle) adjustment is accomplished by tuning the optical carrier wavelength. The experimental results obtained on a compact antenna range clearly demonstrate beam-steering and true time-delay operation over a two-octave bandwidth.