Abstract: In a ground penetrating radar system, A-scan images of subsurface targets lying along the antenna boresight axis can be substantially improved and generated in real-time by employing a synthetic aperture, end-fire array, despite the inhomogeneous nature of the subsurface volume. The synthetic aperture, end-fire array is achieved by generating electro-magnetic (EM) ultra-wideband impulses at a number of precise locations along the antenna boresight access, shifting the returned EM signals in the time domain according to the corresponding antenna boresight location, and then integrating the shifted, returned EM signals.

Abstract: In a ground penetrating radar system, A-scan images of subsurface targets lying along the antenna boresight axis can be substantially improved and generated in real-time by employing a synthetic aperture, end-fire array, despite the inhomogeneous nature of the subsurface volume. The synthetic aperture, end-fire array is achieved by generating electro-magnetic (EM) ultra-wideband impulses at a number of precise locations along the antenna boresight access, shifting the returned EM signals in the time domain according to the corresponding antenna boresight location, and then integrating the shifted, returned EM signals. In addition, an incremental, reverse-coherent integration technique is provided. This incremental technique allows for a more rapid generation of the A-scan image. The reverse-coherent integration technique eliminates unintended, stationary targets from the A-scan image, which are caused by coherent noise/clutter sources.

Abstract: In a ground penetrating radar system, A-scan images of subsurface targets lying along the antenna boresight axis can be substantially improved and generated in real-time by employing a synthetic aperture, end-fire array, despite the inhomogeneous nature of the subsurface volume. The synthetic aperture, end-fire array is achieved by generating electromagnetic (EM) ultra-wideband impulses at a number of precise locations along the antenna boresight access, shifting the returned EM signals in the time domain according to the corresponding antenna boresight location, and then integrating the shifted, returned EM signals.

Abstract: An exclusively digital timing engine that measures extremely short time intervals for use in time of flight systems such as laser range finding systems. This exclusively digital timing engine minimizes the use of high speed, high cost components by employing a novel time multiplexing scheme to execute each of the primary time of flight functions: frequency synthesis, range gating, and time of flight interval measurement. In addition, the timing engine incorporates a random time delay scheme which enhances the resolution of the time interval measurement.

Abstract: A bulk semiconductor laser which uses optically triggered avalanche conduction to initiate the lasing action in the bulk. A semiconductor block has electrodes coupled on opposing sides and a high voltage is applied across the electrodes which is less than the voltage required for avalanche breakdown. The block is irradiated with light which produces charge carriers in the block to initiate avalanche conduction, which results in a large number of charge carriers. The charge carriers recombine to generate a second amount of electromagnetic radiation. This radiation is reflected back into the block on two opposing sides, thus resulting in a laser emission.

Abstract: A switch using an improved method of optically-triggered avalanche breakdown which can produce pulses of 100 picoseconds or longer duration that can deliver five kilovolts into 50 ohms using a standard laser diode. A semiconductor block is provided with contacts on opposing sides across which a high-voltage less than the avalanche breakdown voltage is applied. One of the electrodes is on a mesa on one side of the block. The mesa is then irradiated with electromagnetic radiation. The wavelength of the radiation and the absorption coefficient of the semiconductor block are chosen so that the absorption depth of the majority of the radiation is less than the distance between the contacts. This results in a conduction area where absorption occurs, thus applying most of the high voltage across the distance beyond where the radiation is absorbed. This provides field compression and generates an avalanche breakdown field across the remaining distance of the semiconductor block.

Abstract: Apparatus for switching kilovoltages in times of the order of one nanosecond or less, using optical radiation with energy input 10.sup.-7 Joules, applied to a cryogenically cooled, suitably doped block of semiconductor material that is positioned across an electrical gap.