Abstract: Disclosed is an apparatus for transmitting an optical signal. The apparatus includes a transmitter (12, 14, 18, 20, 26) for transmitting a burst of optical radiation, the burst including first periods of optical radiation having a first wavelength (.lambda..sub.1) and second periods of optical radiation having a second wavelength (.lambda..sub.2). The first and second periods alternate with one another for a duration of the burst, and each of the periods begins with substantially zero transmitted power, increases to a maximum transmitted power, and decreases to substantially zero power. Also disclosed is a receiver (30) and demodulator (90) that includes a wavelength separator (DG) for separating the received optical radiation into a first portion comprising of radiation of wavelength .lambda..sub.1 and a second portion comprising of radiation of wavelength .lambda..sub.2.

Abstract: An extended depth-of-focus synthetic aperture radar (SAR) system (13) mounted on a moving platform, including a controller (120), pulse timer (83), synthesizer (105) and modulator (17) for varying the pulse rate interval (PRI) and/or the radar carrier frequency of radar pulses produced, in order to establish a radar return which, when conventionally processed, results in a SAR terrain map exhibiting extended depth-of-focus under conditions of platform acceleration. Depth of focus is established by ensuring the establishment of two or three separate, independently selected focal points in a target region of interest.

Abstract: An extended depth-of-focus synthetic aperture radar (SAR) system (13) mounted on a moving platform, including a controller (120), pulse timer (83), synthesizer (105) and modulator (17) for varying the pulse rate interval (PRI) and/or the radar carrier frequency of radar pulses produced, in order to establish a radar return which, when conventionally processed, results in a SAR terrain map exhibiting extended depth-of-focus under conditions of platform acceleration. Depth of focus is established by ensuring the establishment of two or three separate, independently selected focal points in a target region of interest.

Abstract: An extended depth-of-focus synthetic aperture radar (SAR) system (13) mounted on a moving platform, including a controller (120), pulse timer (83), synthesizer (105) and modulator (17) for varying the pulse rate interval (PRI) and/or the radar carrier frequency of radar pulses produced, in order to establish a radar return which, when conventionally processed, results in a SAR terrain map exhibiting extended depth-of-focus under conditions of platform acceleration. Depth of focus is established by ensuring the establishment of two or three separate, independently selected focal points in a target region of interest.

Abstract: In-phase (I) and quadrature (Q) radar return signals are converted to phase to provide phase difference between like range bins of successive pulse repetition intervals (PRI's), the phase differences being reconverted to I and Q format for accumulation across multi-range-bin windows surrounding each range bin to be processed, the normalized range bin accumulations being continuously accumulated in the angle domain, in successive PRI's, to provide clutter phase angle estimates used to rotate incoming target video vectors, a single time, back to the estimated zero-doppler phase of the first PRI of a multi-PRI batch for clutter-elimination filtering.

Abstract: Either of two beams of coherent light has components which are phase shifted and/or attenuated; the phase shifting is alternatively provided in different embodiments by (a) transmitting the coherent light through a phase plate (which may be of variable opacity); (b) processing the coherent light in a second laser-acoustic delay line through which an acoustic wave has been transmitted, or (c) providing in the laser acoustic delay line two acoustic traveling waves, one of which interacts at the Bragg angle with the coherent light. An interaction at the Bragg angle between either of the light beams and a traveling wave generated in a laseracoustic delay line by an electrical rf signal provides a diffracted light beam having a frequency equal to the sum of the light beam frequency and that of the rf signal. A photodetector heterodynes the two light beams thereby providing a modulated rf signal with phase or amplitude modulation in accordance with the phase shift or attenuation of either of the light beams.