Radar and Microwave Applications of Holography
The similarity between side-looking radar records and true holograms, noted by the author at the first U. S. — Japan seminar in 1967, is briefly reviewed. Extension of the side-looking radar concept to stationary (doppler-free) coherent radars is discussed, including both monostatic and bistatic versions. The concept of a passive (cooperative) hologram radar system is put forward.
Because holography and side-looking radar both possess the hitherto unachievable ability to provide excellent resolution (focus) for objects at any point in the near field, one is tempted to dismiss as unimportant consideration of the far field performance of stationary coherent radar since ordinary radars perform this task quite well. However, coherent radar may achieve an equivalent performance more simply. It is shown that the array gain achieved by combining the outputs of all array elements of a radar is not lost in a coherent array radar even though the outputs of individual elements are photographically recorded.
Microwave holograms which employ liquid crystals in forming the hologram are discussed; also, a recently described procedure for using the hologram process to record both range and range rate of targets in a coherent radar. A method is described for achieving pulse compression in radars without using the frequency shift or “chirp” process. In this procedure the processing of the received signals is accomplished by photographically recording them and subsequently using laser illumination to obtain accurate range information. Extending the use of such pulse compression techniques to synthetic aperture radars is also discussed.
KeywordsInterference Pattern Synthetic Aperture Radar Pulse Compression Reference Wave Zone Plate
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