The advawea of red-time nuicrowave hdography we reviewed. Red-t&me capabilities require real-time acqua of the raw ?wbgram data and *d-h retrieval of irnagee from tb collected data. Th& paper exmninee in &?a&? the cmpiaitti of microwave hobgrwn data by double chd5r mwming of a tingle receiver in the wnt8xt of qua& real-time operation. The ~~n.oipZe of the o?ouble &x&w acun b pwented and the effect of this sampling form& on the r&ved image andyzed. OpGm? bench .9&d&&m of h&gram reuwo?hg employing thie sampliw format i.e aleo preaenttd. It ia &own that .wch a scanning fomraat ha8 the attrwtive properties of economy, &peed ( N 1 h4h?ograpti frame&x) and exdZent retrieved image quality. FindZy, the compaJ&iZiiy of the double Circe ecan fwmat with scanned tranamitter+ec&er hobgraphy is ~?&cwwed in the context of pra&icaZ low-coat 8ystNna. I. Introduction The extension of Gabor's holographic imaging principle (1) to the microwave region of the electromagnetic spectrum (2~(27) is attractive for the following reasons. (a) By virtue of their longer wavelengths centimeter and millimeter microwaves provide more favorable propagation characteristics through the atmosphere and a variety of dielectric substancea than do optical wavelengths. This provides a capability of seeing through optically opaque media (26) and could lead to numerous applications such aa landing of aircraft and docking of ships in zero visibility weather, nondestructive testing of dielectric products, archeology and microwave antenna design and synthesis. (b) The fringe density and therefore the information content in microwave holograms is considerably less than in their optical counterpart due to the longer wavelengths used. This implies that real-time image formation through computer processing of the raw microwave hologram data is feasible, especially with the aid of the Fast Fourier Transform algorithm (28). (c) Present day microwave technology provides means for recording microwttve hologram information with both high sensitivity and high resolution. This is accomplished by using discrete and highly sensitive microwave sensors whose receiving apertures can be as small as the typical minimum fringe size encountered in the recording of microwave holograms which is of the order of a wavelength. (d) The coherence properties of microwave sourcea and the techniques available for their fkequency stabilization allows long-range microwave holography. Coherence lengths of the order of 12 km for instance are easily