Passive millimeter-wave imaging

Abstract

When "the fog comes on little cat feet," we want to see what it's hiding. The millimeterwave regime of the electromagnetic spectrum can show us-if we have the necessary vision. bed}. :is opposed 1o a perfect reflector, which has ,:' = 0 The emissivity of an object (v_hich is polauization-dcpendent) is a function of the dielectric properties of its co_lstitUClllS, its surf4cc roughness, and the angle of observation (,% samplcc_l-the mea_,uredemissixitiesol dixers materials at various frequencies is ei,,en in the table on the next page.) The radiation intensity of a 300-Kelvit+ blackbody t+all_ e×ponentialt> by about eight orders of magnitude from a peak \alue in the 1R to the millimeter-_,ave regime at around 94 GHz (Figure 1). This large dccrease m mtensit._, is partially corn pensated for bv the lower photon energy, th:tt occurs at millimeter-,aave fre quencies. H_,aexcr this '-,iluatioll is dramaticall\ reversed in fog and other inclenlent _ve_tther \_hcn one lakes into accotlilt the _,ignal attelltlation bv atlnospheiic constituents. Ilele the ,qrength of the propagated signal peaks in the millimeter _._,:l_.c region, as the figtire sho_,s. Fhu-,,ecnml reas(m, haldv, 41c Itlllitalions, is due tO the low inillilneler-wave pnv, cl Ilu,, hul i,, not the probleln it once ,aas. Se',eral recent technological advances haxe enabled the exploitation of millimeter waves. Receivers with mixcl ll(ml ends ti_,hlg Scholtky-b;_uricr diodes have demonstrated double ",idchand i_oise figure', :_I (_,to l(} dB over the _4 to 300 GHz regime,

Development of Scale and Rotation Invariant Neural Network based Technique for Detection of Dielectric Contrast Concealed Targets with Millimeter Wave System

“…The MMW based imaging technique has been considered diligently for the military, scientific and industrial [9][10][11][12] . MMW imaging has been usually categorised into two classes, active and passive type [13][14] . In passive mode, a very high sensitive receiver has been required due to very low received signal intensity, on the other hand, a high signal-tonoise ratio has been acquired with the help of the active imaging system.…”

Influence of surface roughness on polarization property in passive millimeter-wave imaging

“…Passive millimetre-wave (PMMW) imaging has been applied to many fields such as remote sensing and security detection on account of its excellent applicability in all time and penetrability in fog, smoke, clothing and so on [1,2]. PMMW polarimetric measurement is an active field because it can acquire some additional information that complements the insufficiency of other electromagnetic radiation attributes.…”

A microstrip-fed <i>W</i>-band waveguide filter using H-shaped coupling slots

“…The interest in radio astronomy and image radar applications at W-band (75-110 GHz) has increased recently [1,2]. Filters with low insertion loss and high selectivity are key components of RF front-ends in these systems.…”