<title>Microwave and millimeter-wave systems for wall penetration</title>

Abstract

The need for through-the-wall surveillance sensors has existed for many years. Recent advances in microwave and millimeter-wave (MMW) technologies provide new applications for law enforcement use. These applications include the potential to conduct surveillance through walls and the ability to detect the presence of living persons behind doors or other barriers. Covert surveillance and personnel detection are of high interest to both the Department ofDefense in support ofSmall Unit Operations (SUO) and the Justice Department for civilian law enforcementapplications. Microwave sensors are under development that can detect the presence of persons (and even weapons) behind walls and track moving persons behind walls. MMW sensors are under development which can provide pseudo-images ofpersons behind walls including radiometric sensors at 95 GHz, active 95 GHz real aperture radars, and heartbeat detection radars. Radiometric sensors include 2-D FPA systems, 1 -D FPA, scanned systems, and single element scanned sensors. Active FPA radars include illuminated radiometric systems and coherent radar systems. Real aperture MMW radar systems include raster scanned and non-scanned (hand-held) sensors.Keywords: through-the-wall surveillance, millimeter wave radar, millimeter wave radiometry, microwave radar 1. MICROWAVE-MILLIMETERWAVE PHENOMENOLOGY Microwaves are used for many conventional radar applications because atmospheric propagation is good, high powers can be generated, and many types of non-metallic materials can be penetrated. However, microwaves generally yield poor resolutions because ofthe relatively large wavelengths. Infrared(IR) lies below conventional visible light in the spectrum but retains much of the high resolution imaging properties of light due to the short wavelengths. On the other hand, propagation through rain and fog is significantly curtailed and little or no penetration though solid materials can be achieved. MMW's lie between the above frequency bands and retain some the properties ofeach. MMW can achieve relatively good imagery while penetrating many types of materials. Figure 1 gives the total attenuation though various objects and materials measured by Hughes Advanced Electromagnetic Technology Center1 .At low frequencies of a few tenths to a few GHz (3 to 0.3 m wavelength) , attenuation is very low even through block walls. At 95 GHz (3 mm wavelength) the attenuation though paper, fiberglass, plastic, glass, wood, and drywall is relatively low while the attenuation through brick and concrete is high. Thus, a few GHz is suited for through the wall surveillance (TWS) though outer walls while 95 GHz is an excellent TWS candidate for thinner walls that are not composed ofbrick or concrete.On the other hand, the production of high quality imagery of scenes requires high resolution. (The rule of thumb is for good recognition ability, a resolution of 10 times the objects maximum dimension is needed by the sensor2.) The one-way cross range resolution (3 dB) in azimuth or elevation for a focused RF an...

Moving Target Position with Through-Wall Radar

“…Assuming that the target's delay time from TA to RAt and RA2 are tI, t2 respectively, and we can get two ellipses, the intersection point of them will be the target's position [11]. LUT technology is adopted to lessen the burden of DSP, and the result is depicted in Fig.7, xcoordinate and y-coordinate are the width and length of detected region respectively, the z-axis is the delay time.…”

“…For same range cell, td can be regarded as constant and gotten by correlation with an auto-adaptive threshold. As a result, the moving target's range to RA would be estimated, cross-range information can be further gotten based on two RAs and dual-ellipse method [11].…”

“…They share one common drawback of convergence problem and require knowledge of the variance and the distribution of the time delay estimation error [9,10]. Given Cartesian reference, dual-ellipse method and LookUp Table (LUT) technology The signal with frequency under 1OGHz has a good ability to penetrate concrete wall, and this ability is inverse proportional to frequency [11]. And aiming to get high resolution, the transmitting signal must have a wide-band.…”

Through-wall imaging: Historical perspective and future directions

“…Through-wall sensing grew from the application of ground-penetrating radar systems to walls, with specific applications documented in the literature since the late 1990s showing abilities to sense beyond a single wall from near range [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28]. Applications can be divided based upon whether information is sought on movement within a structure or on imaging the structure and its contents.…”

Scattering and Image Simulation for Reconstruction of 3d Pec Objects Concealed in a Closed Dielectric Box

“…Detection and localization of the concealed targets in unaccessible environment have been of interest in both military and civilian applications [1][2][3][4][5][6][7][8][9][10][11], such as the surveillance and detection of the target concealed in the closed surrounding walls, which is visually opaque, the early-warning for possible dangers, e.g., bomb and grenade, and the rescue mission for searching survivors in earthquake or avalanche, etc. A key issue is how to quickly identify the target from the blurred image caused by complicated interactions between the object and surrounding obstacle in real-time situation, especially for surveillance and earlywarning.…”