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Description:
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Two new stepped -frequency continuous wave (SFCW ) radar sensor prototypes , based on a coherent super -heterodyne scheme , have been developed using Microwave Integrated Circuits (MICs ) and Monolithic Millimeter -Wave Integrated Circuits (MMICs ) for various surface and subsurface applications , such as profiling the surface and subsurface of pavements , detecting and localizing small buried Anti -Personnel (AP ) mines and measuring the liquid level in a tank . These sensors meet the critical requirements for subsurface and surface measurements including small size , light weight , good accuracy , fine resolution and deep penetration . In addition , two novel wideband microstrip quasi -TEM horn antennae that are capable of integration with a seamless connection have also been designed . Finally , a simple signal processing algorithm , aimed to acquire the in -phase (I ) and quadrature (Q ) components and to compensate for the I /Q errors , was developed using LabView . The first of the two prototype sensors , named as the microwave SFCW radar sensor operating from 0 .6 -5 .6 -GHz , is primarily utilized for assessing the subsurface of pavements . The measured thicknesses of the asphalt and base layers of a pavement sample were very much in agreement with the actual data with less than & #61590 ;0 .1 -inch error . The measured results on the actual roads showed that the sensor accurately detects the 5 -inch asphalt layer of the pavement with a minimal error of & #61590 ;0 .25 inches . This sensor represents the first SFCW radar sensor operating from 0 .6 -5 .6 -GHz . The other sensor , named as the millimeter -wave SFCW radar sensor , operates in the 29 .72 -35 .7 -GHz range . Measurements were performed to verify its feasibility as a surface and sub -surface sensor . The measurement results showed that the sensor has a lateral resolution of 1 inch and a good accuracy in the vertical direction with less than & #61590 ; 0 .04 -inch error . The sensor successfully detected and located AP mines of small sizes buried under the surface of sand with less than 0 .75 and 0 .08 inches of error in the lateral and vertical directions , respectively . In addition , it also verified that the vertical resolution is not greater than 0 .75 inches . This sensor is claimed as the first Ka -band millimeter -wave SFCW radar sensor ever developed for surface and subsurface sensing applications . |