Communications: directive radio wave systems and devices (e.g. – Transmission through media other than air or free space
Patent
1985-07-10
1987-10-06
Tubbesing, T. H.
Communications: directive radio wave systems and devices (e.g.,
Transmission through media other than air or free space
342159, 324337, G01S 728
Patent
active
046986340
ABSTRACT:
A radar system for subsurface inspection comprising a short pulse transmitter, an antenna for radiating signals to and receiving external reflections from the surface and from below the surface being inspected, a receiver connected to the antenna for generating an output signal in response to the external reflections, and a clutter cancellation circuit for eliminating internal reflections developed in the system to prevent interference by such internal reflections with the desired external reflections to enhance the system detection capability and reliability of evaluation of such external reflections. Clutter cancellation is accomplished by storing the internally generated clutter and subsequently subtracting it from each incoming radar range sweep consisting of surface and subsurface signals plus unwanted clutter. An internal signal recognition circuit rejects all return signals except that generated internally to the radar by the antenna structure, and this internal antenna echo is used as an internal reference signal whereby the radar system is relatively insensitive to wide variations in external reflection characteristics caused by wide variations in the nature of materials present in the surface being inspected. This in turn provides for a reliable control of the receiver sampling process which is indpendent of external signals and of their amplitude variations. A circuit for compensating for thermal drift permits long term cancellation of the internally generated clutter. The drift compensation circuit, the internal signal recognition circuit and the receiver provide a closed loop stabilization to allow the internal clutter to remain correlated on a range sweep by range sweep basis.
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Alongi Anthony J.
Alongi Anthony V.
Gregory Bernarr Earl
Tubbesing T. H.
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