초록 ▼

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 ex

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.

대표청구항 ▼

A radar system for subsurface inspection comprising: (a) transmitter means for generating short pulse signals; (b) antenna means spaced from and movable over a surface to be inspected for radiating said signals to and receiving external reflection from said surface and from below said surface, said

A radar system for subsurface inspection comprising: (a) transmitter means for generating short pulse signals; (b) antenna means spaced from and movable over a surface to be inspected for radiating said signals to and receiving external reflection from said surface and from below said surface, said external reflections being developed external to said system and comprising a plurality of signals spaced in time and each having a characteristic waveshape; (c) receiver means coupled to said antenna means for providing output signals in response to said external reflections; and (d) clutter cancellation means operatively connected to said receiver means for eliminating internal reflections developed in said system to prevent interference by said internal reflections with the desired external reflections to enhance the system detection capability and reliability of evaluation of said external reflections, said internal reflections comprising signals generated within said system by said antenna means, said transmitter means and said receiver means.