The project motivating this paper is the deployment of a frequency independent antenna on the transceiver of a monostatic ground-penetrating radar used to detect mines. The design goal is that the radiation pattern and input impedance be nearly uniform over a band from 1 GHz to 5 GHz if the antenna is partially immersed in a typical soil medium. The contemplated method of deployment is to have the antenna straddle the air-soil interface i.e. partly in free space and partly underground, radiating into the ground. The particular subclass of frequency-independent antenna under investigation for this application is the conical equiangular-spiral antenna, in which thin wires are wound around a conical frame and the radiation is from the apex and reaches its peak in the axial direction. The conical structure, about 50 cm long and with a maximum diameter of 12 cm, is thrust into the ground apex-first at an angle of about 70 degrees to the vertical. The subject of this paper is an analysis of this antenna, first solving the integral equation to find the currents on the wire, then determining the radiation pattern at frequencies between 500 MHz and 5 GHz. The theory of this antenna in infinite free space was developed by K. K. Mei and others in the 1960s. The analysis reported in the present paper is based on these sources. An ultimate objective of the reported work is to determine theoretically the degree of frequency uniformity attainable when the antenna geometry is as indicated above. The ideal "frequency independent" property is theoretically possible if the cone is infinitely long, so the finite length and width of the frustum imposes limits on the attainable bandwidth. In order to begin to determine the feasibility of this antenna in the contemplated application, this paper will be limited to the analysis of the antenna positioned with its axis in the vertical direction and immersed in an infinite lossy dielectric medium (e.g. clay loam soil).


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    Titel :

    GPR application of the conical spiral antenna probe


    Beteiligte:
    Raemer, H. (Autor:in) / Rappaport, C. (Autor:in)


    Erscheinungsdatum :

    2001


    Format / Umfang :

    12 Seiten, 15 Quellen




    Medientyp :

    Aufsatz (Konferenz)


    Format :

    Print


    Sprache :

    Englisch