Adaptation capabilities of a wire bow-tie antenna for ground penetrating radar

We have demonstrated three possibilities of adaptation of a wire bow-tie antenna over different ground types. By varying its flare angle, a wire bow-tie antenna can be optimized to provide one of three aspects: minimal reflection at its terminal, maximal transmitted field strength in the ground, or an optimal size of antenna footprint. The choice of optimization will strongly depend on the application. The given approach is the frequency-domain solution of the electric field integral equation (EFIE) using the thin-wire approximation. The solution is obtained numerically by means of the method of moments. The fields above and below the air-ground interface are calculated using the expressions formulated by Banos (1966). The required time-domain fields are determined by means of the inverse Fourier transform of the calculated frequency-domain data. The characteristic impedance (which corresponds to the input impedance in time domain) of the bow-tie antenna is found by removing reflections in the obtained time history before transforming it back to frequency-domain.