Simulation and Design of Directional Antenna in Borehole Radar

A directional antenna of four directions is designed based on the broadband miniaturization technology of distribution medium load and concentrated resistance load. The gain of antenna main lobe is 5.4 dB and in the center frequency the gain of anterior lobe is 28 dB larger than the back lobe. The ratio of the peak-to-peak value of forward time-domain radiation pulse to backward time-domain radiation pulse is greater than 3. The trailing of time domain radiation pulse waveform is less than one fifth of main peak amplitude. The joint simulation of both omni-directional and directional borehole radar antennas shows that the directionality of the designed antenna is improved. The antenna is fabricated to make the test and the measured results of the antenna's S11 are consistent with the simulation results.