Characteristics of cavity‐isolated and cavity‐connected bow‐tie antennas for subsurface pulse radar

Abstract

SUMMARYThe characteristics of metal cavity-attached resistorloaded bow-tie antennas, which are widely employed as antennas for subsurface detection radars using broadband pulses, are investigated theoretically and experimentally in this paper. Two kinds of antennas are considered: isolated antennas having a structure which separates electrically the bow-tie antenna and the metal cavity, and connected-type antennas which connect the bow-tie antenna and the metal cavity via a resistor. The inner cavity surfaces of both types are coated with ferrite. In this paper, the characteristics of both types of antennas are discussed from the point of view of the effects of the ferrite absorber on the above-ground and subsurface underground radiation power, the coupling between the transmitter and the receiver, and the effects on the transient reception characteristics. The reasonableness of the analysis of the ferrite absorber is verified experimentally.

Design of Shielding System for Impulse Ground Penetrating Radar Applications

“…Radiation pattern of bow-tie antenna is omni-directional in H-plane since we desire single side radiating which is facing to ground for improved radiation efficiency and avoid noise from upper side. A metal cavity structure shown in figure 8 is designed for a bow-tie antenna to prevent external noise as well as to reduce unnecessary air radiation [15]. Effective back-cavity design could reinforce the radiation towards ground surface as well as shielding the interference signals and suppressing the back-radiation.…”

“…As discussed above, undesired multiple reflection exists between antenna and back shield, which will deteriorate the GPR performance [15]. Thus, preventing multiplexed reflection by loading absorbing material inside the cavity must be considered.…”

“…Back-cavity shielded bow-tie antenna system working at 900MHz center frequency for ground-coupled GPR application is investigated in [14]. Other key research is Characteristics of Cavity-Isolated and Cavity-Connected Bow-Tie Antennas for Subsurface Pulse Radar [15].…”