Low-Profile VHF Antennas for Seismic Detection Systems.

摘要

The paper describes the design,fabrication,and evaluation of three different types of low-profile VHF antennas and their applications with seismic detection systems at or near ground level. These electrically small antennas (vertically polarized) include a capacitively tuned multi-turn loop over a small metal ground plane, a spiral transmission line top-loaded monopole,and a capacitor-plate antenna that can be inductively tuned over a wide frequency range. The radiation pattern of each is essentially that of a dipole,omnidirectional in the horizontal plane and represented by a solid of revolution generated by a rotating figure of 8. All of the above elemental 'dipole'antennas were designed for optimum performance in the 100-to 200MHz frequency range,compatible with various physical,electrical,and environmental constraints determined by the terminal delivery vehicle (TDV) of the seismic detector system. Distinctive features of these low-profile antennas include small size (3in. maximum),simplicity of construction,and low fabrication costs. (Author)