Broadband counter-wound spiral antenna for subsurface radar applications

A new antenna structure called the counter-wound spiral antenna (CWSA), which is suitable for subsurface radar applications, is examined in this paper. The CWSA has a broad bandwidth and a linear polarization with a controllable plane of polarization from a compact planar geometry. This dual linear polarization property offers a reduction in antenna polarization loss when a radar is imaging long slender targets, and allows the extraction of maximum information from the echoes. CST Microwave Studio simulations were used to examine the return loss and axial ratio as a function of several design parameters, such as spacing between the two spirals. The CWSA far-field polarization was shown to be linearly polarized when an appropriate delay was set to the excitation input of the front planar antenna to compensate for the physical spacing. The research has resulted in a successful design that has a broad bandwidth and linear polarization with an electronically controllable plane of polarization from a planar geometry.