Single‐layer and bilayer four‐arm mode 1 spiral antennas and their feed structures

다국어 초록 (Multilingual Abstract)

<P><B>Abstract</B></P><P>Single‐layer and bilayer four‐arm spiral antennas and their feeding methods for Mode 1 operation are discussed in this article. Important design parameters such as metal‐to‐slot ratio and growth rate for better impedance matching and reduced far‐field contamination are studied. Three feeding methods for Mode 1 operation are compared: a bundle of four coaxial cables for a single‐layer spiral and vertical and horizontal feeds by two coaxial cables for bilayer spirals. It is shown that the single‐layer spiral maintains beam symmetry with Wobble on Wave better than 1 dB at θ = 30° over 10:1 bandwidth. However, the required beamformer is complex and expensive. Proposed, horizontally and vertically fed bilayer spirals need simpler beamformer while maintaining similar far‐field performance over narrower 6:1 and 2:1 bandwidths, respectively, thus making them useful for many wideband applications. Modeling is conducted by a method of moments and validated with a finite element method and measurements. © 2012 Wiley Periodicals, Inc. Int J RF and Microwave CAE 22: 652–662, 2012.</P>