International Journal Of Rf And Microwave Computer-Aided Engineering, vol.1, no.1, pp.1-18, 2021 (Journal Indexed in SCI Expanded)
This article presents a 2 to 18 GHz absorber‐loaded cavity‐backed (AL‐CB) two‐arm Archimedean spiral antenna fed by a 186 Ω Phelan balun for direction finding (DF) and radar warning receiver (RWR) applications. The balun's cross‐sectional area diameter at the antenna feeding region is less than the diameter of the active region ring at 18 GHz. This feature provides a lower axial‐ratio (AR) and wobble‐on‐wave (WoW) at higher operating frequencies and far theta angles and distinguishes the proposed AL‐CB spiral antenna from its counterparts and commercial off‐the‐shelf (COTS) products. The proposed antenna is 60 mm in diameter and 50 mm in height. The voltage standing wave ratio is typically less than 2 (max. 2.6), which is within 2 to 18 GHz frequency range, and the AR is less than 1 dB with a peak of 3.1 dB in off‐axis Ɵ < 60°. The WoW is less than 2 dB in off‐axis Ɵ < 60°. This study's simulation and measurements both demonstrate the ultrawideband (UWB) with 1:9 bandwidth, unidirectional, symmetric, and circularly polarized radiation characteristics of the proposed antenna for DF and RWR applications.