Design of a conformal end-fire array antenna

Abstract

This project aims to build a conformal log-periodic end-fire array antenna, which can cover an ultra-wideband of 2-18GHz. The array consists of 7 monopoles with progressively increasing heights for the high-frequency band, 6 top-hat monopoles for the middle-frequency band, and 8 folded top-hat monopoles for the low-frequency band. The top-hats are used to maintain the low-profile characteristic since the array will be mounted on the surface of a conducting cylinder. And the folded top-hats are to ensure decent input resistance at low-frequency band. The substrate of this array antenna consists of 3 parts: 1. A conducting surface (Perfect E) served as ground plane, 2. Rogers 4003 with permittivity of 3.55 and thickness of 0.5mm, 3. Feed line which is a moderated meandering microstrip line, functioning as the feed of the array. The width and length of the feedline are calculated and modulated to achieve good impedance matching. ANSYS HFSS software is used for simulation. Simulated results show that VSWR < 3 is achieved from 2GHz to 18GHz. Also, this array antenna has a very low profile of 0.053 λL and gain better than 7dBi, (The highest length of monopoles is 8mm, so that 8mm/150mm=0.053) which could be quite useful in many real-world communication systems, for example some missile applications.