Wideband and multiband antennas for aerospace applications

Abstract

In the aerospace field, the use of compact, low cost and lightweight devices is essential. Printed antenna technology meets these criteria due to its ease of integration into modern wireless systems as satellite communication, mobile communication or RFID systems. Moreover, the implementation of various functions such as localization, communication, and navigation necessitates placing multiple printed antennas on a limited space. All these constraints need specific requirements in terms of frequency and radiation characteristics. One conceivable solution is the use of microstrip wideband or multiband antenna backed with artificial reflectors. This solution overcomes aerodynamic constraints by reducing the thickness of directive antennas and eliminating the need of quarter-wavelength distance between the antenna and its reflector. The objective of this thesis is to propose novel antenna structures based on wideband and multiband artificial reflectors which is a crucial challenge. The first study concentrates on designing artificial reflectors for wideband antennas, with a specific focus on achieving a stable gain in the whole target band, reducing significantly the antenna thickness and enhancing the front-to-back ratio. The first prototype propose a directive low profile bowtie antenna backed with a novel AMC reflector for aerospace C-band applications. It allows a stable gain with a variation of only 0.85 dB over a wide impedance bandwidth of 50% (3.94-6.61 GHz) while maintaining a low profileof 0.084?L(?Lis the wavelength at 3.94 GHz). The second structure is dedicated to UHF-RFID applications, where the AMC allowed a reduction of 45% of the antenna profile height while maintianing high gain and a front-to-back ratio of more than 5 dB and 24 dB, respectively, across the entire UHF-RFID band. The second study proposes the design of two prototypes using multiband artificial reflectors. A trap-loaded pyramidal antenna backed with a triband artificial magnetic conductor is designed for GNSS system. The triband AMC reflector has been proposed to replace the bulky metallic cutoff open-ended waveguide used in a previous version of the pyramidal antenna. Indeed, a significant reduction in the overall antenna size by 37%,37% and 67% along x, y, and z-axes, respectively, is achieved while maintaining similar performances. Finally, a dual-band antenna associated with a dual-band AMC reflector for 5G systems is proposed for gain enhancement. The proposed structure exhibits a broadside gains of 6.83 dB and 5.20 dB at the operating frequencies of 3.40 GHz and 6.10 GHz, respectively. The proposed Antenna structures have been simulated using CST Microwave Studio software, fabricated, and measured, confirming their proper operation.