Joel E. Patniotis

This paper presents the design and experimental validation of an optically programmable Digital Impedance Surface (DIS). Utilizing discrete binary impedance switching, a novel triangular unit cell that can be adapted for compound conformal surfaces has been explored. The DIS integrates commercially available RF PIN diode switches using phototransistors as part of the logic control layer. The phototransistors are controlled using a low-cost AMOLED display. Fabricated on a three-layer PCB, the DIS was tested under two configurations consisting of a holographic antenna and reflect array. Validation measurements were carried out on the DIS using a 3D near-field scanner and anechoic chamber. Results verify the DIS beam-steering capability, although limitations in efficiency were noted due to the small wavelength scale of the tested panel. Despite these challenges, the study successfully demonstrated the potential of an optically switched DIS for advanced reconfigurable electromagnetic structures.

This study investigates the impact of mechanical loading on the electromagnetic performance of conformal load-bearing antenna structures (CLASs), focusing on the resonant frequency response. Using 6-ply [0/90] GFRP as the CLAS substrate, the research evaluated the effects of two mechanical loading scenarios: the quasi-static uniaxial tensile test and cyclic fatigue. The quasi-static tests explore the response of CLASs to significant elongation, while the cyclic fatigue tests simulate localised damage propagation under operational loads. The results from the quasi-static tests demonstrated that the dominant effect under uniaxial tensile loading is the increase in substrate permittivity due to damage, causing a decrease in resonant frequency. The cyclic fatigue tests employed two configurations: removeable antenna patch (RAP), which isolates the antenna from mechanical loading to focus on substrate damage; and surface-mounted antenna patch (SMAP), which examines the combined effects of substrate damage and antenna elongation. The RAP results showed a consistent correlation between substrate damage and resonant frequency decrease, while SMAP demonstrated complex frequency behaviour due to competing effects of substrate damage and antenna elongation. A comparison with [±45]₆ GFRP results showed that the resonant behaviour remained consistent regardless of ply configuration during the initial damage accumulation induced by cyclic fatigue. However, with significant elongation in quasi-static tests, resonant frequency behaviour was affected by the specimen’s ply configuration, with substrate permittivity changes due to mechanical loading being the dominant factor. These findings provide valuable insights into the relationship between damage sustained by the CLAS system and resonant frequency shifts, providing critical information for predicting CLAS’s reliability and service life.

Glass fibre-reinforced polymer (GFRP) is a suitable substrate material for constructing a Conformal Load-Bearing Antenna Structure (CLAS). The relative permittivity of the CLAS substrate, which determines its resonant frequency, is affected by damage sustained by GFRP. This paper investigates the effects of damage (induced by mechanically loading the substrate) on the resonant response of the CLAS. Decoupling the antenna from the substrate was essential to evaluate the CLAS’s true response to the induced damage. This paper details a systematic investigation examining how the frequency response of a “pristine” antenna and a surface-mounted antenna respond to a substrate subjected to quasi-statically induced mechanical damage and cyclic fatigue loading. The results demonstrate that the resonant frequency of the CLAS varies as a function of the substrate’s mechanical damage. The prepared CLAS is tolerant to a certain degree of mechanical loading and related damage with its resonant frequency remaining within an acceptable bandwidth.

One of the important functions of antennas is to facilitate wireless communication. The IEEE 802.11 is part of the IEEE802 set of local area network technical standards, and specifies the media access control and physical layer protocols for implementing wireless local area network computer communication. The network physical layer protocol with a centre frequency of 2.4 GHz has a bandwidth of 22 MHz. A conformal load-bearing antenna structure (CLAS) facilitating this communication band that is tuned to 2.4 GHz must remain within this bandwidth. The aim of this paper is to investigate the effects of mechanical loading imposed on a load-bearing patch antenna with respect to its ability to remain within the specified bandwidth. The mechanical loading configurations considered include tensile, biaxial, and twisting. This paper will also report on the response of the antenna patch to the presence of a disbond between the metallised antenna and its substrate, which can arise due to fabrication anomalies and operational usage. This numerical work will assist in the design of experimental testing of the mechanical and electromagnetic properties of an embedded CLAS, which will ultimately be used to inform selection of appropriate regions to place patch antennas on load-bearing deformable surfaces.