Directional and isolated UWB‐MIMO antenna‐based uniplanar UWB‐FSS array and T‐strip for bi‐static microwave imaging: Baggage‐scanner

Abstract

This article presented a novel compact multi‐input‐multi‐output (MIMO) hexagonal monopole antenna with a uniplanar compact frequency‐selective‐surface (FSS) array for microwave imaging (MWI). The ultra‐wideband (UWB) dual‐element linear MIMO antenna was designed on the FR4 substrate with 50 Ω coplanar waveguide feed, T‐strip isolation, novel numerical calculation and equivalent circuit analyses. The main issues of realising high‐resolution images based on planer UWB antenna for MWI are the low gain, omnidirectional pattern, design size and mutual coupling of MIMO design. A novel technique was proposed to solve a hybrid issue (mutual coupling) of the MIMO reflected‐waves from the FSS array and direct‐wave. The uniplanar UWB‐FSS unit cell was compacted by combining a square‐loop and cross‐dipole with a size of 0.095λ × 0.095λ. The novel‐isolated UWB‐MIMO antenna and UWB‐FSS array (IMAF) were integrated, after investigating the distance between the antenna and FSS. The fabricated IMAF with a stable gain improvement of 4.5 dBi higher than the antenna without FSS, directional radiation pattern, size of 30 × 73.8 × 21.6 mm3 observed that a low mutual coupling of −27 dB, and operation bandwidth of 3.0–11.7 GHz. Moreover, a handbag was scanned experimentally via the bi‐static approach to detect a small concealed object. The MWI system based on the MIMO antenna with FSS was displayed image resolution of 55% higher than that of MIMO antenna without FSS. The new baggage‐scanner approach confirmed that the proposed MIMO antenna with FSS array can lead the humanity for healthy MWI applications.

A New Technique of FSS-Based Novel Chair-Shaped Compact MIMO Antenna to Enhance the Gain for Sub-6GHz 5G Applications

“…To visualize the MIMO antenna configuration more clearly, the equivalent circuit of the proposed MIMO antenna is depicted in Figure . 4 [58]. The patch radiators can be modelled through a lumped-element equivalent circuit comprising inductance (𝐿 𝑘 ), capacitance (𝐶 𝑘 ) and resistance (𝑅 𝑘 ).…”

“…it is worth mentioning that the coupling between the patch and the parasitic element isolator is a combination of inductive (𝐿 𝑐 ) and Capacitive (𝐶 𝑐 ) coupling. This coupling is influenced by the gap (g1+ g2) between the parasitic element isolator and the radiator patch, as illustrated in Figure . 4 [58][59][60].…”