Artificial Magnetic Conductor-based Millimeter Wave Microstrip Patch Antenna for Gain Enhancement, Journal of Telecommunications and Information Technology, 2021, nr 1

In this paper, a small (20 × 20 × 2.4 mm) loaded microstrip patch antenna (MPA) with an asymmetric artificial magnetic conductor (AMC) as a ground plane is designed for millimeter wave applications. Two AMC structures are proposed; one has the property of a 0 ◦ reflection phase around 28.4 GHz, with a symmetric geometry, which makes the reflection phase insensitive to variations in both polarization and incident angle. This symmetric AMC structure ensures angular stability which is considered as a major requirement when periodic structures are used as antenna ground planes. The other structure is characterized by an asymmetric geometry and shows an interesting behavior around 28.6 GHz, where a discontinuity in the reflection phase appeared due to the fact that surface impedance nature changed from purely capacitive to purely inductive. This paper studies the effects of the two proposed AMC structures on the performance of MPAs, by using an array of 8 × 8 unit cell elements as an artificial ground plane. Simulation results show that an MPA with a symmetric AMC ground plane offers better impedance matching and a wider bandwidth. Compared with conventional MPAs, gain is enhanced and directivity is improved as well. As far as an MPA with an asymmetric AMC ground plane is concerned, its performance in terms of gain and directivity is higher than that of the conventional solution

Novel design of optical sensor based on two-dimensional photonic crystals for the detection of volatile organic compounds that can infect human health

Background: In recent research, optical sensors gained a growing interest motivated by the increasing need for specific sensors that allow for routine and effective measurements in several fields and analysis such as, safety, environment, and human health. Among optical sensors are photonic crystal sensors, which are characterized by high sensitivity and biocompatibility. The variations inside and around the photonic crystal can give important information by measuring the wavelength, the band gap, the output power…etc. Through defects created in photonic crystals such as missing rows of holes or rods, light is guided through and the goal is to achieve a very high sensitivity and spatial selectivity to changing superior bulk devices. In this study, we model a new structure of an optical channel drop filter (CDF) based on 2-dimensional photonic crystals to detect volatile organic compounds that can infect human health. Objective: Detect the variation of the refractive index by fixing the radius (r) at 99.37nm and the lattice constant (a) at 523nm for various volatile organic compounds such as H2CO, CH2Cl2, and C2Cl4 with refractive indexes that are: 1.3746, 1.421 and 1.503 respectively in the optical sensor based on photonic crystals for reasons related to the protection of human health. Methods: The structure is made of square lattice silicon rods immersed in air. The dielectric constant of silicon and air is 11.9716 and 1 respectively. First, we created a cross shape resonator and designed an optical channel drop filter in the heart of the structure; our method is based on plane wave expansion method (PWE) by using MATLAB software and the finite element method (F.E.M) with COMSOL software. Results: Three volatile compounds have been studied, such as Dichloromethane used as synthesis intermediate by the chemical industry or solvent used in the pharmaceutical or medical industry. Acute inhalation exposure may cause severe optic neuropathy and liver attack (Hepatitis). Then, the Methanal is used to dry or kill the skin taking as an example, the medical treatment of warts. And perchlorethylene is used for the dry cleaning of tissues and for degreasing metals because it is in category 3 carcinogens, toxic to the nervous system and the kidney. These three volatile compounds where introduced and studied in the proposed structure. The results obtained through this study are as follows: diagram of the TM and TE bands of the photonic crystal in a square array of silicon rods embedded in the air, schematic diagram of the filter, distribution of the refractive index along the structure, structure meshing, propagation and transmission for different refractive indices such as methanal (H2CO), dichloromethane (CH2Cl2) and perchlorethylene (C2Cl4). Conclusion: In this article, we have been able to simulate, analyze and control our proposed structure with MATLAB and COMSOL software based on the finite element method. The results show that for the three volatile organic compounds, the variation of the signal is due to the wavelength of the resonance which is related to the refractive index (n). This can be seen by the small Δλ between three volatile organic compounds, which is 0.4nm between (H2CO, C2Cl4) and 2.9 nm between (CH2Cl2, H2CO). Thanks to this change, this structure can be used as sensor for the detection of toxic organic pollutants that can infect human health (16)

Artificial Magnetic Conductor-based Millimeter Wave Microstrip Patch Antenna for Gain Enhancement

In this paper, a small (20 × 20 × 2.4 mm) loaded microstrip patch antenna (MPA) with an asymmetric artificial magnetic conductor (AMC) as a ground plane is designed for millimeter wave applications. Two AMC structures are proposed; one has the property of a 0 ◦ reflection phase around 28.4 GHz, with a symmetric geometry, which makes the reflection phase insensitive to variations in both polarization and incident angle. This symmetric AMC structure ensures angular stability which is considered as a major requirement when periodic structures are used as antenna ground planes. The other structure is characterized by an asymmetric geometry and shows an interesting behavior around 28.6 GHz, where a discontinuity in the reflection phase appeared due to the fact that surface impedance nature changed from purely capacitive to purely inductive. This paper studies the effects of the two proposed AMC structures on the performance of MPAs, by using an array of 8 × 8 unit cell elements as an artificial ground plane. Simulation results show that an MPA with a symmetric AMC ground plane offers better impedance matching and a wider bandwidth. Compared with conventional MPAs, gain is enhanced and directivity is improved as well. As far as an MPA with an asymmetric AMC ground plane is concerned, its performance in terms of gain and directivity is higher than that of the conventional solution

High-Gain Wideband Circularly Polarised Fabry–Perot Resonator Array Antenna Using a Single-Layered Pixelated PRS for Millimetre-Wave Applications

In this paper, a wideband and high-gain circular polarised Fabry–Perot Resonator Antenna (FPRA) with a single partially reflective surface (PRS) layer is automatically generated and optimised using a VBA-based interface system between CST Microwave studio and Matlab. The proposed PRS layer is a promising superstrate for wideband and high-gain FP resonator antennas due to its relatively high reflection coefficient magnitude and positive phase gradient, which resemble that of the optimum PRS over the relevant frequency band. The circular polarisation was achieved using a sequential feeding network for a 2 × 2 array air-gapped slot-coupled elliptical patch antenna. The proposed design achieved an impedance bandwidth of 48.58% (15.3 GHz) ranging from 23.84 GHz to 39.14 GHz, and the −3 dB gain bandwidth was 22.42% (6.25 GHz) from 24.75 to 31 GHz, with a peak gain of 17.12 dB at 29 GHz, and an axial ratio bandwidth of 21.75% (6.2 GHz). In addition, the achieved radiation efficiency was 90%. Consistent and almost invariant radiation patterns are achieved over the millimetre-wave frequency band of interest. The experimental and simulated results are in good agreement, justifying the feasibility of the proposed design as a high-gain and wideband FP resonator array antenna for Mm-wave applications