Performance Enhancement of Semicircular Shaped Array Antenna using Metasurface

A metamaterial approach to wideband radar cross section reduction that is thin, low-cost and doesn't dictate object shaping is presented in work from Iran. The approach uses principles potentially applicable to infrared and visible light as well as radar. The wideband RCS reducing surface is produced on a commercial high-frequency circuit substrate using conventional printed circuit manufacturing techniques Reducing an object's detectability to radar systems is now a well established priority for military applications, most famously in aircraft applications. ‘Stealth’ aircraft that were once well kept secrets are now a familiar concept to the general public and even fly in air shows. The radar cross section (RCS) of an object is essentially a measure of how detectable an object is to radar systems and so reducing an object's RCS is the basic goal of radar focused ‘stealth’ technologies. There are three main approaches to reducing RCS; radar absorbing material (RAM), object shaping and reflected wave cancelling by object coating. RAM materials, as the name suggests, are designed to reduce radar reflections back to the detector by absorbing the electromagnetic energy transmitted by the radar system, converting it into heat. However, they can be bulky and high maintenance. Object shaping works by shaping the surface of the object to minimise reflections of the radar waves back to the radar system, instead reflecting them in other directions. The obvious disadvantage to this approach is that it dictates the shape of the object, which can compromise the performance of the object for its primary purpose. For example, above all an aircraft must be shaped to enable it to fly, an aircraft that is very hard to detect but cannot take off is of no use to anyone. The work reported in this issue, by researchers at Iran University of Science and Technology (IUST) uses the third approach, in which a surface coating reflects the radar waves in such a way as to reduce the amount of radar energy that returns to the detector. This approach is low profile, low bulk and doesn't dictate the shape of the object. In the IUST team's work it can also be cheaply and simply manufactured using printed circuit board manufacturing techniques. Their proposed structure consist of a chessboard arrangement of two different artificial magnetic conductor (AMC) unit cell patterns, each of which reflects the radar waves differently. The key difference in the reflections is a 180° phase shift, which causes the reflections from the two different AMC cell types to interfere destructively and so significantly reduces the useful energy returned to the radar system's detector. “Since radar systems usually send out a short pulse signal in the time domain, wide bandwidth of the RCS reducer is necessary. The proposed AMC structure achieves a RCS reduction over a very wide bandwidth, about 85%,” said Dr Seid Hasan Sedighy, one of the IUST researchers on this project. The wide bandwidth achieved is possible because the critical 180° phase difference in the reflections is produced by the AMC unit cells over a wide frequency range, from 9.4 GHz to 23.28 GHz, providing 10 dB RCS reduction in that range. The peak RCS reduction is in excess of 40 dB, at 15 GHz. Printed circuit manufacturing techniques were used to create the AMC patterns on a commercial high-frequency circuit substrate, providing a low-cost manufacturing method. As flexible circuit board technologies are now available and continue to develop, this AMC-based, effective and relatively cheap approach to RCS reductions could be applied to arbitrary shapes. AMCs are metamaterial structures that behave as perfect magnetic conductors in a limited range of frequencies. The two unit cell AMC patterns used in this work are an arrangement of ‘E’ shapes and saltire arrows. The patterns were optimised to achieve the desired 180° phase difference in their reflections by simulation before being confirmed by experiment. The RCS reducer consists of a chessboard pattern of AMC patches using two different AMC unit cell designs, which produce reflections 180° out of phase with each other. The resulting destructive interference provides the intended RCS reduction The principles of AMCs and using destructive interference to reduce reflected energy are of course applicable to other frequencies of the EM spectrum, not just the band used for radar. This means that similar effects could be achievable in very different frequencies if the structures can be manufactured. Dr Sedighy expects this to lead to developments closer to photonic frequencies “It seems that this design approach will develop in the other frequency bands such as visible and infrared frequencies, which have many civil and military applications.”

Purpose Planar periodic metallic arrays behave as artificial magnetic conductor (AMC) surfaces when placed on a grounded dielectric substrate, and they introduce a zero-degree reflection phase shift to incident waves. The antenna designers have new challenges while designing the AMC structure. The steps followed in designing the structure are as follows: 1) Designing the antenna, aimed to operate at millimetric wave frequencies, (2) Designing the AMC at desired frequencies, (3) Integrating the antenna design and AMC to resonate at millimetric wave frequencies and (4) Validate the output parameters of the antenna to be suitable for Internet of Things (IoT) applications. Design/methodology/approach The antenna is integrated with artificial material known as high impedance surface (HIS) for performance enhancement. A miniaturized, multiband, enhanced gain, AMC-integrated CPW-fed antenna is proposed and aimed to operate at millimetric wave frequencies, which is most suitable for IoT applications. The developed antenna operates at an extremely high range (30–300 GHz), i.e. from 40 to 60 GHz with the return loss values at lesser than −20 dB, and gain is greater than 10. The antenna is developed and simulated by using HFSS software. Findings An extensive research study has been carried out to develop a low profile, high gain and optimized antenna. The first two steps are separately designing the antenna and the AMC unit cell at the desired frequencies. The third step is finding the antenna or AMC radiating parts responsible for each resonant frequency by analysing the surface current distribution. CPW fed along with AMC integration has made the antenna feasible to achieve the extremely high frequency (EHF) range, i.e. 40–60 GHz, which is highly adoptable in IoT applications. Originality/value The result represented that the developed antenna is resonating at EHF rank with high gain and good imped matching when it is being compared with the previous models and has only CPW fed without having AMC structure integration. It is evident that the antenna which has only CPW fed has resonated at lower frequency than EHF range and justified output characteristics. But when it is embedded with the AMC structure, it resonates at the EHF range, which makes the antenna highly suitable for IoT applications, with more accuracy and high data rate possibility.

A perfect magnetic conductor (PMC) surface reflects electromagnetic waves without any change in the electric field phase. However, there is no natural PMC material. Instead, artificial magnetic conductors (AMCs) have been developed, which mimic the behavior of PMCs at a particular frequency. There has been an extensive amount of research to increase the bandwidth in different AMC structures and to characterize its operating frequency. Here, the general reflection characteristics from an AMC surface is demonstrated. A theoretical upper limit for AMC bandwidth is derived in terms of AMC structural parameters and validated for different AMC structures. Finally the effects of AMC structural parameters on the operating frequency of an AMC are investigated.

This paper focuses on different High Impedance Surface (HIS) geometries, also known as artificial magnetic conductors (AMC), to compare their performances in terms of frequency bandwidth and size. The main objective is to maximize the HIS bandwidth to perform an antenna association. Most of well known HIS cells are introduced and compared to new cells' geometries able to perform HIS properties in a wider frequency range. For each cell geometry, we have compared the HIS bandwidth (i.e. the frequency band where the reflexion coefficient phase is between -90° and 90°) and the cell size (with the aim of reduce their dimensions). This paper shows that cells geometries based on spirals allow to increase the HIS performances and bringing to light several optimization parameters increasing HIS bandwidth.

Artificial Magnetic Conductors (AMCs), a real version of Perfect Magnetic Conductors (PMCs), are widely used to replace surfaces of high impedance. Based on unit cells of Multiple Split-Ring Resonators (MSRRs) that are printed on low-cost dielectric grounded substrate, AMCs are employed as a ground plane for antennas. In this paper, the performance of a low profile dipole antenna positioned above a planar AMC surface is examined. The characteristics of the AMC return loss are initially investigated at the resonant frequency of 2.4 GHz. Two arrays having 49 and 81 MSRR unit cells are then simulated and modeled with the dipole antenna placed above. The results are of great importance as the directivity reaches 6 dB for the configuration of 9 × 9 unit cells. This confirms that the MSRR can perfectly replace the conventional ground plane antenna in order to improve the gain and the directivity of their radiations.

This paper presents a compact, low‐profile, and wideband two‐arm monopole antenna tailored to operate efficiently within the 3.7–7.3 GHz frequency spectrum. The monopole antenna is traditionally known for its omnidirectional radiation pattern and relatively low gain. To enhance its performance, this design integrates the monopole with an artificial magnetic conductor (AMC). The AMC is configured as a 3 × 3 array of specially modified square unit cells, covering a surface area of 9 × 9 cm. The antenna is positioned 1.7 cm above the AMC surface, a strategic placement that significantly enhances gain across the entire frequency range. In this configuration, the antenna's gain is markedly improved, increasing from an initial range of 1.5–3.25 dBi to an enhanced 4.6–8.5 dBi. Impedance matching is evaluated for both configurations, demonstrating consistent wideband performance. Analysis of the radiation patterns indicates that the monopole maintains an omnidirectional pattern without the AMC but shifts to more directive beams when the AMC is integrated. This combination results in a radiation efficiency of approximately 98% across the operating frequency band. Prototypes of the antenna and AMC were fabricated using the Rogers RO4003C substrate, which has a dielectric constant of , a loss tangent of tan δ = 0.0027, and a thickness of 1.52 mm. Experimental testing of these prototypes closely matched the simulation data, verifying the accuracy and effectiveness of the design. This study not only confirms the potential of the two‐arm monopole enhanced with AMC for high‐gain, wideband applications but also demonstrates its viability through rigorous simulation and practical experimentation. The results suggest that this antenna system is well‐suited for modern communication systems that require efficient, wideband, and high‐gain performance within the specified frequency range.

A dual-frequency substrate integrated waveguide (SIW) cavity backed slot antenna over an Artificial Magnetic Conductor(AMC) is presented in this paper. The Artificial Magnetic Conductor is designed as a dual-band structure having an array of unit cells and operates at 7.5GHz and 12.8GHz. A circle and crisscross slot into a square metallic patch as a back-plane. By comparing the performance of the antenna loaded with AMC and without AMC. It is found that the gain of the antenna loaded with the AMC increase is obviously. The distance between the dual-frequency antenna and the AMC is $0.12\lambda$ , Improvements of front lobe to back lobe ratio are achieved as a result of using dual resonant AMC which has surface wave suppression characteristic. The simulated results show that the combination of the AMC reflector and the antenna provide directional properties at both frequency bands.

In this study, a corrugated fan-shaped dipole antenna with a ferrite-loaded artificial magnetic conductor (AMC) is introduced. Ferrite, which has high permeability in the HF/VHF/UHF band, is employed to design a compact size AMC operating in the HF/VHF/UHF band, and the reflection phase frequency bandwidth of the designed AMC is 25.5:1 (19∼485 MHz). Subsequently, a corrugated fan-shaped dipole antenna was designed and combined with the AMC. The proposed antenna with the AMC was fabricated and measured to verify its performance. The measured voltage standing wave ratio (VSWR < 3.5) bandwidth ratio was 31:1 (10∼310 MHz), and the overall size of the proposed antenna was 0.002×0.002×0.00005 λL3 (λL is the wavelength of the lowest operating frequency). A comparison of the measured receiving power between the reference antenna and the proposed antenna was also conducted.

This paper presents a microstrip patch antenna operated at the fifth generation (5G) frequency range, which is at 3.5 GHz. To enhance the performance of the proposed antenna, an Artificial Magnetic Conductor (AMC) structure is implemented into the design. The 1x3 AMC is sandwiched between two FR-4 substrates and the performance of the proposed antenna is compared with the antenna without AMC structure. The simulated results prove that the proposed antenna offers better reflection coefficient with -50.45 dB compared to only -15.55 dB for the conventional antenna. Wider bandwidth is also achieved with 427 MHz of frequency bandwidth as opposed to only 135 MHz for the antenna without AMC. Besides that, the integration of AMC enhances the gain of the antenna when 3.7 dBi is achieved in contrast to only 3.21 dBi for the conventional antenna. Moreover, the efficiency of the antenna with AMC is also improved up to 68.54%. Furthermore, the ability to shrink 52.23% of the size of the antenna without AMC making it very favorable to be applied in 5G bands.

This paper proposed a design of dual substrate layer Artificial Magnetic Conductor (AMC) which operates at operating frequency of 2.45 and 5.8 GHz. The top circular ring and the bottom rectangular AMC patch correspond to higher and lower frequency respectively. The offset effect due to distance and angular variations on the reflection phase has also been studied. The study further extended to the effect of double and quadruple circular ring AMC on the top substrate layer of stacked AMC. The dual band stacked AMC is then integrated onto two dipole antennas operating at 2.45 and 5.8 GHz band. The performance of antenna with and without AMC is observed in terms of reflection coefficient, directivity and radiation patterns.

SummaryA low‐profile eight‐element printed dipole antenna (PDA) array backed by broadband rhomboid artificial magnetic conductor (AMC) is introduced for wireless communication systems. By loading a 4 × 27 AMC reflector into the eight‐element array of PDA, a low‐profile wideband structure with enhanced radiation properties is achieved. The measured S parameters show the broad bandwidth from 4.75 to 7.05 GHz in C‐band with enhanced gains of eight elements (more than 8 dBi) and the suitable isolation between the array elements of more than 23 dB for multi‐input multi‐output (MIMO) systems. The suggested PDA with a pair of the microstrip meandered folded poles excited by an E‐shaped microstrip feedline expands the bandwidth in the range of 5.85–6.95 GHz (S11 ≤ −10 dB). The novel AMC unit cell is realized based on the recognized method as rhomboid coupled parasitic patches. The rhomboid AMC design operates at 6.26 GHz with an AMC bandwidth of 5.20–7.24 GHz (32.8%). Then, the suggested rhomboid AMC surface as a reflector of the antenna is inserted into the PDA to exhibit −10 dB measured impedance bandwidth from 4.94 to 6.93 GHz (more than 33%) for wireless local area network (WLAN) and worldwide interoperability for microwave access (WiMAX) applications. The suggested PDA with AMC compared to the PDA without AMC exhibits a size reduction of 34%, enhanced gain up to 8 dBi, and excellent impedance matching (at least −20 dB) with directional radiation patterns.

In this paper, a high gain tetra-band microstrip patch antenna fed by a modified L-shaped strip has been designed, simulated and measured. The antenna consists of three concentric square-loop patches to support four operating modes and cover WLAN/Bluetooth, WiMAX, Mobile/Fixed satellite services, and WLAN/V2X commercial applications. In order to enhance gain of the antenna, the incorporating effect of the antenna with a superstrate and an artificial magnetic conductor (AMC)---perfect electric conductor (PEC) ground plane is investigated. It is demonstrated that the antenna gain is enhanced significantly when the superstrate is placed over the AMC---PEC ground plane based antenna. It shows a realized gain of 10.1 dBi at the first frequency band and achieves an increase in the gain by 7.5 dB. One outstanding result of the proposed design is that the air thickness between the square loops and the superstrate is about ?/40, because of the AMC---PEC ground plane. The proposed antenna has a low profile with overall dimensions of 0.64? × 0.64? × 0.08? for the frequency at 2.42 GHz. A prototype of the antenna is fabricated and tested to verify the design.

Recently the realization of Artificial Magnetic Conductors (AMCs) has attracted a great deal of interest among researchers as they can replace perfect electric conductors (PECs) for low profile antennas and other microwave applications. In this paper, the design of ultra thin low profile dipole antenna using AMC ground plane with an overall height of 0.045λ at 3 GHz is presented. The AMC ground plane is realized by using low cost planar square split ring resonators (SRRs) printed on a thin PEC backed dielectric substrate. First, the performances of the proposed AMC surface is investigated and then a comparative investigation has been conducted to study the radiation characteristics of dipole antennas closely and parallel above an ideal PEC surface and the proposed AMC structure. Both Ansoft HFSS™ and Ansoft Designer™ have been used to predict the reflection phase stop band of the proposed AMC structure and the dipole antenna characteristics.

In this letter, the combination of a multilayered dielectric structure, a capacitive frequency selective surface (FSS) and a perfectly electric conducting (PEC) ground plane is proposed for realizing high-impedance surfaces. These surfaces behave like an artificial magnetic conductor (AMC) in a specific frequency range; the inclusion of the dielectric layers allows us to enhance the angular properties of the AMC as well as the frequency bandwidth of the device. In order to obtain the proper values of the design parameters, a genetic algorithm (GA) is employed that makes use of an electromagnetic solver based on the method of moments (MoM) to evaluate the scattering properties of the structure. A key step in the design procedure is the inclusion in the fitness function of the electromagnetic response of the high-impedance surface with respect to the illumination angle. The synthesized structure shows the desired frequency performance and reveals robust as concerns the stability of the solution with respect to a wide interval of illumination angles.

We present a general method to design multiband absorber by replacing the ground plane in a conventional metamaterial absorber with an artificial magnetic conductor. Due to its unique property of in-phase reflection at some specific frequency, the artificial magnetic conductor is used to introduce new absorption in the operation band. Meanwhile, out of the in-phase reflection band, the original absorbing capability of the absorber is reserved. To demonstrate it, we design a metamaterial absorber comprising three layers which are grids patterned resistive frequency selective surface, dielectric layer and the ground plane respectively. With an appropriate design, the absorber performs an absorbing peak at about 10 GHz. Then, we utilize a single band artificial magnetic conductor at 6.25 GHz and a dual-band one at 6.27 GHz and 8.17 GHz, which are both lossy and comprised of patches array varying in periodic size with a thickness of 0.6 mm, to replace the ground plane in the metamaterial absorber separately. The reflectivity of these multiband absorbers are simulated, and experiments are carried out later. Experimental results agree well with the simulations. All results verified that the method presented at the beginning is effective. The results show that additional absorptions exist at the frequencies where microwaves are nearly reflected in phase on the artificial magnetic conductor. Meanwhile the original absorbing capability of the metamaterial absorber has been preserved mostly. Based on the artificial magnetic conductor, the multiband absorber performs better with an increasing absorption bandwidth from 8.5 GHz to 10 GHz compared to the metamaterial absorber.