Electromagnetic Band-gap Reflector Research Articles

Wideband Low-Profile Dual-Polarized Antenna Based on a Gain-Enhanced EBG Reflector

This letter proposed a wideband dual-polarized antenna based on a gain-enhanced electromagnetic bandgap (EBG) reflector. The proposed reflector is studied with a purpose of mitigating the problem of deformed radiation patterns for a mushroom-like EBG reflector backed wideband crossed-dipole antenna, which is caused by undesirable surface current distribution on the patches of the EBG reflector. Introducing the gain-enhanced EBG reflector raises the average broadside gain of the antenna from 4.27 to 8.03 dBi. The antenna is designed to have a working bandwidth of 42.89% (3.04–4.70 GHz) for both ports, with a profile height of 6.26 mm.

Integrated design of large and medium‐sized low profile frequency reconfigurable antenna array

In this paper, in order to solve the limitations of conventional technology schemes, a new scheme for large and medium-sized frequency reconfigurable antenna array (FRAA) with low profile is proposed by combining advanced technologies such as new electromagnetic materials, reconfigurable antenna and integrated design. The proposed FRAA operating in X and Ku bands consists of a 4 × 4 antenna array, a w ide-band feed network, a dual-band electromagnetic band gap (EBG) plate and integrated bias network. The distance between antenna array and reflective plate has been reduced by 80.0% by applying an EBG structure. The influence of bias network on antenna performance is effectively reduced, and the performance of X/Ku two-band antenna is ensured through the integrated optimization design of the bias network, EBG reflector plate and antenna array. Both simulation and test results show that the proposed FRAA has good performance.

A circular polarized reflectarray antenna with electronically steerable beam and interchangeable polarizations

AbstractThe purpose of this paper is the design of a novel single layer reflectarray antenna in X-band, which can electronically steer the antenna beam and change its polarization. Each antenna element includes a circular patch and rings around it, equipped with two varactor diodes, which are positioned perpendicular together to create a circular polarization. First, using these elements, a circular polarized active electromagnetic band-gap (EBG) reflector is implemented. Then, a special feed is placed in a proper distance with respect to EBG reflector and a circular polarized reflectarray antenna is designed, which has capability of switching electronically between right- and left-handed circular polarizations. An electronic active board is designed and fabricated to provide the biasing voltages, control signals, and indicators. The elements of the reflectarray are designed and arranged in such a way that the varactor diodes can be biased independently. Consequently, a 3D beam is created, which can steer up to ±40o. For evaluating the antenna performance, the radiation patterns and the axial ratio of the antenna are determined at the operational frequency of 11.4 GHz. It is illustrated that, increasing the steering angle in θ direction decreases the directivity and the gain of the reflectarray antenna.

Compact Patch Antenna Array for 60 GHz Millimeter-Wave Broadband Applications

In this study, a wide-band compact patch antenna array is developed for 60 GHz band applications. The antenna array consists of eight identical elements. Each element is a simple microstrip-fed rectangular radiating patch printed on the top side of a Rogers 5880 substrate. A rectangular ground plane is printed on the bottom side. To adjust the impedance matching for broadband operation, a complete circular-shaped slot and a part of circular-shaped slot are etched off the ground plane and the patch, respectively. A technique to feed the array elements unequally is employed for design a more compact antenna structure with improved gain and impedance bandwidth. An electromagnetic band-gap (EBG) reflector below the array structure is employed to decrease backward radiation and improve front-to-back (F/B) radiation ratio. The antenna array with the EBG reflector has a compact size with overall dimensions of 17.5 × 22 × 1.262 mm3. It achieves operation bandwidth from 56.5 to 65.2 GHz (|S11| ≤ − 10 dB), which covers the 60 GHz unlicensed band (57–64 GHz). The gain variation is from 12 to 16 dBi over the entire operating band. These features make the proposed antenna array system a suitable candidate for industrial, scientific and medical (ISM) broadband applications at 60 GHz band.

Printed millimeter-wave MIMO-based slot antenna arrays for 5G networks

In this work, a broadband millimeter-wave (mm-wave) multiple-input–multiple-output (MIMO) antenna system for upcoming fifth generation (5G) networks is presented. The MIMO antenna system is two ports and realized using two antenna arrays, aligned in opposite directions. Each array consist of three elements in each, as each element is a simple recognized printed wide-slot antenna proximity excited by microstrip line with a widened tuning stub; manipulated for operating in the Ka-band, which includes the 28 and 38 GHz bands, as potential candidates for 5G communications. An electromagnetic band-gap (EBG) reflector is placed behind the antenna structure toward the feeding network to decrease the backward radiation and improve the front-to-back (F/B) ratio. Results show that the proposed MIMO antenna system with EBG reflector provides wideband impedance bandwidth >27 GHz (from 22.5 to >50 GHz) and good radiation characteristics with a total realized gain up to 11.5 and 10.9 dBi at the two frequencies of interest, respectively. The envelope correlation coefficient (ECC) and diversity gain (DG) were evaluated and showed good MIMO performance. These remarkable features with the benefits of design simplicity and easily expansion to large-scale antenna system make the proposed design suitable for mm-wave communications.

A Wideband Square-Slot Antenna Array With Superstrate and Electromagnetic Bandgap Reflector for 60-GHz Applications

A $1 \times 4$ antenna array with wideband and high gain is proposed for 60-GHz applications. The operating bandwidth is from 57 to 66 GHz. A superstrate above and an electromagnetic bandgap reflector below the array structure increase peak gain and decrease backward radiation, respectively. This paper elaborates the design guidelines. The slot stubs are designed appropriately to increase the bandwidth of square-slot antenna and maintain the radiation pattern. The simulated and measured impedance bandwidth ( $\vert S_{11}\vert \le -10$ dB) are 28.8% (52.6–69.9 GHz) and 23.2% (52.6–66.5 GHz), respectively. The peak antenna gain ranging from 57 to 66 GHz is simulated to be 14.2–12.4 dBi, while the measured peak gain at 57, 60, 63, and 66 GHz are 13.6, 13.4, 12.6, and 11.3 dBi, respectively. The above results can satisfy requirement of many commercial applications.

EBG 표면 위의 단일 방향 복사 등각 안테나의 성능 해석

본 연구에서는 원형편파를 양방향으로 복사하는 등각 스파이럴 안테나에 EBG(electromagnetic bandgap) 반사판을 사용하여 단일 방향으로 복사가 발생하게 하였다. EBG 반사판에서 스파이럴 암 까지의 높이가 가장 낮은 동작 주파수의 0.07 파장 높이로 한 경우, 원형편파의 축비가 손상되는 것이 발생하였다. 본 논문에서는, +z 방향에서의 동일 편파인 우선 원형 편파를 발생시키는 <TEX>$E_{\theta},E_{\phi}$</TEX>의 크기와 시간 위상차를 해석하여, 전 주파수 영역에서 축비를 개선하는 조건을 제시하였다. 그 결과, 3 ~ 10[dB] 주파수 범위에서 축비는 3[dB] 이하이고, 이득은 자유공간에서의 양방향 복사와 비교해서 약 3[dB] 정도 개선되었고, <TEX>$S_{11}$</TEX>은 전 주파수 영역에서 -10[dB]이하를 얻었다. In this study, we used EBG(electromagnetic band gap) reflector to change bi-directional radiation of circular polarization into uni-directional radiation of equiangular spiral antenna. When the height of spiral arm from EBG reflector is 0.07 wavelength of the lowest operating frequency, the axial ratio of the circular polarization was deteriorated. In this paper, we analyzed the magnitude and the time phase difference of <TEX>$E_{\theta},E_{\phi}$</TEX> that generates right hand circle polarization that is co-polarization at +z direction and proposed the improving condition for axial ratio at all related frequency range. As a result, we obtained that the axial ratio was below 3[dB] at range of 3 ~ 10[dB], the gain was improved about 3[dB] with comparison to bi-directional radiation at free space, and <TEX>$S_{11}$</TEX> was below -10[dB] at all related frequency range.

Isolation enhancement between tightly spaced compact unidirectional patch-antennas on multilayer EBG surfaces

In this article, ultracompact unidirectional patch antennas are used in different two-antenna systems for biomedical applications at 5.2 GHz. Multilayer mushroom type electromagnetic bandgap (EBG) structures are designed as slow-wave medium to reduce the size of the individual patch antennas to 0.1λ0 by 0.18λ0. Various techniques are investigated herein to improve antenna isolation for an enhanced Multiple-Input Multiple-Output (MIMO) performance. First, the coupling between 0.3λ0-spaced antennas is verified to occur dominantly through radiation and near-field coupling between the patches rather than through substrate-bound modes. Second, various configurations are proposed to suppress antenna coupling. These approaches include reorientation of the antennas and employment of parasitic radiators between the patches. A novel design is presented in which a unidirectional parasitic slot radiator on an EBG reflector is inserted between the antennas to decouple them. Measurement results confirm efficacy of these approaches in mitigating antenna coupling by more than 11 dB in the operating bandwidth of the antennas. The compact patch antennas maintain efficiency values of higher than 70%. © 2014 Wiley Periodicals, Inc. Int J RF and Microwave CAE 25:30–38, 2015.

Low‐profile circularly polarised loop antenna assisted with an effective PMC bandwidth

Proposed is an ultra-low-profile loop antenna backed by an electromagnetic bandgap (EBG) surface reflector, where the EBG surface can effectively exhibit the property of a perfect magnetic conductor (PMC) inside a deliberately designed bandwidth. It is shown that, assisted by the effective PMC bandwidth, while the proposed antenna is with a 0.07-λ spacing between the loops and the EBG reflector, its axial ratio (AR) and voltage standing wave ratio (VSWR) performances are significantly improved. Experimental measurements show that the prototype antenna has a 3 dB AR bandwidth of 17% with an input VSWR less than 1.6. The proposed approach can find a wide range of low-profile circularly polarised (CP) antenna applications.

Low-Profile Equiangular Spiral Antenna Backed by an EBG Reflector

The bi-directional beam from an equiangular spiral antenna (EAS) is changed to a unidirectional beam using an electromagnetic band gap (EBG) reflector. The antenna height, measured from the upper surface of the EBG reflector to the spiral arms, is chosen to be extremely small to realize a low-profile antenna: 0.07 wavelength at the lowest analysis frequency of 3 GHz. The analysis shows that the EAS backed by the EBG reflector does not reproduce the inherent wideband axial ratio characteristic observed when the EAS is isolated in free space. The deterioration in the axial ratio is examined by decomposing the total radiation field into two field components: one component from the equiangular spiral and the other from the EBG reflector. The examination reveals that the amplitudes and phases of these two field components do not satisfy the constructive relationship necessary for circularly polarized radiation. Based on this finding, next, the EBG reflector is modified by gradually removing the patch elements from the center region of the reflector, thereby satisfying the required constructive relationship between the two field components. This equiangular spiral with a modified EBG reflector shows wideband characteristics with respect to the axial ratio, input impedance and gain within the design frequency band (4-9 GHz). Note that, for comparison, the antenna characteristics for an EAS isolated in free space and an EAS backed by a perfect electric conductor are also presented.

A Double-sided Printed Dipole Array with an Electromagnetic Band-Gap Reflector

Electromagnetic band-gap (EBG) structures have unique properties in controlling the propagation of electromagnetic wave and have been applied to a wide range of electromagnetic devices design. In this paper, a double-sided printed dipole (DSPD) array backed by an EBG reflector is proposed for achieving a low-profile design as well as gain enhancement. Simulation results show that a reduction of more than 55% in antenna height can be obtained by placing the DSPD array over an EBG reflector rather than a perfect electric conductor (PEC) reflector. And the obtained gain of the antenna with an EBG reflector is about 1.9 dB higher than that with a PEC reflector at the operating frequency 2.77 GHz. The EBG reflector can be utilized to reduce a cavity-backed antenna height and enhance the antenna radiation efficiency. The design has a good potential application to antenna arrays with more elements in wireless communication.

Employing EBG Structures in Multiantenna Systems for Improving Isolation and Diversity Gain

This letter investigates the effect of mutual coupling on the operation of a multiantenna system. Radiation pattern, input impedance, gain, and efficiency of a slot antenna in proximity of another slot antenna are studied through simulations. A mushroom-type electromagnetic band-gap (EBG) structure is designed to isolate the antennas and reduce the influence of coupling on radiation characteristics. Two multiantenna prototypes are fabricated and experimentally evaluated. Measurement results confirm the improvement of isolation between the antennas by 28 dB at the radiation frequency of 5.2 GHz when the EBG reflector is utilized. In addition, the diversity gain of the two prototypes are measured using a reverberation chamber demonstrating an increase of 3.3 dB in the combined received power for 99% of transmission trials when the EBG structure is added in the substrate of the multiantenna system.

Switched-Beam Slot Antenna over Electromagnetic Band-Gap Reflector

This paper presents the switched-beam slot antenna over the electromagnetic band-gap (EBG) reflector. This antenna is composed of two slot elements fed with a phase difference and the EBG reflector, which is used in order to realize a low profile structure. The radiation characteristics of this antenna are calculated using the FDTD method. Calculations show that the height of the antenna using the EBG reflector is 60 % lower than that of the antenna using a perfect electric conductor (PEC) reflector. The radiation characteristics at the center of the operating frequency band in the EBG reflector are equivalent to that in the PEC reflector. It is shown that the tilt angle of the main beam in the elevation plane varies with the operating frequency, and the variation in the case of the EBG reflector is caused by its frequency-dependent reflection phase. Moreover, the radiation pattern of the fabricated antenna is measured. The results demonstrate that the low profile design can be achieved by using the EBG reflector, and reveal the influence of the EBG reflector on the antenna efficiency.

Effects on the radiation characteristics of using a corrugated reflector with a helical antenna and an electromagnetic band-gap reflector with a spiral antenna

An axial-mode helical antenna backed by a perfect electric conductor (PEC reflector) is optimized to radiate a circularly polarized (CP) wave, using the finite-difference time-domain method (FDTDM). After the optimization, the PEC reflector is replaced with a corrugated reflector. The effects of the corrugated reflector on the current distribution along the helical arm and the radiation pattern are investigated. A reduction in the backward radiation is attributed to the reduction in the current flowing over the rear surface of the corrugated reflector. A spiral antenna backed by a PEC reflector of finite extent is also analyzed using the FDTDM. As the antenna height decreases, the reverse current toward the feed point increases, resulting in deterioration of the axial ratio. To overcome this deterioration, the PEC reflector is replaced with an electromagnetic band-gap (EBG) reflector composed of mushroom-like elements. Analysis reveals that the spiral radiates a CP wave even when the spiral is located close to the reflector (0.06 wavelength above the EBG surface). The input impedance for the EBG reflector is more stable over a wide frequency band than that for the PEC reflector.