Hemispherical Dielectric Resonator Research Articles

Wideband Millimeter-Wave Perforated Hemispherical Dielectric Resonator Antenna

This paper presents a novel wideband circularly polarized millimeter-wave (mmWave) hemispherical dielectric resonator antenna (HDRA). Two distinct configurations of alumina dielectric resonator antennas (DRAs) are investigated, each featuring a different coating: the first configuration incorporates a polyimide layer, while the second involves a perforated alumina. Both configurations demonstrate promising characteristics, including impedance and axial ratio (AR) bandwidths of 58% and 17.7%, respectively, alongside a maximum gain of 10 dBic at 28 GHz. Leveraging additive manufacturing technology, the HDRA with the perforated coating layer is fabricated, simplifying assembly and eliminating potential air gaps between layers, thereby enhancing the overall performance. This innovative approach yields a circularly polarized (CP) HDRA suitable for Beyond 5G (B5G) communication systems. Agreement between measurements and simulations validates the efficacy of the proposed design, affirming its potential in practical applications.

Wideband Circularly Polarized Millimeter Wave Hemispherical Dielectric Resonator Antenna

A novel approach is proposed to design a circularly polarized (CP) hemispherical dielectric resonator antenna (DRA) with a wide axial ratio (AR) bandwidth by incorporating an additional dielectric substrate between the antenna and the ground plane. This is in addition to the lower feeding substrate that is located between the ground plane on one side and the feeding microstrip line on the other side. Adding another substrate on top of the ground plane provided an additional degree of freedom in the design that facilitated the achievement of ab 18% AR bandwidth. In addition, an integrated hemispherical DRA and perforated substrate configuration was utilized to achieve optimum effective substrate permittivity and overcome the DRA alignment and assembly challenges while maintaining the achieved wide CP bandwidth. A close agreement was achieved between measurements and simulations.

Wideband mm-Wave Hemispherical Dielectric Resonator Antenna with Simple Alignment and Assembly Procedures

A wideband hemispherical dielectric resonator antenna (DRA) with enhanced gain is proposed for a frequency band of 20 to 28 GHz. The precise alignment and assembly of the DRA represent key challenges at such frequencies that were addressed using three approaches: the first was based on outlining the DRA position on the ground plane, the second involved creating a groove in the compound ground plane in which the DRA is placed, and the third was based on the 3D-printing of the DRA on a perforated substrate. In all cases, the same DRA was utilized and excited in a higher-order mode using an annular ring slot. The high gain was achieved by exciting a higher-order mode, and the wideband was obtained by merging the bandwidths of the two excited modes. The alignment methods used expedite the DRA prototyping by saving substantial time that is usually spent in adjusting the DRA position with respect to the feeding slot. The proposed configurations were measured, with an impedance bandwidth of 33.33% and a maximum gain of 10 dBi observed. Close agreement was achieved between the measured and simulated results.

Analysis of Hemispherical Dielectric Resonator Antenna With an Imperfect Concentric Conductor

This work presents a full-wave Green’s function approach for the rigorous investigation of a probe-coupled dielectric resonator antenna (DRA) configuration with an imperfect inner conductor. The impedance boundary condition is applied over the imperfect conductor in the formulation to derive the fields inside and outside the dielectric region, considering all higher-order modes. The technique enhances the applicability of the full-wave Green’s function in the evaluation of input impedance and radiation characteristics for an antenna structure with imperfectly conducting spherical surface, which to the best of our knowledge has not been reported before in the DRA literature. The role of the surface impedance on the antenna resonance and quality factor is thoroughly characterized. A suitable choice of the surface reactance depending on the radius of the imperfect conductor and dielectric-coating thickness enables the simultaneous reduction in the resonant frequency and quality factor for the antenna configuration. The effect of the surface reactance with varying coating permittivities is also investigated. The parametric variations in the input impedance, reflection coefficient, and antenna bandwidth with change in the surface impedance and coating permittivity for the antenna configuration are analyzed. The radiation characteristics for the antenna configuration are also examined.

High-Gain Dual-Band Waveguide-Fed Dielectric Resonator Antenna

A distinctive configuration of rectangular waveguide-fed hemispherical dielectric resonator antenna (HDRA) for high-gain dual-band operation is described in this letter. A cylindrical-shaped hard rubber with a circular slot and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\epsilon_r = 3$</tex-math></inline-formula> is inserted between HDRA and ground plane to achieve dual-band, excellent coupling, enhanced bandwidth, and high gain. The structure of the antenna is very simple to fabricate. Measured results show that the proposed antenna radiates in two bands with resonant frequencies 7.65 and 10.04 GHz. The first band provides a bandwidth of 4.98% and a high gain of 11.72 dBi with a broadside radiation pattern. The second band enables wideband operation with an impedance bandwidth of 12.68% and a gain of 11.5 dBi. The structure attains high coupling efficiency in both bands.

Parametric Study of a Fully 3D-Printed Dielectric Resonator Antenna Loaded With a Metallic Cap

This article presents a parametric study of a fully 3D-printed hemispherical dielectric resonator antenna (DRA) using low loss dielectric filament and high-conductive filaments jointly with a low-cost customized dual-extruding 3D printer. The parametric study consisted in the design and evaluation of five different hemispherical DRA topologies with different internal shapes and the same overall size, in which the printing infill percentage of the DRA was reduced. A 3D-printed metallic cap was included in the antenna to compensate for the resonant frequency shift in order to maintain its original dimensions. Measurement results show that all evaluated antennas kept the same resonant frequencies and similar radiation patterns while reducing the overall weight of the topology in 22% of the nominal weight.

WIDEBAND HIGH-GAIN MILLIMETRE-WAVE THREE-LAYER HEMISPHERICAL DIELECTRIC RESONATOR ANTENNA

A wideband high gain three-layer hemispherical dielectric resonator antenna (HDRA) that operates at TE511 and TE711 higher order modes is proposed. The HDRA is composed of three layers, which has permittivities of 20, 10 and 3.5. The multilayer structure has been chosen in order to reduce the Q-factor and achieve a wider impedance bandwidth. Cross slot feeding mechanism has been utilized taking into account the excited higher order modes for gain enhancement. The proposed antenna provides an impedance bandwidth of 35.8% over a frequency range of 20.8 to 29.9 GHz in conjunction with a high gain of ~9.5 dBi. The proposed DRA represents the first attempt in utilizing a mm-wave hemispherical DRA.

Design and Simulation of Slot Dimensions in Aperture Coupled Hemispherical Dielectric Resonator Antenna

Aperture coupled novel shaped Hemispherical Dielectric Resonator Antenna (HDRA ) and the various dimensions of slots are designed and analyzed by hfss software. The dielectric constant of dielectric hemisphere is € =9.8 and the substrate of dielectric constant is 2.96. aperture coupled novel shaped Hemispherical Dielectric Resonator Antenna (HDRA ) parameters are presented in this paper.. The effects of changing the slot length , slot width and position of slot on the antenna parameters and are presented in this paper, which are used for directive gain applications. As the change of slot dimension , it is observed that at the resonant frequency, it gives high gain and high negative return loss

Compact and Circularly Polarized Hemispherical DRA for C-Band Applications

Abstract A novel circular polarized Hemispherical Dielectric Resonator Antenna (HDRA) has been proposed in this paper. The Circular Polarization (CP) and enhanced gain characteristics of the antenna are attributed to the fractal geometry applied on the HDRA. Probe coupling is used to excite the proposed antenna which resonates at 4.16 GHz and offers an impedance bandwidth of 2.6 GHz (57 %), from 3.3 to 5.9 GHz. The gain and efficiency of the antenna are 6.38 dBi and 93 % respectively at 4.16 GHz. The Proposed DRA is designed using FR-4 material having a dielectric constant (εr ) of 4.3 and dissipation factor (tan δ) of 0.025. The designed Antenna is experimentally verified and offers a close agreement between simulated and measured results. This Antenna offers a 3-dB Axial Ratio (AR) bandwidth of 1.1 GHz from 4.2 to 5.3 GHz.

DRA gain enhancement using a planar metamaterial superstrate

This article analyzes the radiation principle of a slot-coupled hemispherical dielectric resonator antenna (DRA) integrated with a single-layer metamaterial (MTM) superstrate, investigating it both numerically and experimentally. It creates a compact high directive DRA incorporating MTM superstrate. The proposed MTM medium consists of broadside coupled planar E-shaped resonator periodic unit cell exhibiting low loss and a low refractive index over a broad frequency band. Measurements on fabricated prototypes to verify numerical results from full-wave simulations, and they show more than 6 dB increase in directivity of the DRA.

Generation of microwave orbital angular momentum states using hemispherical dielectric resonator antenna

A hemispherical dielectric resonator antenna (DRA) generating two orbital angular momentum (OAM) states of l = +1 and −1 is studied theoretically and experimentally. The DRA is fed with two orthogonal signals, exciting two degenerate higher-order TE221 modes that generate the two OAM states. It was simulated with full-wave simulation software to verify the design method. A prototype operating in the microwave band (5.8 GHz) was fabricated and measured. Its S-parameters, intensity profile, and phase pattern are simulated, and the results are compared with measurements. Also, its far-field radiation pattern, realized antenna gain, and total antenna efficiency are shown for a complete study of the antenna.

Study of a single-frequency retrodirective system with a beam pilot signal using dual-mode dielectric resonator antenna elements

A terrestrial microwave power transmission system is considered as an effective method for collecting natural energy. In this system, frequency dependence of the refractive index and multipath propagation due to the ground surface poses problems. In the study, a single-frequency retrodirective system was proposed with a beam pilot signal using dual-mode dielectric resonator antenna elements. The results confirmed that the beam pilot signal radiated from the entire surface of the receiving antenna and accurately used the same propagation space as that of microwave power by beam propagation method simulation. A dual-mode dielectric resonator antenna was proposed as a common array antenna element for the beam pilot signal and microwave power. This involves a cross-shaped hemispherical dielectric resonator structure, and an isolation level exceeding 60 dB was experimentally measured between the orthogonal ports of the fabricated antenna. The dual-mode dielectric resonator antenna with an isolation exceeding 60 dB was successfully developed as an enabling device to realize a single-frequency retrodirective system with a beam pilot signal.

Mode excitation in the microstrip slot‐coupled three‐layer hemispherical dielectric resonator antenna

In this study, a microstrip slot-coupled multilayer dielectric resonator antenna (DRA) structure is rigorously analysed from the modal perspective, taking into account all layers. The choice of layer permittivities of the multilayer structure to reduce the Q-factor and obtain optimum bandwidth performance of the antenna is outlined. Next, the mechanism of bandwidth enhancement for the centred and offset slots is examined taking into account the excited modes in the structure. It is found that while the centred slot couples to one DRA mode, an offset slot can couple to multiple DRA modes together with the slot mode. Thereafter, the excitation efficiency of modes in the multilayer DRA structure is highlighted to thoroughly characterise the modal contribution in the coupling behaviour for the centred and offset-slots.

Simulation of plasma filled hemispherical cavity as dielectric resonator antenna

Plasma antennas are becoming an increasingly interesting research topic because of their uncommon characteristics. They are highly configurable, can be turned on and off rapidly, and exhibit lower thermal noise compared to metal antennas. In recent years, research has been conducted on cylindrical plasma columns sustained by DC, RF or microwave field, and their application as leaky wave antennas or as regular monopole antennas.Dielectric resonator antennas (DRA) with high dielectric permittivity are known for their small size and excellent operating characteristics for modern mobile communications (WiMAX, LTE). Hemispherical dielectric resonator antennas are characterized by simple shape, high radiation efficiency and wide bandwidth. Hemispherical DRA with a low density weakly ionized plasma as dielectric material will combine the positive features of plasma and dielectric antennas, and is particularly interesting, as antennas of this type have not been studied yet. The hemispherical plasma antenna is simulated with Ansoft HFSS in the microwave S-band. Obtained radiation pattern and bandwidth show the advantages of hemispherical plasma antennas for future communication technology.

Analysis and experiment of stair‐shaped waveguide‐fed dielectric resonator antenna

Theoretical analysis of a stair-shaped waveguide-fed hemispherical dielectric resonator antenna (DRA) using method of moments (MoM) is presented in this study. Waveguide steps are used to enhance the coupling of direct coupled waveguide-fed DRA. Theoretical analysis is performed by solving coupled integral equations obtained by imposing magnetic field boundary conditions at various apertures using MoM. DRA and the steps are analysed using Green's function. For waveguide, modal analysis is performed. In order to determine the effects of various design parameters, parametric analysis has been carried out using the code developed. Experimental results confirm the validity of the proposed theory. The antenna has a maximum gain of 5.7 dBi at 9.09 GHz with a 3 dB gain bandwidth of 11.08%. Reasonable agreement is observed between the measured and simulated radiation patterns. The proposed coupling enhancement technique guarantees more than 98% coupling.

A novel half Hemispherical Dielectric Resonator Antenna with array of slots loaded with a circular metallic patch for wireless applications

In this paper, effect of loading of a circular metallic patch on a half Hemispherical Dielectric Resonator Antenna (HDRA) with array of slots is investigated. The half HDRA with array of slots operate from 5.3GHz to 6.05GHz. The circular patch controls the frequency tuning of the antenna geometry. The radius of the patch governs the resonant frequency and subsequently the bandwidth of operation. The patch also plays a role of reflector to improve the gain of the antenna. An optimized radius of patch of r=0.6cm on the proposed geometry offers 0.82GHz of impedance bandwidth (S11<−10dB) at 4.55GHz. The gain is significantly improved to 8.5dBi at 5.05GHz. A prototype is fabricated and the measured results are found to be in good agreement with the simulations. The resonant frequency is most suitable for standard wireless communications with wide band and high gain applications.

Rectangular waveguide fed DRA using tapered waveguide section

ABSTRACTA novel technique for coupling enhancement of rectangular waveguide fed hemispherical dielectric resonator antenna (DRA) is presented in this article. Waveguide with tapered section at the end is terminated by a thick ground plane and a slot is cut at the center of the ground plane for exciting the DRA. Introduction of tapering at the end of the waveguide provides substantial improvement in matching between the waveguide and DRA. The effects of different antenna parameters on return loss characteristics are studied. The experimental results show reasonable agreement with simulated results. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:2025–2028, 2015

A Novel Hemispherical Dielectric Resonator Antenna With Complementary Split-Ring-Shaped Slots and Resonator for Wideband and Low Cross-Polar Applications

In this paper, a novel hemispherical dielectric resonator antenna (HDRA) with complementary split rings and slots is proposed and investigated. The complementary split-ring resonators (CSRRs) are etched from the ground plane, which are pierced though slots extending from the ground plane up to the HDRA. The dielectric material used is Rogers TMM10, which has a dielectric constant of r ¼ 9:2. The CSRR-shaped slot on HDRA lowers down the quality factor (Q-factor) of the antenna, thus enhancing the bandwidth. Furthermore, the current distribution across the CSRR slots on the ground plane is out of phase, which results in current cancelation along the CSRR and hence reduces the cross-polar component of the radiation pattern significantly. The measured value of bandwidth of the proposed structure is 30% centered at 1.9 GHz, offering a gain of 6 dBi. The cross-polar level is more than 40 dB, which is much lower than the copolar pattern. The first two modes of the HDRA are preserved.

Coupling Enhancement of Waveguide fed Dielectric Resonator Antenna using Tapered Section of Waveguide

A novel technique for coupling enhancement of waveguide fed hemispherical dielectric resonator antenna (DRA) is proposed in this paper. A tapered section of waveguide is inserted between the rectangular waveguide and the ground plane to improve coupling. The tapered section acts as an impedance matching device that increases the coupling from waveguide to DRA. The proposed structure has been simulated using Ansoft HFSS and compared the results with CST Microwave Studio. The effect of various design parameters of the antenna on return loss characteristics is studied.

Design of Wideband Omnidirectional Two-Layer Transparent Hemispherical Dielectric Resonator Antenna

This communication investigates the wideband omnidirectional two-layer hemispherical dielectric resonator antenna (DRA), excited in its omnidirectional TM101 mode by an axial probe. For the first time, design formulas of the omnidirectional two-layer hemispherical DRA are found by using the covariance matrix adaptation evolutionary strategy (CMA-ES). The formulas are used to design a two-layer transparent hemispherical DRA which simultaneously serves as the covering of a light source. Acrylic and glass are used for the inner and outer transparent layers, respectively. ANSYS HFSS was used to simulate the DRA, and the simulation agrees reasonably well with our measurement. It was found that the transparent two-layer DRA has a measured impedance bandwidth of 31.9%, which is over two times wider than that of the single-layer TM101-mode glass DRA.