Dielectric Resonator Magnetoelectric Dipole Arrays with Low Cross Polarization,Backward Radiation,and Mutual Coupling for MIMO Base Station Applications

Dielectric resonator magnetoelectric dipole(DRMED)arrays with enhanced isolation,reduced cross-polarization,and backward radiation are proposed for base station(BS)applications.The proposed antenna comprises an elevated dielectric resonator antenna(DRA)on a small metal plate above a sizeable common ground plane.The DRA is designed in its T Eδ11 mode,acting like a magnetic dipole.The surface current excited by the differential probes flowing on the small ground plane is equivalent to an electric dipole.Since these two equivalent dipoles are orthogonal,they have the magnetoelectric dipole characteristics with reduced backward radiation.Meanwhile,the small ground planes can be treated as decoupling structures to provide a neutralization path to cancel the original coupling path.A linearly-polarized 4-element prototype array was verified experimentally in previous work.Here,a dual-polarized DRMED antenna is presented to construct a 2-element and 4×4 array for BS applications.To investigate its MIMO performance,sophisticated multi-cell scenario simulations are carried out.By using the proposed dualpolarized DRMED array,the cellular system capacityis improved by 118.6%compared to a conventional DRA array.This significant MIMO system improvement is mainly due to the reduced backward radiation and,therefore,reduced inter-cell interferences.Measurements align well with the simulations.

Triple-Band Circularly Polarized Dielectric Resonator Antenna (DRA) for Wireless Applications

This paper proposes a new dielectric resonator antenna(DRA)design that can generate circularly polarized(CP)triple-band signals.Atripleband CP DRA antenna fed by a probe feed system is achieved with metal strips structure on side of DRA structure.The design start with conventional rectangular DRA with F shaped metal strips on DRA structure alongside the feed.Then,the F metal strip is enhanced by extending the length of the metal strip to obtain wider impedance bandwidth.Further improvement on the antenna performance is observed by improvised the conventional DRA structure.The method of removing part of DRA bottom resulted to higher antenna gain with triple band CP.The primary features of the proposed DRA include wide impedance matching bandwidth(BW)and broadband circular polarization(CP).The primary features of the proposedDRAinclude wide impedance matching bandwidth(BW)and broadband circular polarization(CP).The CP BW values recorded by the proposed antenna were∼11.27%(3.3–3.65 GHz),12.18%(4.17–4.69 GHz),and 1.74%(6.44–6.55 GHz)for impedance-matching BW values of 35.4%(3.3–4.69 GHz),1.74%(5.36–5.44 GHz),and 1.85%(6.41–6.55 GHz)with peak gains of 6.8 dBic,7.6 dBic,and 8.5 dBic,respectively,in the lower,central,and upper bands.The prototype of the proposed antenna geometry was fabricated and measured.A good agreement was noted between the simulated and the measured results.

A Review of Wideband Circularly Polarized Dielectric Resonator Antennas

This article presents a technical review of circularly polarized(CP) dielectric resonator antennas(DRA) for wideband applications.The primary objective of this review is,to highlight the techniques used by different researchers for generating circular polarization in DRA.First,a general idea of circular polarization and it advantages over linear polarization is presented,and then all the major developments made in the CP DRA are highlighted.The emphasis of the paper is on the wideband circularly polarized dielectric resonator antenna.The current state of the art and all the realizable features of the CP DRA are addressed comprehensively.Finally,some recommendations for future CP DRAs are given and the paper ends with concluding remarks.

A Novel Kind of Wideband Low-Profile Dielectric Resonator Antenna Suitable for Beam-scanning Applications

In this paper, a low-profile wideband dielectric resonator antenna(DRA) with a very compact planar size is investigated. The antenna consists of a high permittivity dielectric sheet on the top, a low permittivity substrate in the middle, and a probe feeding structure at the bottom. By digging an annular slot in the designated area of the square dielectric sheet, the resonant frequency of fundamental TE111 mode can be effectively increased to be close to the high-order TE131 mode. The two modes can be finally merged together, yielding a wide impedance bandwidth of16.6%. Most importantly, the combination of the two modes is done on the premise of a fixed antenna planar size, which can be very compact and suitable for beam-scanning applications. A probe feeding structure is used to excite the DRA, making the antenna simple and practical to be integrated with other RF circuits. For verification, antenna prototypes with singlefeed linear polarization and differential-feed dual polarization were fabricated and measured. Reasonable agreement between the measured and simulated results is observed.

Ultra-Wideband Annular Ring Fed Rectangular Dielectric Resonator Antenna for Millimeter Wave 5G Applications

In this article an ultra-wideband rectangular Dielectric Resonator Antenna is designed for millimeter wave 5G frequency band applications.Indoor 5G communications require antenna system with wide bandwidth and high efficiency to enhance the throughput in the channel.To fulfill such requirements a Dielectric Resonator Antenna(DRA)is designed here which has achieved an ultra-wide bandwidth of 20.15%(22.32–27.56 GHz)which is 5.24 GHz of bandwidth centered at 26 GHz as resonating frequency.This covers the complete band 30(24.3–27.5 GHz)of 5G spectrum.26 and 28 GHz are considered as most popular frequencies in millimeter wave 5G communications.The aperture fed DRA designed here has also achieved an efficiency of 96 percentage with maximum radiation in the broadside direction(Phi=0,Theta=0).The measured gain of the DRA is 6.3 dB.The DRA designed here has dimensions of 0.25λ0×0.22λ0×0.12λ0.under the characteristic’s mode.The DRA is placed over a substrate with dimensions 0.5λ0×0.5λ0×0.02λ0.A cross slot aperture has been made on the ground plane which is placed above to the substrate.Here a full ground plane is used to resonate the antenna and is of similar dimension to the substrate.A microstrip line with two concentric rings makes an annular feed structure is used to excite the DRA and is placed below the substrate.The DRA is excited here in characteristics mode TE1Y1 and is the only mode of excitation.The DRA is linearly polarized,and the characteristic mode of excitation is maintained with 50 Ohm input impedance of the antenna.The DRA also gives here a good difference between the co-pol and cross pol approximately 15 to 20 dB.This antenna is more suitable for 5G indoor applications in millimeter wave frequency band centered at 26 GHz.

Simulation of dielectric resonator for a high-T_c radio frequency superconducting quantum interference device

Nowadays, the high-critical-temperature radio frequency superconducting quantum interference device （high-Tc rf SQUID） is usually coupled to a dielectric resonator that is a standard 10× 10×1 mm^3 SrTiO3 （STO） substrate with a YBa2Cu3O7-δ （YBCO） thin-film flux focuser deposited on it. Recently, we have simulated a dielectric resonator for the high-Tc rf SQUID by using the ANSOFT High Frequency Structure Simulator （ANSOFT HFSS）. We simulate the resonant frequency and the quality factor of our dielectric resonator when it is unloaded or matches a 50-Ω impedance. The simulation results are quite close to the practical measurements. Our study shows that ANSOFT HFSS is quite suitable for simulating the dielectric resonator used for the high-Tc rf SQUID. Therefore, we think the ANSOFT HFSS can be very helpful for investigating the characteristics of dielectric resonators for high-Tc rf SQUIDs.

Gain Enhancement of Dielectric Resonator Antenna Using Electromagnetic Bandgap Structure

High gain antennas are highly desirable for long-range wireless communication systems.In this paper,a compact,low profile,and high gain dielectric resonator antenna is proposed,fabricated,experimentally tested,and verified.The proposed antenna system has a cylindrical dielectric resonator antenna with a height of 9 mm and a radius of 6.35 mm as a radiating element.The proposed dielectric resonator antenna is sourced with a slot while the slot is excited with a rectangular microstrip transmission line.The microstrip transmission line is designed for a 50impedance to provide maximum power to the slot.As a result,the proposed antenna operates at 5.15 GHz with a 10-dB absolute bandwidth of 430 MHz(4.98–5.41 GHz).It is important to mention that the gain of the dielectric resonator antenna is enhanced by the introduction of an electromagnetic bandgap(EBG)structure.In fact,EBG units are placed below the antenna,which enhances the realized peak gain from 5.32 dBi to 8.36 dBi at 5.15 GHz.More specifically,a gain enhancement of 3.04 dB is observed with the introduction of the EBG array.This antenna has several good features such as high gain,compact size,large bandwidth,and lower losses which make it a suitable choice for long-range wireless communication systems.

All-dielectric left-handed metamaterial based on dielectric resonator:design,simulation and experiment

Dipoles with Lorentz-type resonant electromagnetic responses can realise negative effective parameters in their negative resonant region. The electric dipole and magnetic dipole can realise, respectively, negative permittivity and negative permeability, so both the field distribution forms of electric and magnetic dipoles are fundamentals in designing left-handed metamaterial. Based on this principle, this paper studies the field distribution in high-permittivity dielectric materials. The field distributions at different resonant modes are analysed based on the dielectric resonator theory. The origination and influence factors of the electric and magnetic dipoles are confirmed. Numerical simulations indicate that by combining dielectric cubes with different sizes, the electric resonance frequency and magnetic resonance frequency can be superposed. Finally, experiments are carried out to verify the feasibility of all-dielectric left-handed metamaterial composed by this means.

All-dielectric frequency selective surface design based on dielectric resonator

In this work,we propose an all-dielectric frequency selective surface（FSS） composed of periodically placed highpermittivity dielectric resonators and a three-dimensional（3D） printed supporter.Mie resonances in the dielectric resonators offer strong electric and magnetic dipoles,quadrupoles,and higher order terms.The re-radiated electric and magnetic fields by these multipoles interact with the incident fields,which leads to total reflection or total transmission in some special frequency bands.The measured results of the fabricated FSS demonstrate a stopband fractional bandwidth（FBW）of 22.2%,which is consistent with the simulated result.

Wideband Polarization Reconfigurable Dielectric Resonator Antenna

A wideband polarization reconfigurable dielectric resonator antenna excited by quasilumped quadrature coupler（ QLQC） is proposed. By adjusting the value of varactor diode on the QLQC feed network,both the wideband LP and CP dielectric resonator antennas（ DRA） modes can be achieved. By selecting a different feed port,left-and right-handed CP conversion can be realized.It is found that the 10 dB impedance bandwidth of the LP and CP modes are 10. 1% and 44. 9%,respectively.For the CP mode,a very wide 3 dB axial ratio bandwidth of 37. 7% can be obtained which is much larger than that of the microstrip patch counterpart（ 3. 8%）. It is worth mentioning that the wideband CP DRA has a stable broadside radiation pattern across the whole operating band where the boresight gain is larger than 3 dBi.

Novel circularly-polarized ceramic dielectric resonator antenna excited by a corner-cut square patch

A ceramic dielectric resonator antenna excited by a corner-cut square patch for the circularly-polarized operation is introduced. The effect of patch size and cut size is investigated, showing that the resonant frequency of the antenna can be changed by simply changing the patch size. The reflection, axial ratio, and radiation characteristics of the antenna are found. Measurements were carried out to verify the design. The antenna is compact in structure, which is attractive in the application as the satellite communication terminals.

A Dual Mode Dielectric Resonator and Its Design to Bandpass Filter

In this paper, the resonant frequency of a dual\|mode dielectric resonator is calculated using a finite difference time\|domain method. A new type of bandpass filter is designed with the calculated coupling coefficient. The filter designed in this paper has reached the design goal, verified by simulation with Ansoft HFSS.

Design of a 5.305 GHz Dielectric Resonator Oscillator with Simulation and Optimization

The design of a 5.305 GHz series feedback free running dielectric resonator oscillator （DRO） is presented. Its simulation and optimization are realized by obtaining the unloaded Q factor of the cavity dielectric resonator （DR） and analyzing the linear and nonlinear models of the DRO. CAD packages of DR_Rez and Agilent Advance Design System （ADS） are used and the best tradeoff among the output power, phase noise, and frequency stability is achieved. With the result of simulation, a physical oscillator prototype is constructed. The measured results show the good agreement with those of simulation.

UltrahighQ Sr_(1+x)Y_(2)O_(4+x)(x=0-0.04)microwave dielectric ceramics for temperature-stable millimeter-wave dielectric resonator antennas

Microwave dielectric ceramics should be improved to advance mobile communication technologies further.In this study,we prepared Sr_(1+x)Y_(2)O_(4+x)(x=0-0.04)ceramics with nonstoichiometric Sr^(2+)ratios based on our previously reported SrY_(2)O_(4) microwave dielectric ceramic,which has a low dielectric constant and an ultrahigh quality factor(Q value).The ceramic exhibited a 33.6% higher Q-by-frequency(Q×f)value(Q≈12,500)at x=0.02 than SrY_(2)O_(4).All Sr_(1+x)Y_(2)O_(4+x)(x=0-0.04)ceramics exhibited pure phase structures,although variations in crystal-plane spacings were observed.The ceramics are mainly composed of Sr-O,Y1-O,and Y_(2)-O octahedra,with the temperature coefficient of the resonant frequency(τ_(f))of the ceramic increasing with Y_(2)-O octahedral distortion.The ceramic comprises uniform grains with a homogeneous elemental distribution,clear grain boundaries,and no obvious cavities at x=0.02.The Sr_(1+x)Y_(2)O_(4+x)(x=0-0.04)ceramics exhibited good microwave dielectric properties,with optimal performance observed at x=0.02(dielectric constant(εr)=15.41,Q×f=112,375 GHz,and τ_(f)=-17.44 ppm/℃).The τ_(f) value was reduced to meet the temperaturestability requirements of 5G/6G communication systems by adding CaTiO_(3),with Sr_(1.02)Y_(2)O_(4.02)+2wt% CaTiO_(3) exhibiting ε_(r)=16.14,Q×f=51,004 GHz,andτf=0 ppm/℃.A dielectric resonator antenna prepared using Sr_(1.02)Y_(2)O_(4.02)+2wt%CaTiO_(3) exhibited a central frequency of 26.6 GHz,with a corresponding gain and efficiency of 3.66 dBi and 83.14%,respectively.Consequently,Sr_(1.02)Y_(2)O_(4).02-based dielectric resonator antennas are suitable for use in 5G millimeter-wave band(24.5-27.5 GHz)applications.

Dielectric Patch Resonator and Antenna

This paper presents an overview of dielectric patch(DP)antennas developed in recent years.The employed DP resonator composed of a DP and a bottom substrate is analyzed comprehensively here,enabling the easy realization of a quasi-planar DP antenna.It combines the dual advantages of the conventional microstrip patch(MP)antenna and dielectric resonator(DR)antenna in terms of profile,gain,bandwidth,radiation efficiency,and design freedom.Furthermore,the DP antenna inherits the multi-mode characteristic of the DR antenna,thus it has a large number of high-order modes,including TMmn mode and TEmn mode.The high-order modes are widely applied,for example,by combining with the dominant TM10 mode to expand the bandwidth,or selecting multiple higher-order modes to implement a high-gain antenna.Additionally,the non-radiation high-order modes are also utilized to produce natural radiation null in filtering antenna design.In this paper,the design theories and techniques of DP antenna are introduced and investigated,including calculation and control methods of the resonant mode frequencies,analysis of the radiation mechanism,and applications of the multi-mode characteristic.This overview could provide guidance for the subsequent antenna design,thus effectively avoid time-consuming optimization.

Compact Interlaced Dual Circularly Polarized Sequentially Rotated Dielectric-Resonator Antenna Array

In this study,a compact 2×2 interlaced sequentially rotated dual-polarized dielectric-resonator antenna array is proposed for 5.8 GHz applications.The array is composed of a novel unit elements that are made of rectangular dielectric resonator(RDR)coupled to an eye slot for generating the orthogonal modes,TEδx 21 and TE1yδ1 to acquire circular polarization(CP)radiation.For the purpose of miniaturization and achieving dual polarized resonance,the array is fed by two interlaced ports and each port excites two radiating elements.The first port feeds horizontal elements to obtain left hand circular polarization(LHCP).The second port feeds vertical elements to obtain right hand circular polarization(RHCP).A quarter-wave length transformer is employed to reduce the attenuation and consequently increase the array gain performance.The 35×35 mm2(0.676λ0×0.676λ0)gains were 8.4 and 8.2 dBi for port 1 and port 2,respectively,with port isolations of−33.51 dB.The design achieves a voltage standing-wave ratio(VSWR)<−10 dB and an axial ratio(AR)<−3 dB bandwidth of 2.48%(5.766 to 5.911 GHz)for LHCP at port 1 and a VSWR<−10 dB and AR<−3 dB bandwidth of 2.28%(5.788 to 5.922 GHz)for RHCP at port 2.The findings of the proposed design validate its use for ISM band applications.

A Low-Profile Cylindrical Dielectric Resonator Antenna with Bandwidth-Enhancement Under Triple-Mode Resonance

A low-profile cylindrical dielectric resonator antenna(CDRA)with enhanced impedance bandwidth is proposed via sharing a single triple-mode dielectric resonator.Initially,the resonant frequencies of TM01d and TM02d modes of a conventional CDRA are maintained far away from each other under central probe feed.Next,a circular disk with an annular ring is loaded around the conventional CDRA,aiming to excite an additional mode between these dual modes.The electric fields demon-strate that the previous TM_(02δ) mode is transformed into the TM03d mode for the modified CDRA,and an additional TM_(02δ) mode is successfully excited between the TM_(01δ) and TM_(03δ) modes.As a result,the resonant frequencies of these three radiative modes are reallocated in proximity to each other,thus achieving the desired bandwidth enhancement.In addition,considering the small input impedance of the CDRA,a microstrip feeding line is introduced underneath the central probe for good impedance matching.With these arrangements,the resultant antenna can generate an extended bandwidth under simultaneous radiation of TM_(01δ),TM_(02δ),and TM_(03δ) modes.Finally,the proposed CDRA is designed,fabricated,and measured to validate the predicted per-formance.The simulated and measured results show that the impedance bandwidth(|S11|<-10 dB of the antenna is dramatically extended from 8%to about 62%(2.835.36 GHz),while keeping a stable conical radiation pattern.In particular,a low profile property of about 0.15 free space wavelength is achieved as well.

Low-Loss Dielectric Material Characterization and High-Q Resonator Design from Microwave to Millimetre Waves Frequencies

Dielectric resonators are key components in many microwave and millimetre wave circuits and applications, including high-Q filters and frequency-determining elements for precision frequency synthesis. Multilayered and bulk low-loss single crystal and polycrystalline dielectric structures have become very important for designing these devices. Proper design requires careful electromagnetic characterisation of low-loss material properties. This includes exact simulation with precision numerical software and precise measurements of resonant modes. For example, we have developed the Whispering Gallery mode technique, which has now become the standard for characterizing low-loss structures. This paper will review some of the common characterisation techniques used in the microwave to millimetre wave frequency regime.

Ba_3La_2Ti_2Ta_2O_(15):A New Microwave Dielectricof A_5B_4O_(15)-type Cation-deficient Perovskites

The synthesis, structure and properties of a new A5B4O15-type cation-deficient perovskite Ba3La2Ti2Ta2O15 were discribed. The compound was prepared by the conventional solid-state reaction route. The phase and structure of the ceramics were characterized by X-ray diffraction （XRD）, scanning electron microscopy （SEM）. The results reveal that the compound is successfully synthesized. The compound crystallizes in the trigonal system with unit cell parameter a=5.6730（2） A, c=11.6511（2） A, V=324.93（1） A^3 and Z=1. The microwave dielectric properties of the ceramic are studied using a network analyzer, and it shows a high dielectric constant of 45.1, a high quality factors with Q×fof21 029 GHz, and a positive τf of 5.3 ppm℃^-1.

Controlling optical responses through local dielectric resonance in nanometre metallic clusters

Optical responses in dilute composites are controlled through the local dielectric resonance of metallic clusters. We consider two located metallic clusters close to each other with admittances ε1 and ε2. Through varying the difference admittance ratio η[= （ε2 - ε0）/（ε1 - ε0）], we find that their optical responses are determined by the local resonance. There is a blueshift of absorption peaks with the increase of η- Simultaneously, it is known that the absorption peaks will be redshifted by enlarging the cluster size. By adjusting the nano-metallic cluster geometry, size and admittances, we can control the positions and intensities of absorption peaks effectively. We have also deduced the effective linear optical responses of three-component composites εe=ε0 （1＋∑^n n=1[（γn1＋ηγn2）/（ε0（s-sn））]） and the sum rule of cross sections：∑^n n=1（γn1＋ηγn2）=Nh1＋Nh2,, where Nh1and Nh2 are the numbers of εl and ε2 bonds along the electric field, respectively. These results may be beneficial to the study of surface plasmon resonances on a nanometre scale.