Resonator Antenna Research Articles

Triple‐mode resonant null frequency scanning antenna with positive scanned slope

A novel design approach to triple-mode resonant null frequency scanning antenna (NFSA) with positive scanned slope is proposed. Firstly, a circular sector patch radiator with short-circuited circumference is introduced to generate multiple TM0m (m = 1, 2, …) mode resonances. Then, as theoretically predicted and numerically proved, the first three TM0m (m = 1, 2, 3) modes can be effectively combined to yield null frequency scanning functionality with positive scanned slopes. Next, a prototype antenna is designed, fabricated, and measured. As numerically demonstrated and experimentally validated, the proposed NFSA can exhibit a null frequency scanning functionality in xz-plane with positive scanned slope ranging from θ = −90° to +45° (for null depth smaller than −10 dB) within a fractional impedance bandwidth of about 34.3% (i.e., 2.97‑4.20 GHz).

A Compact Dual Band MIMO Dielectric Resonator Antenna with Improved Performance for mm-Wave Applications.

A compact multiple-input-multiple-output (MIMO) dielectric resonator antenna (DRA) that is suitable for internet of things (IoT) sensor networks is proposed with reduced coupling between elements. Two rectangular-shaped DRAs have been placed on the opposite sides of a Rogers substrate and each is fed using a coplanar waveguide (CPW) feed with slots etched in a dedicated metal ground plane that is located under the DRA. Moreover, locating the elements at the opposite sides of the substrate has improved the isolation by 27 dB without the need to incorporate additional complex structures, which has reduced the overall antenna size. Furthermore, a dual band operation is achieved since each antenna resonates at two frequencies: 28 GHz and 38 GHz with respective impedance matching bandwidths of 18% and 13%. As a result, the corresponding data rates are also increased independently. In addition to the advantages of improved isolation, compact size and dual band operation, the proposed configuration offers a diversity gain (DG), envelope correlation coefficient (ECC) and channel capacity loss (CCL) of 9.98 dB, 0.007, 0.06 bits/s/Hz over the desired bands, respectively. A prototype has been built with good agreement between simulated and measured results.

Pattern-Reconfigurable Dielectric Resonator Antenna With Endfire Beam-Scanning Feature

A novel pattern-reconfigurable dielectric resonator (DR) antenna with endfire beam-scanning feature is proposed in this letter. The proposed antenna consists of a DR, a switchable director with 10 p-i-n diodes, and a differential feeding structure. The differential-fed DR operating in TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">01δ</sub> mode can provide a primary endfire pattern with wide beam. Based on this, a large-coverage beam-scanning performance can be obtained by introducing a switchable director placed in front of the DR. A prototype is fabricated and measured to verify the proposed design. By switching the p-i-n diodes of the switchable director, the proposed antenna enables a near-continuous beam scanning from −48° to +48° in the azimuth plane with a gain fluctuation of less than 0.5 dB. Besides, the 3 dB scanning coverage is up to 164° (from −82° to +82°), which shows good beam-scanning performance.

Mode Recognition of Rectangular Dielectric Resonator Antenna Using Artificial Neural Network

A new method powered by an artificial neural network (ANN) is studied for resonant-mode recognitions of a rectangular dielectric resonator antenna (DRA). Different rectangular DRAs were simulated with ANSYS HFSS to generate a large dataset for training the model. Their resonance frequencies, dimensions, and 3-D electric fields are input to the ANN. The output end is a 12-element array representing the corresponding probabilities of 12 different resonant modes. Using this trained ANN model, the mode recognition accuracy can reach 96.74%. Apart from identifying the resonant modes, our proposed approach can suggest how to modify a rectangular DRA to improve the purity of a resonant mode for better antenna performance.

Broadband Dielectric Resonator Antenna Array With Enhancement of Isolation and Front-to-Back Ratio for MIMO Application

Dielectric resonator antenna (DRA) arrays with enhanced isolation and front-to-back ratio (FBR) are proposed in this letter. Specifically, each DRA element is mounted on a small and separated ground plane; all the DRA elements (with small ground planes) share a large common ground plane. Each DRA element is excited by two differential probes at its edges. The DRA element in its <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${\boldsymbol{TE}}_{{\boldsymbol{\delta }}11}^{\boldsymbol{x}}$</tex-math></inline-formula> mode is equivalent to a magnetic dipole. Meanwhile, the differential probes also excite electric current on the small grounds that can be viewed as an electric dipole. The equivalent magnetic and electric dipoles are orthogonal, behaving like a magnetoelectric dipole (ME-dipole). By properly adjusting the small ground planes’ size and their height above a sizeable common ground plane, a broadside unidirectional radiation pattern with low backward radiation is realized; moreover, the small ground structures can provide neutralization paths to counteract the original coupling waves. A <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$1 \times 4$</tex-math></inline-formula> single-polarized DRA array is designed, fabricated, and measured. Measurements align well with the simulations, demonstrating significant isolation and FBR improvements compared with the conventional DRA array. The proposed array has about 20% relative bandwidth.

A broadband Fabry–Perot resonator antenna using partially reflecting surface with positive reflection phase gradient

A novel Fabry–Perot resonator antenna with a wide impedance- and gain-bandwidth is proposed in this paper. A wideband aperture-coupled microstrip antenna is used as the primary source, and a single-layer frequency selective surface with a positive reflection phase gradient is designed as a partially reflective surface. To validate the proposed approach, a prototype antenna operating in the X-band is designed, fabricated, and measured. Both simulation and measured results indicate that the proposed antenna exhibits wideband characteristics. The measured impedance bandwidth (|S11| &amp;lt; −10 dB) is 64.4%, ranging from 8.68 to 15.12 GHz. The experiments demonstrate that a 3 dB gain bandwidth of 31.9% from 8.61 to 11.80 GHz with a peak gain of 14.0 dBi at 10 GHz is achieved. In addition, the proposed antenna reveals good directional radiation patterns, low side-lobe level, and low cross-polarization over the whole working band.

Wideband Circularly Polarized Cavity-Backed Dielectric Resonator Antenna With Low RCS for Aerial Vehicle Communications

This letter explains the design of a wideband circularly polarized dielectric resonator antenna (DRA) with a dual-cylindrical conformal cavity for aerial applications. The proposed dielectric resonator (DR) element uses multilayer cross-shaped elements of varying dimensions with an off-centered circular slot that is inserted inside the DR geometry. Combining the wideband DRA with a conformal cavity (bending angle, α = 5°) that provides wider impedance bandwidth of 111% from 5.02 to 17.52 GHz and axial ratio bandwidth of 32.29% from 6.18 to 8.56 GHz. The proposed antenna provides a higher gain of 10.77 dBi at 8.5 GHz, gain values better than 7.21 dBi, and radiation efficiency better than 90% for the complete band. Also, the proposed antenna provides good radar cross-section reduction mechanism for the entire working band.

Efficient Online Data-Driven Enhanced-XGBoost Method for Antenna Optimization

The tremendous progress in artificial intelligence promotes the wide application of machine learning (ML) technology in the field of electronic science. Recently ML-based antenna optimization provides a distinct candidate and attracts considerable attention. However, the large number of training samples generated through time-consuming EM simulations becomes a significant challenge. In this article, an efficient online data-driven enhanced-XGBoost (E-XGBoost) method for antenna optimization is proposed, which is mainly composed of two parts, i.e., an input variable filter module (IVFM) and an antenna optimization module (AOM). Specifically, IVFM serves as a variable sensitivity analyzer, which is accomplished by E-XGBoost to efficiently reduce the dimension of design variable and hence save the training samples. Next, the design variables obtained by IVFM are fed into AOM to find the near-optimal solution. In AOM, an online learning strategy is proposed to train a local E-XGBoost model to evaluate the population in the metaheuristic optimization algorithm (MOA). Compared to the global ML model that can mimic the entire design space, this local E-XGBoost model can further cut down the training samples. To verify the performance of the proposed method, several different antenna examples, i.e., U-slot patch antenna, Fabry–Perot resonant antenna, and dual-polarized cross dipole antenna and 5G MIMO antenna array, are simulated. Numerical results support the proposed method in terms of its superior performance and potential advantage of saving computational overhead.

3-D-Printed Wideband Circularly Polarized Dielectric Resonator Antenna With Two Printing Materials

A new 3-D-printed wideband circularly polarized (CP) dielectric resonator antenna (DRA) with two printing materials is investigated. The DRA has a multilayer comb-shaped structure at its top for generating CP fields. Three dielectric strips are embedded inside the DRA body to support multiple transverse-electric (TE) DRA modes to widen the DRA bandwidth. To slightly improve the axial-ratio (AR) performance, the DRA is twisted in the horizontal plane. For demonstration, a prototype operating in C-band was designed and printed with two different materials. The reflection coefficient, AR, radiation pattern, antenna gain, and efficiency of the antenna are measured, and reasonable agreement between the measured and simulated results is observed. The prototype has a measured 10 dB impedance bandwidth of 69.7% (4.80–9.94 GHz) and 3 dB AR bandwidth of 68.6% (4.52–9.24 GHz), achieving a wide overlapping bandwidth of 63.2% (4.80–9.24 GHz). Both the AR and overlapping bandwidths are record-high for a single-fed CP DRA. The prototype has a measured peak antenna gain of 8.3 dBic inside the overlapped passband.

Influence of the addition of CaTiO3 on the microwave dielectric properties of the BaMoO4 matrix

This work presents the study of the dielectric properties in the microwave region (MW) of BaMoO4 ceramic and composites with CaTiO3 (CTO). The BaMoO4 matrix was synthesized by solid state reaction and characterized by X-ray diffraction. Ceramic composites were obtained by adding 20–80 mol% of CTO in the BaMoO4 matrix. The Silva-Fernandes-Sombra method was used to measure the resonant frequency temperature coefficient (τf), and the BaMoO4 composite with 20% CTO showed an adequate value of relative dielectric permittivity (εr = 8.90), low dielectric loss tangent (tan δ = 9.89.10−4) and τf close to zero (τf = 3.48 ppm °C−1). BMO and its composites were applied as dielectric resonator antennas, and their far-field parameters were obtained through numerical simulation.

Mutual coupling reduction between the cylindrical dielectric resonator antenna using split ring resonator based structure

In this work, the design of a compact Multiple Input Multiple Output (MIMO) Cylindrical Dielectric Resonator Antenna (CDRA) with an efficient technique for mutual coupling reduction is investigated and validated experimentally. Two cylindrical dielectric resonators (CDR) are excited by the microstrip line through the rectangular slot underneath the CDRAs. Isolation between the CDRAs is improved by a separator wall loaded with Split Ring Resonator (SRR) placed in between the elements. A maximum improvement of isolation up to 40 dB is achieved over the frequency band 7.40–7.80 GHz centered at 7.56 GHz. Broadside radiation patterns at both the principal planes justify the use of the proposed MIMO antenna for commercial applications.

Aperture coupled dielectric resonator antenna optimisation using machine learning techniques

In this article, various machine learning (ML) algorithms such as Artificial neural network (ANN), Random Forest, XG boost, K nearest neighbor (KNN), and Knowledge-based neural network (KBNN) are used for efficient optimization of dielectric resonator antenna (DRA). ML models are used to predict the |S11| for a particular set of frequency, resonator height, aperture radius, and resonator radius. Finally, a comparative performance analysis of different ML algorithms has been done with the outcomes of the HFSS EM simulator. Error percentage is in between 1.0% and 7.0% with different ML algorithms. Antenna design is also fabricated and tested. The performance of the fabricated prototype is very close to different ML algorithms and HFSS obtained outcomes.

Broadbanding and multi-frequency in dielectric resonator antennas: a comprehensive review

Abstract Dielectric resonator antennas (DRAs) are developed antennas that are lightweight, wideband, small-sized and have high radiation efficiency. A DRA is an appropriate candidate for any radio communication including radar applications mainly because of its high efficiency and wideband performance. As the development of DRAs has been a continuous process for more than five decades the plethora of the same has become magnificent in all possible ways. Scientists have walked the technical path for more than centuries and tried to meet the various challenges in the most graceful ways. Reduction of loss, lightweight, and desired radiation patterns are some of the issues which are effectively met by DRAs. This paper presents a brief comprehensive review of the state of art techniques, giving an exhaustive idea of achieving broadband and multi-frequency operations in the areas of DRAs. The paper associates the references of the past and correlates with the current and future trends of research in DRAs that could be of immense help to the young upcoming researchers interested in this field.

Cold sintering optimized SrF2 microwave dielectric ceramics for the development of dielectric resonator antenna at 5G millimeter-wave band

SrF2 is a promising low-εr fluoride with outstanding microwave dielectric properties, while densification of SrF2 ceramics is challenging via traditional thermal sintering (TTS). In this work, dense SrF2 ceramics with 93.4%–97.2% relative density have been obtained via cold sintering (300 MPa–900 MPa, 150 °C, 1 h) and subsequent post-annealing at 950 °C/3 h. The pretreated cold sintering process is beneficial for microstructure optimization, where the maximum Qf value (62,037 GHz) is obtained at 750 MPa, nearly three times higher than the TTS sample (21,080 GHz). An ultra-low dielectric constant (εr) of 5.94 is simultaneously obtained, together with a temperature coefficient of resonant frequency τf = −78.26 ppm/°C. Good chemical compatibility between SrF2 ceramics and silver is verified, indicating great promise for their use in LTCC technology. Moreover, the low-εr and high Qf values of the cold sintering optimized SrF2 ceramics suggest great potential in the 5G millimeter-wave antenna systems. A SrF2-based dielectric resonator antenna is designed and fabricated, which resonates at the desired 24.5 GHz and exhibits an outstanding S11 of −43.95 dB and a broad bandwidth of 4.51 GHz.

A low cost and efficient breast cancer detection method with a staircase shaped ultrawide band dielectric resonator antenna using monostatic radar based microwave imaging technique

In this article, a staircase-shaped ultra-wide band dielectric resonator antenna (DRA) has been used as a sensor for the detection of breast tumor by monostatic radar-based microwave imaging (MRMWI). The proposed DRA has fractional bandwidth (BW) 98.5% and a high peak gain 5.98 dB along with dual polarization behaviour from 5.12 to 8.2 GHz and 11.02-13.8 GHz. In the MRMWI setup, DRA is placed over the breast phantom at a distance of 7 mm and provides a safe exposure of radiation (<1.6 W/Kg). For simulation, it rotates around the phantom at a fixed interval in elevation (0-180°) and azimuthal (0-360°) planes. It works as a radiate and receives the reflected signals towards and from the scanned area simultaneously. To validate the results, fabricated DRA is connected to a vector network analyzer and rotates (as done for simulation) around the artificial breast phantom. That is a replica of the human breast made from gelatin+sugar, Vaseline and wheat flour+water equivalent to skin, fat and tumor respectively. Afterward S11 responses are recorded in the presence and absence of tumor inside the phantom. A significant variation in recorded values leads to the detection of tumors that are processed further in beam-forming algorithms; delay and sum (DAS) and delay-multiply and sum (DMAS) to reform the 2-dimensional image of tumor in MATLAB.

Compact half H‐shaped dielectric resonator antenna for wideband applications

AbstractIn this study, the authors present the design of a half H‐shaped dielectric resonator antenna (DRA) for compact size and wide bandwidth. The trapezoidal patch feed is used to excite the DRA, which results in TE113Y and TE115Y resonant modes of the rectangular DRA (RDRA). It is found that the broad‐side higher‐order TE113Y with the TE115Ymode is used in the proposed design to make it wideband. The effective dielectric constant of the proposed DRA is reduced by the slots and then the structure is made half to make it compact. Finally, for further improvement in bandwidth, the size of the ground plane is reduced, which increases the parallel capacitive reactance and decreases the Q‐factor. The proposed structure achieves measured impedance bandwidth S11 ≤ −10 dB of 75% (4.30–9.50 GHz) with a maximum gain of 7.20 dB. The proposed DRA is applicable for WLAN (5.15–5.72 GHz) and orthogonal frequency‐division multiplexing 802.11a (5.72–5.85 GHz).

Compact Four-Port Circularly Polarized MIMO X-Band DRA.

A circularly polarized (CP) multi-input multioutput (MIMO) dielectric resonator (DR) antenna (DRA) with compact size and four ports is implemented. CP radiation was achieved using the deformed DR geometry excited with aperture coupled feeding. A CPDRA with a single and two ports is investigated. The defected ground structure (DGS) was incorporated into the antenna for improving the isolation between the ports. The DGS was incorporated in such a way that the required phase difference between the generated orthogonal degenerate modes is preserved. This concept could be utilized in implementing a compact four-port CP antenna. The MIMO antenna provides a 10 dB impedance bandwidth of 38% (8.5–12.5 GHz) and a 3 dB AR bandwidth of 9.32% (9.2–10.1 GHz). The gain of the implemented antenna was around 6 dBi in the band where CP radiation was achieved. The MIMO performance parameters were calculated, and their values remained within the acceptable limits. The implemented antenna could suitably be used in X-band applications.

A CPW fed quad-port MIMO DRA for sub-6 GHz 5G applications

The present work investigates a novel four-port, multiple-input multiple-output (MIMO), single element dielectric resonator antenna (DRA) for sub-6 GHz band. The DRA is designed and fabricated into a symmetric cross shape and fed using a coplanar waveguide (CPW) feed. A single radiator with four ports is rarely found in the literature. The -10 dB impedance bandwidth covered by the antenna is from 5.52 GHz to 6.2 GHz (11.6%) which covers fifth generation (5G) new radio (NR) bands N47 and wireless local area network (WLAN) IEEE 802.11a band. The isolation between orthogonal ports is about 15 dB while the isolation between opposite ports is 12 dB. The radiation pattern of the proposed antenna is bidirectional due to the absence of a ground plane below the DRA. The orthogonal modes excited in the DRA are and through the four symmetrical CPW feeds. The simulated and measured results of the proposed design show that MIMO characteristics are achieved by pattern diversity between the ports. Due to the perfect symmetry of the design, the proposed work could be extended to MIMO array applications as well.

Design and Analysis of Dual-band Circularly Polarized Hybrid Ring Cylindrical Dielectric Resonator Antenna for Wireless Applications in C and X-Band

Design and Analysis of Dual-band Circularly Polarized Hybrid Ring Cylindrical Dielectric Resonator Antenna for Wireless Applications in C and X-Band

Dual circularly polarized semi‐cylindrical hybrid dielectric resonator antenna for X and Ku ‐band applications

A hybrid dielectric resonator antenna (HDRA) with a single-probe generating circular polarization (CP) simultaneously at X and Ku-bands is presented in this article. A novel hybrid structure of semi-circular patch and semi-cylindrical dielectric resonator (DR) of equal radius are combined with a single-point probe feed to achieve dual-functional wide CP bands. The asymmetric nature of the semi-circle and semi-cylinder produces two orthogonal modes in their respective bands for CP radiation. The measured impedance bandwidth obtained by the proposed structure is 36.49% (3750 MHz) at X-band and 14.23% (2100 MHz) at the Ku-band range of frequencies. Axial ratio (AR) bandwidth of 30.39% (3100 MHz) is obtained at X-band and 13.24% (1950 MHz) at Ku-band. The measured gains are 9.54 dBic at 9.6 GHz and 6.55 dBic at 15 GHz. An excellent agreement between the computed and measured results validates the design of the dual functional circularly polarized HDRA.