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© 1963-2012 IEEE. A low-loss multifeed antenna with controlled polarization and beam steering is presented. A low-profile resonant cavity antenna is fed by multiple spherical dielectric resonators (DRs), demonstrating its multifeed capabilities. Each of the DRs are themselves fed from four different sides by microstrip resonators on a planar circuit board. The beam pointing direction and polarization of the antenna are controlled by the signal phases at the respective input ports. Several antennas with varying feed topology are investigated, showing the versatility of this method. A 16-way 34 GHz prototype is built and measured, demonstrating high overall efficiency (considering power combining loss and antenna loss) of 80%.

In this paper, a low-profile broadband antenna is presented for 60 GHz applications. It is demonstrated that the entire unlicensed 60 GHz frequency band can be covered using a dielectric based aperture type antenna. The antenna consists of a single-layer dielectric superstrate and an aperture type feed, which are separated by an air-cavity. The diameter of the superstrate is 15 mm, which is $2.75\lambda _{0}$ at the lowest operating frequency of 55.2 GHz. The simulated total efficiency of the antenna is greater than 88% over the entire operating band (55.2 GHz-65 GHz), which is unprecedented relative to medium-to-high gain millimeter-wave printed antenna arrays, used for similar applications. A prototype antenna was constructed, which exhibits a measured peak gain of 19.5 dBi. This value remains greater than 17 dBi over the entire operating bandwidth. The measured 3-dB beamwidths of the proposed antenna remain between 16° to 20° in the E-plane and 19.5° to 25° in the H-plane, respectively. The proposed antenna provides broadside directed radiation patterns with cross-polarization in the order of -30 dB over the entire operating band.

A simple 3D printable meta-structure is proposed for use as a partially reflecting surface (PRS) in resonant cavity antennas (RCAs). The meta-structure acts as a spatial phase transformation device placed in close proximity above the RCA, thereby improving its gain by nearly 3dB. The aperture efficiency of the RCA with the proposed 3D printable PRS is 39%, with a half-power directivity bandwidth extending from 11.6 to 12.3 GHz. Material properties of ABS-M30 plastic filament are used in this preliminary design and numerical studies, making the PRS suitable for rapid prototyping using commonplace 3D printing methods.

A multi-layer partially reflecting surface(PRS) based antenna is proposed. The PRS is designed such that it meets the considerations to increase the broadside directivity of the antenna, yet is suited for manufacturing with a common benchtop 3D printing technology. The resulting antenna is wideband in nature (40% directivity-bandwidth) predicts a best-case improvement of 15 dBi in broadside directivity. Overall, profile of the antenna is $2\lambda^{2}$ , where $\lambda=25\text{mm}$ .

This paper presents the performance of an optimized wideband beam-steering antenna system for mm-wave applications. The antenna is passive and can provide continuous two-dimensional beam scanning up to $\pm \mathbf{40}^{\mathbf{o}}$ away from broadside direction in elevation and any direction in azimuth. It uses a pair of near-field dielectric phase transformers, inspired from optical prisms, introducing a pre-determined phase gradient to the incoming wave front from a source antenna, and redirecting the radiated beam to specified direction with in a conical region with an apex angle of 80°. A prototype of the antenna system along with the mounting structure has been fabricated and tested.

© 1963-2012 IEEE. This article presents a wideband beam-steering antenna system for high-mobility millimeter-wave (mm-wave) systems. It can provide both continuous and discrete beam steering in two dimensions (elevation and azimuth) at a speed that is sufficient for various applications including some in defense. The antenna is completely passive and beam steering is achieved using near-field phase transformation by employing a pair of distinct rotatable stepped-dielectric phase transformers (SPTs) placed in the near-field region of a fixed radiating source. The antenna system has a steering and impedance-matching bandwidth of 40.6% from 26.5 to 40 GHz. A prototype of the beam-steering antenna system including a mechanical system to rotate each of the SPTs around the antenna axis has been fabricated and tested. The rotating SPT pair introduces a predetermined phase gradient to the input near-field and creates an output near-field that will radiate in an arbitrarily selected direction, which can be varied within a large conical region with a maximum apex angle of 104°. The system exhibits predicted and measured peak gains of 21.5 and 21.25 dBi, respectively, and the measured gain variation over 2-D beam steering is less than 3 dB except at 36 and 39 GHz, where it rises to 3.6 and 3.1 dB, respectively. This beam steering method obviates the need for expensive phase shifters and distribution networks, which are also lossy at mm-wave frequencies. The measured results validate the predicted wideband matching and steering performance of the system with close agreement.

This communication presents a simplified approach to design compact, wideband resonant-cavity antennas (RCAs) with partially reflecting surfaces (PRSs) made out of only a single dielectric material. Gain enhancement over a large bandwidth is obtained by using a high-permittivity dielectric PRS, which is flat at the bottom and has a stair-case profile on the top. The resulting RCA demonstrates a measured directivity-bandwidth product (DBP) of 5990 and a DBP per unit area of 1222. To the best of our knowledge, these figures are comparable to the figures for RCAs with transverse permittivity gradient PRSs, which require multiple dielectric materials. The measured radiation patterns of this RCA demonstrate low sidelobe levels (

This paper studies the cause of low-broadside directivity and high sidelobe levels (SLLs) in compact resonant-cavity antennas (RCAs) (footprint < 8 λ 0 2 ). An approach to determine an optimal near-field distribution to significantly improve the broadside directivity and SLL of RCAs is presented. A near-field to far-field transformation routine developed in MATLAB is used to study the individual effects of amplitude and phase distributions, above the partially reflecting superstrate (PRS) of RCAs. Unlike the direct use of a full-wave simulator design, this new approach allows the designers to understand the individual effects of amplitude and phase distributions in the radiating near-field region, on the broadside directivity and on the SLL in the far-field radiation pattern. A method to realise a desired complex near-field distribution is demonstrated, using a dielectric PRS. The RCA with the new PRS showed a significant improvement of 5.0 and 6.4 dB in the broadside directivity and SLL, respectively, compared with a uniform PRS without compromising the footprint and profile of the antenna. The predictions of MATLAB are validated using computer simulation technology (CST) microwave studio (MWS) and experiments

This paper presents a method to achieve high gain (>20 dBi) and wide bandwidth (>55%) from a compact antenna that is less than one wavelength tall and only $2.6\lambda _{0}$ in diameter at the lowest operating frequency. The antenna comprises of an optimized single-layer superstrate, made out of four dielectric sections, and a ground plane, which are separated by an air cavity. The permittivity and thickness of the dielectric sections decrease in the transverse direction. Two-step optimization method was implemented employing a customized full-wave optimizer to optimize the width and thickness of each dielectric section in the superstrate, while maintaining a fixed overall diameter of the antenna. This optimization results in an antenna with a high gain and a large 3-dB gain bandwidth, without compromising on antenna footprint. A prototype of the new antenna having a superstrate with stepped thickness was fabricated and tested. It exhibits a measured peak broadside directivity and a peak realized gain of 20.7 and 20.2 dBi, respectively. Its measured gain-bandwidth product of 5969 and directivity-bandwidth product (DBP) of 6580 are almost three times the best figures for resonant cavity antennas (RCAs). The total area of the new antenna prototype is $5.3\lambda _{0}^{2}$ and its overall height is $0.89\lambda _{0}$ at the lowest operating frequency. It is significantly more compact and its DBP per unit area and aperture efficiency are significantly greater than those of lens-based antennas. Its measured 3-dB gain bandwidth of 57% is unprecedented for high-gain short antennas, including RCAs. Moreover, over the entire bandwidth, sidelobe levels of the antenna are around −12 and −21 dB in the E- and H-planes, respectively.

This letter demonstrates a novel integration approach to design high gain chip-fed antennas in V -band and W -band. An on-chip spherical dielectric resonator is integrated with a resonant cavity antenna, which resulted in high radiation efficiency and increased gain. The proposed approach minimizes the use of chip area and provides several advantages, such as, low profile and ease of assembly in comparison to similar antennas, reaching 17.8 dBi and 18.4 dBi gain for V -band and W -band, respectively.

© 2019 IEEE. Near field phase transformation lattice structure is presented to correct the electric field phase variation above a source antenna. A high gain resonant cavity antenna (RCA) is used as a source, which operates at 12 GHz. The 3D printed phase transformation structure, with two different arrangements of the unit cells, is designed above the RCA at the one-eighth of wavelength. The rectangular arrangement exhibits a more uniform field distribution than that of the circular arrangement. Additionally, in the rectangular arrangement, the gain of the antenna is enhanced by 2.11dB from 21.98 to 24.09 dBi, whereas in the circular arrangement, this value increased by 2.08 dB from 21.98 to 24.06 dBi. For both the cases, the aperture efficiency and bandwidth aperture efficiency product (BAEP) increased from 34.24 to 55.78% and 55.024 to 109.33%2, respectively.

This paper demonstrates the resonant cavity antenna's (RCA) integration capability with the millimeter-wave (mm-wave) transceiver chips. A broadband RCA fed by a probe-fed microstrip patch, which is readily integrated with transceiver chips, is designed at 60 GHz. It exhibits a peak broadside gain of 19 dBi with a VSWR 2:1 bandwidth ranging from 57 GHz to beyond 70 GHz. Radiation performance of the RCA fed by a traditional waveguide aperture is also presented to demonstrate the feasibility of the proposed RCA in mm-wave practical applications.

© 1963-2012 IEEE. In this communication, a broadband low-profile partially reflecting superstrate (PRS)-based antenna is presented for 60 GHz applications. The PRS with an asymmetric pattern of circular metallic patches printed on one side of a thin dielectric slab improves the feed antenna gain from 6.5 to 18.5 dBi. A prototype antenna exhibits a peak gain of 18.8 dBi with a 3 dB gain bandwidth of 16.7%. Simulated and measured radiation patterns of the proposed antenna are highly directive toward broadside over a large operating bandwidth. The prototype antenna is well matched with a measured voltage standing wave ratio (VSWR) below 2 over a frequency range from 55.6 to 69.6 GHz, corresponding to a matching bandwidth of 22.4%. Fabrication limitations and assembly tolerances are also discussed. Overall, the prototype validates the high gain and wideband performance of the proposed antenna. The total area of the PRS is 5.2\lambda -{0}^{2} and the overall height of the antenna is only 0.66\lambda -{0} at the lowest operating frequency of 55.6 GHz.

This paper presents the performance of a pathfinder beam reconfigurable antenna system for mm-wave applications. The system is completely passive and can provide continuous three-dimensional beam scanning in a conical region of ±40° from boresight direction. It uses a pair of near-field dielectric structures, inspired from optical prisms, introducing a pre-calculated phase gradient to the incoming wave front from a source antenna, and redirecting the radiated beam to an arbitrary direction with in a conical region with an apex angle of 80°. The proposed system can provide a peak gain of 20.7 dBi and does not require expensive phase shifters and a power distribution network.

© 2019 by the authors. This paper presents a new planar feeding structure for wideband resonant-cavity antennas (RCAs). The feeding structure consists of two stacked dielectric slabs with an air-gap in between. A U-shaped slot, etched in the top metal-cladding over the upper dielectric slab, is fed by a planar stripline printed on the back side of the dielectric slab. The lower dielectric slab backed by a ground plane, is used to reduce back radiation. To validate the wideband performance of the new structure, in an RCA configuration, it was integrated with a wideband all-dielectric single-layer partially reflecting superstructure (PRS) with a transverse permittivity gradient (TPG). The single-layer RCA fed by the U-slot feeding structure demonstrated a peak directivity of 18.5 dBi with a 3 dB directivity bandwidth of 32%. An RCA prototype was fabricated and experimental results are presented.

A simple metasurface integrated with horn antenna exhibiting wide bandwidth, covering full Ku-band using 3D printing is presented. It consists of a 3D-printed horn and a 3D-printed phase transformation surface placed at the horn aperture. Considering the non-uniform wavefront of 3D printed horn, the proposed 3D-printed phase transformation surface is configured by unit cells, consisting of a cube in the centre which is supported by perpendicular cylindrical rods from its sides. Placement of proposed surface helps to improve the field over the horn aperture, resulting in lower phase variations. Both simulated and measured results show good radiation characteristics with lower side lobe levels in both E- and H-planes. Additionally, there is an overall increment in directivity with peak measured directivity up to 24.8 dBi and improvement in aperture efficiency of about 35% to 72% in the frequency range from 10&ndash, 18 GHz. The total weight of the proposed antenna is about 345.37 g, which is significantly light weight. Moreover, it is a low cost and raid manufacturing solution using 3D printing technology.

This paper presents a quantitative comparison of superstrates with transverse permittivity gradient (STPG) when used in RCAs, as compared to stand-alone lens configurations. RCAs with TPG superstrates are often compared with lens antennas, considering the apparent structural similarity between the two. However, these two classes of antennas present inherent differences in terms of characteristics as well as principle of operation. Detailed comparisons are carried out using full-wave simulations. It was found that nearly 50% reduction in 3dB bandwidth was observed when a TPG superstrate was used as a lens antenna, as opposed to in an RCA.

This paper describes an effective approach to reduce the high sidelobe levels (SLLs) in resonant cavity antennas (RCAs) with small footprints. The objective is to first understand the reason behind the high SLL in compact RCAs and than improve its radiation characteristics. For this, a near-field to far-field transformation routine is implemented in MATLAB, which allows to understand the individual effects of near-field amplitude and phase distributions on the SLL in the far-field patterns. This approach resulted in an optimal electric-field distribution, which is realized by a dielectric partially reflecting superstructure (PRS) exhibiting a broadside directivity of 19.5 dBi with significantly low sidelobe levels of -30dB in both the principle planes. It is important to note that the proposed approach can be linked easily with global optimization techniques to fit the radiation patterns within specific pattern masks.

In this paper, customized full-wave optimization of resonant cavity antennas (RCAs) is presented. The objective was to design RCAs with a high directivity-bandwidth product (DPB) for medium-to-high-gain space-limited applications. For this, a speed-constrained particle-swarm optimization (SMPSO) algorithm was implemented in MATLAB, which iteratively interacted with the 3D full-wave simulator of CST Microwave Studio during the optimization process. The optimization resulted in a stepped dielectric superstrate, which when used in an RCA demonstrated a measured broadside directivity of 20.7 dBi with an extremely large directivity bandwidth of greater than 50%.

This paper presents results of an investigation carried out on the large directivity bandwidth of a multi-layer all-dielectric resonant cavity antenna (RCA). This RCA comprises of a multi-layer all-dielectric superstructure, which exhibits a measured broadside directivity of 18.1 dBi with an extremely large 3-dB directivity bandwidth of 51%. Unit cell model of the superstructure is studied by employing superstructure reflection model (SRM) and defect cavity model (DCM). This study reveals that by optimising the frequency separation between two positive phase gradients bands generated by resonant cavities, significant improvement in the directivity bandwidth can be achieved.

In this paper, a method to combine MATLAB-based optimization with a 3D electromagnetic simulator is described. The work-flow is presented using five main files (.m, .text, .bas, .sig and .rd1), which are required to establish the connection between the two software systems. Speed constrained particle swarm optimization (SMPSO) algorithm was implemented in MATLAB, which utilized the transient 3D simulator of CST Microwave Studio to carry out iterative full-wave analyses during the optimization process. As a design example, this customized optimization method was then employed to maximize the directivity-bandwidth product (DBP) of a mono-slab resonant cavity antenna (RCA). This optimization yielded a compact RCA, with a peak directivity of 21dBi and an extremely large directivity-bandwdith of 56%. The DBP of this optimized RCA is around 6500 and its total area is only 5.6λ2 0 .

A 1 £ 3 element linear array using cylindrical dielectric resonator antennas (CDRAs) is designed and presented for 802.11a WLAN system applications. The top and bottom elements of CDRA array are excited through the rectangular coupling slots etched on the ground plane, while the slots themselves are excited through the microstrip transmission line. The third element (i.e., central CDRA) is excited through the mutual coupling of two radiating elements by its sides. This mechanism enhances the bandwidth (96.1%) and gain (14.3%) as compared to aperture coupled technique. It is also observed that the side lobe levels are reduced over the designed frequency band. Using CST microwave studio, directivity of 10.5dBi has been achieved for operating frequency of 5.6GHz. Designed antenna array is fabricated and tested. Simulated and measured results are in good agreement. The equivalent lumped element circuit is also designed and presented using Advanced design system (ADS) for this proposed array.

In this paper, we review two new classes of superstructures for single-feed wideband resonant cavity antennas (RCAs). Both the superstructures are composed of only dielectric materials and have non-uniform permittivity in either the axial direction, i.e., perpendicular to the antenna axis, or in the transverse plane. These superstructures not only make the resulting RCAs significantly wideband, along with their excellent directive characteristics, but also add compactness to the overall design. The presented RCAs have the advantages of simple configurations, low-cost manufacturing, polarization versatility, and controlled structural sensitivity for extension to millimeter wave designs.

In this paper, a simple wideband electromagnetic bandgap (EBG) resonator antenna (ERA) with an all-dielectric superstructure is presented to operate at 60 GHz. The antenna superstructure consists of two circular dielectric slabs with different relative permittivity values. A waveguide-fed slot antenna is used to excite the antenna's cavity and is placed about half a wavelength from the superstructure. The single ERA element exhibits a peak directivity of 16.6 dBi with a directivity bandwidth of 35%. In addition to this, the antenna's directivity remains greater than 14.3 dBi over the entire unlicensed 60 GHz wireless band from 59 GHz to 67 GHz. The feed antenna is well matched over the frequency band and the overall ERA has total footprint of only 1.5λ20.

In this paper, preliminary results of an array of resonant cavity antennas (RCAs) to operate at 60 GHz are presented. Each RCA in the array has a two-layers all-dielectric superstructure with permittivity variation in axial direction. The single RCA element exhibits a peak directivity of 16.6 dBi and its 3dB directivity bandwidth covers the entire unlicensed 60 GHz band from 59 GHz to 67 GHz. The RCA array has a peak directivity of 22.8 dBi with a 3dB directivity bandwidth of 33%. The inter-element spacing between the array elements is optimized to achieve the best performance in terms of peak directivity and radiation bandwidth. The total area of the RCA array is 3.8λ 0 × 3.8λ 0 .

A simple method is proposed to signifi cantly enhance the broadside directivity of a simple slot antenna over a wide bandwidth. This improvemen t is achieved by introducing a simple optimised dielectr ic superstructure with an axial variation of permittivity. In this antenna, both the superstructure and ground plane are cylind rical in shape with an area of 1.62λ02. The antenna has a measured peak directivity of 18.1 dBi and an extremely wide 3 dB directivity bandwidth of 51.1%. A WR-75 waveguide is used to feed the slot antenna. The antenna is well matched over the entire directivity bandwidth, which extends from 8.75 to 14.75 GHz. The measured average aperture effi-ciency is ∼88% over the 3 dB directivity bandwidth.

This paper presents recent advances related to electromagnetic band gap (EBG) resonator antennas (ERAs). In particular, we briefly review three new classes of ERAs (a) ERAs having extremely small footprints and superstructures with axial permittivity variation (APV), (b) ERAs with dielectric superstructures having transverse permittivity gradients (STPG), and (c) ERAs with phase-correcting structures (PCS). These classes present significant performance improvements compared to classical designs. State-of-the-art performance figures for each of these classes are presented after summarizing the key developments in this area.

In this paper, electrical models of single element cylindrical dielectric resonator antenna (CDRA) and two element CDRA array made of Calcium Copper Titanium Oxide (CCTO) material are presented. The 50 Δ microstrip transmission line is used to excite the CDRAs through coupling slots etched on the ground plane. The electric models of single element CDRA and two element CDRA array are designed by using Advanced Design System (ADS). The electrical circuits are used to validate the CST design feasibility. The validity of RLC model is verified by comparing the return loss of the ADS model against those obtained through computer simulation technology (CST) and fabricated prototype. The results obtained through simulated (CST and ADS) designs and fabricated prototype of single element CDRA (0.20 GHz and 0.23 GHz) and two elements CDRA array (0.375 GHz and 0.510 GHz) are in good agreement.

In this paper, theoretical and experimental study on cylindrical dielectric resonator antenna (CDRA) made of CCTO material is reported. The CDRA with high dielectric constant (eΓ = 55) is fed with aperture coupled 50 ς microstrip transmission line. The TE011+S mode of CDRA is excited to operate at 5.15-5.35 GHz for wireless local area network (WLAN) application. The electrical model of the aperture coupled CDRA is built to verify the antenna feasibility. The validity of the electrical model is confirmed by comparing the values of the return losses obtained through an electrical model using Agilent Advanced Design System (ADS) against those obtained through antenna geometry using computer simulation technology (CST) and fabricated prototype.

A single element circular slot aperture coupled Cylindrical Dielectric Resonator Antenna (CDRA) with a box shaped reflector is designed and presented. The simulated bandwidth achieved for the designed antenna is about 1.11% (5.32 GHz-5.44 GHz) while the measured bandwidth is about 1.8% (5.32 GHz-5.52 GHz). This method enhances the directivity of the CDRA upto 53% i.e from 5 dBi to 7.5 dBi. The analysis of the effects of changing the slot size, slot position and different parameters of the reflector to increase the directivity and to reduce the backlobe level has been carried out. The experimental results illustrate that the designed antenna works over 5 GHz band, therefore it can be used in WLAN application IEEE 802.11a.

A 1 × 3 element linear array of cylindrical dielectric resonator antenna (CDRA) is designed and presented for 802.11a WLAN system applications. The two elements of CDRA array are excited by rectangular shaped aperture slots placed on the ground plane, while the slots themselves are excited through the microstrip line. The third element (i.e., central CDRA) is excited through the mutual coupling of two radiating elements by its sides; this mechanism enhances the bandwidth of the array by 10%. Designed antenna array is fabricated and tested. Using the CST microwave studio and fabricated prototype, directivity of 10.5 and 10.8 dBi respectively has been achieved for operating frequency of 5.6 GHz. Good agreement is achieved between the simulated and measured results. The comparison between the proposed and previous work is also reported in this article.

In this paper, the experimental study on cylindrical dielectric resonator antenna (CDRA) with an aperture coupled dielectric image line (DIL) is presented using a CCTO material. The CDRA is fed by a 50Ω dielectric image line at a frequency around 2.45 GHz. High permittivity (er = 55) DIL samples with different heights are employed. The CST microwave studio is used to analyze the different results in term of return loss, bandwidth and radiation pattern. The DIL feeding technique has shown a better directivity for CDRA as compared to microstrip line coupling.

A single element circular slot aperture coupled Cylindrical Dielectric Resonator Antenna (CDRA) with a flat reflector is designed and presented. The measured bandwidth of the antenna is about 1.8 % (5.32 - 5.52) while the simulated bandwidth is 1.11% (5.32 - 5.44 GHz). A comprehensive parametric study has been conducted to realize the effects of slot size, slot position and reflector parameters to increase the directivity of the designed antenna. The experimental results show that the antenna covers 5 GHz band, which satisfies the basic requirement of the WLAN application IEEE 802.11a.

In this paper, the tuning technique of 3-elements cylindrical dielectric resonator antenna (CDRA) array for wireless LAN 802.11 a/b/g standard applications is studied experimentally. The rectangular shaped aperture slots are used to excite the first and last radiating element. The aperture slots etched on the ground plane are excited by using the 50Ω microstrip transmission line. The electromagnetic coupling technique is used to excite the middle radiating element to enhance the antenna bandwidth as well as gain. The effects of changing the dimensions of slot width on the resonance frequency are also analyzed using a CST microwave studio. The simulated and measured results have successfully given the resonance at 2.45 and 5.0 GHz. The 2-D and 3-D radiation patterns of the proposed dual band antenna are addressed in this paper.

Wideband and high gain linear 3-element cylindrical dielectric resonator (CDR) array antenna is designed and proposed for 802.11a wireless local area network (WLAN) system applications. The mutual coupling mechanism is used to excite the middle element of the CDRA array which enhances the 10% bandwidth and reduces the back lobe level of the proposed antenna without using reflector. The other two neighboring elements are excited by rectangular shaped aperture slots placed on the ground plane, while the slots themselves are excited through the microstrip line. The designed array antenna performance is analyzed using a CST microwave studio. The maximum directivity of 9.6 dBi has been achieved at operating frequency of 5.5 GHz. 2-D and 3-D radiation pattern results are also reported in this paper. Designed antenna array is fabricated and tested. The comparison between the proposed and previous work is also tabulated in this paper.

This paper presents some recent developments in microwave reflector antenna technology. The main focus of this research is on novel reflector antenna designs to overcome the challenges caused by the rising communication systems. Prototype implementation will be described in this paper; published microwave reflector antenna frequency range, low profile and compact designs, wideband reflector antennas, low sidelobe level, low cross polarization and enhanced gain microwave reflector antenna's review is brought up.