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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.

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.

© 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 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.

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.

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.