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Affan A. Baba

Bio: Affan A. Baba is an academic researcher from Macquarie University. The author has contributed to research in topics: Directivity & Wideband. The author has an hindex of 7, co-authored 39 publications receiving 194 citations. Previous affiliations of Affan A. Baba include Petronas & University of Technology, Sydney.

Papers
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Journal ArticleDOI
TL;DR: In this paper, a simplified approach to design compact, wideband resonant-cavity antennas (RCAs) with partially reflecting surfaces (PRSs) made out of only a single dielectric material is presented.
Abstract: 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 (<−15 dB in the E-plane and −20 dB in the H-plane, with a peak directivity of 20.3 dBi), which are consistent across the half-power directivity bandwidth.

57 citations

Journal ArticleDOI
TL;DR: In this article, a rotatable stepped-dielectric phase transformers (SPTs) are placed in the near-field region of a fixed radiating source to provide both continuous and discrete beam steering.
Abstract: 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.

45 citations

Journal ArticleDOI
TL;DR: In this paper, the authors presented 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 ε in diameter at the lowest operating frequency.
Abstract: 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.

41 citations

Journal ArticleDOI
TL;DR: In this article, a broadband low-profile partially reflecting superstrate (PRS)-based antenna is presented for 60 GHz applications, which exhibits a peak gain of 18.8 dBi with a 3 dB gain bandwidth of 16.7%.
Abstract: 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.

26 citations

Journal ArticleDOI
TL;DR: In this article, a simple method is proposed to significantly enhance the broadside directivity of a simple slot antenna over a wide bandwidth, which is achieved by introducing a simple optimised dielectric superstructure with an axial variation of permittivity.
Abstract: A simple method is proposed to significantly enhance the broadside directivity of a simple slot antenna over a wide bandwidth. This improvement is achieved by introducing a simple optimised dielectric superstructure with an axial variation of permittivity. In this antenna, both the superstructure and ground plane are cylindrical in shape with an area of 1.62λ0 2. 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 efficiency is ∼88% over the 3 dB directivity bandwidth.

26 citations


Cited by
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01 Jul 1981
TL;DR: The paper presents a tutorial review of theoretical developments emphasizing techniques appropriate to finite arrays, but indicating parallel developments in infinite array theory, which has become the useful tool for analysis of large arrays.
Abstract: This review of array antennas highlights those elements of theory and hardware that are a part of the present rapid technological growth. The growth and change in array antennas include increased emphasis on "special-purpose" array techniques such as conformal and printed circuit arrays, wide angle scanning arrays, techniques for limited sector coverage, and antennas with dramatically increased pattern control features such as low sidelobe, adaptively controlled patterns. These new topics have substantially replaced large radar arrays in the literature and constitute a major change in the technology. The paper presents a tutorial review of theoretical developments emphasizing techniques appropriate to finite arrays, but indicating parallel developments in infinite array theory, which has become the useful tool for analysis of large arrays. A brief review of the theory of ideal arrays is followed by a generalized formulation of array theory including mutual coupling effects, and is appropriate to finite or infinite arrays of arbitrary wire elements or apertures in the presence of a conducting ground screen. Some results of array tolerance theory are summarized from the literature and retained as reference throughout discussions of array component requirements and device tolerance for low sidelobe arrays. Examples from present technology include conformal and hemispherical coverage arrays, lightweight printed circuit arrays, systems for use with reflectors and lenses in limited sector coverage applications, and wide-band array techniques.

181 citations

Journal ArticleDOI
TL;DR: In this paper, the authors presented a design methodology for a compact low-cost partially reflecting surface (PRS) for a wideband high-gain resonant cavity antenna (RCA) which requires only a single commercial dielectric slab.
Abstract: This communication presents a design methodology for a compact low-cost partially reflecting surface (PRS) for a wideband high-gain resonant cavity antenna (RCA) which requires only a single commercial dielectric slab. The PRS has one nonuniform double-sided printed dielectric, which exhibits a negative transverse-reflection magnitude gradient and, at the same time, a progressive reflection phase gradient over frequency. In addition, a partially shielded cavity is proposed as a method to optimize the directivity bandwidth and the peak directivity of RCAs. A prototype of the PRS was fabricated and tested with a partially shielded cavity, showing good agreement between the predicted and measured results. The measured peak directivity of the antenna is 16.2 dBi at 11.4 GHz with a 3 dB bandwidth of 22%. The measured peak gain and 3 dB gain bandwidth are 15.75 dBi and 21.5%, respectively. The PRS has a radius of 29.25 mm ( $1.1\lambda _{0}$ ) with a thickness of 1.52 mm ( $0.12\lambda _{g}$ ), and the overall height of the antenna is $0.6\lambda _{0} $ , where $\lambda _{0}$ and $\lambda _{g}$ are the free-space and guided wavelengths at the center frequency of 11.4 GHz.

89 citations

Journal ArticleDOI
TL;DR: In this article, a compact, high gain, directive, and superstrate configuration-based metasurface (MS) antenna has been designed, which incorporates a fractal-shaped slotted patch having a periodic arrangement of square patches along with a shorting via at its center and a couple of rectangular slots in the ground plane.
Abstract: In this paper, a novel, compact, high-gain, directive, and superstrate configuration-based metasurface (MS) antenna has been designed, which incorporates a fractal-shaped slotted patch having a periodic arrangement of square patches along with a shorting via at its center and a couple of rectangular slots in the ground plane. The MS is designed over the FR4 dielectric by introducing a periodic arrangement of unit cells in which the unit cell is structured by a C-type patterned patch in the center surrounded by a couple of L-type-shaped patches. The MS is separated by a layer of Teflon from the conventional patch antenna designed over the FR4 dielectric, thereby acting as a superstrate. The proposed antenna provides good impedance matching across the frequency region of 10.14–10.94 GHz with a unidirectional radiation pattern. A fractional bandwidth of 7.6% and a maximum return loss of 24 dB have been realized at 10.44 GHz. The measured realized gain of 7.57 dBi was obtained at the same operating frequency. As the proposed antenna is more efficient, it can be promoted for $X$ -band operations, such as satellite communication, defense purpose, and medical supervision.

64 citations

Journal ArticleDOI
Hao Li1, Yue Li1, Le Chang2, Wangyu Sun1, Xu Qin1, Hanyang Wang2 
TL;DR: In this paper, an end-fire dual-polarized phased antenna array with small ground clearance is proposed for the 5G millimeter-wave (mmW) applications with a wide bandwidth in which each antenna element consists of a dipole fed by a microstrip line for horizontal polarization and an H-plane horn using substrate-integrated waveguide (SIW) for vertical polarization.
Abstract: In this article, an endfire dual-polarized phased antenna array with small ground clearance is proposed for the fifth-generation (5G) millimeter-wave (mmW) applications with a wide bandwidth In this array, each antenna element consists of a dipole fed by a microstrip line for horizontal polarization and an H-plane horn using substrate-integrated waveguide (SIW) for vertical polarization To achieve a wide bandwidth for vertical polarization, two metal vias are added at the aperture of the horn antenna Then, a four-element antenna array is designed by partially overlapping the aperture of each horn element A prototype has been fabricated using multilayer printed circuit board (PCB) process The measured results agree well with the simulated ones The antenna is with an impedance bandwidth of $\vert \text{S}_{11}\vert dB from 244 to 295 GHz for both polarizations The maximum gains of vertical and horizontal polarizations are 916 and 927 dBi, with the scanning angle from −34° to 33° for both polarizations with gain deterioration less than 3 dB The proposed antenna is a promising solution for 5G mmW cellphones or antenna-in-package applications

63 citations

Journal ArticleDOI
TL;DR: In this paper, a simplified approach to design compact, wideband resonant-cavity antennas (RCAs) with partially reflecting surfaces (PRSs) made out of only a single dielectric material is presented.
Abstract: 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 (<−15 dB in the E-plane and −20 dB in the H-plane, with a peak directivity of 20.3 dBi), which are consistent across the half-power directivity bandwidth.

57 citations