Quad‐ridged conical horn antenna for wideband applications

This article presents a quad‐ridged conical horn antenna with high gain and low side lobe level for broadband applications. To the best of authors' knowledge, the proposed structure presented in this article is completely new. The designed antenna introduces a low VSWR, which is lower than 2.2 for the frequency range of 8–18 GHz, and simultaneously achieves high gain as well as dual‐polarizations with high isolation between the corresponding excitations. The common impedance exponential tapering is used at the flare section of the horn, and a coax to waveguide transition, namely quadruple‐ridged circular waveguide, with a conical cavity is used to improve the VSWR. The proposed antenna structure is designed and simulated by two well established packages, namely the CST microwave studio and the Ansoft HFSS, showing there is a close agreement between the results obtained by the aforementioned softwares. © 2009 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2009.     

Double‐ridged conical horn antenna for wideband applications

In this article, the design and analysis of a double‐ridged conical horn antenna with high gain and low cross polarization for wideband applications is presented. Double‐ridged pyramidal horn antennas have been investigated in many references. There are no papers in the literature which are devoted to design and analysis of double‐ridged conical horn antenna. The designed antenna has a voltage standing wave ratio (VSWR) less than 2.1 for the frequency range of 8–18 GHz. Moreover, the proposed antenna exhibits extremely low cross polarization, low side lobe level, high gain, and stable far‐field radiation characteristics in the entire operating bandwidth. A new technique for synthesizing of the horn flare section is introduced. A coaxial line to circular double‐ridged waveguide transition is introduced for coaxial feeding of the designed antenna. The proposed antenna is simulated with commercially available packages such as CST microwave studio and Ansoft HFSS in the operating frequency range. Simulation results for the VSWR, radiation patterns, and gain of the designed antenna over the frequency band 8–18 GHz are presented and discussed. © 2008 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2009.     

Design and experiment of a conical double‐ridged horn antenna for 6–18 GHz

A broadband conical double‐ridged horn (DRH) antenna with symmetrical radiation patterns, low side lobe level, and low cross polarization is presented. Experimental investigations and detailed simulations are conducted to understand its behavior and to optimize for broadband operation. Good agreement between the measurement and simulation has been achieved. The designed conical DRH antenna introduces a low voltage standing wave ratio (VSWR), which is lower than 2.3 for the frequency range of 6–18 GHz and simultaneously achieves slant polarization as well as stable far‐field radiation characteristics in the entire operating bandwidth. The common impedance exponential tapering is used at the flare section of the horn. Moreover, a new cavity back with a conical structure is used to improve the VSWR. The simulated and measured results for VSWR, far field E‐plane and H‐plane radiation patterns, and gain of the designed antenna are presented and discussed. © 2011 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2011.     

Design and analysis of a quad‐band substrate‐integrated‐waveguide cavity backed slot antenna for 5G applications

A planar and compact substrate integrated waveguide (SIW) cavity backed antenna and a 2 × 2 multi‐input multi‐output (MIMO) antenna are presented in this study. The proposed antenna is fed by a grounded coplanar waveguide (GCPW) to SIW type transition and planned to be used for millimeter‐wave (mm‐wave) fifth generation (5G) wireless communications that operates at 28, 38, 45, and 60 GHz frequency bands. Moreover, the measured impedance bandwidth (|S₁₁| ≤ ? 10 dB ) of the antenna covers 27.55 to 29.36, 37.41 to 38.5, 44.14 to 46.19, and 57.57 to 62.32 GHz bands and confirms the quad‐band characteristic. Omni‐directional radiation characteristics are observed in the far‐field radiation pattern measurements of the antenna over the entire operating frequency. The reported antenna is compact in size (9.7 × 13.3 × 0.6 mm³) and the gain values at each resonance frequency are measured as 3.26, 3.28, 3.34, and 4.51 dBi, respectively. Furthermore, the MIMO antenna performance is evaluated in terms of isolation, envelope correlation coefficient and diversity gain.     

Design of conical DRH antennas for K and Ka frequency bands

Two conical double‐ridged horn (DRH) antennas for K and Ka frequency bands are presented. Detailed simulation and experimental investigations are conducted to understand their behaviors and optimize for broadband operation. The designed antennas were fabricated with 0.01 mm accuracy and satisfactory agreement of computer simulations and experimental results was obtained. The designed conical DRH antennas have voltage standing wave ratio (VSWR) less than 2.1 and 2.2 for the frequency ranges of 18–26.5 GHz (K band) and 26.5–40 GHz (Ka band), respectively. Meanwhile, the proposed antennas exhibit low cross‐polarization, low sidelobe level, and simultaneously achieve slant polarization as well as symmetrical radiation patterns in the entire operating bandwidth. An exponential impedance tapering is used at the flare section of the horns. Moreover, a new cavity back with a conical structure is used to improve the VSWR. Numerous simulations via Ansoft HFSS and CST Microwave Studio CAD tools have been made to optimize the VSWR performance of the designed antennas. Simulation results show that the VSWR of the proposed antennas is sensitive to the probe spacing from the ridge edge and the cavity back structure. The designed conical DRH antennas are most suitable as a feed for the reflectors of radar systems and satellite applications. Results for VSWR, far‐field E‐plane and H‐plane radiation patterns, and gain of the designed antennas are presented and discussed. © 2011 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2011.     

Design of optimum gain pyramidal horn using self‐adaptive differential evolution algorithms

In this work, we apply classical and new self‐adaptive differential evolution (DE) algorithms to the design of optimum gain pyramidal horns. The application of DE algorithms to pyramidal horn design allows the accurate calculation of their physical dimensions in a short amount of time. Moreover, self‐adaptive DE does not require the prespecified choice of control parameters reducing significantly the users' effort. Representative examples demonstrate the applicability of our proposal. Our study shows that self‐adaptive DE algorithms outperform or produce similar results with other methods in the literature in terms of solution accuracy and convergence speed. © 2010 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2011.     

Quasi‐corrugated substrate integrated waveguide H‐plane horn antenna with wideband and low‐profile characteristics

A wideband H‐plane horn antenna based on quasi‐corrugated substrate integrated waveguide (SIW) technology with a very low profile is presented in this article. Open‐circuited microstrip stubs are applied to create electric sidewalls of the quasi‐corrugated SIW structure. The quasi‐corrugated SIW H‐plane horn antenna shows high performance and simple structure. A specify‐shaped horn aperture is utilized, so that the poor impedance matching owing to the structure restriction can be smoothened. The structure is simulated by ANSYS HFSS and a prototype is fabricated. The measured results match well with the simulated ones. An enhanced impedance bandwidth ranging from 5.3 GHz to 19 GHz (VSWR < 2.5) is achieved. The presented antenna also brings out stable radiation beam over the same frequency band.     

Radiation pattern and properties of double‐flared diagonal horn antenna

This article is concerned with analytical model for radiation pattern of a new double‐flared diagonal horn antenna using “plane wave spectra technique for 3D fields”. The double‐flared diagonal horn antenna is accomplished by adding one more set of flares in E‐ and H‐planes with equal flare angles into conventional diagonal horn. The copolarized and cross‐polarized radiation patterns in E‐, H‐, and D‐planes have been computed utilizing the analytical model and reported in the article. The parametric studies on peak cross‐polarization level have carried out. The radiation performance of double‐flared and conventional diagonal horns for same length and aperture size are also compared. It is investigated that double‐flared diagonal horn antenna posses better peak cross‐polarization level (≈?16.5 dB) in D‐plane (±45° plane) in comparison of conventional diagonal horn (≈?15.5 dB) at design frequency and retains almost circularly symmetric radiating beam at lower values of elevation angles. Also, double‐flared diagonal horn has better matches with free‐space and has slightly lower gain (≤0.5 dB) in comparison of conventional diagonal horn. The work presented here can provide useful design guidelines for development of prototypes of double‐flared diagonal horn, which may find potential application in satellite communication and imaging applications etc. © 2008 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2009.     

Compact wideband circularly polarized horn antenna with tapered slot‐coupled feeding for Ku‐band applications

A compact wideband circularly polarized (CP) horn antenna with slot‐coupled feeding structure at Ku band for satellite communication is devised. The proposed design is based on a square aperture horn antenna with two orthogonal ridges, which is fed by nonuniform curved slot along the diagonal of the horn on the bottom cavity. And in order to improve the impedance matching, a staircase typed ridge is connected the feeding probe as a matching network. Moreover, two orthogonal ridges are excited with a tapered slot coupled by the staircase ridges via feeding probe. Wideband CP performance is achieved with an overall physical dimension of 9 mm × 9 mm × 14 mm (0.045λ₀ × 0.045λ₀ × 0.07λ₀ at frequency of 15 GHz). It is experimentally demonstrated that the proposed antenna achieves: a wide 10‐dB return loss bandwidth of about 2.4 GHz, a 3‐dB axial ratio bandwidth of 1 GHz, and a peak gain of 6.5 dBi.     

A Ka band microstrip to waveguide transition using a quasi‐triangle probe

In this article, a new Ka band microstrip to waveguide transition with combination of electric and magnetic coupling is introduced by using a quasi‐triangle structure. Consequently, the length of the proposed transition has been significantly diminished. A back‐to‐back prototype was fabricated based on the optimized dimensions to validate the design concept. The measured and simulated results are in a good alignment. The experimental results show that the return loss is better than 14.8 dB across the frequency range of 32‐40 GHz with an insertion loss of lower than 0.9 dB. The conversion efficiency for the single transition, therefore, is larger than 90.5%. Because of its broad operation bandwidth, low insertion loss, and compact size, the proposed embedded transition could find wide applications in most modern miniaturized MMIC devices and systems.     

A cavity‐backed quad‐slot antenna with novel aperture‐coupled feed for circular polarization

This article describes a novel aperture‐coupled feed, for the excitation of a cavity‐backed quad‐slot antenna with circular polarization. Firstly, a quad‐slot cavity‐backed antenna with linear polarization (LP) is proposed. Then, a novel aperture‐coupled feed, which is composed of a cross‐shaped coupling aperture and a T‐shaped feeding microstrip line, will be applied to this LP antenna. By differing the lengths of the four radiation slots together with the novel aperture‐coupled feed, 90° phase difference and equal magnitude between the radiations from the two pairs of slots can be generated. As a result, a good performance of axial ratio will be achieved for the proposed antenna. A prototype is fabricated at Ka band for a demonstration. Investigations show that the antenna can present a minimum axial ratio (AR) of only about 0.37 dB, as well as a fractional AR bandwidth of about 0.94%. A relative high gain of 6.9 dBic at 32.1 GHz is also achieved for the prototype. The proposed substrate integrated cavity backed antenna with circularly polarization has great potential to be integrated into millimeter‐wave transceiver modules. © 2016 Wiley Periodicals, Inc. Int J RF and Microwave CAE 26:588–594, 2016.     

A compact substrate integrated waveguide H‐plane horn antenna with dielectric arc lens

An H‐plane horn antenna constructed into SIW (substrate integrated waveguide) is proposed. It has a dielectric arc lens for better directivity and a simple microstrip transition as feed. The horn, the lens and the transition share the same substrate. The resulting formula from optical principles shows that the suitable dielectric lens can improve the directivity of the antenna significantly. A prototype was fabricated; the antenna size is 39.175 × 14 × 2 mm³. The frequency band is from 25.5 to 28.5 GHz. The measured gain of this antenna is about 9 dB; the bandwidth, at 10 dB return loss, is over 12%. © 2007 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2007.     

Modeling and optimization of cylindrical antennas using the mode‐expansion method and genetic algorithms

For monopole antennas with cylindrically symmetric structures, a mode‐expansion method is highly time efficient, which is a realistic approach for integrating function‐optimization tools, such as genetic algorithms (GAs), in order to extract the best bandwidth property. In this article, a mode‐expansion method is used to simulate the impedance characteristics of the cylindrical antennas. As examples, two new types of monopole antennas are presented, one of which possesses a two‐step top‐hat structure while the other has an annulus around the stem. After the modeling scheme is examined for convergence and data validity, the associated optimization problem, with dimensions as decision variables, structural limitations as linear constraints, and desired bandwidth performance as an objective function, is solved using GAs. The effects of the geometric parameters on the impedance characteristics are investigated in order to demonstrate the optimality of the calculated solutions. Two optimized practical antennas are designed based on our numerical studies. One has a broad bandwidth of 3 GHz while the other shows a dual‐band property, which can satisfy the bandwidth requirements for both Bluetooth (2.45‐GHz band) and WLAN (5‐GHz band) systems. © 2005 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2005.     

A novel dual‐mode patch antenna with pattern diversity and beam‐tilting for aircraft applications

A dual‐mode patch antenna with pattern diversity that is beam‐tilted in a specific direction is presented. By placing a rectangular metal cavity below the circular patch and simultaneously shorting one end of the patch, the antenna produces tilted beams for dual‐mode radiation patterns. One pattern is excited using a proximity‐fed L‐shaped probe that generates a beam with a tilt angle of 25° from the broadside direction. The second pattern is excited using a coplanar waveguide (CPW)‐based feeding network that generates two beams with a tilt angle of θ_max = ±45° in the directions of ?_max = 70° and ? 70°. The tilt angle can be varied by adjusting the metal cavity's length. A prototype antenna for operation at 2.38 GHz was fabricated and measured. The results indicate that the overlapped bandwidth (|S₁₁| < ?10 dB) for the two patterns is 330 MHz (2.22‐2.55 GHz). The measured peak gains for the two patterns are 6.74‐6.94 dBi and 5.82‐6.74 dBi, respectively. The isolation between the two ports is 18 dB.     

Reduced‐cost surrogate modeling of input characteristics and design optimization of dual‐band antennas using response features

In this article, a procedure for low‐cost surrogate modeling of input characteristics of dual‐band antennas has been discussed. The number of training data required for construction of an accurate model has been reduced by representing the antenna reflection response to the level of suitably defined feature points. The points are allocated to capture the critical features of the reflection characteristic, such as the frequencies and the levels of the resonances, and supplemented by the additions (infill) points, which is necessary to provide sufficient data that allows restoring the entire response through interpolation. Because the coordinates of the feature points exhibit less nonlinear behavior (as a function of antenna geometry parameters) compared to S‐parameters as a function of frequency, surrogate model construction can be realized with a smaller number of data points. The presented modeling approach is demonstrated using an example of a planar dipole antenna. Also, the feature‐based method is favorably compared to direct modeling of reflection characteristics using kriging. The relevance of the technique is further verified by its application for design optimization.     

Coplanar waveguide‐fed electrically small dual‐polarized short‐ended zeroth‐order resonating antenna using Ω‐shaped capacitor and single‐split ring resonator for GPS/WiMAX/WLAN/C‐band applications

This work explains the design and analysis of a triple‐band electrically small (ka = 0.56 < 1) zeroth‐order resonating (ZOR) antenna with wideband circular polarization (CP) characteristics. The antenna compactness is obtained due to ZOR frequency of composite right/left‐handed (CRLH) transmission line (TL) and wideband CP radiation are achieved due to the introduction of single‐split ring resonator and asymmetric coplanar waveguide fed ground plane. The proposed antenna obtains an overall electrical size including the ground plane of 0.124 λ₀ × 0.131 λ₀ × 0.005 λ₀ at 1.58 GHz and physical dimension of 23.7 × 25 × 1 mm³ are achieved. The antenna provides a size reduction of 44.95% compared to a conventional monopole antenna. The novelty behind the ohm‐shaped capacitor is the generation of extra miniaturization with better antenna compactness. The antenna provides dual‐polarized radiation pattern with linear polarization radiation at 1.58 and 3.54 GHz, wideband CP radiation at 5.8 GHz. The antenna measured results shows good impedance bandwidth of 5%, 6.21%, and 57.5% for the three bands centered at 1.58, 3.54, and 5.8 GHz with a wider axial ratio bandwidth (ARBW) of 25.47% is obtained in the third band. The antenna provides a higher level of compactness, wider ARBW, good radiation efficiency, and wider S₁₁ bandwidth. Hence, the proposed antenna is suitable for use in GPS L1 band (1.565‐1.585 GHz), WiMAX 3.5 GHz (3.4‐3.8 GHz) GHz, WLAN 5.2/5.8 GHz (5.15‐5.825 GHz), and C‐band (4‐8 GHz) wireless application systems.     

Gain enhancement and mutual coupling reduction of multiple‐intput multiple‐output antenna for millimeter‐wave applications using two types of novel metamaterial structures

A method to significantly increase the gain and reduce the mutual coupling of microstrip multiple‐intput multiple‐output (MIMO) antenna based on metamaterial concept is presented. The μ‐negative and ε‐negative features of the proposed modified peace‐logo planar metamaterial (MPLPM) and two‐sided MPLPM (TSMPLPM) structures are calculated. The antenna structure consists of eight MPLPM slabs and two TSMPLPM, which are embedded in azimuth plane of a MIMO antenna vertically. The dimensions of MIMO antenna are 28 × 16 × 6.3 mm³ at 40 GHz. As a result, a compact MIMO antenna is simulated in comparison with primary microstrip structures. The corresponding return‐loss of the antenna is better than 10 dB over 34.5 to 45.5 GHz for Ka‐band applications. Good consent between the measured and simulated result is tacked. The maximum simulated gain of the structure is 15.5 dB at 40 GHz, creating a maximum gain improvement of 11.5 dB in comparison with a MIMO antenna without any metamaterial combinations. The value of the insertion‐loss (isolation) is 33 dB, which has improved by more than 25 dB compared to the conventional sample.     

Dual open‐slot antennas integrated in metal frame and metal case of tablet computer for long‐term evolution applications

Dual open‐slot antennas were integrated in the metal back case and metal frame of a tablet computer for long‐term evolution applications. The single feed dual excitation source antennas were sufficiently narrow (2 mm) for installation between the metal frame and metal back case of the tablet computer. Each antenna had two open‐slot radiators (slot 1 and slot 2) with embedded filter circuits to enable wideband (699‐906 and 1710‐2690 MHz) operation required for LTE applications. The filter circuit values were adjusted to make the impedance more smooth and excite the desired modes. The proposed multiple‐input‐multiple‐output antennas were installed lengthwise on the long sides of the tablet and facing in operate directions. In this configuration, the user hand grip did not interfere with antenna performance, and isolation was improved (> 20 dB). The operating mechanism of the proposed antenna with matching circuits is described in detail. The effects of the user hand grip and the embedded display panel are also discussed.     

Pattern synthesis for opportunistic array radar using least square fitness estimation‐genetic algorithm method

Pattern synthesis in three‐dimensional (3D) opportunistic array radar becomes complex when a multitude of antennas are considered to be randomly distributed in a 3D space. To obtain an optimal pattern, several freedoms must be constrained. A new pattern synthesis approach based on the improved genetic algorithm (GA) using the least square fitness estimation (LSFE) method is proposed. Parameters optimized by this method include antenna locations, stimulus states, and phase weights. The new algorithm demonstrates that the fitness variation tendency of GA can be effectively predicted after several “eras” by the LSFE method. It is shown that by comparing the variation of LSFE curve slope, the GA operator can be adaptively modified to avoid premature convergence of the algorithm. The validity of the algorithm is verified using computer implementation. © 2011 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2011.     

Wideband constant beamwidth coplanar waveguide‐fed slot antennas using metallic strip loadings and a widened tuning stub with shaped reflectors

Sectored antennas with wideband operation for wireless communication systems are presented. The proposed configurations are based on a coplanar waveguide fed slot antenna using metallic strip loadings and a widened tuning stub above various reflector shapes. By shaping the reflector, noticeable enhancements in both unidirectional radiation pattern and beamwidth can be achieved while maintaining the simple fabrication and installation. Based on the results obtained, three sector antennas covering 72°, 90°, and 120° beamwidths suitable for five, four, and three sectors, respectively, have been proposed and designed. The simple structural configurations, low cost, and ease of half power beamwidth control of the proposed antennas make the design very attractive for practical implementation. © 2011 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2011.