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.     

Pattern squint elimination for quad‐ridged conical and pyramidal horn antennas using bended probes

This article describes a new technique for pattern squint elimination of quad‐ridged conical and pyramidal horn antennas by introducing bended coaxial probes. Because of the phase difference and mutual coupling between vertical and horizontal polarizations, the radiation patterns of the conventional quad‐ridged conical and pyramidal horn antennas squint over a wide bandwidth. The proposed technique substantially reduces the phase difference and coupling between the two probes, so a significant improvement in the radiation patterns over the frequency band of 8–18 GHz can be achieved. The designed modified horn antennas are most suitable as a feed element in reflectors of radar systems and EMC applications. The proposed modified antennas have a voltage standing wave ratio (VSWR) less than 2.2 for the frequency range of 8–18 GHz. Moreover, the proposed antennas exhibit high gain, dual‐polarization performance, good isolation, low SLL, low back lobe, low cross polarization, and satisfactory far‐field radiation characteristics for the entire frequency band. © 2009 Wiley Periodicals, Inc. Int J RF and Microwave CAE 2010.     

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.     

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.     

Microwave conical horn antenna with dual circular polarization—Close‐form design equations

In this article, we have proposed the closed form expressions for the optimized dimensions of different parts of the metallic stepped septum in a circular waveguide. Using these relations, a dual circularly polarized (CP) horn can be realized with good AR bandwidth, impedance bandwidth, and interport isolation. The relations are generalized for application at all frequency bands. Using these relations, horns have been designed and simulated at different frequency bands. Prototypes have been fabricated at some frequency bands and are experimentally validated. This design yields impedance bandwidth (S₁₁ ≤ ?10 dB) of about 18%, AR bandwidth more than 15%, and interport isolation about 24 dB at the band center. Experimental data for the Ka‐band prototype are provided in detail. At the design frequency, the measured axial rations are <1 dB revealing cross‐polar discrimination over 25 dB.     

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.     

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.     

A coplanar waveguide‐fed flexible antenna for ultra‐wideband applications

This paper presents a novel ultra‐wideband (UWB) antenna printed on a 70 μm thick flexible substrate. The proposed antenna consists of a hybrid‐shaped patch fed by coplanar waveguide (CPW). The ground planes on opposite sides of the feeding line have different height to improve antenna bandwidth. Simulation shows that the proposed antenna maintain wide bandwidth when changing its substrate's thickness and dielectric constant, as well as bending the antenna on a cylindrical foam. The proposed antenna is fabricated in laboratory with a simple and low‐cost wet printed circuit board (PCB) etching technique. Measured bandwidths cover 3.06 to 13.58, 2.8 to 13.55, and 3.1 to 12.8 GHz in cases of flat state and bent with radii of 20 and 10 mm, respectively. Measured radiation patterns show the antenna is omnidirectional in flat and bent cases.     

A low‐profile,dual‐polarized,and wideband square cavity‐backed antenna

A cavity‐backed antenna with low‐profile, dual‐polarization, and wide operating bandwidth characteristics is proposed. In this design, two orthogonally positioned triangular bowtie antennas printed on a low‐cost substrate are loaded onto a square cavity, so that two orthogonal linear polarizations can be excited. By further introducing four extended ground stubs from each side of the square cavity, the proposed antenna can also acquire low‐profile characteristic of approximately 0.1λ (15 mm). To achieve good impedance matching, additional circular slots are introduced into each bowtie design. The measured results show that the proposed antenna can cover a wide operating bandwidth of 62% (2.0–3.8 GHz) with a VSWR of 2:1. Besides exhibiting good isolation (>20 dB) between the two feeding ports, desirable realized gains (6.0–10.5 dBi) over the wide operation band are also demonstrated. © 2016 Wiley Periodicals, Inc. Int J RF and Microwave CAE 26:724–730, 2016.     

Propagation characteristic analysis of ridged circular waveguide using 2D finite‐difference frequency‐domain method

The propagation characteristics of ridged circular waveguides are analyzed by using 2D finite‐difference frequency‐domain (2D FDFD). Based on the 2D FDFD method in a cylindrical coordinate system, general difference formulas for the ridged circular waveguide are deduced, and modified difference formulas are built at some special points of the ridged circular waveguides. To verify the proposed method, three ridged circular waveguide structures are investigated and the numerical results are compared with available ones obtained by other research methods. © 2005 Wiley Periodicals, Inc. Int J RF and Microwave CAE 15, 2005.     

A wideband circularly polarized slot antenna with antipodal strips for WLAN and C‐band applications

A single‐fed circularly polarized square shaped wide slot antenna with modified ground plane and microstrip feed has been presented. The field in the slot is perturbed by introducing an antipodal strips section attached with a microstrip line to produce circular polarization in a wide band of frequencies. The antipodal strip section consists of a group of four strips of unequal length and separation. The presence of asymmetric perturbations in the slot is mainly responsible for exciting two orthogonal modes in the slot having equal magnitude and 90° phase difference which results in circular polarization. A wide bandwidth of 3.3 GHz (4.4 GHz‐7.7 GHz) has been achieved for an axial ratio value AR < 3 dB with the minimum axial ratio value being 0.3 dB. The impedance bandwidth for |S₁₁| < ?10 dB ranges from 4.3 GHz to 8 GHz, and therefore covers most of the C‐band communication systems. The antenna exhibits stable radiation patterns throughout the circular polarization bandwidth with a gain around 6 dBi in entire operational bandwidth. A prototype of antenna was fabricated and measured. The antenna has a planar size 0.40λ₀ × 0.40λ₀ and thickness of 0.02λ₀ where λ₀ is the wavelength in free space at the lowest frequency. With its compact size and low profile, the antenna is a favorable choice for WLAN (5.15‐5.85 GHz) and a wide variety of C‐band wireless applications.     

Single‐feed wideband circularly polarized patch antenna using dual mode defected ground waveguide coupling structure

A dual mode square‐ring defected ground waveguide (SR‐DGW) with defected square patch is first proposed to excite a single‐feed dual mode circularly polarized (CP) patch antenna, which can improve the impedance bandwidth and achieve the CP radiation pattern. The defected square patch is called the perturbation element. By optimizing the size of the perturbation, the degenerate modes of the dual mode SR‐DGW are split and their orthogonal modes can be excited simultaneously. Due to the dual mode of the SR‐DGW, the TM₀₁ mode, and TM₁₀ mode of the square patch antenna are excited simultaneously, which can improve the impedance bandwidth of the antenna. Meanwhile, owing to the orthogonal modes, CP radiation pattern of the antenna is obtained. Then, for a better impedance matching, an L‐shaped spurline embedded in the feedline is introduced. The simulated and measured results show a good performance of the proposed antenna. The measured ?10 dB impedance bandwidth is 10.4% (3.56 GHz‐3.95 GHz). The measured 3 dB axial ratio bandwidth is 5.36% (3.63 GHz‐3.83 GHz). Detailed designs and experiments are described and discussed.     

Wideband circularly polarized leaky‐wave antenna with flat gain using printed ridge gap waveguide

A wideband beam scanning circularly polarized (CP) leaky‐wave antenna (LWA) at Ku band is proposed based on the printed ridge gap waveguide (PRGW). In this design, the printed technology is used to realize the ridge gap waveguide (RGW) structure, and a substrate layer is introduced to replace the air gap layer in conventional RGWs. The proposed beam scanning CP LWA has been fabricated. Measured results of the fabricated antenna prototype are carried out to verify the simulation analysis. It provides a wide impedance bandwidth of 22% ranging from 12 to 15 GHz while performing continuous frequency beam scanning from ?2° to +47°. Furthermore, it maintains the excellent CP characteristic with axial ratio (AR) below 1.5 dB and a flat gain response with variation less than 2 dB in the entire operation frequency band.     

CAD of evanescent‐mode bandpass filters based on the short ridged waveguide sections

The paper presents the internal details of a developed full‐wave algorithm for the computer‐aided design of evanescent‐mode bandpass filters formed by single‐ or double‐short ridged waveguide sections. New filter configurations with an enlarged cross section of filter housing and nonconventional notch‐strip‐notch elements providing improved stopband performance are given special considerations. Additional input–output transformers built on rectangular waveguide sections are used in designing broadband filters. Characteristics of one of the designed filters are verified by measured data. © 2001 John Wiley & Sons, Inc. Int J RF and Microwave CAE 11: 354–365, 2001     

Bandwidth and gain‐enhanced composite right/left‐handed antenna for ultra‐wideband applications

A coplanar waveguide‐fed metamaterial antenna is presented for ultra‐wideband (UWB) applications. The proposed antenna is designed with single unit‐cell composite right/left‐handed transmission line (CRLH‐TL) loaded with a split‐ring resonator (SRR). The UWB characteristic is obtained by merging the zeroth‐order resonance of CRLH‐TL with two additional resonances due to the ground plane and SRR respectively. Subsequently, a partial reactive impedance surface is embedded on the rear side of the proposed antenna to enhance the realized gain without affecting the UWB response. The overall size of the antenna is 0.241λ_o x 0.267λ_o x 0.013λ_o (28.8 x 32 x 1.6 mm³), where λ_o is the free space wavelength at 2.51 GHz. The measured results indicate –10 dB fractional bandwidth of 139.19% (2.51‐14 GHz) with realized gains of 2.3, 4.6, and 6 dBi at the resonant frequencies 4, 7.84, and 10.29 GHz respectively. The measured peak realized gain is 6.6 dBi at 10.6 GHz. The radiation efficiency is above 63.85% for the entire UWB range with a peak value of 86.84%. A fairly stable group delay with variation within 1 ns is obtained throughout the operating frequency band. A good agreement has been observed between the measured and simulated results.     

Flower‐shaped ultra‐wideband fractal antenna

A flower‐shaped ultra‐wideband fractal antenna is presented. It comprises a fourth iterative flower‐shaped radiator, asymmetrical stub‐loaded feeding line, and coplanar quarter elliptical ground planes. A wide operating band of 12.12 GHz (4.58‐16.7 GHz) for S ₁₁ ≤ ? 10 dB is achieved along with an overall antenna footprint of 15.7 × 11.4 mm². In addition, other desirable characteristics, that is, omnidirectional radiation patterns, peak gain upto 5 dB, and fidelity factor more than 75% are achieved. A good agreement exists between the simulation and measured results. The obtained results illustrate that this antenna has wide operating range and compact dimensions than available structures.     

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.     

Broadband conical beam antenna in planar environment

In this article, a substrate‐truncated microstrip circular patch antenna with shorting vias is proposed for X‐band applications. The bandwidth of the designed antenna is substantially increased by making two slots—one circular and another annular ring—at the top of the structure which actually helps in bringing two individual resonating frequencies closer to each other. The antenna is simulated using the Ansoft HFSS, and various parameters are optimized for better performance. The deigned structure is finally fabricated and tested, and the measured data fairly agree with the simulated results. The measured relative impedance bandwidth (|S₁₁| < ?10 dB) is found to be 28.5% (8.9‐11.85 GHz). The proposed antenna is behaving like a monopole with the radiated beam of conical shaped in the entire operating band having a maximum gain of 7.2 dBi.     

Improved design procedure for double‐ridged waveguides

This article presents a novel methodology for designing double‐ridged waveguides by numerically optimizing their geometric shape such that they sustain the two prescribed lowest order modes. The field solution to the problem is obtained by using the finite element method. The performance of the microgenetic algorithm and the quasi‐Newton methods is studied for carrying out geometry optimization. This generalized formulation is capable of handling inhomogeneous material fillings in the guide, and computational results are presented to demonstrate the versatility of the proposed technique. © 2002 Wiley Periodicals, Inc. Int J RF and Microwave CAE 12, 530–539, 2002. Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mmce.10053     

High‐gain waveguide slot antenna using simple parasitic patch's cover

In this article, a way based on using miniature patch cells has been proposed to increase gain and bandwidth of the waveguide slot antenna. In the presented approach, an array of 3 × 3 metal patches has been used as superstrate to create Fabry Perot theorem resonance cavity. The proposed high ‐ gain and simple antenna is composed of a conventional waveguide slot antenna with an extended broad wall, and an array of parasitic patches which are symmetrically placed over slot at a distance of about free ‐ space half wavelength. The slot has been created on a rectangular waveguide WR90 with 22.86 mm × 10.16 mm × 52.5 mm dimension, also extended wall dimension is 2λ₀ (67.5 mm) × 3λ₀ (107 mm). It has been shown that the proposed structure compared with the conventional waveguide slot antenna improves antenna peak gain from 6.5 to 16.5 dBi and, in the same time, antenna bandwidth from 11% to around 16.2%. More important advantage of the proposed antenna is that unlike to other Fabry Perot antenna with the same gain, there is not any dielectric material in the proposed structure. A prototype antenna was simulated, fabricated, and measured for verification.