Spur line integrated single‐/dual‐/triple‐notched ultra‐wideband monopole antenna

Design and realization of spur line loaded frequency‐notched planar ultra‐wideband (UWB) antenna is proposed in this article. Accommodating the spur line (lines) of quarter wavelength long on the feeding microstrip line of UWB antenna, contributes to the notch‐filtering action in the feeding section itself which in turn can provides single/double/triple notch (notches) within the UWB spectrum of the antenna. The proposed technique is very simple and radiator independent as the filtering is performed in the feed region and hence the UWB radiator can be independently designed. The spur line based filtering sections are first separately designed and verified by S‐parameter measurements of the fabricated prototypes. Single, double, and triple spur line loaded microstrip sections are separately used as the feed section of a circular monopole antenna (MPA) to invoke single‐, dual‐, and triple‐notched UWB response of the MPA. All the designed prototypes are fabricated and characterized in terms of impedance and radiation parameter measurements, yielding very close correspondence with that of results obtained from full wave simulation.     

Multi‐band pattern reconfigurable Yagi‐Uda antenna

In this study, novel designs of single‐band and tri‐band pattern reconfigurable antennas are proposed. The design of single‐band pattern reconfigurable antenna is accomplished by the use of varactor diodes with the parasitic elements placed on both sides of the driven conventional printed dipole antenna. By tuning the capacitance of varactor, the antenna operates in four different configurations of radiation pattern which include bi‐directional end‐fire, broadside, and uni‐directional end‐fire radiation patterns. The tri‐band pattern reconfigurable antenna design is achieved by the use of parasitic elements on both sides of a tri‐band driven dipole antenna. Dual‐band LC resonators are used as loading elements along the arms of printed dipole to get two lower order modes in addition to the reference dipole mode, resulting in a triband operation of the driven element. The electrical lengths of the parasitic elements with respect to the tri‐band driven element are controlled by suitably embedding varactor and PIN diodes with them. The proposed tri‐band antenna operates in ten different configurations of radiation patterns in the three operating bands. Fully functional prototypes of single‐band and tri‐band pattern reconfigurable antennas along with the DC bias networks have been fabricated to validate the results obtained in simulation.     

Design of a compact protrudent‐shaped ultra‐wideband multiple‐input‐multiple‐output/diversity antenna with band‐rejection capability

In this endeavor, a new multiple‐input‐multiple‐output antenna with a sharp rejection at wireless local area network (WLAN) band is designed and practically examined for portable wireless ultra‐wideband applications. The intended diversity antenna possess a small size of 15 mm × 26 mm and two inverted L‐strip are loaded over the conventional rectangular patch antenna to form protrudent‐shaped radiator that acts as a radiating element. The sharp band‐rejection capability at WLAN is established by incising the L‐shaped slits at the decoupling structure. More than ?21 dB isolation is accomplished for the complete working band (ie, 2.87 ‐17 GHz). Degradation in the antenna efficiency at the center frequency of band rejection corroborates the good interference rejection capability. The working capabilities of the intended antenna are tested by using the isolation between the ports, total efficiency, gain, envelope correlation coefficient, radiation pattern, mean effective gain, and total active reflection coefficient.     

Carbon fiber‐based deca‐port multiple‐input‐multiple‐output antenna with pattern diversity and high inter‐element isolation

In this article, a deca‐port carbon fiber‐based multiple‐input‐multiple‐output (MIMO) antenna with pattern diversity is presented. The radiating elements of the proposed antenna consist of low cost, light weight, environmental friendly graphite material. The 10 radiating elements of the MIMO antenna are arranged in a group of two (termed as sub‐MIMO structure), in a cubical manner to cover all the propagating directions. Furthermore, the two carbon fiber‐based radiating elements of the sub‐MIMO structure are placed in an orthogonal arrangement to generate different radiation patterns. The antenna exhibits high inter‐element isolation and low envelope correlation coefficient due to orthogonal placement of the radiating elements. The antenna is fabricated and the measured results confirm that the proposed MIMO/diversity antenna may be useful for vehicle‐to‐network applications. The MIMO performance parameters such as diversity gain, total active reflection coefficient, mean effective gain, channel capacity loss are evaluated and found within suitable limits. The three‐dimensional pattern diversity helps to communicate in all directions.     

A high‐gain dual‐band directional/omnidirectional reconfigurable antenna for WLAN systems

A high‐gain dual‐band antenna for the wireless local area network system is presented in this article. Two symmetrical linear arrays can be dynamically reconfigured that could switch radiation pattern with a switchable feed circuit between direction and omnidirection. The antenna can also be used for a pattern diversity antenna for the multiple‐input–multiple‐output communication systems. The design process for the antenna system is given, and the parameters and characteristics of the antennas are achieved by the method. Measured return losses, isolation, and radiation patterns are in good agreement with the simulated ones, which illustrates that the method is valid and the antenna system can be integrated with pattern reconfigurable and pattern diversity applications. © 2008 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2008.     

Novel wide‐beam cross‐dipole CP antenna for GNSS applications

A wide‐beam circularly polarized (CP) cross‐dipole antenna for GNSS applications is proposed in this article. This cross‐dipole antenna is fed by a coaxial cable, on which the slots is added to optimize the impedance matching. These two pairs of dipole arms are designed with different lengths to obtain the circularly polarized radiation. Enhanced wide‐beam CP radiation characteristics can be achieved by curving the dipole arms and adjusting the distance between the arms and the metallic ground plane. The study of proposed antenna performance with different geometric parameters has been conducted. The final antenna exhibits a good impedance bandwidth (IBW) of ～13.1% (1.50‐1.71 GHz), and the 3‐dB axial‐ratio bandwidth is over 7% (1.52‐1.64 GHz). Broad pattern coverage of more than 140°, pure CP radiation at all designed bands and a wide 3 dB axial‐ratio beamwidth (ARBW) of nearly 150° makes this antenna an excellent candidate for satellite communications and navigation systems.     

Design of a 16‐beam pattern‐reconfigurable antenna for vehicular environment

This article presents the design of a multipattern antenna with pattern switching for vehicular communications. The proposed antenna has four triangular patches integrated onto a split square ring (SR) resonator to operate at two distinct frequencies, viz. 2.4 and 3.5 GHz. The proposed antenna is designed with a view to enhancing the link reliability of Wireless Local Area Network (WLAN), WiMax, and vehicle to vehicle communication frequencies. Each triangular patch is separately excited using a microstrip line feed to enable beam steering. The ground plane of the antenna is embedded with two SR slots to improve the bandwidth and radiation performance. Further gain enhancement is achieved by loading the antenna with a plane reflector located at a distance of 20 mm from the antenna's ground surface. In reality, this reflector is realized using the vehicle's roof which provides gain enhancement up to 5.2 dBi at 2.4 GHz and 4 dBi at 3.5 GHz. By exciting single to multiple ports sequentially 16 different radiation patterns are obtained, which provides high‐gain omnidirectional coverage. The prototype antenna is fabricated and the simulation results are verified using experimental measurements. From the results, it is evident that the proposed antenna is suitable for vehicular communication applications.     

Compact‐size linearly tapered slot antenna for portable ultra‐wideband imaging systems

A compact‐size asymmetrical linearly tapered slot antenna required for portable ultra‐wideband (UWB) imaging systems is presented. The total antenna size is reduced compared with the conventional linearly tapered slot antenna by using a triangular slot on the left‐hand side of the tapered‐shaped radiator, whereas introducing a corrugated pattern of cuts on the right side. The antenna operates over a wide bandwidth extending from 3.1 to 10.6 GHz with a maximum gain of 8.5 dBi. Stable radiation patterns are observed across the operational bandwidth, with cross‐polarization levels below ?20 dB. The realized antenna structure occupies a volume of 35 × 36 × 0.8 mm³, and possesses the essential time domain fidelity needed for UWB imaging applications. © 2012 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2013.     

Radiated cross‐polar levels and mutual coupling in patch radiators

This article presents the relation between the cross‐polar signal radiated by a dual feed patch antenna and the mutual coupling existing between the antenna feeds. The theoretical analysis is based on the S‐parameters of the antenna element, providing a clear understanding of the physical relation between cross‐polar level and coupling. Analytical expressions are given for the radiation pattern computation, including the cross‐polar level and the effect of higher order modes on the pattern. Finally, the results of the study are illustrated with measured patterns. © 2000 John Wiley & Sons, Inc. Int J RF and Microwave CAE 10: 342–352, 2000.     

A compact planar inverted‐F antenna with U‐shaped strip for all‐metal‐shell handset application

A compact dual‐band planar inverted‐F antenna (PIFA) with U‐shaped strip is proposed in this work for all‐metal‐shell mobile telephone application. As metal‐shell handsets are getting more and more popular nowadays, it raises a big challenge in antenna design as the metal‐shell associated with surrounding electronic components like front‐back‐cameras and telephone receiver would affect the antenna performance. This work provides an optional solution to alleviate this problem, where the metal shell of the handset and a U‐shaped strip are utilized as part of the antenna. The proposed antenna is able to generate radiation at 2.4 GHz for Wi‐Fi application with the help of the metal shell while using the U‐shaped strip can achieve a resonance at 1.575 GHz for GPS application. A prototype has been fabricated to verify the radiation performance in a practical handset test environment.     

A novel substrate integrated waveguide cavity‐backed self‐diplexing antenna array with frequency beam scanning characteristic

This article presented a substrate integrated waveguide (SIW) cavity‐backed self‐diplexing antenna array with frequency beam scanning characteristic. The proposed array consists of 16 SIW cavity‐backed slot antennas. The SIW cavity‐backed slot antenna can be fed by two separate ports to resonate at two different frequencies and achieve high isolation better than 20 dB between two input ports. The proposed element is a typical self‐diplexing antenna. These cavity‐backed slot antennas are shunt‐fed by a compact 1 to 16 SIW power divider and series‐fed by a set of microstrip lines, respectively. As a result, this array achieves an unidirectional radiation pattern at 10.2 GHz with high gain of 15.10 dBi, and a frequency beam scanning characteristic from 7.0 to 9.0 GHz ranging from ?50° to 46°.     

Design of a dual‐polarized omnidirectional antenna for broadband applications

A broadband dual‐polarized omnidirectional antenna is presented. The proposed antenna consists of two parts, an asymmetric biconical antenna and a cylindrical multilayer polarizer. To have an almost perfect omnidirectional radiation pattern in the horizontal plane and the main radiating beam position at around , in the elevation plane, the asymmetric biconical antenna is used. Moreover, to provide dual polarization performance over the 2–18 GHz operational bandwidth, a multilayer polarizer is designed and optimized. Numerous simulations via Ansoft HFSS and CST microwave Studio CAD tools have been made to optimize the radiation pattern, gain, polarization, and the reflection coefficient of the antenna. Simulation results show that the radiation characteristics of the proposed antenna are extremely sensitive to the configuration and dimensional parameters of the multilayer polarizer. The designed antenna was fabricated with high mechanical accuracy and measured. Satisfactory agreement of computer simulations and experimental results was obtained. The main feature that distinguishes this antenna from the previous designs is the ability to provide the omnidirectional radiation pattern with small ripples, dual polarizations performance, and the wide bandwidth simultaneously. Based on these characteristics, the proposed antenna can be useful for broadband communication applications. © 2015 Wiley Periodicals, Inc. Int J RF and Microwave CAE 25:591–600, 2015.     

Substrate integrated waveguide based cavity‐backed self‐triplexing slot antenna for X‐Ku band applications

A planar substrate integrated waveguide (SIW) based cavity‐backed self‐triplexing slot antenna is proposed for X‐Ku band applications. The antenna comprises of the SIW cavity, radiating slots, and feeding networks. The radiating slots; that are etched on the upper metallic plane of the SIW, are backed up by the three radiated quarter cavities (QCs). The radiating slots in the respective QCs are of different lengths, excited by three separated orthogonal feed lines to resonate at three different frequencies as 11.01, 12.15, and 13.1 GHz. By fine‐tuning the antenna parameters, an intrinsic input port isolation of better than 26 dB is realized which helps in achieving the self‐triplexing property. The behaviors of individual cavity modes at three resonant frequencies are explained with the help of Z‐parameter. The proposed antenna layout is easy to integrate with the planar circuit. The proposed antenna is fabricated and measured results display a close concern with the simulated results. Moreover, a unidirectional radiation pattern and gain of 5.1, 5.54, and 6.12 dBi at resonant frequencies are realized.     

Novel planar dual‐band balanced antipodal slot‐dipole composite antenna with reduced ground plane effect

A novel planar, dual‐band antenna composed of a symmetrical dipole and balanced antipodal slot radiator with low ground plane effect is proposed and investigated. Operation principle of the antenna is analyzed and design equations are drawn first. Then, the return loss, surface current distribution, radiation patterns, and gain are numerically and experimentally studied in detail. The impedance bandwidth of the antenna is from 2.36 to 2.56 and 5.13 to 12 GHz for return loss larger than 10 dB. The antenna has omnidirectional pattern at the lower band and quasi‐directional pattern at the higher band, and it has good immunity to a neighboring, large ground plane. The proposed antenna should be useful for dual‐band communication or identification systems. © 2012 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2012.     

Design of a single null compensation dipole antenna

In this paper, a single null compensation dipole antenna for Wi‐Fi band (2.4 GHz) is developed. The antenna is fed by the parallel transmission lines, and its radiation unit consists of a printed dipole antenna and a Yagi antenna. The proposed antenna has three layers. The top and bottom layers are printed with the dipole antenna and the driver arm of the Yagi antenna. The director and the reflector of the Yagi antenna are placed on the middle layer. The three layers are separated by two FR‐4 substrates. This antenna satisfies the omnidirectional radiation characteristic in its H plane and can compensate a null point in the E plane. Simulation results show that the 10 dB bandwidth is 2.32 to 2.46 GHz. The maximum realized gain is 1.13 dB in the frequency band. The non‐roundness of the H plane is less than 2 dB, which shows good omni‐directivity. A null point in the radiation pattern of the E plane is compensated to ?1.4 dB at 2.4 GHz, while the other null point of the E plane remains below ?15 dB. The antenna has been manufactured and tested, and the measurement results validate the design and the simulation results.     

Characteristic analysis of reverse‐L‐shaped microstrip‐fed large‐bandwidth printed slot antenna

The characteristics of a reverse‐L‐shaped microstrip‐fed structure is analyzed using the finite difference time domain method, and the characteristics of the proposed antenna are compared with a conventional antenna. The return loss, radiation resistance, and voltage–standing wave ratio in the frequency domain are calculated by Fourier transforming the time domain results. When the proposed feed structure is used, the bandwidth is extended in proportion to the slot width and the radiation resistance has the low value. When the slot width is 16 mm, the experimental bandwidth is approximately 50% (?10 dB ≥ S₁₁) at the center frequency of 2.3 GHz. In addition, the experimental data for the impedance and radiation pattern of the antenna are described. They are in good agreement with the calculated results. © 2002 Wiley Periodicals, Inc. Int J RF and Microwave CAE 12, 496–502, 2002. Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mmce.10055     

A π/4 bi‐orthogonal monopole antenna for operation on and beyond of the UWB band

An ultra‐wideband (UWB) π/4 bi‐orthogonal monopole antenna with a highly omnidirectional radiation pattern in the azimuthal plane with a quasi‐independent on the frequency behavior is presented in this article. Here, it is shown that by combining two orthogonal UWB planar monopole elements rotated 45° with respect to each other in a single structure, it is possible to enhance the performance of the radiation pattern at high frequencies of the operational bandwidth without affecting the radiation pattern at lower frequencies. The measured antenna bandwidth goes from 2.82 to 16.7 GHz for a reflection coefficient lower than ?10 dB. The radiation pattern remains almost omnidirectional, and it is enhanced with respect to a conventional single planar monopole antenna of similar characteristics. The basic element used for both the single and the proposed π/4 bi‐orthogonal UWB planar monopole antenna has a rectangular shape, whose impedance bandwidth ratio is achieved based on the bevelling and height‐width ratio techniques. Although the antenna prototype presented in this article has an operational bandwidth of 13.88 GHz, it is possible to design a UWB monopole antenna with the shape and structure proposed here, but for different bandwidths following a design methodology suggested also in this article. © 2010 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2011.     

S‐shaped planar antenna with 45° tilted bidirectional radiation pattern for motorcycle helmets

An S‐shaped planar antenna (SPA) with a bidirectional radiation pattern and beam tilt characteristic is proposed to achieve maximum communication distance for helmet applications. The proposed SPA is comprised of an S‐shaped radiation strip (consisting of a microstrip meander line and two main arms with two inverted L‐shaped parasitic elements) and a rectangular ground plane, where a simplified microstrip power divider is introduced by modifying the feed structure in the center of the SPA, such that the S‐shaped radiation strip works in the second resonant mode. The proposed SPA generates a tilted beam in the E‐plane with an angle of 45°, which is attributed to the obliquely staggered arms of the antenna at a distance. By introducing inverted L‐shaped parasitic elements at the end of the two arms, the directivity of the bidirectional radiation pattern can be further improved, thereby increasing the antenna gain. The working principle is analyzed theoretically, and the effects of the antenna structural parameters on the radiation pattern are also analyzed. The experimental results indicate that the 3:1 VSWR impedance bandwidth is 120 MHz, with a realized peak gain of 1.5 dBi at 2.45 GHz. The proposed antenna is designed for real‐world applications, allowing the antenna to be obliquely installed while keeping the peak gain direction horizontal for maximum communication distance.     

A novel pattern‐reconfigurable grid array antenna

This article presents the design of a grid array antenna with pattern reconfigurable ability. Discussion of various factors that affect the radiation pattern is presented. Interdigital structure, which serves as short radiation line of grid array antenna is then introduced to reconfigure radiation pattern. Change of main beam direction is realized via state change of PIN diodes loaded in interdigital structure and variation of feed point. The scanning angle varies from ?33° to +38° and the average gain is about 10 dBi. The proposed antenna was fabricated and measured. Measured results show the proposed antenna possesses good beam‐scanning characteristics and has potential value in long‐distance power supply for various passive nodes.     

Compact ultra‐wideband slot antenna with three notched‐band characteristics

A very compact ultra‐wideband (UWB) slot antenna with three L‐shaped slots for notched‐band characteristics is presented in this article. The antenna is designed and fabricated using a new stepped slot with different size, integrated in the ground plane, and excited by a 50 Ω microstrip transmission line. The stepped slot is used to minimize the dimensions of the antenna and to achieve an impedance bandwidth between 2.65 and 11.05 GHz with voltage standing wave ratio (VSWR) less than 2. The length of the stepped slot is equal to a quarter wavelength to create a resonance in the desired frequency. Three L‐shaped slots with various sizes are etched in the ground plane to reject three frequency bands in C‐band (3.7‐4.2 GHz), WLAN (5.15‐5.825 GHz), and X‐band (7.25‐7.75 GHz), respectively. The notched‐band frequency can be controlled by changing the length of the L‐shaped slot. The proposed antenna has a very small size (20.25 × 8 × 1.27 mm³) compared with previous works. The measured and simulated results show a good agreement in terms of radiation pattern and impedance matching.