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.     

A wideband circularly polarized antenna using mutual coupling method

A novel wideband circularly polarized (CP) antenna is presented in this article. The proposed antenna consists of a four‐leaf clover patch, four L‐probes, and wideband networks. Based on the tightly coupled mechanism, the four L‐probes are formed as a ring with the adjacent ones kept close for strong mutual coupling. Consequently, the proposed antenna realizes a wideband impedance matching. Meanwhile, the four‐leaf clover patch is put closely inside of the ring for further improving the impedance bandwidth, which is proximity‐coupled fed by the four sequential‐rotation L‐probes with phase of 0°, 90°, 180°, and 270°. The four L‐probes are connected to the respective ports of a wideband feeding network by a two‐stage impedance transforming network. The measured results indicate that the proposed design has an impedance bandwidth of 66.7% from 1.0 to 2.0 GHz for VSWR ≤ 2 and a 3‐dB axial ratio bandwidth of 56.5% from 1.08 to 1.93 GHz. Furthermore, in the operating bandwidth, stable and symmetry radiation patterns and high gain are obtained. The design has a 3‐dB gain bandwidth of 38% from 1.3 to 1.9 GHz with a peak gain of 8.5 dBic.     

A dual‐band and wideband omnidirectional circularly polarized antenna based on VO2

In this article, a dual‐band and wideband omnidirectional circularly polarized (CP) antenna based on the vanadium dioxide (VO₂) is investigated. The operating bandwidth of such an antenna can be regulated by altering the outside temperature (T), which is attained by the insulator‐metal transition of VO₂. The omnidirectional CP antenna is based on a loop antenna‐dipole model, which is composed of four tilted metal and VO₂ resonant units that are loaded around a cuboid and a feeding network for broadening bandwidth. The simulated results show that when T = 50°C (State I), the 10‐dB impedance bandwidth is 45.7% (1.67‐2.66 GHz), and the 3‐dB axial ratio (AR) bandwidth is 40% (1.9‐2.85 GHz). When T = 80°C (State II), the 10‐dB impedance bandwidth is 13.8% (1.62‐1.86 GHz), and the 3‐dB AR bandwidth is 21.8% (1.68‐2.09 GHz). In order to further characterize the concept of the proposed antenna, the related parameters of such an antenna are studied using simulation software HFSS.     

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 wideband compact antenna with quad‐circular polarized bands in its operating regions

This article presents the design of an offset CPW‐fed slot antenna which exhibits a narrow impedance bandwidth (IBW; |S₁₁| ≤ ?10 dB) extending from 1.20 GHz to 1.45 GHz and another wide impedance bandwidth from 1.86 GHz to 8.4 GHz thus covering almost all the conventional operating frequencies. The antenna is loaded with semicircular and rectangular stubs and meandered microstrip lines to realize circular polarization at 1.35 GHz, 3.3 GHz, 4.9 GHz, and 7.5 GHz with axial ratio bandwidth (axial ratio ≤ 3 dB) of 19.25% (1.2‐1.46 GHz), 4.24% (3.24‐3.38 GHz), 4.1%(4.8‐5 GHz), and 5.2% (7.3‐7.69 GHz) respectively thus covering the GPS, WiMAX, WLAN, and X‐band downlink satellite communication application bands. The mechanism of generation of CP is discussed using vector analysis of surface current density distribution. The gain is fairly constant in the wide IBW region with maximum fluctuation of 1.2 dB. The structure is compact with an overall layout area of 0.27λ × 0.27λ, where λ is the free‐space wavelength corresponding to the lowest circular polarized (CP) frequency. A comparison of the proposed antenna with previously reported structures is performed with respect to impedance bandwidth, compactness, number of CP bands, LHCP to RHCP isolation and gain to comprehend the novelty of the proposed design. A prototype of the proposed antenna is fabricated and the measured results are in accord with the simulated results.     

A spoof surface plasmon leaky‐wave antenna with circular polarization

In this article a circularly polarized (CP) leaky‐wave antenna (LWA) based on spoof surface plasmon (SSP) is proposed. Corrugated circular patches are loaded on either side of the SSP waveguide periodically and asymmetrically, which enables continuous CP beam steering from backward to forward quadrant eliminating “the open stopband” at broadside. The antenna exhibits an impedance bandwidth of 43.5% (<?10 dB) and a 3‐dB axial‐ratio bandwidth of 27.8%; within the impedance bandwidth from 4.5 to 7 GHz the radiation beam can be steered from 120° to 70°. With a ground plane placed underneath, the antenna can achieve average radiation gain and efficiency of about 10 dBic and 84.2%, respectively, showing a radiation gain increase of about 3 dB over that without a ground plane. The proposed SSP‐based CP LWA is expected to find applications in wireless communication systems based on planar antennas.     

A compact wideband circularly polarized antenna with two pairs of driven patch arrays

In this article, a new wideband circularly polarized (CP) antenna is presented. The antenna is composed of a circular‐loop feeding structure which provides sequential phase (SP), four primary‐parasitic crown patches and four secondary‐parasitic crown patches. The circular‐loop SP structure is used to feed the two pairs of crown patches by a capacitively coupled way. The presented antenna features a wide 10‐dB impedance bandwidth (IBW) of 23% (6 GHz, 5.31‐6.69 GHz), and a wide 3‐dB axial ratio bandwidth (ARBW) of 11.1% (5.875 GHz, 5.55‐6.2 GHz). The proposed antenna features compact structure and broad 3 dB‐ARBW, which could include the WLAN (5.725‐5.85 GHz), ITS (5.8 GHz), and WIFI (5.85‐5.925 GHz) band.     

Analytic study on CP enhancement of millimeter wave DR and patch subarray antennas

This article presents a comparative analysis for the performance of single, 2 × 2, and 4 × 4 dielectric resonator (DR) and patch circularly polarized (CP) antenna subarrays at 30 GHz. In order to enhance the CP bandwidth, the subarray elements are fed by two kinds of sequential feeding techniques using parallel and hybrid ring feeds. The 4 × 4 patch antenna subarrays fed by parallel and hybrid ring feeding networks are fabricated and tested. Measurements show acceptable agreement with simulation results. The experimental results show a bandwidth of 36.9% for both (?10 dB) impedance matching and (3 dB) axial ratio CP patterns for the patch subarray antenna with hybrid ring feeding. For the parallel feeding, the corresponding bandwidth is 28.81%. The proposed antennas combine desirable features such as wide impedance and AR bandwidths, low profile, and easiness of fabrication and therefore is a good candidate for millimeter wave systems around 30 GHz.     

A high gain wideband circularly polarized antenna with asymmetric metasurface

An asymmetric‐metasurface based wideband circularly polarized (CP) microstrip antenna using a coaxial probe is proposed for L‐band applications. The antenna involves a stacked asymmetric‐metasurface, a radiating rectangular‐patch and a coaxial feed. An asymmetric‐metasurface is designed using rectangular unit cells and smaller size unit cells along one of the diagonal lines. The asymmetric‐metasurface is placed above a radiating rectangular‐patch with support of foam layer to achieve a wideband CP radiation. The measured performance of the prototype antenna achieves an impedance bandwidth (?10 dB return loss bandwidth) of 15.7% (1.58‐1.85 GHz) with CP bandwidth (3‐dB axial ratio) of 13% (1.58‐1.80 GHz) and gain of ≥9 dBic.     

A new modified CPW‐fed wideband circularly polarized half‐split cylindrical dielectric resonator antenna with different permittivity of two layers in radial direction

In this article, a wideband circularly polarized half‐split cylindrical dielectric resonator antenna (HS‐CDRA) having two layers with different permittivity in radial direction is investigated. Designed antenna is excited by a new modified CPW fed which consists of signal line, helps to realization of circular polarization, half‐split cylindrical dielectric resonator (HS‐CDR), to confirm that circular polarization in proposed antenna. HS‐CDR is made of two different materials which can supports to enhance the input impedance bandwidth and 3‐dB axial ratio bandwidth. From the distributions of E‐fields in HS‐CDRA, it is observed that TM_11δ mode has been excited. To confirmed the circular polarization in proposed antenna, E‐field distribution on different phases (φ = 0º, 90º, 180º, and 270º) have been plotted. This antenna provides measured ?10 dB input impedance bandwidth of 25.94% (centered on 4.70 GHz) and 3‐dB axial ratio bandwidth in broadside direction of 17.34% (centered on 4.90 GHz). The average gain and radiation efficiency in working band are 1.56 dBi and 93.43% in broadside direction, respectively. CP radiation pattern shows that the proposed antenna has left hand circular polarization and this developed antenna could be useful for wireless applications like WLAN/Wi‐MAX bands.     

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.     

Broadband circularly polarized printed falcate‐shaped monopole antenna

In this study, a simple broadband circularly polarized (CP) printed monopole antenna for S/C‐band applications is proposed. The CP antenna is composed of a falcate‐shaped monopole with a right‐angle trapezoid stub, then wide impedance and axial ratio (AR) bandwidths are achieved. By placing one rectangular split‐ring resonator above the stub for generating upper CP mode, both of impedance and CP performances are further improved. The proposed antenna is fabricated on a FR4 substrate and measured. The measured ?10‐dB impedance bandwidth is 107%, ranging from 2.4‐7.9 GHz, and the measured 3‐dB AR bandwidth is 94% (2.4‐6.6 GHz), covering the entire wireless local area network (WLAN) and WiMAX bands.     

A dual‐patch polarization rotation reflective surface and its application to wideband wide‐beam low‐profile circularly polarized patch antennas

This study investigates the use of a polarization rotation reflective surface (PRRS) to construct a wideband, wide‐beam, low‐profile circularly polarized (CP) patch antenna. The device is composed of a feeding monopole antenna and a novel PRRS‐based dual‐patch artificial magnetic conductor (AMC) cell structure. The PRRS has two polarization rotation (PR) frequency points, generated by properly adjusting the width between square and L‐shaped metallic patches. A large PR band of 35.5% (5.1‐7.3 GHz) was achieved by combining two adjacent PR frequency points. The PRRS‐based patch antenna impedance bandwidth was measured to be 28.6% (5.1‐6.35 GHz), with a 3 dB axial ratio (AR) bandwidth of 21.8% (4.8‐6.4 GHz) and a profile of 0.045λ₀. Additionally, the proposed antenna exhibited the largest AR beamwidth (to our knowledge) of 175° and 128° in the xoz and yoz planes, respectively. It also produced a high broadside gain of 6.7 dBic within the operational bandwidth.     

Design of a compact wideband CP metasurface antenna

In this article, a new compact metasurface circularly polarized (CP) antenna is presented, where the rotating 45° periodic ellipse patch is used to achieve polarization conversion from linearly polarized to CP. The meta‐surface is composed of 4 × 4 ellipse patches with 45° rotation, which are etched on the top layer of upper substrate. A slot ground plane and a coplanar waveguide structure are printed on both sides of bottom substrate, and the bottom substrate is directly connected to the upper substrate, which can make the antenna profile lower. As demonstrated in this article, the presented antennas have good characteristics of excellent 3‐dB axial ratio bandwidth of 17.4% (5.25‐6.25 GHz), and wide 10‐dB impedance bandwidth of 20.6% (5.0‐6.15 GHz).     

Wideband circularly polarized rectangular DRA fed with dual pair of right‐angled microstrip line

In this article, design and development of wideband circularly polarized (CP) rectangular dielectric resonator antenna (RDRA) is presented. To generate wideband CP in proposed antenna, different feeding mechanism have been studied. Three antenna configurations based on different feeding have been discussed using single and dual pair of microstrip lines aligned perpendicular to each other to generate orthogonal modes resulting in circular polarization. It has been claimed here that excitation of RHCP/LHCP field and its direction of radiation could be controlled using height of microstrip feed lines. Finally antenna configuration‐3 is fabricated and measured which shows 36.8% of input impedance bandwidth (3.48–5.05 GHz) and axial ratio bandwidth of 14.46% (3.67–4.24 GHz) in broadside direction (at Φ = 0°, θ = 0°). The final proposed structure exhibits consistent far‐field characteristics with average LHCP gain of 6.4 dB and almost stable radiation efficiency in entire operational frequency range. © 2016 Wiley Periodicals, Inc. Int J RF and Microwave CAE 26:713–723, 2016.     

A broadband circularly polarized monopole antenna

A compact modified C‐shaped monopole antenna with broadband circular polarization is proposed, fabricated and measured. The antenna structure is simple and only consists of combined modified C‐shaped radiation patch and an improved ground plane with the overall size of 25 × 25 × 1 mm³. By cutting the corner on the modified C‐shaped patch and adding triangular stubs on the ground plane, the wide impedance bandwidth and axial ratio bandwidth are achieved. The design process of the antenna is given, and the circular polarization mechanism of the circularly polarized antenna is analyzed from the surface current distributions. The measured impedance bandwidth is 95.2% (4.4‐12.4 GHz) with return loss better than 10 dB, and the measured 3 dB axial ratio bandwidth is 96.8% (4.42‐12.72 GHz). The peak gain is above 3.0 dBi within the working band, which indicates that it is suitable for application of ultra‐wideband (UWB) wireless communication systems and satellite communication systems.     

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.     

Bandwidth enhancement of a circularly polarized tapered crossed slot antenna with corner parasitic directors

This paper presents a single‐feed wideband circularly polarized (CP) antenna with tapered crossed slots and corner directors. According to the multi‐mode resonance concept, the antenna uses two identical cross placed Vivaldi‐like tapered slots as the wideband radiating elements, and four rectangular parasitic patch directors are connected on each corner of the ground for further enhancing the bandwidth. A simple second‐order stepped microstrip line with a via on the other side of the substrate is used to feed the antenna. Two pairs of capacitors and inductors are placed on each slot to realize a 90° phase difference for CP operation. The proposed antenna is designed, fabricated and measured. Simulation results are in good agreement with the measured results that demonstrate a 10 dB impedance bandwidth (IMBW) from 1.98 to 5.71 GHz (3.73 GHz, 97.01%) and a 3 dB axial ratio bandwidth (ARBW) from 2.13 to 3.91 GHz (1.78 GHz, 58.94%). The antenna outperforms most of the reported cross slot antennas for its wide IMBW and ARBW.     

Dual‐band circularly polarized aperture‐coupled stack antenna with fractal patch for WLAN and WiMAX applications

This article presents a novel circular polarized (CP) aperture coupled stack antenna for wireless local area network and worldwide interoperability for microwave access dual‐band systems. The compact stack antenna consisted of square fractal patch, aperture couple, feed line and the perturbation. The square patch is constructed with the complementary Minkowski‐island‐based fractal geometry. By way of adjusting the relevant parameters, we can obtain the dual‐band responses at 3.5 and 5.25 GHz respectively. The CP of each band are presented. The measured 10 dB return loss impedance bandwidth are 270 MHz (7.5%) for 3.5 GHz band and 450 MHz (8.6%) for 5.25 GHz band. The 3 dB axial ratio bandwidths for each bands are 1.4 and 0.76%, the polarization of radiation patterns are both left‐hand CP, and the antenna power gain are 2.84–3.1 and 0.16–2.2, dBic respectively. The proposed antenna is successfully simulated and measured with frequency responses, radiation patterns and current distributions. © 2013 Wiley Periodicals, Inc. Int J RF and Microwave CAE 24:130–138, 2014.     

Circularly polarized 1 × 4 square slot array antenna by utilizing compacted modified butler matrix and branch line coupler

Circularly polarized (CP), beam steering antennas are preferred to reduce the disruptive effects such as multi‐path fading and co‐channel interference in wireless communications systems. Nowadays, intensive studies have been carried out not only on the specific antenna array design but also their feeding networks to achieve circular polarization and beam steering characteristics. A compact broadband CP antenna array with a low loss feed network design is aimed in this work. To improve impedance and CP bandwidth, a feed network with modified Butler matrix and a compact ultra‐wideband square slot antenna element are designed. With this novel design, more than 3 GHz axial ratio BW is achieved. In this study, a broadband meander line compact double box coupler with impedance bandwidth over 4.8‐7 GHz frequency and the phase error less than 3° is used. Also the measured impedance bandwidth of the proposed beam steering array antenna is 60% (from 4.2 to 7.8 GHz). The minimum 3 dB axial ratio bandwidth between ports, support 4.6–6.8 GHz frequency range. The measured peak gain of the proposed array antenna is 8.9 dBic that could scan solid angle about ～91 degree. © 2015 Wiley Periodicals, Inc. Int J RF and Microwave CAE 26:146–153, 2016.