Wide Circular Polarization Research Articles

A Miniaturized and Circularly Polarized L-Shaped Slot Antenna for Ultra-wideband Applications

A miniaturized microstrip-fed, wideband and circularly polarized L-shaped slot antenna is designed for ultra-wideband applications. To realize L-shaped slot antenna with wide impedance bandwidth, a stub of size 10.7 mm2 is added to a rectangular shaped slot of the ground plane. The position of the feedline is optimized to attain wide circular polarization bandwidth. The proposed antenna size is very small i.e., 25×25 mm2. A prototype of the design is fabricated and measured. The axial ratio bandwidth (ARBW< 3 dB) of 2.2 GHz (from 6.2 GHz to 8.4 GHz) and the impedance bandwidth (S11<-10 dB) of 7.4 GHz (from 2.5 GHz to 9.9 GHz) is achieved by the proposed design. Moreover, the antenna achieves a stable radiation pattern and a gain of more than 2.8 dBi over the complete ARBW. The advantages of the structure are miniaturized design, having wide impedance bandwidth, and broad ARBW.

Hybrid wideband dual‐cylindrical circularly polarized dielectric resonator antennas excited with S‐shaped microstrip feed for sub‐6 GHz frequency range

In this article, a hybrid microstrip fed dual-cylindrical dielectric resonator antenna (dual-CDRA) has been proposed for the sub-6 GHz band application with a wide circular polarization band. The proposed hybrid microstrip feed cylindrical dielectric resonator antenna utilizes an S-shaped microstrip feed line to excite fundamental HE11δ like mode and hybrid mode in dual-CDRAs. The presented antenna structures are acting as monopole antenna separately with 48.75% (3.88-6.38 GHz) bandwidth whereas both radiators called dual-CDRAs enhances the bandwidth up to 93.06% (2.16-5.92 GHz) in addition with an axial ratio bandwidth of 15.2% (3.52-4.1 GHz). The proposed antenna is applicable for WiMAX (3.4-3.69 GHz), and WLAN application of 802.11d and 8.02.11e IEEE standard. For validation of simulated results, an antenna prototype has been fabricated and experimentally verified. A good agreement between simulation and measured results are obtained. The simulation results have been carried out by using Ansys HFSS 14.0 version software.

Wideband circularly polarized dielectric resonator antenna loaded with partially reflective surface

A wideband circularly polarized (CP) dielectric resonator antenna (DRA) loaded with the partially reflective surface for gain enhancement is presented in this article. First, the DRA is excited by a microstrip line through modified stepped ring cross-slot to generate the circular polarization. Four modified parasitic metallic plates are sequentially placed around the DRA for greatly widening the axial-ratio bandwidth. Then, a partially reflective surface is introduced for enhancing the gain performance and further improving the CP bandwidth as well. Finally, an optimized prototype is fabricated to verify the design concept. The measured results show that the proposed DRA achieves 54.3% impedance bandwidth (VSWR<2) and 54.9% 3-dB AR bandwidth. Besides, its average and peak gains are 10.7 dBic and 14.2 dBic, respectively. Wide CP band and high gains make the proposed DRA especially attractive for some broadband wireless applications such as satellite communication and remote sensing.

Rapid Redesign and Bandwidth/Size Tradeoffs for Compact Wideband Circular Polarization Antennas Using Inverse Surrogates and Fast EM-Based Parameter Tuning

Design of compact wideband circularly polarized (CP) antennas is challenging due to the necessity of simultaneous handling of several characteristics [reflection, axial ratio (AR), and gain] while maintaining a small size of the structure. Antenna redesign for various operating bands is clearly more difficult yet practically important because intentional reduction of the bandwidth (e.g., by moving the lower edge of the operating band up in frequency) may lead to a considerable size reduction, which can be beneficial for specific application areas. This article proposes a rigorous approach to rapid redesign of miniaturized CP antennas involving inverse surrogate models and fast electromagnetic (EM)-based parameter tuning. Our methodology allows for a precise control of the lower operating frequency of the CP antenna (both in terms of the impedance and AR bandwidth) and accomplishing the geometry parameter scaling at an extremely low cost of a few EM analyses of the structure at hand. Our methodology is demonstrated by redesigning a compact wide slot CP antenna in the range of 3.2–5.8 GHz. The proposed approach can be used for fast rendering of the bandwidth/size tradeoffs (the footprints obtained for the verification structure range from 783 to 482 mm2), thus determining the most suitable designs for particular applications. The numerical findings are experimentally validated.

Metasurfaced, Broadband, and Circularly Polarized Liquid Antennas Using a Simple Structure

A novel broadband circularly polarized (CP) antenna using organic ionic liquid resonators is presented in this communication for the first time. The antenna is excited by inserting a new feeding structure into the liquid which is relatively simple but significantly improves the bandwidth and CP performance of traditional single probe-fed dielectric resonator antennas (DRAs). The proposed liquid antenna is loaded with a metasurface (MS) to further improve the impedance matching and CP characteristics. A design example of the proposed antenna shows a relatively wide fractional impedance bandwidth and CP bandwidth of 51.4% and 34.2%, respectively. In addition, the proposed liquid DRA has a reduced structural complexity and a compact size compared with the conventional DRAs with a similar performance. The design methodology presented in this communication can be further exploited for a range of new liquid DRA designs and expand the design freedom and flexibility of such antennas which may have significant implications in future antenna designs using the new liquid materials.

Wideband Circularly Polarized Fabry–Perot Resonator Antenna in Ku-Band

A gain enhancement method is proposed for the circularly polarized (CP) magneto-electric dipole antenna (MEDA) over the whole Ku-band in this letter. Together with the CP MEDA as a feeding antenna, a single-layer partially reflecting surface made by a substrate with arrays of metal patches printed on both the top and bottom forms a Fabry–Perot resonator antenna. Five types of symmetrical patch, i.e., double printed circular, square, circular-ring, square-ring patches, and single printed circular patch, are compared and optimized for a better reflective phase property. Finally, the circular patch type is chosen because of its gentler reflective phase gradient, and hence the gain value of the CP MEDA is much enhanced over the whole operating band. A prototype is optimized and fabricated to verify the analysis. Measured results show that the 10 dB return-loss bandwidth is about 54% (11.7–19.8 GHz), the 3 dB gain bandwidth is 42.3% (11.7–17.2 GHz), and the 3 dB axial-ratio bandwidth is about 29.3% (12.4–16.8 GHz). The overlapped bandwidth of the three is 29.3%, and the maximum CP gain is 11.45 dBic at 14 GHz. A gain enhancement of about 2.1–5.2 dB is achieved as compared with the unloaded type. This method is a good option to design antennas in satellite communication with the merits of wide CP bandwidth.

Compact Ultra-Wideband Monopole Antennas Using Novel Liquid Loading Materials

An ionic liquid (IL) is used to make antennas for the first time. Unlike water, the proposed material has a large liquid range (-69.8 °C-350 °C), a relative permittivity of 3, an extremely low dielectric loss, and very stable thermophysical material properties. It can be used for liquid dielectric resonator antennas (DRAs) or as a loading material for performance enhancement. Importantly, the proposed liquid loading scheme is relatively simple and of low cost, but it can markedly improve the antenna performance. As design examples, a liquid-loaded wideband linearly polarized (LP) monopole antenna with an omnidirectional radiation pattern is first presented. Then, the LP antenna is modified to a wideband circularly polarized (CP) antenna with boresight radiation. These antenna examples demonstrate a frequency coverage of 1.25-5 GHz, a wide CP bandwidth, a relatively high gain (>4 dBi), high radiation efficiency >85%, and an electrical size of 0.42 λ 0 x0.42λ 0 x0.17λ 0 . The experimental results show that the liquid loading works well under a wide range of temperatures. It effectively reduces the antenna electrical size by 40% and improves the impedance matching by 5 dB. Therefore, the proposed liquid loading scheme can be applied to a variety of antenna/RF designs.

Reconfigurable, Wideband, Low-Profile, Circularly Polarized Antenna and Array Enabled by an Artificial Magnetic Conductor Ground

A reconfigurable, wideband, and low-profile circular polarization (CP) antenna is presented. Its wideband CP reconfigurability is realized by incorporating RF switches into a cross-bowtie radiator. A compact, wide bandwidth, and polarization-independent artificial magnetic conductor ground plane is developed to minimize the overall profile of the antenna while maintaining its wide bandwidth. The simplicity of this single-element design facilitates the realization of a reconfigurable, wide bandwidth CP array that achieves higher directivity without changing its overall profile. Prototypes of the single element and of a $1 \times 4$ array of these elements were fabricated and tested. The measured results for both prototypes are in good agreement with their simulated values, validating their design principles. They are low profile with a height $\sim 0.05\lambda _{\mathrm {\mathbf {0}}}$ . The array exhibits a wide fractional operational bandwidth: 1.65 GHz (21.7%), and a high realized gain: 13 dBic. Since they would enhance their channel capacity and avoid polarization mismatch issues, these reconfigurable CP antenna systems are very suitable for modern wireless systems.

A dual-band CP dual-orthogonal arms monopole antenna with slanting edge DGS for C-band wireless applications

This communication describes a novel design of circularly-polarized (CP) monopole antenna for dual-band performance. The proposed design offers an impedance bandwidth (IBW) of 3.7 GHz in the frequency range 2.9–6.6 GHz in the lower band and 1 GHz (7.7–8.7 GHz) in the upper band. Proposed antenna has a wide CP (3 dB axial-ratio) bandwidth of 2.42 GHz (46.6%) in lower band (4.08–6.5 GHz) and 300 MHz in upper frequency band (8.1–8.4 GHz). The CP bandwidth is achieved through dual orthogonal arms and slanting edge defected ground structure (DGS). Proposed antenna is suitable for the C-Band wireless applications including WLAN, Wi-MAX communication systems.

Compact, Highly Efficient, and Fully Flexible Circularly Polarized Antenna Enabled by Silver Nanowires for Wireless Body-Area Networks.

A compact and flexible circularly polarized (CP) wearable antenna is introduced for wireless body-area network systems at the 2.4GHz industrial, scientific, and medical (ISM) band, which is implemented by employing a low-loss composite of polydimethylsiloxane (PDMS) and silver nanowires (AgNWs). The circularly polarized radiation is enabled by placing a planar linearly polarized loop monopole above a finite anisotropic artificial ground plane. By truncating the anisotropic artificial ground plane to contain only 2 by 2 unit cells, an integrated antenna with a compact form factor of 0.41λ0 × 0.41λ0 × 0.045λ0 is obtained, all while possessing an improved angular coverage of CP radiation. A flexible prototype was fabricated and characterized, experimentally achieving S 11 <- 15dB, an axial ratio of less than 3dB, a gain of around 5.2dBi, and a wide CP angular coverage in the targeted ISM band. Furthermore, this antenna is compared to a conventional CP patch antenna of the same physical size, which is also comprised of the same PDMS and AgNW composite. The results of this comparison reveal that the proposed antenna has much more stable performance under bending and human body loading, as well as a lower specific absorption rate. In all, the demonstrated wearable antenna offers a compact, flexible, and robust solution which makes it a strong candidate for future integration into body-area networks that require efficient off-body communications.

Inverted-S Antenna With Wideband Circular Polarization and Wide Axial Ratio Beamwidth

A novel broadband circularly polarized (CP) antenna with wide axial ratio (AR) beamwidth is proposed. It is composed of two curved arms shaped like an inverted “S.” The mechanisms of wideband CP operation and wide AR beamwidth are explained. To validate the concept, a prototype at C-band is manufactured and measured. Experimental results confirm that the antenna achieves an impedance bandwidth of 63% and a CP bandwidth of 42%. Furthermore, maximum AR beamwidth of 140° is achieved and wide AR beamwidth can be maintained in a frequency bandwidth of 35% in nearly all elevation planes. In addition, the antenna has the advantage of being easily extended to arrays. A four-element array using the proposed antenna is investigated through both simulations and experiments, and achieves 60% CP bandwidth and wide AR beamwidth. The proposed inverted-S antenna can realize wide CP bandwidth and wide AR beamwidth, and can easily form wideband CP arrays.

Polarization conversion of metasurface for the application of wide band low-profile circular polarization slot antenna

In this letter, based on a corner-cut square metasurface, a planar polarization conversion structure is presented and the application for wide band low-profile circular polarization (CP) slot antenna is proposed. The mechanisms for achieving the CP state from a linearly polarized incident wave and for broadening the working bandwidth of conventional slot antenna are analyzed theoretically. The wide band low-profile CP slot antenna is achieved with numerical optimizations and parameter studies. Both simulations and measurements are performed to demonstrate the proposed antenna, and good agreements are obtained. Such results will open the path for polarization conversion metasurfaces used in the CP antenna area.

Circularly Polarized Microstrip Yagi Array Antenna with Wide Beamwidth and High Front-to-Back Ratio

A circularly polarized (CP) Microstrip Yagi array antenna (MSYA) is designed in order to achieve high front-to-back ratioR(F/B)and high gain over wide range in the forward radiation space. A Wilkinson power divider owning two output ways with the same magnitude and different phase is used to feed the antenna. Parametric studies are carried out to investigate the effects of some key geometrical sizes on the antenna’s performance. A prototype of the antenna is fabricated, and good agreement between the measured results and the numerical simulations is observed. The overlap bandwidth of VSWR ≤ 1.5 and AR ≤ 3 dB is about 11%. The steering angle (α) between the peak gain direction and the broadside can achieve 35°,R(F/B)reaches 19 dB, and the gain at the front point (G0) is only 4.3 dB lower than the maximum gain (Gm). The antenna has a wide beamwidth CP radiation pattern over wide spatial range including 0° ≤θ≤ 90° in vertical plane and −35° ≤φ≤ 55° in horizontal plane.

A Single-Point-Fed Wideband Circularly Polarized Rectangular Dielectric Resonator Antenna

A single-point-fed circularly polarized (CP) rectangular dielectric resonator antenna (DRA) with wide CP bandwidth is presented. By usingTE111andTE113modes of the rectangular DRA, a wideband CP performance is achieved. The coupling slot of the antenna contains a resistor loaded monofilar-spiral-slot and four linear slots. Design concept of the proposed antenna is demonstrated by simulations, and parameter studies are carried out. Prototype of the proposed antenna was fabricated and measured. Good agreement between the simulation and measurement is obtained. The measured impedance bandwidth (|S11|&lt;-10 dB) and 3 dB axial-ratio (AR) bandwidth are 51.4% (1.91–3.23 GHz) and 33.0% (2.15–3.00 GHz), respectively.

Size reduction of circularly polarized slot antenna using open C-slot for WiMAX application

A new wideband circularly polarized (CP) open C-slot antenna fed by a microstrip line for size reduction is presented. The proposed antenna consists of an open C-slot with a straight slit on the ground plane, and a microstrip line with a semicircle-shaped patch on the other side of the substrate. The antenna size is reduced by about 35% compared with the circular slot antenna. By using the semicircle-shaped patch to disturb the magnetic current distribution on the open C-slot, a wider CP bandwidth can be achieved. The measured results show that the proposed antenna can provide a 3 dB axial ratio (AR) bandwidth of 40% (4.1–6.2 GHz) and a 10 dB return loss impedance bandwidth of 107% (2.3–7.6 GHz). The measured gain variation is from 2.8 to 4.3 dBic in the 3 dB AR bandwidth. A prototype of the proposed antenna has a simple and compact size of 30 × 55 × 1.6 mm3.

Compact Circularly Polarized Composite Cavity-Backed Crossed Dipole for GPS Applications

In this paper, we present a circularly polarized (CP) composite cavity-backed crossed dipole antenna for global positioning system (GPS) applications. We produce the CP radiation by crossing two dipoles through a <TEX>$90^{\circ}$</TEX> phase delay line of a vacant-quarter printed ring, which also has a broadband impedance matching characteristic. Two techniques, insertion of meander lines in the dipole arm and arrowhead-shaped trace at its end, are employed to reduce the sizes of the primary radiation element. The compact radiator is backed by a cavity reflector to achieve a wide CP radiation beamwidth. The proposed antenna exhibits a measured bandwidth of 1.450~1.656 GHz for a voltage standing wave ratio (VSWR) < 2 and 1.555~1.605 GHz for AR < 3-dB. At 1.575 GHz, the antenna has a gain of 7 dBic, a frontto-back ratio of 27 dB, AR of 1.18 dB, and 3-dB AR beamwidths of <TEX>$130^{\circ}$</TEX> and <TEX>$132^{\circ}$</TEX> in the x-z and y-z planes, respectively.

Broadband CPW-fed circularly polarized antenna with machine-gun-shaped feeding line and symmetric-aperture

This paper presents a new design for wide slot circularly polarized (CP) antenna (WSCPA). Compared with existing WSCPA, the proposed design possesses much wider return loss S11 bandwidths and CP bandwidths. The main features of the antenna structure include a machine-gun-shaped CPW feeding line and a wide symmetric-aperture along the diagonal axis. Wideband return loss and CP radiations have been achieved by properly tuning circular-shaped aperture and feeding line. The measured bandwidths of 10 dB return loss and 3 dB axial ratio (AR) are around 110.2% (2.2-7.6 GHz) and 105.9% (2- 6.5 GHz), respectively. Throughout this letter, the improvement process of the AR and S11 properties is completely presented and discussed.

Circularly Polarized Cross-Slot-Coupled Stacked Dielectric Resonator Antenna for Wireless Applications

This paper presents a stacked cylindrical dielectric resonator antenna with wide circular polarization (CP) bandwidth (axial ratio < 3dB) of 16.0%. This wide CP bandwidth is achieved by stacking low permittivity dielectric (9.2) resonator on high permittivity dielectric (9.8) resonator to obtain improved impedance and axial ratio bandwidths as compared to conventional DRA. It is also shown that the asymmetrical structure used in the geometry results in a very high impedance bandwidth (more than 100%) in the frequency range of 2.1 GHz-12.0 GHz but at the expense of distorted CP operation on the off-broadside. This essentially covers the FCC band of operation (3.1GHz to10.6 GHz).

A Novel Circularly Polarized Microstrip Antenna With Two Connected Quasi Monopoles for Wideband Applications

A novel microstrip antenna with an interesting radiation structure and L-shaped ground plane is presented to generate a wideband circular polarization (CP) characteristic. For this purpose, the radiation structure comprises of two truncated monopole resonators, connected to each other by a microstrip link. By adjusting the position of the link between the resonators, CP quality and bandwidth can be controlled. A single microstrip line is employed to feed one of the monopoles, and the other monopole is only matched by a proper chip resistor. Two triangle sections are also sliced from the other radiation edges to improve the impedance and CP characteristics. Moreover, because of the symmetric design of the antenna, a high purity between the right- and left-handed CP patterns and wide CP beamwidth are achieved. The antenna is fully studied and manufactured that its results are 53% (1.69~2.92 GHz) for 3-dB axial-ratio bandwidth, 62% (1.68~3.2 GHz) for 10-dB return-loss bandwidth, and gain range between 2 and 4.2 dBi across the CP band.

UWB monopole antenna with circular polarization

AbstractIn this article, ultra‐wideband (UWB) monopole antenna with circular polarization (CP) is designed and implemented. The proposed antenna consists of an asymmetric shaped radiator fed by a microstrip line and a limited ground plane on the back side of the substrate. The overall size of proposed antenna is 28 mm × 29 mm, which is suitable for mobile devices. The antenna is fabricated on inexpensive FR4 a dielectric constant of, loss tangent tan δ = 0.019 with thickness of 1.6‐mm. The measured results show that the proposed monopole antenna has a very wide bandwidth from 2.98 to 10.93 GHz that covers the UWB application range and defined by 10‐dB return loss. Furthermore, a very wide CP bandwidth of 3‐dB axial ratio bandwidth that ranges from 7.18 to 10.01 GHz is achieved. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:949–953, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26741