dB Axial Ratio Beamwidth Research Articles

A single-feed circularly polarized antenna with a low vertical profile and hemispherical axial-ratio beam coverage

ABSTRACT A novel wide axial-ratio beamwidth (ARBW) circularly polarized (CP) antenna with a single layer substrate fed by a single probe is proposed. It consists of an inner annular slotted radiator containing eight outer sector units with arc branches, a ground plane, and eight grounded vias. The antenna has an ARBW covering the upper hemisphere and has a low vertical profile. The ultra-hemispherical ARBW is formed by ingeniously merging the endfire omnidirectional CP radiation pattern with the boresight CP radiation pattern. The two radiation patterns can be excited by a central coaxial probe without an additional feeding network. An antenna prototype of dimensions 1.15 × 1.15 × 0.02 (λ 0 3) is fabricated and measured to validate the design concept. Measured results show that the impedance bandwidth of the proposed antenna is 2.0% (3.328–3.394 GHz) and the 3 dB axial ratio (AR) bandwidth is 1.3% (3.332–3.374 GHz). The 3 dB AR beamwidth can cover more than 217° and the maximum gain is 0.79 dBic at 3.35 GHz. A good agreement between the simulated and measured results is obtained.

Two-dimensionally high AR performance beam scanning utilizing randomly-rotated single-PIN-diode elements for circularly-polarized programmable metasurface

In this paper, we introduce a novel technique that utilizes randomly rotated elements (RREs) for the cross-polarization and axial ratio (AR) control of a circularly polarized programmable metasurface (CPPMS). We evaluate the CPPMS performance by comparing RREs layout with uniform elements (UEs) layout, and analyze far-field radiation parameters for 50 groups of CPPMS with different RREs layouts. Simulation results demonstrate consistent and improved performance across various RREs layouts, showcasing reduced cross-polarization and enhanced AR beamwidth. To validate these findings, we design a 1-bit CPPMS in Ku-band comprising 20 × 20 elements with the optimal RREs layout, and conduct measurements in an anechoic chamber. The CPPMS prototype achieves high gain (22.34 dBi), low cross-polarization (-20.5 dB), and a narrow 3 dB AR beamwidth (8.93°). Notably, it offers wide-angle beam scanning capabilities of up to ±60°. The gain bandwidth at -3 dB ranges from 14.54 to 16.65 GHz, with a relative bandwidth of 7.3%, while the 3 dB AR bandwidth extends from 14.24 to 16.07 GHz. Consequently, the proposed 1-bit CPPMS exhibits high-performance two-dimensional AR beam scanning, presenting promising applications in satellite communications.

Dual-band circularly polarized asymmetric dipole array antenna for GPS L1 and L2 bands

A dual-band, circularly polarized (CP) asymmetric dipole array antenna for Global Positioning System (GPS) applications with a wide beam is presented in this paper. The proposed antenna comprises two different-sized printed crossed dipoles with integrated baluns fed by an asymmetric feeding network to achieve dual-band functionality. Using two branch-line couplers with different dimensions in the feeding network performs Right-Hand Circular Polarization (RHCP) operation at GPS L1 and L2 bands. According to the experiments, the proposed antenna has wide impedance bandwidths of 24.82% (1139.5–1462.4 MHz) and 14.82% (1500.4–1740.5 MHz), and 3 dB Axial-Ratio (AR) bandwidth of 37.4% (1132.3–1653.2 MHz) to cover the GPS L1 and L2 bands. Furthermore, at 1227 MHz frequency, the antenna has a gain of 4.65 dBic, and a 3 dB AR beamwidth of 148.2° facing the sky. Also, at 1575 MHz frequency, a gain of 5.25 dBic and a 3 dB AR beamwidth of 139.3° are achieved.

Axial ratio beamwidth enhancement of a low-profile circularly polarized antenna using defected ground structures

AbstractThis article explores the possibilities of incorporating a defected ground structure (DGS) for widening the 3 dB axial ratio beamwidth (ARBW) of a simple low-profile planar circularly polarized (CP) antenna. Two pairs of DGSs are etched symmetrically along the diagonals of the ground plane to overcome the limited 3 dB ARBW performance of a crossed-slotted circular-shaped planar CP antenna. Here, one pair of DGSs is orthogonal to another pair of DGSs. The distance between the pairs of DGSs plays a key role in enhancing the 3 dB ARBW by 40.62%. A gap of 0.18λ0 is considered between the DGSs to maintain the symmetrical electric field distribution in the substrate. It also helps to reduce orthogonal current components and provides uniformly distributed patch surface currents. These phenomena collectively help the proposed CP antenna to exhibit right-handed circular polarization radiation with the 3 dB ARBW of 186° and 188° in the E-plane and H-plane, respectively. The measured results yield impedance bandwidth (S11 ≤ −10 dB) of 2.6% (2.283–2.342 GHz), CP bandwidth of 0.9% (2.294–2.315 GHz), gain higher than 4.8 dBic, and total antenna efficiency more than 64% across the entire CP band.

Broad axial ratio bandwidth circularly polarized with wide angle coverage planar monopole antenna

A G-shaped circularly polarized broad axial ratio bandwidth (ARBW) and high gain monopole antenna is proposed. The proposed design is imprinted on low cost, lossy FR4 substrate with relative permittivity 4.4 and loss tangent 0.025. The physical dimension of the proposed antenna is 0.36λ0×0.39λ0×0.02λ0. The G-shaped patch is developed by modifying conventional monopole radiator to create circular polarization (CP) for strong horizontal and vertical current components. The stubs, L – shaped, and T-shaped parasitic strips (PSs) are loaded at the finest positions on the ground layer of the antenna to improve the performance of ARBW and gain. The achieved percentage impedance bandwidth (IBW), ARBW, angle coverage and gain are 106%, 97%, 102° (3 dB axial ratio beam width from −46° to + 56° in XZ – plane) at 4.26 GHz and 5 dBic respectively. The fabricated antenna is reliable for IEEE standard WLAN and broadband wireless communication system.

Circularly Polarized Corporate-Feed Beam-Scanning Array With Low Profile

A low-cost low-profile circularly polarized (CP) corporate-feed beam-scanning array is presented. As the main part of the feed network, we found that the sidewall reflection of the parallel plate waveguide (PPW) is the major reason for the deterioration of the beam-scanning performance at large angles. Therefore, a hybrid feed network composed of PPW and substrate integrated waveguide (SIW) is proposed. Mechanical beam-scanning is realized by a planar parabolic reflector-based line source generator (LSG). To expand the beam-scanning range, an SIW delay line-based phase compensation structure is introduced after theoretically analyzing the phase deviation generated by the LSG. The CP radiation is realized by improved CP antenna elements with a wide 3 dB axial ratio (AR) beamwidth. These CP antenna elements are fed by a corporate-fed network to avoid the frequency-dependent squint beam. A K-band prototype of an <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$8\times14$ </tex-math></inline-formula> array is fabricated and measured to verify the design. According to the measured results, the beam-scanning range of 0°–51° in elevation with the peak gain of 22.3 dBi is realized. The gain variation and ARs in this scanning range are less than 2.9 and 2.5 dB, respectively.

A reconfigurable polarization converter and related application as horn antenna cladding

In this paper, a transmissive reconfigurable polarization converter (RPC) based on an active metasurface is proposed, which can regulate the ideal plane wave and the spherical wave as a cladding of the horn antenna. The metasurface unit is composed of a single-layer F4B dielectric substrate and two double-cross metal strips with a p–i–n diode on the top and seven vertical metal strips on the bottom. One RPC prototype with 15 × 15 units has been fabricated and measured when it regulates an ideal plane wave. By controlling the states of diodes, the RPC can realize the linear-to-circular polarization conversion (LCPC) or the linear polarization maintaining (LPM) function from 2.5 to 3.64 GHz. Furthermore, the RPC is used as the cladding of a horn antenna for high integration in practical applications. The measured results show that this RPC-antenna system can still achieve LCPC or LPM function from 3.1 to 4.5 GHz. It is worth mentioning that the 3 dB axial ratio beam width of RPC can cover from −65° to 65° in LCPC. The proposal has advantages of a wideband, simple biasing network, and easy fabrication and integration, which can be widely applied in modern wireless communication systems.

A Dual Circularly Polarized SIW-Fed Phased Array Antenna With Wide-Angle Beam Scanning Range

We propose a dual circularly polarized (CP) substrate integrated waveguide (SIW) cavity-backed antenna with wide axial ratio (AR) beamwidth, which can generate the right-hand CP (RHCP) or left-hand CP (LHCP) radiation through exciting different ports. Dual CP radiations are accomplished by an SIW directional coupler (DC) in the bottom layer, which provides the desired amplitude and phase conditions for two orthogonal slots. By superposing phase centers of linearly polarized (LP) electric field elements, the proposed antenna achieves a good performance of 3 dB AR beamwidth of 165° in the desired azimuth cut plane. Furthermore, an eight-element dual CP linear phased array with a wide-angle beam scanning ability is comprised by this antenna prototype. Numerical and measured results show that the array antenna can scan its main lobe from – 59° to 58°. In general, the proposed antenna array fed by the SIW structure satisfies the requirement of a multipolarization wireless communication system for low profile, simple structure, and easy integration with planar circuits.

Novel series fed dual band circular polarization antenna for navigational satellite system

A novel series fed dual band stacked microstrip patch antenna (SMPA) offering circular polarization (CP) over wide beam is proposed for Indian regional navigation satellite system (IRNSS). The antenna is designed to function at far apart dual frequencies 1.176 GHz (L5 band) and 2.492 GHz (S band) intended for the receiver terminals of IRNSS system. The dual band performance with large frequency ratio (about 1:2.1) has been obtained by two stacked patches with an air layer between them. The square notches at the corners along the diagonal of lower square patch, one sided corner truncation along the diagonal of upper square patch and feeding along central axis is used to obtain CP (with axial ratio &lt; 2) at both the operating bands. The square patches are excited with novel series feed technique. The proposed novel antenna has been designed, simulated and developed to meet the stringent design requirements for IRNSS navigation system. The antenna has achieved an impedance bandwidth of 2.6% and 2.2% at L5 and S band frequency respectively. It possesses positive gain beamwidth of 120and 3 dB axial ratio beamwidth of 120 ◦ and 60 ◦ at L5 and S band frequencies respectively.

Smart antenna with circular polarization for high accuracy indoor localization system

This article presents a new switched beam antenna (SBA) for indoor localization applications. The SBA consists of seven circularly polarized (CP) element antennas using a novel feeding network. The attractive characteristics of the proposed CP antenna are high gain, wide bandwidth (BW) with the BW of 36.2% at the reflection coefficient less than −10 dB (4.6–6.7 GHz), the 3 dB axial ratio (AR) BW of 22.4% (5.4–6.7 GHz), wide 3 dB AR beamwidth as about 60 degrees, and maximum gain of 9 dBi within the total bandwidth. Experimental results show good agreement with simulated ones in terms of radiation pattern, AR, and reflection coefficient. We proposed a low-cost and simple RF-based indoor localization system based on a single anchor node equipped with this SBA. The system is demonstrated through experimental validations in a 6 m × 6.5 m × 3.5 m office room with a mean localization error of 0.72 m.

Hemispheric Conformal Wide Beamwidth Circularly Polarized Antenna Based on Two Pairs of Curved Orthogonal Dipoles in Space

A wide axial-ratio beamwidth (ARBW) and half-power beamwidth (HPBW) circularly polarized (CP) antenna is realized by arranging two curved patch dipole pairs orthogonally in a cruciform contour that conforms with a hemispheric shell. First, two orthogonal curved dipole pairs are designed via step-by-step investigation of the evolution of traditional crossed dipoles. Then, an antenna with a wide CP working bandwidth and wide ARBWs and HPBWs is developed by enlarging the diameter of the curved arms, replacing the narrow arms with the wide patches and making these patches conformal with the shell surface; this improves the impedance bandwidth (IBW) and further reduces the antenna’s size. Finally, a prototype with reduced dimensions of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.52\times 0.52\times0.15$ </tex-math></inline-formula> ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\lambda _{0}^{3}$ </tex-math></inline-formula> ) is designed, fabricated, and measured. The resulting antenna exhibits a −10 dB IBW of 55.8% (1.06–1.89 GHz) and a 3 dB AR bandwidth of 70.9% (1–2.1 GHz), within which the ARBW and HPBW reach maximum values of 202°/196° and 113°/111° in the two orthogonal principal planes at 1.602 and 1.268 GHz, respectively. Furthermore, a 3 dB ARBW exceeding 100°, an HPBW exceeding 96°, and efficiency exceeding 60% are acquired within the 1.252–1.89 GHz (40.6%) target service coverage band.

Dual-Sense Circularly Polarized Antenna With a Dual-Coupled Line

This letter presents a dual-sense circularly polarized (CP) microstrip patch antenna with a dual-coupled line. The rectangular patch antenna operating in TM01 mode is utilized as a basic design, and a single-coupled line is introduced to excite the TM10 mode with a phase difference of 90°, generating CP operation. As different polarizations can be obtained by changing the position of the single-coupled line, a dual-coupled line is introduced to the rectangular patch antenna to excite two CP modes with different polarizations. The prototype of the dual-band dual-sense CP antenna is fabricated and measured. The measured results illustrate that the dual-sense CP antenna obtains a wide impedance bandwidth of 7.95% and dual axial ratio (AR) bandwidth of 0.33% for the left-hand circular polarization (LHCP) and 0.72% for the right-hand circular polarization (RHCP). Furthermore, the antenna has a wide 3 dB axial-ratio beamwidth and a small frequency ratio of 1.04.

A novel analytical model for a circularly-polarized, ferrite-based slot antenna by solving an integral equation for the electric field on the circular slot

We propose and analyze a circularly polarized slot antenna built on a ferrite substrate which is saturated normal to its plane and metalized on both sides. The antenna is built by etching a circular slot in the top metal layer. The antenna operates in the frequency range where the effective permeability of ferrite is negative. An accurate analytical model is derived for the antenna by solving the integral equation for the electric field on the circular slot. The results obtained are in good agreement with numerical simulations. Using the analytical results, a practical antenna is designed that uses a microstrip feed line. For an antenna with inner and outer radii of 4.9 and 5.9 mm, the results show a 3 dB axial ratio (AR) beam width of 2000 which is highly desirable in mobile or fixed satellite communication systems such as GPS. Furthermore, the operating frequency can be tuned in the 3.78–3.98 GHz range by changing the magnetic bias field from 15 to 30 kA/m. Compared to other CP antennas, our proposed antenna is compact, has at least twice 3-dB AR beamwidth (2000), and is tunable.

An L-Shaped Slot Circularly Polarized Patch Antenna for Wireless Communication

A circular-polarized patch antenna with compact size operating at 2.3 GHz band is presented. The antenna utilizes L shaped slot in the radiator in order to achieve circularly polarized radiation pattern. The prototype of the antenna is fabricated and is fed by a 50Ω strip line. The antenna achieves a symmetrical radiation pattern around zenith. The measured impedance bandwidth of |S11| less than -10dB is from 2.3GHz to 2.35GHz and is in good agreement with simulation results. The antenna achieves better cross-polarization isolation of -19 dB and wider 3dB axial ratio beamwidth (ARBW) of -50 ‍ o≤ARBW≤45 ‍ o at its resonating frequency. The antenna finds application in modern wireless communication system.

Low-Profile Circularly Polarized Patch Antenna With Wide 3 dB Beamwidth

In this letter, a low-profile circularly polarized (CP) narrow-slots slotted-patch antenna for wide 3 dB axial-ratio beamwidth (ARBW) performance is presented. It consists of two pairs of narrow slots along the diagonal lines of a square patch with a single feed. These pairs of narrow slots are conceived and placed to serve as magnetic dipoles with quarter-wavelength separation, forcing the amplitude of the orthogonal electric field components to be equal across a wide angle. The 3 dB ARBW of the CP antenna is a strong function of the mutual magnetic field, which is feasible to alter with different parameters of the slot. The location, dimensions, and gap between the slots are tuned to achieve wide 3 dB ARBW. Measured results of the fabricated prototype exhibit 3 dB ARBW of 226° with ARmin of 0.52 dB and 198° with ARmin of 1.61 dB in two principal planes at $\boldsymbol{\varphi } = \text{0}^\circ $ and $\boldsymbol{\varphi } = \text{90}^\circ $ , respectively. The antenna offers impedance bandwidth of 85 MHz (2.448–2.533 GHz) and CP bandwidth (CPBW) of 23 MHz (2.474–2.497 GHz). The minimum peak gain is 3.87 dBic in the broadside direction.

Single‐feed microstrip antenna for wide angle circular polarisation with six metal columns

A circularly polarised microstrip antenna with a wide beamwidth and wide axial ratio (AR) beamwidth is presented. The antenna is mainly composed of a dielectric substrate, a single-feed patch, a reduced ground, and six metal columns. The reduced ground and six metal columns are primarily used to broaden the radiation beamwidth and improve the AR performance of the wide angle. According to the measured results, the antenna achieves a bandwidth of 3.78% from 7.78 to 8.08 GHz with an AR 10 dB. In addition, half-power beamwidth of 211° × 209° and 3 dB AR beamwidth of 222° × 239° at 8.0 GHz are observed. The antenna is a single-feed type with a simple structure and no additional feed network, which can be extended to some wide beamwidth and wide AR beamwidth applications in the X-band, even higher than the Ku-band.

Pair of diagonal slots loaded low‐profile circularly polarised patch antenna with wide 3 dB axial ratio beamwidth

A low-profile circularly polarised (CP) antenna with wide 3 dB axial ratio beamwidth (ARBW) is proposed in this study. The possibilities of widening the 3 dB ARBW of single diagonal slot-loaded conventional CP antenna have been explored successfully by incorporating a pair of rectangular slots along the diagonal line of a square patch antenna. The design parameters and the symmetrical arrangement of this pair of slots across the centre of the patch are crucial to adjust and achieve the wide 3 dB ARBW with high CP purity. Coupling between the two diagonal slots provides nearly equal E θ and E φ radiation patterns over a large angular range, and hence the 3 dB ARBW has been enhanced by 85.71 and 55.4% for φ = 0° and φ = 90° planes, respectively, in comparison to the conventional slot-loaded CP antenna. The minimum 3 dB ARBW of 208° and a maximum of 230° have been achieved across different planes of radiation φ = 0°, 45°, 90°, and 135° with a minimum axial ratio of 0.20 dB only. The absolute planar antenna of size (0.29 × 0.29 × 0.013)λ0 3, where λ0 is the free-space wavelength corresponding to the CP frequency, has been fabricated and tested. The measured and simulated results show fair consistency to each other.

Wideband Inhomogeneous-Polarizer Loaded Circularly Polarized SIW Horn Antenna for Broadband Millimeter-Wave Applications

An inhomogeneous-polarizer loaded substrate integrated waveguide (SIW) horn antenna is proposed to obtain wideband circularly polarized (CP) radiation. First, by introducing extended substrate and extra dielectric slabs around the horn radiating aperture, broadband impedance matching of the SIW horn can be realized. Then, a pure dielectric near-field CP polarizer is designed and placed in front of the horn to obtain broadband CP radiation. The polarizer is designed to feature inhomogeneous property for different polarization orientation illuminations. With this property, 90° phase difference for a pair of orthogonal linearly polarized waves can be realized. Two methods are utilized to analyze the inhomogeneous property of the polarizer and to provide detailed parameter estimation steps/formulas. The effects of polarizer size and oblique incidence are also studied, and a very wide 3 dB axial-ratio beamwidth of 104° is achieved. Measured results indicate that the proposed CP SIW horn can obtain a matching bandwidth greater than 40% (22–34 GHz) and a CP radiation bandwidth of 30% (22–29.8 GHz). Simple structure and wideband CP performance make it an attractive candidate for broadband millimeter-wave applications.

A Novel Coplanar-Strip-Based Excitation Technique for Design of Broadband Circularly Polarization Antennas With Wide 3 dB Axial Ratio Beamwidth

In this communication, a novel excitation technique for the design of a single-point-fed compact low-profile wide-slot antennas with broadband circular polarization (CP) and wide 3 dB axial ratio (AR) beamwidth is presented. Two inverted L-shaped parasitic strips placed coplanar to the microstrip line of an asymmetric coplanar waveguide (CPW) and a horizontal strip that protrudes from the vertical edge of the backside ground plane of the substrate are used for CP excitation. The overall footprint of the structure is only $L_{s} \times W_{s} = 0.3\lambda _{0} \times 0.28\lambda _{0}$ when measured at the lowest operating frequency. The antenna prototype has been experimentally validated. The measured results indicate that a wide impedance bandwidth of 72% (2.26–4.85 GHz) and a CP bandwidth of 66% (2.44–4.87 GHz) can be achieved. In addition to the wideband characteristics in terms of the impedance bandwidth and CP, a stable bidirectional radiation pattern with a wide 3 dB beamwidth of 85° ± 5° is obtained for 58% of the total CP bandwidth without involving any complex circuitry. Furthermore, by placing a flat metallic reflector behind the antenna, a unidirectional radiation pattern is produced without changing the geometrical dimensions of the proposed antenna. The average realized gain of the antenna without a reflector is 3.3 dBi, whereas it increases up to 6.3 dBi with the substrate-size reflector.

A Broadband Wide-Beam Circularly Polarized Antenna Array for Urban Macrocell Base Stations

An eight-element broadband wide-beam circularly polarized (CP) antenna array is developed for mobile wireless communications. The CP antenna element consists of two rectangular loops with gaps for circular polarization and parasitic elements for bandwidth enhancement. A wide beamwidth is achieved in the horizontal plane because the CP antenna elements have a narrow cross section in the plane. The CP antenna array also has higher isolation between antenna elements than a linear polarized (LP) array with the same element space, which is due to the polarization mismatch caused by the currents in the CP antenna elements. The eight-element CP antenna array achieves a bandwidth of 40% (1.7–2.55 GHz) for return loss >15 dB and a bandwidth of 47% (1.67–2.7 GHz) for axial ratio (AR) < 3 dB. The half-power beamwidth and the 3 dB AR beamwidth in the horizontal plane are ~65° ± 8° and approximately 100°, respectively. The antenna gain for the array is about 17 dBi. The CP antenna array is suitable for applications in urban macrocell base stations.