dB Axial Ratio Beamwidth Research Articles

Circularly Polarized Multibeam Antenna Array of ME Dipole Fed by 5 × 6 Butler Matrix

A circularly polarized multibeam antenna array based on magnetoelectric (ME) dipole is proposed, which is fed by a substrate integrated waveguide 5 × 6 Butler matrix. There are two points that are key to completing the design—the wide axial-ratio (AR) beamwidth antenna element and the appropriate beamforming network. By adjusting the shape of the radiation patch of ME dipole, the amplitude of the orthogonal field becomes flatter at a wide angle, and the phase difference is maintained at 90°; hence, an antenna element with a wide 3 dB AR beamwidth can be achieved. In order to ensure the generation of normal beam, a 5 × 6 Butler matrix using the 3 × 3 Butler matrix is selected as the beamforming network. The proposed structure operates in the range of 27.5–28.5 GHz and generates five circularly polarized beams that cover the range of ±40°. The gain of all these beams is approximately 12.5 dBi.

Design of Rhombus-Shaped Slot Patch Antenna for Wireless Communications

A single feed circularly polarized patch antenna is presented. The antenna consists of a rhombus-shaped slot incorporated in the radiating patch at its center. The antenna is designed to operate at 2.3 GHz band. The antenna achieves left-hand polarization or right-hand polarization based on the orientation of the slot in the radiating patch. The antenna parameters are synthesized using a high-frequency structure simulator and its characteristics are validated by the Agilent network analyzer (N9925A) and antenna test systems. The measured results obtained agree with simulated results and show that the antenna achieves −10 dB impedance bandwidth of 85 MHz (2.27 GHz–2.355 GHz) for left-hand polarization and 85 MHz (2.26 GHz–2.345 GHz) for right-hand polarization. The antenna gives a 3 dB axial ratio beamwidth of 95°(−35° ≤ AR ≤ 60°) for both left-hand polarization and right-hand polarization along with better 3 dB axial ratio bandwidth of 140° in the operating band. The antenna also achieves a good cross-polarization isolation of −17 dBic for both left-hand and right-hand polarization at its operating frequency. Hence, the antenna is best suited for modern wireless communication systems.

Design of crescent slot circularly polarised patch for 4G wireless communications

A single fed circularly polarised patch antenna operating at 4G long term evolution (LTE) is proposed. The antenna is excited by means of 50 Ω coaxial cable placed near to edge of the patch element. In order to achieve circular polarisation, a crescent-shaped slot is incorporated in the radiating element which perturbs the surface current fields on the radiating patch element. Based on the slot orientation, the antenna radiates either left-hand or right-hand polarisation. The shape of the crescent slot and position of feed point are tuned to improve 3db axial ratio beam width of the antenna. The antenna parameters are characterised using Ansoft high frequency structure simulator and further, parametric analysis on antenna dimensions are carried and its effects on antenna performance are discussed. The antenna attains −10 dB impedance bandwidth (2.55 GHz to 2.6 GHz) in the 4G band and achieves a return loss of −16.06 dB with a peak gain of 5.94 dB at its operating frequency. The antenna also achieves wider axial ratio (AR) beam width of 1050 (AR ≤ −3 dB) and good cross-polarisation isolation of −17.93 dB which makes it more suitable for modern wireless communications.

Single Layer, Differentially Driven, LHCP Antenna With Improved Isolation for Full Duplex Wireless Applications

This paper presents a unidirectional, left handed circularly polarized (LHCP), single layered antenna array with improved interport isolation for simultaneous transmit and receive (STAR) or in-band full duplex (IBFD) wireless applications. The proposed IBFD antenna is comprised of three identical and sequentially rotated LHCP radiating elements where two Rx patches are symmetrically placed with respect to a single Tx patch. The symmetry of proposed antenna structure results in same amount of coupling or self interference (SI) from Tx element and differentially driven Rx patches achieve effective suppression of resulting SI to obtain improved Tx-Rx interport isolation required for STAR applications. The deployed feed network for differential-driven Rx operation is composed of a simple 3dB/180° rat-race coupler (ring hybrid coupler) with nice in-band amplitude and out-of-phase balance characteristics. The implemented single layer, compact (antenna elements and feeding network etched on single-layered PCB) antenna array achieves 10dB return-loss bandwidth ≥ 75MHz for both Tx and Rx ports. The prototype achieves ≥ 47dB interport isolation in 75MHz bandwidth and 3 dB axial ratio beam-width is ~ 60° for implemented antenna.

Enhanced 3 dB AR beamwidth metamaterial antenna for nanosatellite payload communication system

A compact dual-circular polarised metamaterial inspired antenna is proposed for nanosatellite payload communication. The antenna consists of two-layered stacked structure with a sandwich rectangular parasitic layer between two layers. Two double negative metamaterial cells. Two unit cells of DNG metamaterial structure are applied inside the pentagonal radiator to enhance 3 dB axial ratio (AR) bandwidth and beamwidth. Two orthogonal feedings are utilised to generate dual-circular polarisation (CP). The antenna achieves measured 710 MHz (3.06–3.77 GHz) of −10 dB impedance bandwidth with 160 MHz (3.02–3.18 GHz) and 210 MHz (3.05–3.26 GHz) of 3 dB AR bandwidth for port 1 and port 2, respectively. The 3 dB AR beamwidth of 165° for port 1 and 212° for port 2 is exhibited with an average realised gain of 5.15 dB. A 1U nanosatellite structure has been utilised to realise the antenna performance while operation in real-time environment.

A Low-Profile Wideband Circularly Polarized Crossed-Dipole Antenna With Wide Axial-Ratio and Gain Beamwidths

A low-profile wideband circularly polarized (CP) crossed-dipole antenna that has both wide axial-ratio beamwidth (ARBW) and half-power beamwidth (HPBW) is presented in this paper. The crossed dipoles are composed of four trapezoidal patch arms, and they are fed by a pair of vacant-quarter printed rings to generate CP radiation. Four identical parasitic elements that consist of a horizontal triangle patch and a vertical metallic plate are symmetrically intervened between the crossed dipoles and the ground plane. It has been found that the parasitic elements can effectively decrease the antenna profile, increase the operating bandwidth, and simultaneously enhance the ARBW as well as the HPBW. A prototype was fabricated and measured to verify the design. The measured results show that the prototype has a low profile of $0.1\lambda _{0}$ , a −10 dB impedance bandwidth of 78.3% and a 3 dB AR bandwidth of 63.4%. Moreover, a 3 dB ARBW of more than 120° and an HPBW of more than 110° are achieved simultaneously within a wide passband of 50.7%.

A low profile circularly polarized antenna with L-shape energy coupling slot and the S-shaped matched transmission line

ABSTRACTIn this paper, a novel low profile circularly polarized antenna with L-shape energy coupling slot and the S-shaped matched transmission line (SMTL) is presented. It consists of a monopolar radiator and a hexagonal radiator which will generate vertically and horizontally polarized electric field Eθ and Eφ, respectively. To satisfy the required magnitude/phase relationship between two radiators, the double L-shape energy coupling slot and the SMTL are introduced. Also, 12 circular shape patches are arranged sequentially on the hexagonal radiator to obtain a wide AR beamwidth. The measured results show that the realized antenna has an impedance bandwidth of 2.1% (5.76–5.88 GHz). In particular, the 3 dB Axial Ratio (AR) beamwidth at 5.8 GHz is extended to 212° (φ = 0° plane) and 217° (φ = 90° plane). Stable RHCP omni-directional radiation patterns are obtained over the operating bandwidth with a peak gain of 1.25 dBi. A good agreement between the simulated and measured results is obtained.

Single-Fed Wide-Beamwidth Circularly Polarized Patch Antenna Using Dual-Function 3-D Printed Substrate

This letter presents a novel single-fed microstrip patch antenna using three-dimensional (3-D) printed substrate for both circular polarization and wide 3 dB axial-ratio beamwidth (ARBW). Here, the substrate consisting of a photosensitive resin and air with a square mesh-grid structure is dual-function. On the one hand, the permittivity of the substrate in two orthogonal directions is tuned to be slightly different by inserting two resin chunks. Hence, the asymmetry of the substrate can split the two degenerate modes of the patch antenna so as to generate circularly polarized waves. On the other hand, the effective permittivity of the substrate can be freely controlled by the volume fraction of air, and thus influences the 3 dB ARBW. As a result, wide ARBW can be realized by properly configuring substrate through a 3-D printing process. A prototype is fabricated and measured. Measured results are found in reasonably good agreement with the simulated ones, exhibiting a 3 dB ARBW as wide as 120°.

A Novel Annular Slotted Center-Fed BeiDou Antenna With a Stable Phase Center

A novel annular slotted center-fed circularly polarized (CP) antenna with a stable phase center is proposed in this letter. Two symmetric annular slots with tabs are embedded onto a square microstrip patch for CP radiation. Good CP radiation and impedance matching is achieved by reasonably adjusting the radii of the annular slots and the position of the tabs. The symmetric structure brings about a very stable phase center. The proposed antenna can work in the compass satellite navigation system B1 band (1561.098 ± 2.046 MHz). The measured results show that the 10 dB return-loss bandwidth is 148 MHz, 9.24%, and the 3 dB axial-ratio (AR) bandwidth is 39.9 MHz, 2.5%. Moreover, the antenna has a wide 3 dB AR beamwidth of around 210°. The deviation of the phase center is about 0.91 mm at the central frequency. The measured results agree well with the simulated results.

Broadband printed quadrifilar helix antenna using parasitic strip technique

A circularly polarized (CP) printed quadrifilar helix antenna (QHA) with enhanced bandwidth is proposed in this communication. This QHA is fed by a feeding structure with superior performance, which uses wide-band 90° and 180° planar bulun. The feeding network can simply realize the 90° phase shift and four equal power divisions within a wide band range. Enhanced impedance matching and CP radiation characteristics can be achieved with the parasitic strips between helix arms. The study of proposed antenna performance with different geometric parameters has been conducted. The final antenna exhibits a good impedance bandwidth (IBW) of approximately 37.4% (1.65-2.41 GHz), and the 3-dB axial-ratio bandwidth (ARBW) is over 43.9% (1.6-2.5 GHz). Broad pattern coverage, pure CP radiation at all designed bands and a wide 3 dB axial-ratio beam width of 150° makes this antenna an excellent candidate for satellite communications and navigation systems.

Broadbeam Cross-Dipole Antenna for GPS Applications

A broadbeam cross-dipole antenna with improved low-elevation gain for global positioning system (GPS) applications is reported. The cross-dipole consists of two perpendicular dipoles, which are printed on two separate substrates that are vertically placed inside a cylindrical back cavity. Circularly polarized fields are generated by applying two quadrature signals with equal amplitude to the dipoles. To enhance the low-elevation gain, circular dipoles, curved ground planes, and corrugated back cavity are deployed in our design. A prototype operating in GPS L1 band (1.575 GHz) was designed with ANSYS HFSS, and measurement was done to verify the simulations. The reflection coefficient, axial ratio (AR), radiation pattern, antenna gain, and antenna efficiency are studied. It is found that the antenna has a wide 3 dB AR beamwidth of over 230° and a 3 dB gain beamwidth of 150°. The measured and simulated antenna gains at $\theta = 85^{\circ }$ are 0.11 and 0.68 dBic, respectively, which are higher than those of existing designs.

Axial‐ratio beamwidth and gain enhanced circularly polarized antenna using parasitic elements

AbstractA circularly polarized (CP) crossed‐dipole antenna with enhanced 3‐dB axial ratio (AR) beamwidth and gain via the addition of parasitic elements is proposed in this letter. First, a simplified CP crossed‐dipole model loaded with four parasitic elements is constructed to investigate the principle of wide axial‐ratio beamwidth. Theoretical analysis shows that by choosing the length and position of these parasitic elements properly, the 3 dB AR beamwidth of the simplified CP antenna can be enhanced significantly. Then, a practical CP crossed‐dipole antenna designed at 1.575 GHz is utilized to verify the feasibility of this method. Experimental results are in a good agreement with the simulated ones in terms of radiation pattern, gain, AR and |S11| for the proposed antenna. In particular, due to the addition of the four parasitic elements, the 3 dB AR beamwidth of the antenna at the central frequency of 1.575 GHz is increased from 72° to 134°; the gain in the working frequency bandwidth also shows an increase of almost 3 dBi when these parasitic elements are added.

Enhancing cross‐polarisation discrimination or axial ratio beamwidth of diagonally dual or circularly polarised base station antennas by using vertical parasitic elements

The cross-polarisation discrimination (XPD) of a ± 45° dual-polarised base station antenna is enhanced by adding vertical parasitic elements. First, it is established that high XPD can be achieved by employing four vertical parasitic elements between a simple ± 45° dual-polarised radiator and ground. Second, based on the proposed method, a simple ± 45° dual-polarised antenna for a long-term evolution 1.71-2.17GHz base station is designed, fabricated and measured. Compared with the antenna without vertical elements, XPDs are improved by about 7dB in the horizontal plane due to the addition of the vertical parasitic elements. Third, with a wideband quadrature hybrid, the proposed antenna is shown to radiate circularly polarised waves. In particular, the 3 dB axial ratio beamwidth of the proposed antenna is increased from 84 ° to 195 ° with the addition of the four vertical parasitic elements.

Printed quadrifilar helix antenna with enhanced bandwidth

A circular polarised printed quadrifilar helix antenna with enhanced bandwidth is proposed in this study. The helix antenna offers a very compact size and comprises of four arms with varying width, four open stubs, a feeding network and a metal ground plane. The different widths of the helix arms are employed to improve the impedance bandwidth while their varying pitches generate a cardioid radiation pattern. The antenna exhibits a voltage standing wave ratio ≤ 2 in the frequency range of 1.43–1.63 GHz offering impedance bandwidth of 12%. Good radiation characteristics with high gain, a wide 3 dB axial ratio beamwidth of 180° along with small size makes this antenna an excellent candidate for satellite communications and navigation systems.

A Novel Planar Endfire Circularly Polarized Antenna With Wide Axial-Ratio Beamwidth and Wide Impedance Bandwidth

A novel wideband planar endfire circularly polarized (CP) antenna with wide 3 dB axial ratio (AR) beamwidth is presented. The operation principle of the proposed CP antenna is described at first through the combination of a planar magnetic dipole and a V-shape open loop. Then, it is demonstrated how its AR beamwidth can be precisely controlled with resorting to the shape and thickness of the open loop element. Finally, the theoretical design approach is numerically verified, and the results are then experimentally validated. It is observed that a 3 dB AR beamwidth is achieved in an extremely wide angular region up to 250° within the principal elevation plane over a frequency range of 2.41–2.51 GHz. The proposed antenna has exhibited a wide impedance bandwidth of 22.23% in fraction, a 3 dB AR bandwidth of no less than 8.00% in fraction, and a simple planar profile in geometry. In addition, its endfire beam is in parallel with its plane.

A printed wide-beamwidth circularly polarized antenna via two pairs of radiating slots placed in a square contour

A low-profile circularly polarized (CP) slot antenna to achieve a wide axial-ratio (AR) beamwidth is proposed in this paper. The radiating patch consists of two orthogonal pairs of parallel slots etched symmetrically onto a ground plane. Firstly, our theoretical study demonstrates that the CP radiation can be satisfactorily achieved at the broadside, when the vertical and horizontal paired-slots are excited in the same amplitude with 90° phase difference. Secondly, the principle of CP radiation of the proposed antenna on an infinite ground plane is described. Through analyzing the spacing between two parallel slots, the |Eθ| and |Eφ| radiation patterns can be made approximately identical with each other over a large angle range. As such, the slot antenna achieves a wide AR beamwidth. After that, the 3 dB AR beamwidth with respect to the size of a finite ground plane is investigated to constitute a practical CP antenna on a finite ground plane. In final, the proposed CP antenna with a 1–4 probe-to-microstrip feeding network is designed and fabricated on a finite ground plane of a dielectric substrate. Measured results are shown to be in good agreement with the simulated ones about the gain, reflection coefficient, AR bandwidth, and radiation patterns. Most importantly, a wide 3 dB AR beamwidth of 126° and low-profile property with the height of 0.036λ0 are achieved.

AN e‐shaped slotted‐circular‐patch antenna for circularly polarized radiation and radiofrequency energy harvesting

ABSTRACTAn e‐shaped slotted‐circular‐patch antenna is proposed for circularly polarized (CP) radiation and RF energy harvesting. The proposed antenna consists of an e‐shaped slotted‐circular‐patch radiator and a coaxial feed. An e‐shaped slot is cut along the orthogonal axis of a circular‐patch with a coaxial feed along the diagonal axis to generate CP radiation with compact antenna size of 45 × 45 × 1.6 mm. The prototype antenna shows the measured gain more than 5 dBic at 2.4 GHz with 3 dB axial ratio beamwidth more than 140°. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:868–875, 2016

An axial‐ratio beamwidth enhancement of patch antenna with digonal slot and square ring

ABSTRACTA novel circularly polarized (CP) antenna with wide angular coverage is presented. The proposed antenna is formed by a 45 slot cut in the center of a rectangular patch antenna and a square ring around it. It can achieve an impedance bandwidth of 110 MHz and a 3 dB axial ratio bandwidth of 25 MHz. For this design, very stable and symmetrical radiation patterns are obtained. The 3 dB axial ratio beamwidth for the antenna is 160 , compared with the antenna that without the metal square ring, the antenna with square ring has 19 more 3 dB axial ratio beamwidth. This antenna has been successfully applied on passive keyless entry system on door lock. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:672–675, 2016

Gain enhancement for circularly polarized double layered printed hemispherical helical antenna arrays

To improve the performance of mobile satellite communications, such as for INMARSAT-M mobile vehicles, antenna with high gain and circular polarization over a wide angular range is important. With only 3-elements circularly polarized double-layered printed hemispherical helical antenna arrays that incorporated with parasitic helical wire in the structure, the array can produce significant improvement where it has been demonstrated that the gain and the 3 dB axial ratio (AR) bandwidth and beam width can be increased by properly adjusting the relative angular displacement δ1, δ2, δ3, and the inter-element spacing dx and dy. Experimental and theoretical results demonstrate that the array can produce a gain of 11 dBi, the 3 dB AR bandwidth of more than 11% with AR beam width of ~136°, and the mutual couplings between each element less than −23 dB at required 3 dB AR bandwidth frequency range. The antenna design is performed in computer simulation technology and verified by measurement.

A multiarm curl antenna for GPS applications

A single-feed dual-band antenna with wide-beam circularly polarized (CP) radiation is introduced for application in the global positioning system (GPS). The primary radiating element is a planar multiarm curl antenna. The dual-band operation is achieved by dividing the arms of the antenna into two branches of different lengths. To generate CP radiation, the radiator is fed by double vacant-quarter printed rings, which allows direct matching of the antenna to a single 50 Ω coaxial line. To enable unidirectional CP radiation and improve the 3 dB axial ratio (AR) beamwidth, the planar multiarm curl radiator is backed by a rectangular cavity-backed reflector. The final design, with an overall GPS-L2 frequency size of approximately λo/2.45 × λo/2.45 × λo/8, resulted in a |S11|<–10 dB bandwidth of 1.221–1.282 GHz (4.9%) and 1.546–1.660 GHz (7.1%) and a 3 dB AR bandwidth of 1.212–1.240 GHz (2.2%) and 1.560–1.590 GHz (1.9%). Furthermore, it showed excellent right-hand CP (RHCP) radiation at both operating bands, namely wide beamwidth, similar gain, a high front-to-back ratio, and high radiation efficiency.