Maximum Beamwidth Research Articles

Low-Scattering Dipole Antenna Using Mushroom-Shaped Structure for Applications in Dual-Band Shared-Aperture Array

A low-scattering dipole antenna by loading mushroom-shaped electromagnetic structures is proposed and employed to design an aperture-shared antenna array with low blockage effect. The arm of the proposed dipole element consists of a square ring and a short branch, and the mushroom structure is loaded on the arm to realize low scattering characteristics. The low scattering low band (LB) element is used for a dual-band shared-aperture array; the results indicate the pattern distortion of the high band (HB) array caused by the LB element can be greatly reduced accordingly. Compared with HB antenna alone, the simulated maximum gain decrease is 1.55 dB and the maximum beamwidth deviation is 27.4° after adding the reference LB dipole without loading the mushroom-shaped structure. Meanwhile the two values are reduced to 0.55 dB and 6.4°, respectively, after the mushroom-shaped structure is loaded. For demonstration, an aperture-shared antenna array operating in the LB of 0.698–0.96 GHz and the HB of 3.4–3.8 GHz is designed and fabricated. The measured results show that the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">S</i> -parameters and the pattern of the HB subarray with the proposed LB dipole change slightly, indicating that the proposed LB dipole can effectively suppress the scattering on the HB antenna. The results indicate the proposed design is suitable for multiband aperture-shared antennas in modern communication systems.

Circularly Polarized Cross-Dipole Antenna for UHF RFID Readers Applicated in the Warehouse Environment

In this paper, we proposed a broadband circularly polarized antenna with wide beamwidth. The main structure of the proposed antenna is a combined cross-polarized dipole antenna with four metal arms feeding by a single coaxial cable and two 90° phase delay lines. In order to attain a wide beamwidth antenna performance that can be used in a warehouse environment, we innovatively bent the metal arms and added a metal plane at a specific location to gain maximum beamwidth and the highest achievable gain. Especially, the application of folded metal arms not only reduce the space size of antenna, but also possess good axial ratio characteristic. The measurement illustrates that the antenna prototype achieves S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> < -10 dB impedance bandwidth (IBW) of 40% (820 - 1230 MHz), a 3-dB axial ratio bandwidth (ARBW) of 7.3% (895 - 970 MHz), and a maximum half-power beamwidth (HPBW) of 104° (@915 MHz). In addition, the good radiation characteristics of a gain of 6.33 dBic and an average radiation efficiency of 76.3% were measured in the operating bandwidth, in which make the antenna a good candidate for the hasty logistics radio frequency identification (RFID) system.

Investigation of the dependences of the Vivaldi antenna with two curve radii in the electrodynamic modeling software package

Objective. The aim of the study is to build and optimize a computer model of the antenna using software packages for electrodynamic modeling.Method. The study is based on dynamic modeling methods.Result. In this paper, the dependences of the width of the radiation pattern on the curved Vivaldi antenna with a mirror arrangement of the petals are obtained. Graphs of the dependence of the radii of curved petals and aperture values on the width of the radiation pattern in two planes for frequencies of 3 and 24 GHz are plotted. Curve radius, antenna aperture and lower antenna height are plotted as functions of the maximum beamwidth for 24 GHz and the minimum beamwidth for 3 GHz. The obtained dependencies were approximated for two planes θ = 900 (antenna aperture plane) and φ = 00 (plane perpendicular to the antenna aperture plane). By means of regression analy sis, analytical descriptions and graphs of dependences of the maximum beamwidth for 24 GHz and the minimum beamwidth for 3 GHz, on the radii of the curves, aperture and the height of the lower curve of the antenna lobe were obtained.Conclusion. The resulting mathematical model makes it possible to obtain the values of the radius of the curve, the opening and the lower height of the antenna lobes for different frequencies, as a result, to build a Vivaldi antenna with the desired topology.

60 GHz Compact Larger Beam Scanning Range PCB Leaky-Wave Antenna Using HMSIW for Millimeter-Wave Applications

A half-mode substrate integrated waveguide (HMSIW), based on printed circuit board (PCB) technology, is employed to construct a novel V-band leaky-wave antenna incorporating composite right-/left-handed (CRLH) media. Including modified half-sinusoidally varied interdigital capacitive slots on the radiating edge of the HMSIW enables the feature of effective CRLH media to produce adequate radiation coverage and bandwidth with improved sidelobe level (SLL) and higher gain. Unit cell characteristics and space harmonic analysis were thoroughly investigated through dispersion and Bloch impedance analysis. By appropriately tuning the physical parameters of the design, the balanced condition was obtained at a broadside frequency of 60 GHz. The highly directed radiated fan beam covered a scanning range of 120° with beam steering from -72° to 48° of the visible space. The proposed antenna operated over 55-65 GHz with a maximum realized gain of 14.5 dBi, maximum beamwidth of 9.15°, better than 15 dB SLL and 20 dB cross-polar radiation. All simulated responses showed reasonably good accordance with experimental data thereby validating the novel design of the proposed leaky-wave structure for millimeter-wave wireless applications.

A Differentially Fed Dual-Polarized Magnetic Dipole Antenna for Spaceborne Applications

This paper presents a novel differentially fed dual-polarized magnetic dipole antenna with stable radiation pattern, platform independence, wide bandwidth, and robust structure for spaceborne applications. The proposed antenna is formed by a dual-polarized magnetic dipole backed by a specially designed rectangular cavity. The magnetic dipole consists of two perpendicular parallel-plate waveguides with stepped edges to broaden the impedance bandwidth, providing good structural reliability which is critical to spaceborne antennas. A cross-shaped conductor fed by two pairs of capacity coupling feeding probes is utilized to drive the dual-polarized magnetic dipole antenna. The specially designed rectangular cavity has four metal plates in four corners to shape the radiation pattern at E- and H-planes. Furthermore, thanks to the cavity, the size of the conducting platform that the antenna mounted on has limited impact on antenna’s electrical performances, particularly the radiation pattern. A prototype is fabricated and tested. Measured results show that the antenna achieves a fractional bandwidth of 18.5% with −10 dB reflection coefficient. The realized gain is about 8.5 dBi. A stable radiation pattern with a 3 dB beamwidth of 70° ± 3° and −4 dBi maximum beamwidth of 152° is observed. The measured cross-polarization is lower than −20 dB within °65°. Measured results are in good agreement with simulation ones.

Size modulated transition in the fluid–structure interaction losses in nano mechanical beam resonators

An understanding of the dominant dissipative mechanisms is crucial for the design of a high-Q doubly clamped nanobeam resonator to be operated in air. We focus on quantifying analytically the viscous losses—the squeeze film damping and drag force damping—that limit the net quality factor of a beam resonator, vibrating in its flexural fundamental mode with the surrounding fluid as air at atmospheric pressure. Specifically, drag force damping dominates at smaller beam widths and squeeze film losses dominate at larger beam widths, with no significant contribution from structural losses and acoustic radiation losses. The combined viscous losses agree well with the experimentally measured Q of the resonator over a large range of beam widths, within the limits of thin beam theory. We propose an empirical relation between the maximum quality factor and the ratio of maximum beam width to the squeeze film air gap thickness.

Pareto Optimization of Thinned Planar Arrays With Elliptical Mainbeams and Low Sidelobe Levels

A multi-objective Pareto genetic algorithm design methodology is applied to thinned planar arrays to simultaneously minimize peak side-lobe levels and target an elliptical mainbeam with specific minimum and maximum half-power beamwidths. This new radiation pattern synthesis technique for thinned planar arrays provides antenna engineers with a set of tradeoffs between low side-lobe levels and close adherence to mainbeam design objectives (i.e., the specified half-power beamwidths corresponding to the major and minor axes of an elliptical mainbeam). One Pareto optimization example is presented for a thinned low side-lobe planar array with a desired minimum and maximum beamwidth of 8.4° and 12° respectively. Two designs from the Pareto front are discussed, one with a -20.92 dB side-lobe level and beamwidths between 11.5° and 7.5° and a second with a -18.97 dB side-lobe level with beamwidths between 12° and 7.93°.

Pseudohelical Scan for the Dose Profile Measurements of 160-mm-Wide Cone-Beam MDCT

Our objective was to determine what the reasonable total phantom length should be for the measurements and determination of length equilibrium, specifically for the Aquilion ONE cone-beam MDCT system. Radiation dose measurements of a 160-mm-wide cone-beam-MDCT scanner and its radiation dose profile require a different approach than the traditional or conventional method using thermoluminescent dosimeters or small ionization chambers, which have been suggested by some investigators. In order to obtain the radiation dose profile of a cone-beam MDCT, two key elements must be addressed: proper instrumentation for the detection of radiation beam and inclusion of the tails of the radiation dose profile. In this study, a small (2 x 2 x 0.3 mm) solid-state detector was used to measure the dose profile, which required the introduction of a stepping motor to pull the detector through the phantom. Inclusion of the tails of the radiation dose profile meant more than one standard CT dose index phantom would be required to encompass the dose profile tails as much as practically possible. In fact, at minimum, a total of five standard CT dose index (CTDI) phantoms would be required to ensure the entire dose profile is included and detected. In the case of Toshiba Aquilion ONE MDCT with the maximum beam width of 160 mm, the phantom length that is required for the radiation dose profile measurement should be at least 750 mm, or 5 standard CTDI body phantoms. Current CTDI measurements utilizing 150 mm or 350 mm phantom lengths significantly underestimate the total dose of wide cone-beam MDCT. The measurement method outlined in this study amounts to an introduction of a new CT dose profile measurement using a pseudohelical scan.

Dual-frequency dual circularly-polarised patch antenna with wide beamwidth

A dual-frequency dual-circularly polarised patch antenna with wide beamwidth is proposed. The two-layer structure comprises circular patches with offset circular slots connected to rectangular slots. They provide orthogonal perturbations realising RHCP and LHCP for the lower and upper bands, respectively. The wide beamwidth is realised by extending the substrate beyond the groundplane. Measurements show a maximum beamwidth of 180deg and gains of 3.9 and 0.5 dBic for zenith and 10deg elevation, respectively, for the upper band. The measured beamwidth for the low band is 130deg with a maximum gain of 3.9 and -0.7 dBic for zenith and 10deg elevation, respectively. The axial-ratio is less than 3 dB in the hemisphere for elevations greater than 10deg for both bands.

Experimental and theoretical verification of focusing in a large, periodically loaded transmission line negative refractive index metamaterial

We have previously shown that a new class of Negative Refractive Index (NRI) metamaterials can be constructed by periodically loading a host transmission line medium with inductors and capacitors in a dual (high-pass) configuration. A small planar NRI lens interfaced with a Positive Refractive Index (PRI) parallel-plate waveguide recently succeeded in demonstrating focusing of cylindrical waves. In this paper, we present theoretical and experimental data describing the focusing and dispersion characteristics of a significantly improved device that exhibits minimal edge effects, a larger NRI region permitting precise extraction of dispersion data, and a PRI region consisting of a microstrip grid, over which the fields may be observed. The experimentally obtained dispersion data exhibits excellent agreement with the theory predicted by periodic analysis, and depicts an extremely broadband region from 960MHz to 2.5GHz over which the refractive index remains negative. At the frequency at which the theory predicts a relative refractive index of -1, the measured field distribution shows a focal spot with a maximum beam width under one-half of a guide wavelength. These results are compared with field distributions obtained through mathematical simulations based on the plane-wave expansion technique, and exhibit a qualitative correspondence. The success of this experiment attests to the repeatability of the original experiment and affirms the viability of the transmission line approach to the design of NRI metamaterials.

Optimization of apertures and collimators for multi-channel plasma diagnostics

Aperture, pin-hole and collimator detection systems are often used in plasma diagnostics, for example, in soft x-ray detection and bolometer systems. In this article the simultaneous optimization of viewing-beam overlap and light yield is considered in multi-channel aperture and collimator systems for two-dimensional (2D) tomography. This article briefly highlights the relation between beamwidth overlap and spatial aliasing in tomography, and how aliasing can be avoided in theory and in practice. Three-dimensional (3D) single-channel aperture and collimator systems can be approximated by a combination of two planar systems if the aperture is rectangular. Three ways to optimize beamwidth overlap and light yield for planar aperture and collimator systems are considered in detail: overlap of the angular étendue at the full width at half maximum (FWHM), overlap of the geometric function at the FWHM a certain distance from the aperture, and arbitrary overlap for a given maximum beamwidth. The combination of 2D effects from all three optimization methods were used in the design of 3D apertures for a new multi-channel bolometer camera on the Joint European Torus tokamak. The resulting apertures are complex, but the new camera has several advantages over previous cameras.

On Various Optimum-Array Transducer Patterns and Approximations

In this paper the nature of optimum polynomials and functions for equally spaced transducer arrays under various optimum conditions is considered. Optimum patterns considered are for (a) sum patterns with minimum beam width for a given degree of minor lobe suppression, (b) sum patterns with maximum beam width, (c) difference patterns with minimum beam width for a given degree of minor lobe suppression, and (d) difference patterns with maximum beam width and others. The problems of obtaining the optimum polynomials are discussed and various approximately optimum shading schemes are presented.