scholarly journals A New Impedance Matching Method for an Ultra-Wide Band and Dual Circularly Polarised Feed

2016 ◽  
Vol 33 ◽  
Author(s):  
Sha Li ◽  
Yi Hua Yan ◽  
Wei Wang ◽  
Zhi Jun Chen ◽  
Dong Hao Liu ◽  
...  
Keyword(s):  
High Frequency ◽  
Near Field ◽  
Impedance Matching ◽  
Axial Ratio ◽  
Wide Band ◽  
Beam Width ◽  
Metal Ring ◽  
Field Radiation ◽  
Fixed Phase ◽  
Strip Lines

AbstractIn traditional antenna design, metal components are not placed in the central part of the antenna as they change the characteristics of near field radiation. However, we show that placing a metal ring in the centre of the strip lines, which connect the ends of folded high-frequency dipoles, does not damage the performance of the feed. Instead it significantly improves the voltage standing wave ratio of the feed whilst other performance indicators are not compromised. Thus, our findings show an excellent way of improving the wide band feed. Based on this foundation, a new circularly polarised feed for operation between 0.4 to 2 GHz is introduced for the Chinese Spectral Radioheliograph in this paper. The issue of a feed impedance matching network is investigated. By optimising the impedance matching, the performance of the feed is enhanced with respect to the previous realisations of the Eleven feed. The simulation and experimental results show that the gain of the feed is about 10 dBi, and the VSWR is less than 2:1. In addition, the feed has a low axial ratio, fixed phase centre location, and constant beam width in the range of 0.4 to 2 GHz.

scholarly journals Design of Dual Circularly Polarised 2–15 GHz Feed and the Polarisation Degree Measurement for CSRH-II Antenna System

2015 ◽  
Vol 32 ◽  
Author(s):  
Sha Li ◽  
Yi Hua Yan ◽  
Zhi Jun Chen ◽  
Wei Wang ◽  
Fu Shun Zhang
Keyword(s):  
Standing Wave ◽  
Axial Ratio ◽  
Wide Band ◽  
Beam Width ◽  
Antenna System ◽  
Ultra Wide Band ◽  
The Sun ◽  
Fixed Phase ◽  
The Relationship ◽  
The Waves

AbstractThe Chinese Spectral Radioheliograph is an aperture-synthesis telescope observing the Sun in ultra wide bandwidth on the ground. It contains two arrays Chinese Spectral Radioheliograph-I and Chinese Spectral Radioheliograph-II from 0.4 to 15 GHz. In order to obtain ultra wide-band performance, the cascaded folded dipoles are used in this feed. At the same time, in order to get circularly polarised signals coming from the Sun, a wide-band 90° hybrid is added in the output ports of the feed. This feed has characteristics of about 10 dBi gain, less than 1.5 voltage standing wave ratio. It also has characteristics with low axial ratio, fixed phase centre location, and constant beam width in operating frequencies. Through cross-correlating all combinations of two orthogonal polarisations at each antenna, the polarisation state of the waves is measured and give a differential instrumental delay between two data channels. The relationship between the own polarisation degree of the Sun and the observed polarisation degree is also measured for cross-polarised delay in observing the Sun in this paper.

Dual circularly polarized multilayer MIMO antenna array with an enhanced SR-feeding network for C-band application

2017 ◽  
Vol 9 (8) ◽  
pp. 1741-1748 ◽  
Author(s):  
Mahdi Jalali ◽  
Mohammad Naser-Moghadasi ◽  
Ramezan Ali Sadeghzadeh
Keyword(s):  
Antenna Array ◽  
Tai Chi ◽  
Impedance Matching ◽  
Axial Ratio ◽  
Wide Band ◽  
Impedance Bandwidth ◽  
Antenna Element ◽  
Circularly Polarized ◽  
Mimo Antenna ◽  
Feed Network

Wide-band circularly polarized multi-input multi-output (MIMO) antenna array with a 2 × 4 feed network was proposed for C-band application. Different unique techniques were utilized in the proposed array to enhance the antenna characteristics, such as gain, 3 dB axial ratio bandwidth (ARBW), impedance tuning, and ruinous mutual coupling effects. A miniaturized dual-feed Tai chi-shaped antenna element with a pair of feeding points and a pair of eyebrow-shaped strips was presented for enhancing circular polarization (CP) purity and impedance matching. For a better improvement of CP features, a 2*4 MIMO sequentially rotated (MIMO-SR) feed network was used to achieve broader 3 dB ARBW. Besides, the MIMO feature of the feed network could control the left- and right-handed CP, respectively. Ultimately, specific forms of slot and slit structures were applied onto the top layer of MIMO feed network that provided a high isolation between the radiating elements and array network. Furthermore, the diversity gain (DG) was studied. The extracted measured results illustrated an impedance bandwidth of 3.5–8.2 GHz at port 1 and 3.5–8.3 GHz at port 2 for VWSR < 2 and 3 dB ARBW of 4.6–7.6 GHz at port 1 and 4.6–7.5 GHz at port 2. The peak gain of 9.9 dBi was at 6 GHz.

Signature of coseismic off-fault damage in intermediate- and far-field radiation

2020 ◽  
Author(s):  
Kurama Okubo ◽  
Harsha S. Bhat ◽  
Esteban Rougier ◽  
Marine A. Denolle
Keyword(s):  
High Frequency ◽  
Near Field ◽  
Fault System ◽  
Far Field ◽  
Earthquake Rupture ◽  
Length Scales ◽  
Earthquake Sources ◽  
Planar Fault ◽  
Wide Range ◽  
Field Radiation

&lt;p&gt;Off-fault damage is observed around fault cores in a wide range of length scales, which is identified as an aggregation of localized fractures via geological and geodetic observations, or as low-velocity zone via seismological tomography. However, its seismological observables in earthquake traces, e.g. change in source spectra and/or radiation pattern, remains to be investigated.&amp;#160;&lt;/p&gt;&lt;p&gt;Okubo et al. (2019) proposed an approach framework of physics-based dynamic earthquake rupture modeling with coseismic off-fault damage using the combined finite-discrete element method (FDEM). It shows a non-negligible contribution of coseismic damage to rupture dynamics, high-frequency radiation and overall energy budget, whereas the model domain is limited in the near-field region. This study efficiently computes intermediate- and far-field radiation propagating from earthquake sources with coseismic off-fault damage, and to identify its signature in the seismic traces.&lt;/p&gt;&lt;p&gt;We first conduct the dynamic earthquake rupture with coseismic damage and compute synthetic near-field radiation using FDEM-based software tool, HOSSedu, developed by Los Alamos National Laboratory. We then couple the output of HOSSedu to SPECFEM2D in order to compute intermediate- and far-field radiation. The HOSS-SPECFEM2D coupling can resolve complexities over wide range of length scales associated with earthquake sources with coseismic damage and wave propagation.&lt;/p&gt;&lt;p&gt;We conduct 2D dynamic earthquake rupture modeling with a finite planar fault as canonical simplest model. The comparison between the cases with and without allowing for coseismic off-fault damage shows differences in intermediate- and far-field radiation. 1) High-frequency components in ground motion are enhanced all around the fault. 2) The rupture arresting phase, which clearly appears at the stations located orthogonal to the fault for the case without off-fault damage, is damped due to the smoothed rupture arrest by coseismic damage around fault edges. 3) Radiated energy is enhanced in the direction parallel to the fault due to the substantial damage around fault edges.&lt;/p&gt;&lt;p&gt;These fundamental observables will help identify the existence of coseismic off-fault damage in real earthquakes. It would also contribute to resolve the mechanisms of earthquake sources and the potential distribution of aftershock locations. We also attempt to replace the planar fault to the real fault geometry, e.g. the fault system associated with the 2019 Ridgecrest earthquake sequence, and will investigate the signature of off-fault damage in the seismic traces recorded in intermediate- and far-field range.&lt;/p&gt;

scholarly journals Design of a Circularly Polarized Galileo E6-Band Textile Antenna by Dedicated Multiobjective Constrained Pareto Optimization

2015 ◽  
Vol 2015 ◽  
pp. 1-7 ◽  
Author(s):  
Arnaut Dierck ◽  
Frederick Declercq ◽  
Thomas Vervust ◽  
Hendrik Rogier
Keyword(s):  
Return Loss ◽  
Impedance Matching ◽  
Real Life ◽  
Axial Ratio ◽  
Wide Band ◽  
Design Strategy ◽  
Pareto Optimization ◽  
Smart Textile ◽  
Textile Antenna ◽  
Materials Used

Designing textile antennas for real-life applications requires a design strategy that is able to produce antennas that are optimized over a wide bandwidth for often conflicting characteristics, such as impedance matching, axial ratio, efficiency, and gain, and, moreover, that is able to account for the variations that apply for the characteristics of the unconventional materials used in smart textile systems. In this paper, such a strategy, incorporating a multiobjective constrained Pareto optimization, is presented and applied to the design of a Galileo E6-band antenna with optimal return loss and wide-band axial ratio characteristics. Subsequently, different prototypes of the optimized antenna are fabricated and measured to validate the proposed design strategy.

scholarly journals A Wide Beam Printed Quadrifilar Helix based Circularly Polarised Radiating Element for Electronically Steered Antenna

2021 ◽  
Vol 71 (1) ◽  
pp. 66-70
Author(s):  
Raj Kumar ◽  
Pramendra Kumar Verma ◽  
M.V. Kartikeyan
Keyword(s):  
Beam Steering ◽  
Axial Ratio ◽  
Wide Band ◽  
Beam Width ◽  
Impedance Bandwidth ◽  
Band Frequency ◽  
Wide Beam ◽  
Radiating Element ◽  
Structure Simulation ◽  
Half Power

Wide beam and low axial ratio performance of printed quadrifilar antennas result in very attractive circularly polarised radiating element for wide scanned Electronically Steered Antenna. A compact printed quadrifilar Helix antenna (PQHA) has been designed and realised at S-Band frequency. Simulation and optimisation of designed antenna has been performed using ANSYS’s high frequency structure simulation (HFSS) software for its impedance, axial ratio (AR) performance and radiation characteristics. The developed circularly polarised antenna has 3-dB beam width of 130° and peak gain of 3.4dBic at 2.6 GHz. The developed antenna shows excellent AR performance over the frequency band as well as over the radiated beam. Half power axial ratio bandwidth of developed antenna is 27.4% (2.2 GHz - 2.9 GHz) while the impedance bandwidth is 32% (2.1 GHz - 2.9 GHz). Design has been validated through measured results. Designed wide band PQHA can be used as radiating element for electronically steered antenna for large beam steering application.

Spectral Control of Near-Field Radiation Through Surface Plasmon Polariton Interference

2013 ◽  
Author(s):  
Daisuke Hirashima ◽  
Katsunori Hanamura
Keyword(s):  
Surface Plasmon ◽  
High Frequency ◽  
Surface Plasmon Polariton ◽  
Radiation Transfer ◽  
Near Field ◽  
Structured Surfaces ◽  
Pillar Array ◽  
Field Radiation ◽  
Spectral Control ◽  
Plasmon Polaritons

Through interference of surface plasmon polaritons (SPPs), near-field radiation transfer between pillar-array-structured surfaces was enhanced compared with that between plane surfaces. Even in nanoscale channels between the pillars, the SPPs could propagate, and then a kind of interference and resonance took place according to the depth of the channel between the pillars. With decreasing pillar height, the frequency at maximum radiation transfer was shifted to the high-frequency side. That is, spectral control of near-field radiation could be achieved using pillar-array-structured surfaces.

scholarly journals Review Design of Slot Antenna Based on Ansoft HFSS Software

2019 ◽  
Vol 16 (1) ◽  
pp. 65-68
Author(s):  
Mohanad Abdulhamid ◽  
Eugene Ochieng
Keyword(s):  
Impedance Matching ◽  
Beam Width ◽  
Substrate Material ◽  
Slot Antenna ◽  
Feeding Method ◽  
Ansoft Hfss ◽  
Field Radiation ◽  
Half Power ◽  
High Level ◽  
Spurious Radiation

Abstract In this paper, a micro-strip fed slot antenna array for application in the 2.4GHz industrial, scientific and medical(ISM) band is implemented using the Ansoft HFSS software. Standard formulas are used to calculate different antenna parameters. The proposed antenna is designed to work at 2.4GHz frequency band. A half power beam width(HPBW) of 57°. A bandwidth of around 7.7% is attained. This may have been brought about by poor impedance matching and a high level of surface waves. A way of improving the bandwidth would have been to use proximity coupling feeding method which offers the highest bandwidth and is somewhat easy to model and has low spurious radiation. However, its fabrication would have been more difficult. A directivity of 2.01 dB is achieved. This is a fairly high though directivity increase could have been studied through use of different substrate material and thickness. Adjusting length and width of narrow slot loop antenna will influence on the resonance frequency and bandwidth. By using HFSS software, the characteristics of antenna are investigated and analyzed, including voltage standing wave ratio (VSWR), return loss and far field radiation patterns.

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