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Double-spiral linearly polarized RLSA
Abstract and Figures
High gain linearly polarized radial line slot arrays (LP-RLSA) suffer from remarkable degradation of the return loss. To overcome this drawback, this communication presents a novel LP-RLSA design obtained by the superposition of two spirally arranged circularly polarized RLSAs. Indeed, it benefits from the intrinsically low reflection coefficient proper of these circularly polarized spirally arrayed RLSAs. Furthermore, the new layout shows high polarization purity, still maintaining the intrinsic manufacturing simplicity of a RLSA antenna. An antenna prototype has been manufactured and measured to validate the design idea.
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... The distance between the radiating elements is typically of the order of 0.6 λ. The radiation pattern is adjusted by modifying the phase and amplitude of the signal 16 feed to the radiating elements by means of controllable power dividers and phase shifters. For example, by feeding all the radiating elements in phase with the same amplitude, the beam obtained has characteristics similar to those of a beam generated by a reflecting antenna with uniform illumination; ...
... Another proposed approach was to design a Low Cross-Polarized CP-RLSA [16], where the basic idea is to cut down the reflection coefficient globally not by compensating it locally. Specifically, the linear polarization is obtained by using one CP-RLSA designed to radiate with right hand circular polarization and the other one with left hand circular polarization. ...
... When circular shape is tested against squared plate it was noticed that reflection coefficient is greatly improved with the square shaped plate as it provides larger reflection area for radiated waves. This basic structure will be used as a basis for parametric study over the study band (15)(16)(17)(18) which is the uplink Ku-band assigned for satellite applications, and will be basis for the final chosen design as well. ...
Radial line slotted antenna in Ku-band for satellite applications
... Since then, a great amount of research has been devoted to the RLSA development. Adjusting the slot distribution, various polarizations were achieved, such as dual circular [4], linear [5], [6], and dual linear [7]. Research efforts have also been focused on shaping the radiated pattern, obtaining for instance elliptic [8], isoflux [9], conical [10], and tilted beam [11] far-field patterns. ...
This paper presents a circularly polarized Corporate-Fed Radial-Line Slot Antenna (CF-RLSA) operating in Ka-band and realized in low-cost, low-profile printed circuit board (PCB) technology. The radiating aperture is fed by a corporate feed network based on a broadband pillbox-like circular transition. The proposed feeding system results in a 67% gain bandwidth improvement compared to classical center-fed RLSA designs. Pattern stability versus frequency is also achieved. The bandwidth improvement provided by the corporate-feed topology is analytically derived for the general case of circular apertures with uniform amplitude illumination. This predicted improvement is confirmed by measurements. The prototype is optimized using a dedicated numerical tool, then fabricated and characterized. A good agreement is obtained between simulated and measured gain bandwidths, with a demonstrated relative bandwidth of 6.9% at 29 GHz for a maximum gain of 35.5 dBi and a 260 mm diameter for the radiating aperture.
... Several RLSA designs reported in literature focused on improving gain, efficiency and return loss performance [9], [23], [27]- [35]. On the other hand, a thorough investigation on RLSA side-lobe reduction methods is yet to be conducted [10], [36]- [44]. This paper addresses this need by developing a method that substantially reduces CP-RLSA side-lobe levels and at the same time enhances phase coherence across the aperture. ...
The paper presents a circularly polarized radial line slot array (CP RLSA) antenna with a nearly optimal monotonic variation of slot length with radius, in order to simultaneously reduce antenna side-lobe levels and to make the aperture phase distribution nearly uniform. It has additional advantages of excellent radiation efficiency, high gain and good overall bandwidth. The antenna comprises a single-layer radial transverse electromagnetic quasi-TEM waveguide with radiating slots on the aperture. The amplitude tapering is implemented by gradually varying slot lengths on the antenna aperture as a function of radial distance, utilizing a slot coupling analysis. Several antenna designs were investigated, each having a physical diameter of 345 mm (23λ0) and a thickness of 4.6 mm (0.3λ0), where λ0 is the free-space wavelength at the operating frequency of 20 GHz. A prototype was fabricated and measured, showing a good agreement between the predicted and measured results. The sidelobe levels at the operating frequency are less than - 20 dB due to tapering in the near-field amplitude distribution. The measured magnitude of the input reflection coefficient (S11) of the antenna is below -10 dB within the frequency range of 19 GHz to 21 GHz. The antenna has a measured peak directivity and a peak gain of 34.3 dBic and 33.8 dBic, respectively. Both the measured 3dB directivity bandwidth and 3dB gain bandwidth are 5.4%. Aperture efficiency is 48% and radiation efficiency is 94.2% at the operating frequency. The fabricated antenna also successfully fulfilled the condition of circular polarization with an axial ratio bandwidth exceeding 5%.
In linearly polarized (LP) radial line slot arrays (RLSAs), reflection canceling slots (RCSs) are used in addition to the radiating slots (RSs) to reduce the return loss. The densely populated slotted RLSA apertures present the challenge of avoiding physical overlap between the RCSs and RSs. A solution to displace RCSs from their optimal position complicates the design and makes it less predictable. A design presented here addresses this issue using narrower RCSs on the same current-flow lines as their corresponding RSs. A high-gain LP RLSA antenna with diameter 12
$\lambda _0$
was designed, fabricated, and tested using the proposed strategy. The measured prototype demonstrated a wide matching bandwidth of 74.3%. The antenna achieved a maximum gain of 28.3 dBi at the operating frequency of 17 GHz, and a 3 dB gain bandwidth of 6.3%. At this frequency, it has an aperture efficiency of 51%, a total efficiency of 95.3% along with high cross-polar discrimination, which is more than 70 dB in the direction of the beam peak.
Radial line slot array (RLSA) antennas have attractive features such as high gain, high efficiency, and planar low profile, but their gain bandwidths have been limited to less than 10%. This paper presents a method to significantly increase the gain bandwidth of RLSAs to over 30%. The key to the method is the application of a non-uniform radial TEM waveguide as opposed to the radially uniform TEM waveguide used in conventional RLSAs. Hence, the condition for maximum radiation is satisfied at a wide range of frequencies by different sections of the RLSA. To demonstrate the concept, several circularly polarised RLSA designs and one prototype are presented. The measured results of the prototype demonstrate an unprecedented 3dB gain bandwidth of 27.6%, a peak gain of 27.3 dBic, 3dB axial ratio bandwidth greater than 31.1% and a 10dB return loss bandwidth greater than 34.8%. The overall measured bandwidth of the RLSA in which gain variation and axial ratio are within 3dB and return loss is greater than 10dB is from 9.7 GHz to 12.8 GHz or 27.6%. Its extremely high measured gain bandwidth product per unit area (GBP/A) of 88 indicates excellent overall performance in terms of bandwidth, gain and area.
This article presents a method to produce a highly directive circularly polarized radiation beam (gain>35 dBi) from an all-metal circularly polarized radial-line slot array (RLSA) antenna. The antenna comprises a single-layer radial TEM waveguide, fully filled with air, formed between a metal ground plate and a parallel metal slotted sheet, leading to simple, low-cost fabrication. A prototype of the new antenna having a diameter of 0.4 m or 27λ
<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub>
, where λ
<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub>
is the free-space wavelength at the operating frequency of 20 GHz, was fabricated and tested. Its measured peak broadside directivity and measured peak realized gain are 36.3 dBic and 35.9 dBic, respectively. The total thickness of the antenna is only 6.5 mm or 0.43λ
<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub>
. The aperture efficiency of the prototype is 56%, total efficiency is 95.4%, and measured 3-dB axial ratio bandwidth is 4.9 GHz (22.9%). The antenna has excellent cross-polar rejection, with a measured cross-polar level of -24.4 dB in the broadside direction. This antenna has been targeted for low-cost SATCOM terminals and wireless backhauls but due to the lack of dielectrics, it may also be useful for space and high-power microwave applications.
The paper shows the practicability of manufacturing complex antennas, as folded reflectarrays or Radial Line Slot Arrays operating in Ku band, by using a low cost plastic 3D printer. All the antenna parts have been printed, not only the antenna supports. Then, the plastic parts have been opportunely metallized or by using conductive silver based spray, or by sticking an adhesive copper sheet on them, properly cut with a vinyl cutter plotter. Some strategies to reduce the influence of the not accurate knowledge of the material characteristics, and a few manufacturing knacks, are also reported.
Loop distribution is one of the most useful techniques to reduce the execution time of parallel applications. Traditionally, loop scheduling algorithms are implemented based on parallel programming paradigms such as MPI. This approximation presents three main disadvantages when applied in a grid environment, namely: (i) all resources must be simultaneously allocated to begin execution of the application; (ii) it is necessary to restart the whole application when a resource fails; (iii) it is not possible to add new resources to a currently running application. To overcome these limitations, we propose a new approach to implement loop distribution schemes in computational Grids. This approach is implemented using the distributed resource management application API (DRMAA) standard and the GridWay meta-scheduling framework. The efficiency of this approach to solve the Mandelbrot set problem is analyzed in a Globus-based research testbed.
The increase in small, distributed facilities expected in the near future has raised the necessity of having low-cost, transportable radar systems. In turn, this requires the design of high-gain, low-cost, planar, robust, and easy-to-assemble antennas. In this scenario, the possibility of using a laser-cutting technology in manufacturing a linearly polarized radialline slot array (RLSA) has been investigated. An ad hoc optimization algorithm, which takes into account the physical mechanism beyond the radial-line slot array antenna, has been developed to obtain low antenna sidelobe levels, as required by the specific BASYLIS radar application. The optimization technique allows using near-resonance radiating slots and canceling slots that are all closely spaced on the upper plate of the radial-line slot array. The measurements carried out on the antenna prototype showed very good performance, despite the use of low-cost materials and manufacturing technology.
The increase in small, distributed facilities expected in the near future has raised the necessity of having low-cost, transportable radar systems. In turn, this requires the design of high-gain, low-cost, planar, robust, and easy-to-assemble antennas. In this scenario, the possibility of using a laser-cutting technology in manufacturing a linearly polarized radial-line slot array (RLSA) has been investigated. An ad hoc optimization algorithm, which takes into account the physical mechanism beyond the radial-line slot array antenna, has been developed to obtain low antenna sidelobe levels, as required by the specific BASYLIS radar application. The optimization technique allows using near-resonance radiating slots and canceling slots that are all closely spaced on the upper plate of the radial-line slot array. The measurements carried out on the antenna prototype showed very good performance, despite the use of low-cost materials and manufacturing technology.
The increase in small, distributed facilities expected in the near future has raised the necessity of having low-cost, transportable radar systems. In turn, this requires the design of high-gain, low-cost, planar, robust, and easy-to-assemble antennas. In this scenario, the possibility of using a laser-cutting technology in manufacturing a linearly polarized radial-line slot array (RLSA) has been investigated. An ad hoc optimization algorithm, which takes into account the physical mechanism beyond the radial-line slot array antenna, has been developed to obtain low antenna sidelobe levels, as required by the specific BASYLIS radar application. The optimization technique allows using near-resonance radiating slots and canceling slots that are all closely spaced on the upper plate of the radial-line slot array. The measurements carried out on the antenna prototype showed very good performance, despite the use of low-cost materials and manufacturing technology.
In this paper a procedure is presented, allowing the automatic design of circular polarized radial line slot antennas, with either pencil or shaped beam patterns. The antenna slot layout is refined by an optimization scheme based on the physical picture behind the working mechanism of the array. The validity of the approach has been proved by designing very efficient pencil beam antennas, either with maximum directivity or with controlled side lobe levels, and a shaped isoflux beam antenna.
We design a double-layer dipole polarizer to convert circular polarization to linear one with reflection cancellation to mount over a sidelobe-suppressed circularly-polarized radial line slot antenna (RLSA) at 9.3GHz. The measured XPD of only the polarizer is 15.1dB at 9.3GHz. The center frequency of the polarizer in the measurement becomes higher by 400MHz than that in the design. The result of the linearly polarized RLSA integrated with the polarizer nearly equals to that of the polarizer itself.
The purpose of this letter is two-fold: 1) to propose an effective wideband coaxial transition for linearly polarized radial-line slot-array antennas consisting of a set of sleeves surrounding a monopole probe; and 2) to formulate an efficient technique for fast transition optimization taking into account all parts of the antenna. The technique basically obtains an equivalent reflection coefficient of the whole slot array as seen from the transition, thus reducing significantly the unknowns involved in the full-wave description of the problem and hence the optimization time.
Well-matched linearly polarized radial-line slot-array antennas can be designed using strip-loading techniques, avoiding the use of cancelling slots and therefore obtaining high levels of polarization purity and eliminating undesired backward radiation.
The slot design for aperture field synthesis in a single-layered
RLSA (radial line slot antenna) is summarized. In order to realize a
desired slot coupling, the slot length and the spacing are varied on the
basis of a full-wave analysis. An example is presented concerning the
design of the uniform aperture field distribution
In this paper, a computationally efficient method of moments (MoM) formulation is presented that makes use of an approximate asymptotic formula for the slot mutual admittance. The formula accuracy to the asymptotic order O ( r <sup>-</sup> <sup>3/2</sup>) gives sufficient precision for moderate slot distance (1.5-2 wavelengths). In a typical radial line slot array analysis, this permits avoiding the numerical integration in more than 90% of the slot pairs with a savings of CPU time of the same order.