Loop Patch Research Articles

Broadband High-Gain Circularly Polarized Antenna for Conformal Applications

A broadband high gain circularly polarized (CP) antenna with low profile for conformal applications is proposed. The antenna is composed of a complete ground plane, a loop patch, a feeding patch and four parasitic patches. The loop patch with a sequential phase difference of 90 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^\circ$</tex-math></inline-formula> is designed to achieve circular polarization resonating in TM <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$_{11}$</tex-math></inline-formula> mode. The four parasitic patches surrounding the loop patch are designed to excite another CP resonant mode, which will widen the bandwidth and improve the gain. To verify the conformal capability of the proposed antenna, the performance under different bending radii is compared and discussed. Finally, the proposed antenna with a profile of 0.054 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\lambda _{0}$</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">$\lambda _{0}$</tex-math></inline-formula> is the free-space wavelength at the operation frequency of 5.5 GHz) is fabricated and measured. The measured -10 dB impedance bandwidth is 34.8%, 3 dB axial-ratio (AR) bandwidth is 20%, and peak gain is 11.2 dBic.

A Wideband Pattern-Reconfigurable Loop Antenna Designed by Using Characteristic Mode Analysis

In this letter, a pattern-reconfigurable antenna for indoor communication is proposed, which can provide stable conical and broadside beams. Although this type of pattern-reconfigurable antenna can provide large radiation coverage, it usually suffers complex structure, narrow bandwidth, and distorted pattern. In order to get rid of the complex radiators, a simple loop patch is introduced to generate the conical and broadside beams. Through slotting the loop patch with the aid of characteristic mode analysis, the two desired radiation modes can be well excited in the same band. Meanwhile, the modified loop patch can provide stable radiation patterns by suppressing unwanted higher order modes. For achieving the reconfigurable beams, a reconfigurable feeding network is designed to switch two working modes. Finally, the proposed pattern-reconfigurable antenna is fabricated, and the measured overlapped 10 dB operating bandwidth is about 27.3% ranging from 3.61 to 4.75 GHz. The results show that the proposed pattern-reconfigurable antenna has a wide bandwidth and stable radiation patterns, which exhibits attractive potentials for fifth-generation (5G) indoor communication in sub-6 GHz.

Designing Wideband Microstrip Reflectarrays for 10 GHz

This paper presents two microstrip reflectarray designs based on variable size unit cells for 10 GHz. One design uses a 3-layer unit cell with polygon shaped patch and the other uses a unit cell with 1-layer square loop patch. Both arrays have a size of 10λ × 10λ at 10 GHz, can reflect the incoming wave as a high gain pencil beam in the desired direction of θ = 30°. Gains at 10 GHz are 23.6 dB and 26.1 dB for the 3-layer and one-layer structures, respectively. The multi-layer structure resulted in a wider gain banwdith. Simulation results show that the 3-dB gain bandwdith is about 22% for the 3-layer structure reflectarray, as compared to 12% for the one-layer structure

Performance of the Microstrip Patch Antenna Model Design for 900 MHz and 2.4 GHz Working Frequency

The development of communication systems for several processes at this time makes the use of the frequency spectrum of cellular communication more and more. Antenna system which is an important component in a communication system that works on more than one frequency, such as a mobile phone that works with a working frequency of GSM frequency of 900 MHz and Bluetooth frequency of 2.4 GHz. The two antennas with different frequencies are expected to have optimal power in active conditions. This study shows the performance and design analysis of the prototype circular microstrip patch antenna using the coaxial probe feeding method at a frequency of 900 MHz, the dipole microstrip patch antenna using the coaxial probe feeding method at a frequency of 2.4 GHz, and the rectangular microstrip antenna operating at two frequencies, 900 MHz and 2, 4 GHz. The type of substrate used is PCB FR4 with a dielectric of 4.4 and h=1.6. The design of this microstrip antenna uses a mathematical approach. The results obtained from measurements at frequencies of 900 MHz and 2.4 GHz have a loss of less than -58.4897 dB and the two microstrip antennas do not interfere with each other, when the microstrip antenna is in a vertical position the transmit power is optimum and there is no interference when the microstrip antenna is in the vertical position. The loop patch and the dipole microstrip patch antenna are activated simultaneously.

Wideband Vortex Beam Reflectarray Design Using Quarter-Wavelength Element

A wideband vortex beam reflectarray is designed and fabricated to generate the orbital angular momentum (OAM) waves for an $\boldsymbol{l} = 2$ mode. A quarter-wavelength element is proposed to achieve a reflection phase of 360° at the designed frequency of 6 GHz. The element consists of a loop patch, a cross-dipole patch, and four square patches. The symmetric structure of the element makes it suitable for dual polarization. It is revealed that the OAM mode purity and operational bandwidth of the reflectarray are increased by using the quarter-wavelength element. The array size is $\text{50} \times {\text{50 cm}}^2$ , which achieves measured gain of 18.98 dBi at 6 GHz and operational OAM bandwidth of 42%.

Metasurface Antenna Design with Ultra-wideband RCS Reduction

In this paper, two novel Artificial Magnetic Conductor (AMC) structures, based on circular loop patch and substrate, are designed to realize 180° reflection phase difference in a wide frequency band. These two AMCs’ reflection phase property is applied to redirecting the scattering fields of a radar target to reduce its Radar Cross Section (RCS). This method of RCS reduction can be realized by covering with a chessboard surface composed of two proposed AMC structures, so the RCS reduction in a wide frequency band can be achieved as well. Compared with the same-sized metallic surface, this proposed chessboard surface can reduce RCS drastically from 8 to 20 GHz under normally incident waves, and the RCS also can be reduced under obliquely incident waves. Meanwhile, this surface also can be used as antenna. By precisely designing feed network, the metasurface antenna can be designed. This antenna also has a low profile. The simulated impedance matching frequency band is from 9.08 to 10.30 GHz. Excellent agreement is obtained between simulation and measurement for metasurface antenna and chessboard surface. Such method gives a method for integrated design of antenna and metasurface, so the RCS reduction can be achieved, at the same time the radiation properties can be maintained.

A single feed dual-band (2.4 GHz/5 GHz) miniaturized patch antenna for wireless local area network (WLAN) communications

A single feed dual-band miniaturized microstrip patch antenna for Wireless Local Area Network (WLAN) communications has been proposed. The outer rectangular loop patch and inner modified E-shaped patch were used to resonate at 2.4 and 5 GHz, respectively. In order to separate the effect between two frequency bands, a shorting pin was set between two resonance cells. The simulated results show that it can operate at 2.4 and 5 GHz bands with 0.072 GHz (2.407–2.479 GHz) and 0.715 GHz (5.137–5.853 GHz) fractional bandwidth, respectively, which can cover the whole frequency band of WLAN. In addition, the antenna is miniaturized by 31% compared to the conventional rectangular patch without a slot. At last, the proposed microstrip patch antenna has been fabricated and measured for both impedance matching and radiation patterns. A comparison of the measurement and simulation results is given, which show reasonable good agreement.

Compact multiband monopole antenna for WLAN/WiMAX applications

In this article, a compact multiband monopole antenna is proposed to cover the frequency band for wireless local area network and worldwide interoperability for microwave access application. The multiband monopole antenna has the advantage of compact size of 15 × 30 mm2. The proposed antenna is an S-shaped strip connected with a notched rectangle loop radiation patch with a ground plane, and there is a slot in the ground plane. The two lower bands are achieved by the rectangle loop patch and the higher band is achieved by the slot in the ground plane. The impedance bandwidth for 10 dB return loss at 2.46, 3.8, and 5.4 GHz, are from 2.4 to 2.51 GHz, 3.20 to 4.07 GHz, and 5.08 to 5.85 GHz, respectively. Experimental results show that the antenna gives omnidirectional radiation patterns and stable antenna gains in the operating bands with the compact size. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:1809–1812, 2014

Microstructures in front of crack tips for various propagation rates and re-evolution of the dislocation under changing propagation crack rates in pure polycrystalline copper with a large grain size

The dislocation structure in front of crack tips for various crack propagation rates and the redevelopment of the dislocation structure after reducing the fatigue load (i.e., after decreasing the crack propagation rate from approximately 5×10−5 to 5×10−7mm/cycle) are investigated in this study. Pure polycrystalline copper with large grains was used in this study. The materials were annealed at 800°C for 4hours in a 10−5Torr vacuum and then cooled in a furnace. The specimen preparations followed the ASTM E647 instructions for compact tension (CT) specimens. Fatigue crack propagation was achieved using a computerised Instron 8801 hydraulic testing machine at R=0.1 at a frequency of approximately 20Hz. The results are as follows: (1) The dislocation structure includes misoriented cells next to the crack tips for propagation rates greater than 5×10−5mm/cycle. When the crack propagation rate is less than 5×10−7mm/cycle, the dislocation structure next to the crack tips is dominated by a loop patch structure. (2) When crack tips have the same steady crack propagation rate, the dislocation structures are similar regardless of the load history. (3) The dislocation evolution presents an anti-sequence between positive and negative.

The strain amplitude controlled fatigue behavior of pure copper with ultra large grain size

The dislocation structural evolution in polycrystalline copper at constant strain amplitude during low cycle fatigue is well understood. However, the dislocation structural development at variable strain, which changes from high to low strain amplitude, has seldom been reported. Scanning electron microscope (SEM) back-scattering electron imaging was used in this study. Dislocation structure fatigue research was conducted on many copper materials in the literature. Hence, OFHC with an ultra-large grain was used in this work. The fatigue is completed using the Instron 8801 hydraulic fatigue test machine. After fatigue was instituted the microstructures were investigated using BEI of SEM and TEM. The results show that; (1) the S–N curve at reduced strain amplitude reveals softening after hardening at the initiation stage and up to fracture. No plateau area and secondary hardening occurred. (2) A special microstructure with mis-orientation cells embedded in a vein structure was observed in the ultra-large grain. (3) With small strain amplitude from high–low strain amplitude in the ultra-grain specimen, the fracture microstructure includes mis-oriented cells embedded in a loop patch structure. Under this load the micro-cracks are initiated at a small band with a mis-oriented cell structure.

Design of double layer frequency selective surfaces with novel multiresonant elements for four‐frequency bands

AbstractA double layer frequency selective surface (DFSS) composed of modified square loop, cross dipole, and Jerusalem cross loop patch elements is presented to obtain angle and polarization insensitivity and a broad bandwidth. The presented DFSS reflects the X‐ and K‐band signals, while allowing the C‐ and Ku‐band signals to pass through. In this design, a four‐band FSS (including band‐stop FSS and band‐pass FSS) with a broad bandwidth is obtained by controlling the thickness of the air foam between the FSS layers. An equivalent circuit model is developed to provide insight into the response of the DFSS. Experimental verifications are carried out. The computed results agree well with the measured ones. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:2153–2157, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27007

Design of an embedded-feed type microstrip patch antenna for UHF radio frequency identification tag on metallic objects

The design of an embedded-feed type microstrip patch antenna, which can be mounted on metallic objects for radio frequency identification (RFID), is presented. The structure consists of an embedded feed with T-matching networks and a symmetrical radiating rectangular loop patch. The proposed antenna has no shorting plate or via hole and consists of a very thin structure of microstrip patch antenna compared with the conventional metallic tag antennas. The impedance of the presented antenna can be changed to match the impedance values of tag chips by using the T-matching network. The gain radiation pattern performance of the proposed antenna on metal surface is improved so that it can be used for a tag antenna mountable on metal surface in ultra-high frequency (UHF) band RFID applications. The antenna is analysed by full wave simulations, and experimental results are provided for the manufactured prototype.

One‐turn stub‐loaded loop patch antenna on a small ground plane

AbstractA small 1.1‐cm3 one‐turn loop patch antenna located 2.5 mm above an 18 × 25 mm ground plane separated by a dielectric substrate with relative permittivity of 9.8 is presented. By varying the length of a thin quarter‐wavelength matching line, it is possible to change the resonant frequency. An RLC circuit model is used to determine the minimum quality factor Q. It is shown that the proposed loop yields a bandwidth performance close to the theoretical limit. The antenna has a 14.5% bandwidth at the resonant frequency of 2.04 GHz. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 45: 126–128, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20745

The observation of dislocation reversal in front of crack tips of polycrystalline copper after reducing maximum load

The loading at a crack tip varies during fatigue crack propagation. As a result, overloading causes retardation of crack propagation, and underloading causes the acceleration of crack propagation. In addition, reducing the load range by changing either the minimum load or maximum load can cause a reduction or retardation of crack propagation to occur. Examining a fatigue cracked specimen made of polycrystalline copper with back scattered electron images (BEI) in a scanning electron microscope (SEM) revealed that (1) the dislocation structures close to the crack tips gradually evolved from a cell structure into a new loop patch structure during the crack retardation period which follows after reducing the maximum load; (2) restoring the crack propagation rate is a result of re-establishing the cell structure from new loop patches or PSBs; and (3) the evolution of the dislocation structure at the crack tip due to the maximum loading reduction is affected by residual active slip systems.

The observation and analysis of the dislocation morphology of fatigue crack tips at steady state propagation rates subject to a single peak load

During fatigue crack propagation there is large interaction effects of the fatigue cycle for different loading amplitudes. Two examples are the retarding effect of overload and the accelerating effect of underload on the crack propagation. In the former, the result is explained in terms of residual stress effects associated with the overload, and in the latter, the underload partially annihilates the residual stress built up by the positive load. However, at the microstructure level of material under fatigue, the crack propagation is caused by dislocation action. Assuming this, this paper reports studies of the crack propagation interaction effect by using microstructural examination of crack tips. Observations were made with the Back Electron Images (BEI) of the Scanning Electron Microscope (SEM). The results are: (1) the microstructure of cells close to the crack tips formed into vein or loop patch structures upon the overload, so that the crack propagation was reduced. (2) The region of cells s close to the crack tips become enlarged on the underload and the scale of the other microstructure (such as PSB, vein and loop patch) were also enhanced too, so that the crack propagation was accelerated.

Dislocation structures in fatigued polycrystalline copper

The dislocation structures in fatigued polycrystalline copper with small average grain size were investigated over a plastic strain range from 1.5 x 10 −5 to 10 −2. It was found that the dislocation structures are arranged into three types of configurations, which correspond to the three regions in the cyclic stress-strain curve. Cylidirical loop patch structure are present in region A for low strain amplitudes, similar to those observed previously in coarse grained polycrystals. Moreover, irregular loop patches are also formed in this region for small grains polycrystals rather thanin region B at intermediate strain amplitudes for coarse grained polycrystals. In region B, persistent slip band (PSB) structures are formed but with a low volume content compared with the coarse grained polycrystals. In region C, at high plastic strains, the dislocation structures are dominated by dipolar walls. In addition, labyrinth structures are developed in region C instead of region B for coarse grained polycrystals. All the dislocation structures observed are viewed as forms of dipolized structures. A dipolized dislocation arrangement model is proposed to describe the formation process of dislocation structures. It is shown that all the dislocation configurations formed in cycled polycrystalline copper are low energy structures.

Configuration of loop patch at low strain amplitude in polycrystalline copper

Abstract The loop patch structure produced in polycrystalline copper, fatigued at low strain amplitudes below the quasiplateau region of the cyclic stress strain curves, reveals three types of configuration: cylindrical, irregular and cellular shapes. It is identified that the cylindrical loop patches consist of edge dipolar debris with primary Burgers vector and are formed from the deposition of edge segments by sweeping screw dislocations. The irregular loop patches are developed predominantly from stacking of two kinds of dislocation dipolar debris and loops in the grains oriented with double slip. The cellular loop patches are formed from the interaction of four types of dislocation in the grain oriented with multislip. In addition, cubic sessile dislocations are found to coexist with the irregular loop patches and the cellular loop patches. These cubic sessile dislocations are formed from the reaction between edge dislocations and screw dislocations which are perpendicular to each other. It is explai...

Dichroic design for the orbiting VLBI earth station antenna

The design and performance of a single screen frequency selective surface (FSS) with gridded square loop patch element are described for diplexing the Xand Ku-band signals in an orbiting very long baseline interferometer (OVLBI) earth station reflector antenna system. The FSS grids were designed using an analysis code incorporating the accurate integral equation technique. The effects of the dielectric substrate and superstrate are accurately evaluated by this technique. Excellent agreement is obtained between the predicted and measured results. This validates the FSS design using the gridded square loop element. If the grid is sandwiched between two 0.889 mm thick Teflon slabs, the resonant frequency drift is noticeably reduced as the incident angle steered from normal to 40 degrees . >

Dependence of fatigue failure mechanism on the cycling history of polycrystalline copper

In order to determine whether or not starting a test in ramp loading has an effect on the fatigue mechanism when the test is continued in constant stress or strain, polycrystalline copper specimens have been cycled to failure in load or strain control, with and without initial ramp loading. The failure mechanisms were studied by fractography and gauge observations using scanning electron microscopy. Ramp loading is found to extend life and to change the failure mode from intergranular to transgranular provided that the stress or strain amplitude lies below the “plateau” in the cyclic stress-strain curve. Ramp loading emphasizes single-slip behavior and loop patch dislocation structures, strain localization and cracking in persistent slip bands, whereas starting a test in constant stress or strain, at intermediate amplitudes, promotes multislip and the cooperative deformation between adjacent grains which is necessary for intergranular cracking.

Dislocation structures of monocrystalline copper in cyclic latent hardening

The dislocation structures of monocrystalline copper, which had first been cycled in single slip and, subsequently, deformed monotonically on another slip system, were studied by transmission electron microscopy (TEM). The purpose of the research was to study the interactions of dislocations on different slip systems with reference to cyclic latent hardening. A special effort was made to observe and analyze the activity of the secondary dislocations and the interaction between the secondary dislocations and preformed structures, such as persistent slip bands (PSBs) walls, loop patches, and labyrinth structures. It was confirmed that the operation of secondary dislocations is a necessary condition for the formation of a persistent slip band from a preexisting loop patch. “Cord” structures were found to result from non-coplanar slip behavior, and their directions were always along the intersecting trace of the active non-coplanar slip plane on the photograph plane. Labyrinth wall structures were found to form only in cyclic deformation by multislip, and the geometry of labyrinth walls was confirmed to be in accordance with the “sweep theory” of Dicksonet al. The magnitude of the plastic strain amplitude applied during the previous cyclic deformation did not affect the latent hardening ratio but was found to strongly affect the strain hardening rate on the latent slip system, consistent with the observation of higher densities of secondary dislocations produced by cycling at amplitudes greater than 2×10–3.