Compact Band Research Articles

Compact wearable dual wideband circularly polarized L-strip fed slotted textile antenna with parasitic elements for ISM band applications

This paper presents an L-strip fed compact wearable dual wide band circularly polarized textile antenna (DWCPTA) with a pair of parasitic elements and dual wide band operations at frequencies 2.45 and 5.80 GHz for industrial, scientific and medical (ISM) band applications. The antenna is printed on top of denim (jeans) substrate having dielectric constant 1.7 and thickness of 1.43 mm with wide slot ground plane on back side. The proposed DWCPTA of size 40 × 40 × 1.43 mm3 achieves -10 dB simulation impedance bandwidth of 89.16% (2.3 – 6.0 GHz) and 3-dB axial ratio bandwidth (ARBW) of 47.55% (2.34 – 3.80 GHz) and 12.60% (5.20 – 5.90 GHz) and essentially, low specific absorption rate (SAR) values of 0.8 and 0.95 W/Kg over 10 g of human tissues for wide band operations at frequencies 2.45 and 5.80 GHz respectively. The proposed DWCPTA is designed, fabricated and tested, which shows good agreement between measured and simulated ones.

Compaction banding in high-porosity carbonate rocks. Part I: Experimental observations

Compaction banding in high-porosity carbonate rocks. Part I: Experimental observations

Simulating spatial heterogeneity through a CT-FE mapping scheme discloses boundary effects on emerging compaction bands

Deformation experiments on porous rocks conducted at sufficiently high confining pressure may result into localized compaction. While strain localization is expected to be triggered by material heterogeneities, evidence of compaction zones propagating from the specimen boundaries is often observed, thus indicating that sample-platen friction plays a relevant role on the compaction banding patterns. This paper aims to examine this hypothesis and quantify the relative role played by field heterogeneities and boundary effects by using a numerical replica of specimens for which compaction localization was tracked through X-ray micro-tomography. For this purpose, finite element simulations are performed, where spatially-distributed heterogeneities of the porosity field are replicated through a computerized-tomography to finite-element (CT-FE) mapping scheme. The concept of representative elementary volume is used to extract material state variables directly from the CT scans, eventually associating each integration point to a corresponding volume in the digital image. Full-field numerical analyses conducted on the virtual replicas show that frictionless specimens promote the onset of compaction localization in zones characterized by higher porosity (i.e., lower strength). By contrast, the presence of platen-specimen friction nearly eliminates the impact of material heterogeneities, such that compaction localization is forced to occur at the specimen boundaries. Furthermore, the analyses reveals the existence of an intermediate range of platen-specimen friction coefficient which favors the emergence of a transitional regime of strain localization at which material heterogeneity and boundary effects concurrently control the compaction banding patterns. Numerical simulations based on quasi-synthetic spatial fields have also revealed a marked dependence of the three zones on the degree of heterogeneity, showing that increasing values of boundary friction are necessary to offset the effect of material weaknesses in strongly heterogeneous samples.

Compact Circular CSRR Loaded Koch Fractal Inspired Frequency Band Reconfigurable Antenna

A compact frequency band reconfigurable dual-mode antenna utilizing both Koch fractal geometry and circular complementary split ring resonators (CSRRs) is presented in this paper. The proposed antenna can be electrically switched into both dual- and single-band resonance modes. A Koch curve derivative novel fractal curve is used to design the patch boundary of the antenna. Two optimized circular CSRRs are loaded inside the antenna geometry to achieve double-band resonance. The antenna operates at both 5.1[Formula: see text]GHz (upper WLAN band) and 9.6[Formula: see text]GHz ([Formula: see text]-band) in dual resonance mode and resonates only at 8[Formula: see text]GHz ([Formula: see text]-band) in single resonance mode. A properly biased RF-range PIN diode placed at the slotted ground plane reconfigures the antenna in two operating modes by switching into its ON–OFF states. The antenna is fabricated on cost-efficient epoxy (FR-4) substrate consuming the maximum dimension of [Formula: see text] which is much more compact than the conventional rectangular patch antennas designed for similar bands. Stable radiation characteristics with reduced cross-polarization are achieved at all the resonant bands of the antenna. A prototype of the proposed antenna is fabricated and measured. The simulated results are in good agreement with the measured ones.

Microwave photonic frequency down-conversion and channel switching for satellite communication.

We present a photonic approach to realize radio frequency (RF) down-conversion and intermediate frequency (IF) channel switching for satellite communication. Conventionally, photonic RF mixers always suffer from limitations of one operational state and one IF channel. We proposed a photonic repeater that can realize multiple frequency down-conversion states and different IF channel switching. Two separated RF ports and two independent local oscillator ports ensure the repeater can down-convert RF signals in different bands simultaneously. Based on the characteristic that orthogonally polarized optical signals cannot beat with each other, the crosstalk between different channels is alleviated. Since no optical filters are involved, the repeater can process broadband RF signals down-conversion and broadband IF signals channel switching. The proposed photonic repeater features compact structure, broad and different bands of operation, and no physical optical splitting, which is promising for a satellite payload.

A compact flower slotted dual band notched ultrawideband antenna integrated with Ku band for ultrawideband, medical, direct broadcast service, and fixed satellite service applications

AbstractA compact flower slotted antenna (FSA) for dual band eliminated ultrawideband (UWB) integrated with Ku band applications is proposed. The basic FSA with modified ground structure is utilized for obtaining fractional bandwidth of 137% (3.45‐18.45 GHz). The dual band eliminated frequencies are achieved by a via hole to eliminate 5.39 to 5.90 GHz (upper WLAN band) frequencies and by utilizing symmetrical inverted L‐shaped parasitic elements to notch 7.30 to 7.75 GHz (downlink of X‐ band satellite communication link) frequencies. The FSA is having a compact size of 16 × 22 mm2 printed on low cost FR‐ 4 substrate with two band notched characteristics, nearly omnidirectional radiation characteristics and stable gain over UWB frequency range makes it suitable for portable UWB systems.

Compact Ultra-Wide-Band HI Monopole Antenna Loaded with C-Shaped Parasitic Elements for DVB-T and LTE Applications

In this study, a compact ultra-wide band microstrip antenna loaded with C-shaped parasitic elements, for Digital Video Broadcasting – Terrestrial (DVB-T) and LTE 450 / 700 signal reception, is presented. The proposed antenna is named “HI Monopole”, and its geometry has been designed to be simple and intuitive, lightweight, compact, possessing a low fabrication cost as well as an easy installation process inside electronic gadgets. The HI Monopole operates with ultra-wide bandwidth characteristics for operation within Digital Video Broadcasting – Terrestrial (DVB-T) standard, 470–890 MHz, that has been accomplished by: inserting an indent in its ground plane, adjusting the dimension of the feeding line, and adding two C-shaped parasite elements onto the region posterior to the antenna’s main irradiating element. It was verified through electromagnetic measuring that this device is capable of covering the 429-1022 MHz range, thus having 593 MHz of bandwidth. The superior and inferior cutoff frequencies have been chosen as the values in –10 dB of the device’s return loss. Therefore, the proposed antenna can be utilized in DTV and LTE signal reception through broadcasting in any country, independently of its adopted standard.

Simulation of emergent compaction banding fronts caused by frictional boundaries

This study examines the role of boundary friction in promoting heterogeneous compaction in soft rock specimens loaded at high confining pressure outside the domain of compaction localisation. An elastoplastic constitutive model characterised by tunable hardening/softening behaviour is used to conduct the analyses. Finite-element simulations suggest that material instability is a non-necessary condition for the emergence of compaction fronts. Such fronts propagated as a result of a severe deviation in the local responses induced by frictional constraints. These findings suggest that boundary effects can bias the assessment of the extent of the compaction localisation domain. Experimental countermeasures and informed model calibration procedures are therefore necessary to minimise such bias and enable more accurate predictions of soft rock compaction.

Imaging strain localisation in porous andesite using digital volume correlation

Strain localisation structures, such as shear fractures and compaction bands, are of importance due to their influence on permeability and therefore outgassing, a factor thought to influence eruptive style. In this study, we aim to develop a better understanding of strain localisation in porous volcanic rocks using X-ray tomographic images of samples of porous andesite (porosity = 0.26) acquired before and after deformation in the brittle and ductile regimes. These 3D images have been first analysed to provide 3D images of the porosity structure within the undeformed andesite, which consists of a large, well-connected porosity backbone alongside many smaller pores that are either isolated or connected to the porosity backbone by thin microstructural elements (e.g., microcracks). Following deformation, porosity profiles of the samples show localised dilation (porosity increase) and compaction (porosity reduction) within the samples deformed in the brittle and ductile regimes, respectively. Digital volume correlation (DVC) of the images before and after triaxial deformation was used to quantify the tensor strain fields, and the incremental divergence (volumetric strain) and curl (used as an indicator of shear strain) of the displacement fields were calculated from the DVC. These fields show that strain localisation in the sample deformed in the brittle regime manifested as a ~ 1 mm-wide, dilatational shear fracture oriented at an angle of 40–45° to the maximum principal stress. Pre- and post-deformation permeability measurements show that permeability of the sample deformed in the brittle regime increased from 3.9 × 10−12 to 4.9 × 10−12 m2, which is presumed to be related to the shear fracture. For the sample deformed in the ductile regime, strain localised into ~1 mm-thick, undulating compaction bands orientated sub-perpendicular to the maximum principal stress with little evidence of shear. Taken together, our data suggest that these bands formed during large stress drops seen in the mechanical data, within high-porosity zones within the sample, and within the large, well-connected porosity backbone. Pre- and post-deformation permeability measurements indicate that inelastic compaction decreased the permeability of the sample by a factor of ~3. The data of this study assist in the understanding of strain localisation in porous volcanic rocks, its influence on permeability (and therefore volcanic outgassing), and highlight an important role for DVC in studying strain localisation in volcanic materials.

Compact Dual Band Microstrip Patch Antenna for Wireless Applications with Enhanced Bandwidth

Compact Dual Band Microstrip Patch Antenna for Wireless Applications with Enhanced Bandwidth

Compact dual band circularly polarized meta‐structured antenna for GPS application

AbstractIn this letter, a dual band circularly polarized (CP) meta‐structured antenna is designed by −1 mode for L1 band and mu‐zero resonance mode for L2 band, respectively. The antenna consists of two kinds of unit cells which have four unit elements for −1 mode and mu‐zero resonance mode, respectively, in order to utilize the limited space efficiently, and to maximize the gain. Since two modes of −1 mode and mu‐zero resonance mode operate like as loop antenna, these are fed by magnetic coupling of an aperture, simultaneously. In order to reduce mutual coupling between two modes, the orientation of −1 mode antennas are tilted by 45° from that of MZR mode antennas. In this arrangement, magnetic fields with two directions are needed to excite all unit elements, simultaneously. Thus, a cross shaped asymmetric aperture is employed. The RHCP gain of the antenna is measured to be 0.59 dBic at L1 band and −0.02 dBic at L2 band, respectively. The size of the antenna is only 0.14 λ0 by 0.14 λ0 (krground = 1.28) at L2 band. The measured results show a good agreement with those of simulations.

Pattern transitions of localized deformation in high-porosity sandstones: Insights from multiscale analysis

We employ a hierarchical multiscale modeling approach to investigate the transitions of localized deformation patterns in high-porosity sandstone subjected to sustained shear to understand their underlying physics. The multiscale approach is based on hierarchical coupling between finite element method (FEM) with discrete element method (DEM) to offer cross-scale predictions for granular rocks without assuming phenomenological constitutive relations. Our simulations show that when a high-porosity sandstone specimen is subjected to continuous deviatoric loading, compaction bands may occur and evolve, featuring a steady movement of the compaction front (i.e. the boundary between the compaction band and the rest uncompacted zone). The specimen reaches a homogeneous state of reduced porosity when the compaction fronts traverse the entire specimen. A re-hardening response is initiated in the specimen under further shear, which is followed by a shearing dominating stage with the emergence of shear bands. The material responses inside the ultimate shear bands approach a “steady state” of constant porosity and stress ratio. Cross-scale analyses reveal that debonding and pore collapse are dominant mechanisms for the compaction stage of the specimen, and debonding and particle rotation dictate the physics for the shear banding stage. The transitions from compaction to shear banding occurs due to the degradation of the cohesive contact network and significant reduction in porosity. There are limited number of interparticle bonds remaining at the “steady state” under sustained shear, with a preferential direction perpendicular to the loading direction, leading to a higher steady void ratio than the critical state void ratio of non-cohesive sand.

New electromagnetic band gap antenna for multiple ultra wide band applications

This paper presents a compact multiband microstrip electromagnetic band gap (EBG) patch antenna with partial ground used for the 2nd and 3rd mode excitation, allowing multiple band resonance and control of the resonance frequencies. The electromagnetic band gap elements are inserted to improve obviously output parameters (gain directivity, return loss, maximum radiation Intensity, and radiation efficiency). Simulation and measurement results show a multiband antenna WiMAX, WLAN-band applications that can effectively cover three separated bandwidths (2.12, 3.1 and 5.41 GHz). The proposed compact antenna is grounded on a 1.6 mm-thick FR4 epoxy substrate with overall dimension of 0.305λ × 0.305λ × 0.012λ at lower frequency. The whole size of the proposed antenna with an overall area of 25 × 38 × 1.6 mm3 is maintained, and a low cross-polarization level within the operating frequency range. Electromagnetic Band Gap materials, artificially engineered structures, have the main role to improve the output performance of the patch antennas.

Dorsal Colour Patterns of Asian Water Monitor, Varanus salvator Collected for Trade in Cirebon, Indonesia

The Asian water monitor, Varanus salvator, has been exploited for its skin and meat in Indonesia. We found evidence of trade on this species in the greater Cirebon area in the province of Jawa Barat and linked the trade to raw skin supplies for local craft markets. Skins of water monitor distributed on Java were unique in their pattern, where a series of yellowish and dark grey scales that form a round shape called ocelli are arranged into two compact transverse bands on the back near the front limbs. This unique pattern found in our sample may be useful to identify the origin of skins collected for trade and the subsequent craft products. However, this pattern was absent in the craft products available for display in one of the warehouses visited for this study. On the other hand, we observed stockpiles of water monitor raw skins at the warehouses and found a slight difference in the dorsal color pattern. These raw skins in stock were lacking in “double banded” pattern on the dorsal side and were likely to be originated from other areas in Indonesia, possibly Sumatra or Kalimantan. Live animals for sale at the warehouses maybe used for other purposes than to supply materials for local craft industry, for example meat consumption or feed for catfish.

The dynamic evolution of compaction bands in highly porous carbonates: the role of local heterogeneity for nucleation and propagation

The formation of compaction bands in porous brittle rocks such as sandstones and carbonates has a significant impact on the localization mechanisms preceding earth and planetary surface instabilities such as earthquakes, landslides, and plate boundary faults. The micromechanics underpinning the dynamics of the formation of compaction bands and its effect on alteration of pore fluid pathways are not yet fully understood. The current study seeks to understand the mechanical properties of compaction in highly porous carbonate at micro- and macro-scale using time-lapse triaxial experiments in an X-ray transparent flow and deformation cell. Images were obtained with increasing axial strain levels using X-ray computed tomography allowing mapping of the evolution of internal structures. In addition to the X-ray analysis, digital image correlation (DIC) was used to quantify the evolution of strain and precisely identify the nucleation mechanism of compaction bands and its dynamics. The effect of friction on the boundary platens was shown to be minimal as evidenced by shear strain obtained from DIC analysis. This comprehensive analysis allowed assessment of the role of heterogeneity for the initiation of compaction bands. Local regions with high porosity provide the initial seeds for discrete compaction followed by the nucleation of traveling waves that lead to diffuse growth of the compaction zone. This interesting phenomenon is expected to be a fundamental mode of compressional deformation in porous brittle media where discrete, often periodic, deformation bands are observed on compaction.

Compact and wideband microwave bandstop filter for wireless applications

Compact, tunable and wide band stop filter (BSF) for wireless application is presented. The proposed filter is composed of compact rectangular microstrip open loop resonator with stub loaded resonator as building blocks of the filter. First, two vertical lumped capacitors are inserted in the open loop resonator from top to bottom of the substrate at the place which has maximum electric field to decrease the resonance frequency which in turn miniaturize the filter size. The resonance frequency of the fundamental mode is shifted from 5.5 to 4.2 GHz when lumped capacitors of 0.2 pF are added. Second, the capacitance of the open-ended stub can be changed to control the second resonance mode of the filter. Also, by inserting another vertical capacitor at the end of the open-ended stub, the second resonance mode can be controlled and reduced. Finally, by properly selecting the capacitance of the third lumped capacitor, the second resonance mode can be designed to be close to the fundamental mode and hence wide band stop filter can be achieved. The proposed BSF has some appropriate features such as compact size (its size has more than 40% size reduction), wide stopband and most importantly tunability of stopband. The band stop filter has a center frequency of 6.2 GHz, a stop band from 3.5 to 9 GHz, insertion loss lower than − 30 dB, and a return loss higher than 0.4 dB is accomplished inside the stop band. The measured results have good matching with the simulated results.

Design of miniaturized super wideband printed monopole antenna operating from 0.7 to 18.5 GHz

A design of compact Super-Wide Band (SWB) antenna with enhanced- bandwidth for wireless application is presented in this article. The proposed structure has fusion geometry of circular, square and trapezoidal slots on the rectangular radiator with a defected ground plane being used to enhance the VSWR bandwidth. Rectangular and trapezoidal-shaped slots are added in the ground plane to enhance the impedance bandwidth towards the lower cut off frequency. The proposed antenna has VSWR ≤ 2, average gain of 4.68 dBi, radiation efficiency of ≥ 83, fractional bandwidth (FBW) of 185.41%, and good pattern characteristics are achieved throughout the band. Moreover, the proposed SWB antenna is implemented in two ports multiple-input and multiple-output (MIMO)/diversity antenna. The diversified performances of MIMO antenna are calculated and it is observed that the proposed system has an isotropic radiation pattern. Four different configurations of MIMO antennas are designed and good isolation is achieved from port-to-port. The fabricated antenna has good agreement between simulated and measured results. The proposed antenna finds its applications in a wide range of UWB, K and Ku band portable devices.

Compact conformal wide band antenna for high‐speed WLAN applications

This article proposes a compact conformal wideband WiFi antenna based on a wide bandwidth, high-efficiency electromagnetic radiation structure (WHEMS). The concept of the equivalent current model for the WHEMS wideband antenna is described, and an example of a triband WiFi antenna covering 2.4, 5.2, and 5.8 GHz is illustrated. Miniaturization is achieved by cutting the symmetrical structure into half from the original WHEMS model, and wider beam coverage is also obtained. At the same time, the antenna is bent to be conformal with the router system shell and heat sinks, making the antenna more compact. A real award-winning model of a triband mesh WiFi device applying the proposed antenna is shown and tested. The antenna is integrated into a vertically positioned printed circuit board and coexists with a heat sink. The antenna concept and theory, in addition to the simulated and measured results, are provided. The measured | S11 | is lower than −10 dB in the designed wideband (2.4 ~ 2.5 GHz, 5.15 ~ 5.4 GHz, and 5.45 ~ 5.85 GHz). The measured gain at low frequency is about 3 dBi, and the measured gain at high frequency is about 5 ~ 6 dBi. The measured efficiency of the antenna is about 50% to 60%.

Spermatozoa ultrastructure, spermatogenesis and reproductive system of Acanthodasys australis (Gastrotricha, Macrodasyida)

Spermatozoon morphology, spermatogenesis and reproductive system of Acanthodasys australis (Thaumastodermatidae) were studied at ultrastructural level. The spermatozoon is a filiform cell formed by a cork-screw-shaped acrosome, a helical nuclear–mitochondrial complex and a long flagellum. The acrosome contains an axial tubular structure composed of a pile of electron-dense rings. The helical nucleus is thin and wraps a single, giant mitochondrion. A large and thick perinuclear helix surrounds the nuclear–mitochondrial complex extending for its whole length, except the two most basal coils. The flagellum with typical 9 × 2 + 2 axoneme is surrounded by a monolayered obliquely striated cylinder, in the terminal part of which the axoneme disappears. The general architecture of the spermatozoon of Acanthodasys species agrees with the general sperm model described for the family Thaumastodermatidae, and perfectly matches that observed in Acanthodasys aculeatus and Diplodasys ankeli, so confirming the great uniformity of the sperm ultrastructure morphology within the subfamily Diplodasyinae. Spermatogenesis includes the early and simultaneous development of acrosome and flagellum, the elongation of the nucleus and the fusion of mitochondria into a single giant mitochondrion, which later sinks into the nucleus, and the final appearance of a perinuclear helix and a peraxonemal striated cylinder. The process takes place through the same main steps already observed in all Macrodasyida species studied so far. The reproductive system consists of paired testes arrangement laterally to the intestine, a single ovary located dorsally to the posterior part of the intestine, a caudal organ located ventrolaterally to the intestine end, and, a dorsal frontal organ. The latter is in contact with mature oocyte posteriorly and with a compact cellular band connecting to the ‘rosette’ organ anteriorly. The general layout of the reproductive apparatus of A. australis perfectly matches that of the members of Diplodasyinae.

A Compact Ultra Wide Band CPW Fed Fractal Antenna with a Tapered Ground Plane

A Compact Ultra Wide Band CPW Fed Fractal Antenna with a Tapered Ground Plane