Polar Arrays Research Articles

A Circularly Polarized Array Composed of Linear Polarized Microstrip Patches Fed by Metamaterial Transmission Line

A novel single-feed circularly polarized antenna array is constructed by a 2 × 2 array of four square linear polarized microstrip patches with orthogonal orientation and phase shift of 90° in between. The sequential rotation and suitable phasing of linear polarized microstrip patches improve the radiation pattern symmetry and input impedance matching of the array antenna. A metamaterial transmission line is designed and applied to feeding the antenna array. The metamaterial transmission line works at its zeroth order resonant mode and there is no phase shift between its four output ports. A circularly polarized antenna array at 5.8 GHz is built and demonstrated, which is fed by the metamaterial transmission line. The antenna array is compact and the whole dimension is about 1.1λ g 2. The antenna gain reaches 9 dBi, and shows a good axial ratio. Experimental results and simulation agree well.

Parameterized Modeling of Star Patterns for Traditional Latticed Screens

work makes the contribution of developing a parametric modeler for designing Islamic star patterns. The intention here is to innovate with new interpretations of star patterns for latticed screens, which are reminiscent of the Indo-Mughal era. With a motivation for providing traditional appearance to the buildings like resorts and hotels, traditional latticed screens with Islamic star patterns are used as a fundamental resource to archive decorative effects. Such latticed screens have been generated by using computer aided geometric modeling and manufacturing for commercial applications in the domain of architectural as well as interior decoration. Star patterns are realized as periodic and repeated arrangement of a type of motifs/compound-motifs. Further, motif/compound-motif is viewed as polar array of a primitive which is an atomic geometric object required for the representation of motif/compound-motif. Geometry of the primitives for motifs is defined in the form a planar map having a set of points. The positions of points are devised in terms of the modeling parameters and pairs of points are connected to generate a set of edges. By controlling the modeling parameters through a User Interface, patterns are rendered and further submitted to computer controlled laser cutting machine for fabrication.

Joint parameter estimation of DOD/DOA/polarization for bistatic MIMO radar

In the paper, polarization-sensitive array is exploited at the receiver of multiple input multiple output (MIMO) radar system, a novel method is proposed for joint estimation of direction of departure (DOD), direction of arrival (DOA) and polarization parameters for bistatic MIMO radars. A signal model of polarimetric MIMO radar is developed, and the multi-parameter estimation algorithm for target localization is described by exploiting polarization array processing and the invariance property in both transmitter array and receiver array. By making use of polarization diversity techniques, the proposed method has advantages over traditional localization algorithms for bistatic MIMO radar. Simulations show that the performance of DOD and DOA estimation is greatly enhanced when different states of polarization of echoes is fully utilized. Especially, when two targets are closely spaced and cannot be well separated in spatial domain, the estimation resolution of traditional algorithms will be greatly degraded. While the proposed algorithm can work well and achieve high-resolution identification and accurate localization of multiple targets.

Comprehensive embryo analysis of advanced maternal age–related aneuploidies and mosaicism by short comparative genomic hybridization

The short comparative genomic hybridization (short-CGH) method was used to perform a comprehensive cytogenetic study of isolated blastomeres from advanced maternal age embryos, discarded after fluorescent in situ hybridization (FISH) preimplantation genetic screening (PGS), detecting aneuploidies (38.5% of which corresponded to chromosomes not screened by 9-chromosome FISH), structural aberrations (31.8%), and mosaicism (77.3%). The short-CGH method was subsequently applied in one PGS, achieving a twin pregnancy.

A New Double-Directional Channel Model Including Antenna Patterns, Array Orientation, and Depolarization

Multiple-input-multiple-output (MIMO) wireless channel models are often too simplistic to accurately model wireless propagation effects or too complex and/or site specific to be used for analytical purposes. In this paper, we develop a double-directional MIMO channel model that accounts for important propagation effects like scattering, clustering, and channel depolarization and antenna effects like antenna diversity, cross polarization, and random array orientation, while still retaining an intuitive representation. The proposed model can be parameterized using channel measurements obtained from site-specific measurement campaigns or from standard-based channel models. We show, using simulations, that the proposed model captures channel and antenna effects not included in other models, like the third-generation partnership program (3GPP) spatial channel model, the WINNER, and the IEEE 802.11n channel model. We use the model to study the impact of random orientation and channel depolarization on the data rates of a MIMO system.

Fast representation of dipole-dipole geoelectrical data with pseudosections for regional surveys

I propose a fast method for constructing pseudosections of apparent resistivity from geoelectrical data collected for deep studies with continuous polar dipole-dipole arrays. Once a vertical section is fixed, each value of apparent resistivity is assigned to a point on the section and finally pseudosections are obtained by interpolation. This allows the geophysicist to represent a large amount of data in a fast and simple way, to perform a qualitative interpretation and to facilitate the quantitative interpretation.

Performance of Externally Pressurized Grooved Thrust Bearings

Externally pressurized grooved gas thrust bearings for shaft systems were studied both numerically and experimentally. Three thrust bearings composed of a symmetric pair of rings facing a shaft collar were tested. The rings, with inner and outer diameters of 52 and 110 mm, respectively, are equipped with a polar array of eight holes, with a 0.35-mm diameter, distributed on a 65-mm-diameter circumference. The influence of a circumferential groove situated in correspondence with the supply holes is discussed. In particular, two thrust bearings have a rectangular cross-sectional groove of 0.7-mm width and 10- and 20-μm depth. A numerical model based on Reynolds' equation is used to study thrust-bearing performance in relation to geometry (diameter of supply holes, clearance, and groove dimensions). A test rig is used to monitor thrust-bearing axial load capacity and stiffness, and evaluate damping and stability at different supply pressure rates. Experimental and numerical results are compared and discussed.

MIMO capacity convergence in frequency-selective channels

The dependence of multi-antenna capacity on bandwidth is characterized empirically for narrowband, wideband and ultrawideband indoor channels using spatial and polar arrays. It is shown that both the mean and the outage MIMO capacity increase with bandwidth, whilst the capacity coefficient of variation asymptotically vanishes.

Localization and function of Kinesin-5-like proteins during assembly and maintenance of mitotic spindles in Silvetia compressa

BackgroundKinesin-5 (Eg-5) motor proteins are essential for maintenance of spindle bipolarity in animals. The roles of Kinesin-5 proteins in other systems, such as Arabidopsis, Dictyostelium, and sea urchin are more varied. We are studying Kinesin-5-like proteins during early development in the brown alga Silvetia compressa. Previously, this motor was shown to be needed to assemble a bipolar spindle, similar to animals. This report builds on those findings by investigating the localization of the motor and probing its function in spindle maintenance.FindingsAnti-Eg5 antibodies were used to investigate localization of Kinesin-5-like proteins in brown algal zygotes. In interphase zygotes, localization was predominantly within the nucleus. As zygotes entered mitosis, these motor proteins strongly associated with spindle poles and, to a lesser degree, with the polar microtubule arrays and the spindle midzone. In order to address whether Kinesin-5-like proteins are required to maintain spindle bipolarity, we applied monastrol to synchronized zygotes containing bipolar spindles. Monastrol is a cell-permeable chemical inhibitor of the Kinesin-5 class of molecular motors. We found that inhibition of motor function in pre-formed spindles induced the formation of multipolar spindles and short bipolar spindles.ConclusionBased upon these localization and inhibitor studies, we conclude that Kinesin-5-like motors in brown algae are more similar to the motors of animals than those of plants or protists. However, Kinesin-5-like proteins in S. compressa serve novel roles in spindle formation and maintenance not observed in animals.

The 3D Structure of Villin as an Unusual F-Actin Crosslinker

Villin is an F-actin nucleating, crosslinking, severing, and capping protein within the gelsolin superfamily. We have used electron tomography of 2D arrays of villin-crosslinked F-actin to generate 3D images revealing villin's crosslinking structure. In these polar arrays, neighboring filaments are spaced 125.9 +/- 7.1 A apart, offset axially by 17 A, with one villin crosslink per actin crossover. More than 6500 subvolumes containing a single villin crosslink and the neighboring actin filaments were aligned and classified to produce 3D subvolume averages. Placement of a complete villin homology model into the average density reveals that full-length villin binds to different sites on F-actin from those used by other actin-binding proteins and villin's close homolog gelsolin.

Regional variation of microtubule flux reveals microtubule organization in the metaphase meiotic spindle

Continuous poleward movement of tubulin is a hallmark of metaphase spindle dynamics in higher eukaryotic cells and is essential for stable spindle architecture and reliable chromosome segregation. We use quantitative fluorescent speckle microscopy to map with high resolution the spatial organization of microtubule flux in Xenopus laevis egg extract meiotic spindles. We find that the flux velocity decreases near spindle poles by ∼20%. The regional variation is independent of functional kinetochores and centrosomes and is suppressed by inhibition of dynein/dynactin, kinesin-5, or both. Statistical analysis reveals that tubulin flows in two distinct velocity modes. We propose an association of these modes with two architecturally distinct yet spatially overlapping and dynamically cross-linked arrays of microtubules: focused polar microtubule arrays of a uniform polarity and slower flux velocities are interconnected by a dense barrel-like microtubule array of antiparallel polarities and faster flux velocities.

Design and parallel fabrication of wire-grid polarization arrays for polarization-resolved imaging at 155 μm

Polarization-resolved imaging can provide information about the composition and topography of the environment that is invisible to the eye. We demonstrate a practical method to fabricate arrays of small, orthogonal wire-grid polarizers (WGPs) that can be matched to individual detector pixels, and we present design curves that relate the structure to the polarization extinction ratio obtained. The photonic area lithographically mapped (PALM) method uses multiple-exposure conventional and holographic lithography to create subwavelength patterns easily aligned to conventional mask features. WGPs with polarization extinction ratios of approximately 10 at a 1.55 microm wavelength were fabricated, and square centimeter areas of square micrometer size WGP arrays suitable for polarization-resolved imaging on glass were realized.

Source location prediction of subsonic isothermal jet flows

The location of jet noise sources is a far from trivial problem that is of great importance for both understanding the noise production and radiation mechanisms and also for finding new jet noise reduction strategies. This paper presents comparisons of theoretical results with data for a number of jets. The theory used is based on the MGBK method but including a novel time scale based on the rate of energy transfer through the turbulent cascade. This new technique has been shown to give a number of advantages over existing models. The experimental results were obtained using the Polar Correlation Technique and were made at QinetiQ's Jet Noise Facility in the UK as part of the EU FP6 programme CoJeN. The high resolution jet noise images resulted from using a 64 microphone polar arc array set at two reference angles, namely 60 and 90 degrees to the jet axis. Comparisons with experimental data are made for coplanar and short cowl nozzles at different working conditions for predictions from different theoretical models. It is shown that the best agreement is obtained for the prediction methodology using the energy transfer rate timescale

Unpolarized calibration and nonuniformity correction for long-wave infrared microgrid imaging polarimeters

Recent developments for long-wave infrared (LWIR) imaging polarimeters include incorporating a microgrid polarizer array onto the focal plane array. Inherent advantages over other classes of polarimeters include rugged packaging, inherent alignment of the optomechanical system, and temporal synchronization that facilitates instantaneous acquisition of both thermal and polarimetric information. On the other hand, the pixel-to-pixel instantaneous field-of-view error that is inherent in the microgrid strategy leads to false polarization signatures. Because of this error, residual pixel-to-pixel variations in the gain-corrected responsivity, the noise-equivalent input, and variations in the pixel-to-pixel micropolarizer performance are extremely important. The degree of linear polarization is highly sensitive to these parameters and is consequently used as a metric to explore instrument sensitivities. We explore the unpolarized calibration issues associated with this class of LWIR polarimeters and discuss the resulting false polarization signature for thermally flat test scenes.

The area composita of adhering junctions connecting heart muscle cells of vertebrates. V. The importance of plakophilin-2 demonstrated by small interference RNA-mediated knockdown in cultured rat cardiomyocytes

In the adult mammalian heart, the cardiomyocytes are connected by large polar arrays of closely spaced or even fused composite, plaque-bearing adhering junctions ( areae compositae, ACs), in a region usually termed “intercalated disk” (ID). We have recently reported that during late embryogenesis and postnatally these polar assemblies of AC-junction structures are gradually formed as replacements of distinct embryonal junctions representing desmosomes and fasciae adhaerentes which then may amalgamate to the fused AC structures, in some regions occupying more than 90% of the total ID area. Previous gene knockout results as well as mutation analyses of specific human cardiomyopathies have suggested that among the various AC constituents, the desmosomal plaque protein, plakophilin-2, plays a particularly important role in the formation, architectural organization and stability of these junctions interconnecting mature cardiomyocytes. To examine this hypothesis, we have decided to study losses of – or molecular alterations in – such AC proteins with respect to their effects on myocardiac organization and functions. Here we report that plakophilin-2 is indeed of obvious importance for myocardial architecture and cell–cell coupling of rat cardiomyocytes growing in culture. We show that siRNA-mediated reduction of the cardiomyocyte content of plakophilin-2 but not of some other major plaque components such as desmoplakin results in progressive disintegration – and losses – of AC junction structures and that numerous variously sized vesicles appear, which are plaque protein-associated as demonstrable by immunofluorescence and immunoelectron microscopy. The importance of plakophilin-2 as a kind of “organizer” protein in the formation, stabilization and functions of the AC structure and the ID architecture is discussed in relation to other junction proteins and to causes of certain cardiomyopathies.

Molecular recognition and supramolecular self-assemblies of (±)-2,2′-dihydroxy-1,1′-binaphthyl with aromatic aza compounds

(±)-2,2′-dihydroxy-1,1′-binaphthyl (binol) co-crystallized with 1,10-phenanthroline-5,6-dione and acridine to afford co-crystals (Binol)·(1,10-phenanthroline-5,6-dione) 1 and (Binol)·(acridine)2 2, respectively. Co-crystal 1 crystallizes in space group P-42(1)c, with a = 14.9921(4), b = 14.9921(4), c = 20.8102(12) A. Co-crystal 2 crystallizes in space group P2/c, with a = 17.8004(19), b = 10.0093(11), c = 19.393(2) A, and α = γ = 90°, β = 103.187(2)°. In co-crystal 1, the components form an infinite 1D polar array; whereas in 2, the components form discrete three-component aggregates. Molecular recognition and supramolecular self-assemblies of (±)-2,2′-dihydroxy-1,1′-binaphthyl with aromatic aza compounds Baoming Ji, Shaobin Miao, Dongsheng Deng As a result of mutual recognition, (±)-binol with 1,10-phenanthroline-5,6-dione and acridine afforded co-crystals 1 and 2, respectively. In 1 the components form an infinite 1D polar array, whereas in 2 the components form discrete three-component aggregates.

Frequency-Space-Polarization on UWB MIMO Performance for Body Area Network Applications

This letter experimentally investigates the performance of ultrawideband (UWB) radio technologies with multiple-input multiple-output (MIMO) antennas for body area network (BAN) applications. Effects of array spacing, antenna polarization, bandwidth and propagation on UWB-MIMO channel capacity are analyzed. The key finding here is to that in BAN the MIMO channel capacity is mainly determined by the power imbalance between subchannels compared to the sub channel correlation for both spatial array and polar array. For spatial array, the measured results show that the MIMO channel capacity is decreased when the array spacing is increased, despite the spatial correlation coefficient is decreased. This phenomenon is different from that in wide area networks (WAN) and wireless local area networks (WLAN). It is because that power difference among elements of the spatial array is significant in BAN short-range communications compared to that in WAN and WLAN. For polar array, the achievable channel capacity is lower than that of the spatial array in line-of-sight (LOS) conditions due to high cross-polarization discrimination. Furthermore, the MIMO capacity is slightly dependent on the environments due to dominance of human body effect. It is also found that the MIMO channel capacity decreased with frequency or bandwidth.

Retro‐directive array using two‐port dual polarized elements

AbstractIn this article, linear and circular polarized retro‐directive arrays with two‐port dual‐polarized elements are implemented. Pair of elements is arranged so that each vertical port is connected to the horizontal port and vice versa. In this way, reflection field from the ground plane and the reradiated field by way of interconnection can easily be distinguished not only for the linear polarized array but also for the circular polarized array. Simulations and experiments were conducted at 5 and 10 GHz for 2D linear and circular polarized array. respectively. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 450–453, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23113

Measured MIMO Capacity and Diversity Gain With Spatial and Polar Arrays in Ultrawideband Channels

This paper experimentally investigates the performance of multiple-input multiple-output (MIMO) systems in indoor ultrawideband (UWB) channels. The improvement in robustness and information rate due to spatial and polar antenna arrays is evaluated. The subchannel correlation, power gains of supported eigenmodes, and branch power ratios are analyzed. The polar arrays are found to experience lower correlation than that of spatial arrays. SNR gains of up to 3 and 5 dB are reported with 1times2 and 1times3 spatial arrays, respectively; the latter is shown to double the coverage range. The mutual information capacity is found to scale almost linearly with the MIMO array size, with very low variance. It is confirmed that the device compactness achieved by the polar array comes with only a small penalty in the achievable capacity and SNR gain compared to the spatial array. The multiple-antenna UWB techniques explored in this paper offer the potential for high-data-rate, robust communications.

Measured MIMO Capacity and Diversity Gain With Spatial and Polar Arrays in Ultra Wideband Channels

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> This paper experimentally investigates the performance of multiple-input multiple-output (MIMO) systems in indoor ultra wideband channels. The improvement in robustness and information rate due to spatial and polar antenna arrays is evaluated. The subchannel correlation, power gains of supported eigenmodes, and branch power ratios are analyzed. The polar arrays are found to experience lower correlation than spatial arrays. SNR gains of up to 3–5 dB are reported with 1<formula formulatype="inline"><tex>$\,\times\,$</tex></formula>2 and 1<formula formulatype="inline"><tex>$\,\times\,$</tex></formula>3 spatial arrays, respectively; the latter is shown to double the coverage range. The mutual information capacity is found to scale almost linearly with the MIMO array size, with very low variance. It is confirmed that the device compactness achieved by the polar array comes with only a small penalty in the achievable capacity and SNR gain compared to the spatial array. The multiple-antenna UWB techniques explored in this paper offer the potential for high data rate and robust communications. </para>