Collinear Array Research Articles

Appraising the Effect of Null-fill to the Broadcast Coverage of Four-bay Collinear Array

Null-fill is a method of improving the signal level in areas where pattern nulls occur. To take advantage of itin improving FM broadcast coverage, factors such as antenna height in relation to the average terrain, the number of bays in the array and the location of the target area are considered. It is therefore important to understand the radiation characteristics of the antenna system after the application of null-fill. This paper presents an analysis of the radiation characteristics of a four-bay FM collinear antenna array composed of circularly polarized elements with varying upper and lower bank power ratios. The analysis leads to the discussion of the capabilities and limitations of null-fill with the different bank ratios. Results show that, in the elimination of pattern nulls, the bank power ratio of 95:5 produces the best results. Also, irrespective on the value of the bank ratio, there exists a pattern null near the tower base. If left uncorrected, this pattern null poses reception difficulty in that area. An explanation on the existence of this kind of null and a method of eliminating it is worth considering in future studies. Keywords—Broadcast antenna, Collinear array, FM antenna, Null-fill, Pattern null, Polarization

Investigation of structural, optical and magnetic properties of Y3-xCexFe5-yEryO12 compound

Herein, we have studied the structural, optical and magnetic properties of Y3-xCexFe5-yEryO12 (0.00 ≤ x ≤ 0.02), (0.00 ≤ y ≤ 0.06) compound synthesized via sol gel process. Structural characterization by X-ray diffraction (XRD) confirmed the YIG single phase formation, belong to the Ia3‾d cubic centrosymmetric crystal structure. The lattice constant, lattice strain, dislocation density and average crystallite size variations were calculated and discussed in terms of the rare earth's dopant concentrations. Fourier Transform Infrared Spectroscopy (FTIR) analysis showed redshift for the Fe–O stretching modes as the dopant content increase, testifying the crystal lattice expansion. Raman spectra inspection corroborated the YIG single phase formation and shifts in the vibrational modes confirmed the Ce3+ and Er3+ rare earths inclusion in the sites occupied by Y3+ and Fe3+ cations, respectively. The coral-like of YIG nanoparticles were confirmed by scanning (SEM) and transmission (TEM) microscopies, whereas the existence of the elements Y, Fe, O, Ce and Er, were verified by Energy Dispersive Spectroscopy analysis (EDS). The optical band gap (Eg) decreases, while Urbach energy (Eu) increases varying the Er content. The result confirms the effect of Ce3+ and Er3+ addition on the optical properties of YIG, contributing to localized oxygen vacancy defects formation. Using a phenomenological model, it was shown that, the highest probability of Er3+ cations occupation corresponds to octahedral sites. For the Y2.98Ce0.02Fe5-yEryO12 (0.00 ≤ y ≤ 0.06) compound, the theoretical saturation magnetization (Ms) was calculated from the cation distribution obtained by the phenomenological model, resulting a slight increase with the Er content. The result agrees with the experimental Ms measurements, although for y = 0.06 a discrepancy was detected, which can be attributed to the breaking of collinear array of magnetic moments due to high lattice distortions.

A single column plasma photonic crystal (SC-PPC)

In this paper, a reconfigurable one-dimensional single column plasma photonic crystal (SC-PPC) has been investigated. The SC-PPC is a glass column containing standing plasma density patterns (SPDPs) called plasma blobs, where its density varies sinusoidally along the column axis. It appears like a collinear array of the plasma blobs which is produced by having the critical combination of input RF power and gas pressure in a column. The numbers of blobs and plasma density can be controlled by RF power and gas pressure. The value of plasma density is measured for the different numbers of plasma blobs formation by using the experimental setup. These measured data are utilized in the modeling and simulation of SC-PPC for the photonic bandgap (PBG) analysis. The simulation outcomes reveal that the SC-PPC induces PBGs that can be reconfigured with plasma density, lattice constant, and numbers of plasma blobs. This paper explicitly investigates the PBG analysis by modeling two cases, where the plasma density Ne=2.45×1016 m−3 with five plasma blobs and Ne=9×1016 m−3 with six plasma blobs are considered. The obtained outcomes verify the reconfigurable characteristics of SC-PPC.

A Dual-Band Modified Franklin mm-Wave Antenna for 5G Wireless Applications

Franklin array antennas are considered as one of the most competitive candidates for millimeter-wave (mmW) 5G applications due to their compact size, simple geometry and high gain. This paper describes a microstrip Franklin antenna array for fifth generation (5G) wireless applications. The proposed modified Franklin array is based on a collinear array structure with the objective of achieving broad bandwidth, high directivity, and dual-band operation at 22.7 and 34.9 GHz. The designed antenna consists of a 3 × 3 array patch element as the radiating part and a 3 × 3 slotted ground plane operating at a multiband resonance in the mmW range. The dimensions of the patch antennas are designed based on λ/2 of the second resonant frequency. The designed antenna shows dual band operation with a total impedance bandwidth ranging from 21.5 to 24.3 GHz (fractional bandwidth of 12.2%) at the first band and from 33.9 to 36 GHz (fractional bandwidth of 6%) at the second band in simulation. In measurement, the impedance bandwidth ranges from 21.5 to 24.5 GHz (fractional bandwidth of 13%) at the first band and from 34.3 to 36.2 GHz (fractional bandwidth of 5.3%) at the second band, respectively. The performance of the antenna is analyzed by parametric analysis by modifying various parameters of the antenna. All the necessary simulations are carried out using HFSS v.14.0.

Characterization and Optimization of a Collinear Array of Circularly Polarized Side-Mounted Elements

This paper presents the radiation characteristics of a two-element collinear array of shunt-fed, slanted dipoles side-mounted to a metallic tower. It presents the radiation characteristics of the array as commonly implemented by FM broadcasters and suggests methods on how to optimize these characteristics such as the power gain, pattern circularity, side-lobe reduction, and horizontal-vertical polarization component ratio for the array to better conform to broadcast standards. By determining these characteristics using an advance antenna simulation software, optimization variables are identified, and their optimized values are determined. The optimized values lead to improved radiation characteristics of the array in conforming with broadcast requirements. Results show that adjusting the distance between the dipoles to less than one wavelength reduces the sidelobe of the array radiation pattern; varying the dipole physical specifications improves the polarization component ratio and the circularity of the radiation pattern. However, varying the dipole specifications also reduces the gain of the array. For applications requiring higher gains, other methods of realizing high collinear array gains are recommended.

Characterization and Optimization of a Collinear Array of Circularly Polarized Side-Mounted Elements

This paper presents the radiation characteristics of a two-element collinear array of shunt-fed, slanted dipoles side-mounted to a metallic tower. It presents the radiation characteristics of the array as commonly implemented by FM broadcasters and suggests methods on how to optimize these characteristics such as the power gain, pattern circularity, side-lobe reduction, and horizontal-vertical polarization component ratio for the array to better conform to broadcast standards. By determining these characteristics using an advance antenna simulation software, optimization variables are identified, and their optimized values are determined. The optimized values lead to improved radiation characteristics of the array in conforming with broadcast requirements. Results show that adjusting the distance between the dipoles to less than one wavelength reduces the sidelobe of the array radiation pattern; varying the dipole physical specifications improves the polarization component ratio and the circularity of the radiation pattern. However, varying the dipole specifications also reduces the gain of the array. For applications requiring higher gains, other methods of realizing high collinear array gains are recommended.

Generation of optical needles and bright spot arrays through reversing the radiation pattern of collinear antenna array

An optimization-free approach is proposed for generating optical needle and bright spot arrays with controllable distributions. This is achieved by inversely focusing the radiation pattern from a collinear antenna array whose elements are placed along an optical axis and whose currents in each element also flow along that direction, situated at the focus of a 4pi configuration. The shape and central location of the nth focusing field only depend on the length ln and coordinate zn of the nth element in collinear array, respectively. The number of focal fields is determined by the number of elements in the array.

Near-field wireless power transfer for moving vehicle using collinear array antenna

Near-field wireless power transfer for moving vehicle using collinear array antenna

3-D Coverage Beam-Scanning Antenna Using Feed Array and Active Frequency-Selective Surface

This paper presents the design of a smart antenna that can achieve 3-D beam-scanning coverage. The antenna consists of a novel planar feed array and a cylindrical active frequency-selective surface (AFSS). First, an array fed metallic reflector is studied as a reference antenna to validate the beam-scanning characteristics in the elevation plane. Then, the AFSS is assessed through simulation and measurement results. Finally, the complete structure containing the planar collinear array and the AFSS is analyzed. A prototype at S-band has been designed, manufactured, and measured. The resulting antenna is shown to be able to operate at the 2.4–2.5 GHz frequency band and switch beams in both the azimuth and elevation planes. In the azimuth plane, the proposed antenna is capable of sweeping beams toward different directions to cover a full range of 360°. In the elevation plane, it can achieve beam steering within an angle range of +16°/ − 15°. The measured maximum gain of the antenna is 9.2 dBi. This is the first report of a low-cost 3-D coverage beam-scanning antenna based on AFSS.

Analysis of the moments of the sensitivity function for resistivity over a homogeneous half-space: Rules of thumb for pseudoposition, offline sensitivity and resolution

It is instructive to consider the sensitivity function for a homogeneous half space for resistivity since it has a simple mathematical formula and it does not require a priori knowledge of the resistivity of the ground. Past analyses of this function have allowed visualization of the regions that contribute most to apparent resistivity measurements with given array configurations. The horizontally integrated form of this equation gives the sensitivity function for an infinitesimally thick horizontal slab with a small resistivity contrast and analysis of this function has admitted estimates of the depth of investigation for a given electrode array. Recently, it has been shown that the average of the vertical coordinate over this function yields a simple formula that can be used to estimate the depth of investigation. The sensitivity function for a vertical inline slab has also been previously calculated. In this contribution, I show that the sensitivity function for a homogeneous half-space can also be integrated so as to give sensitivity functions to semi-infinite vertical slabs that are perpendicular to the array axis. These horizontal sensitivity functions can, in turn, be integrated over the spatial coordinates to give the mean horizontal positions of the sensitivity functions. The mean horizontal positions give estimates for the centres of the regions that affect apparent resistivity measurements for arbitrary array configuration and can be used as horizontal positions when plotting pseudosections even for non-collinear arrays. The mean of the horizontal coordinate that is perpendicular to a collinear array also gives a simple formula for estimating the distance over which offline resistivity anomalies will have a significant effect. The root mean square (rms) widths of the sensitivity functions are also calculated in each of the coordinate directions as an estimate of the inverse of the resolution of a given array. For depth and in the direction perpendicular to the array, the rms thickness is shown to be very similar to the mean distance. For the direction parallel to the array, the rms thickness is shown to be proportional to the array length and similar to the array length divided by 2 for many arrays. I expect that these formulas will provide useful rules of thumb for estimating the centres and extents of regions influencing apparent resistivity measurements for survey planning and for education.

Design of Arrays of Linearly Polarized Patch Antennas on an FR4 Substrate: Design of a probe-fed electrically equivalent microstrip radiator

A new strategy for designing probe-fed electrically equivalent microstrip radiators based on their electrical dimensions is discussed in this article. Radiators on a Flame Retardant 4 (FR4) substrate are synthesized for equivalent performance, aiming at lower H-plane cross polarization over the bandwidth and resistive input impedance at the operating frequency. The effect of mutual coupling is analyzed for two classical arrangements: side-by-side and collinear configurations. With the proposed strategy, a broadside collinear array of linearly polarized rectangular patches is designed to operate at the center frequency of the industrial, scientific, and medical (ISM) band (2.45 GHz) on a moderately thick FR4 substrate. The array is designed for low cross polarization in the H-plane and to comply with the specified directivity and side lobe level (SLL). Special attention to the beamforming circuit design leads to a radiation efficiency near 70%.

A frequency-independent boundary element method for scattering by two-dimensional screens and apertures

We propose and analyse a hybrid numerical–asymptotic hp boundary element method (BEM) for time-harmonic scattering of an incident plane wave by an arbitrary collinear array of sound-soft two-dimensional screens. Our method uses an approximation space enriched with oscillatory basis functions, chosen to capture the high-frequency asymptotics of the solution. We provide a rigorous frequency-explicit error analysis which proves that the method converges exponentially as the number of degrees of freedom N increases, and that to achieve any desired accuracy it is sufficient to increase N in proportion to the square of the logarithm of the frequency as the frequency increases (standard BEMs require N to increase at least linearly with frequency to retain accuracy). Our numerical results suggest that fixed accuracy can in fact be achieved at arbitrarily high frequencies with a frequency-independent computational cost, when the oscillatory integrals required for implementation are computed using Filon quadrature. We also show how our method can be applied to the complementary ‘breakwater’ problem of propagation through an aperture in an infinite sound-hard screen.

Hydrodynamic correlations in three-particle colloidal systems in harmonic traps

We report on the hydrodynamic correlations between colloids immersed in a low Reynolds number fluid. We consider colloidal arrays composed of three particles; each colloid is trapped in a single harmonic potential and interacts with the other colloids only via hydrodynamic forces. We focus on the role of a third body in the two-body correlation functions. We give special attention to a collinear configuration of particles, although the salient features of an equilateral triangle configuration are outlined. The correlation functions are computed both by means of Brownian dynamics simulations, and by solving analytically and numerically the Langevin equation under the assumption of constant diffusion tensor; this approximation is validated through computer simulations. We explicitly show that the presence of a third body affects the auto- and cross-correlation functions and that their behaviour, in some specific conditions, can be different from that commonly seen in a two-particle system. In particular, we have found that the auto-correlation functions show a slower decay, while the cross-correlation ones exhibit a temporal shift and a weaker amplitude. Moreover, an unexpected behaviour related to a positive correlation and associated with the appearance of new dynamical modes is observed in the case of the collinear array of three particles. This interesting effect might be used to tune the degree of hydrodynamic correlation in few-body colloidal systems.

Vortex-induced vibration of a collinear array of bottom fixed flexible cylinders

An experimental study of vortex-induced vibrations of a collinear array of 10 identical flexible cylinders was conducted between 140<Re<450. The experiments were performed in a water tunnel using 0.13 mass-damping and 1% blockage ratio. Each cylinder response, for tested Reynolds number range, was determined tracking the cylinder free-end by means of a particle tracking velocimetry technique. Free-end displacements, free-end orbits, phase angle between cylinders as well as each cylinder frequency were obtained with data post-processing. The natural frequencies of one of the cylinders, in still water and still air, were measured as a reference throughout the lock-in region. The results show that the maximum displacement in the cross-flow direction for the first cylinder in the array is 28% higher compared to when it is isolated. Synchronization is reached from cylinder 2 throughout cylinder 8 for 340<Re<450. Under these conditions the cylinders have a CCW rotation and the cylinder frequency matches very accurately the cylinder natural frequency in still water. Moreover, the phase angle with respect to cylinder 2 shows a gradual delay as the Reynolds number is increased. The phase angle and the cylinder response are correlated with the vortex wake behavior and with the number of coherent vortices in the gaps between cylinders, respectively.

INVESTIGATION OF NEAR FIELD INDUCTIVE COMMUNICATION SYSTEM MODELS, CHANNELS AND EXPERIMENTS

Near-fleld inductive channels created between two or more magnetically coupled inductive nodes are studied in this paper. Peer- to-peer conflgurations and array architectures are discussed. The array channels are used for cooperative relaying with inductive methods with potential to provide range extension and enhanced data rate access in magnetic induction communication systems. The received power shows the presence of the nearest neighbour interactions and the in∞uences of higher order coupling from nodes two or more positions away from the receiver. This in∞uence causes phase changes in the communication system. Four methods of exciting the antenna arrays are proposed. These are array edge excitation, center excitation, collinear array excitation and multi-array excitation. Experiments with hardware nodes show that while array edge excitation provides increased power at the array edge, it is out performed by array center excitation which results to twice the power captured at the array center node compared to the power captured at edge excited flrst element. We demonstrate by example that a receiver is in∞uenced most by its neighbouring nodes on both sides and that the efiects of second and third tier neighbours are relatively insigniflcant.

Parasitic Current Reduction on Electrically Long Coaxial Cables Feeding Dipoles of a Collinear Array

The reduction of parasitic currents induced on the outer conductor of electrically long coaxial cables feeding the dipoles of a collinear array is addressed. Firstly, an experimental model is presented, and its appropriateness has been verified through validation with simulations data. The above model has been used to show the effectiveness of a low-cost technique to suppress the RF currents induced on the coaxial cables running inside the metallic mast of a collinear dipole array. The proposed solution consists of a dielectric-loaded coaxial choke, realized as a shorted quarter-wavelength coaxial cylinder mounted on the external conductor of the coaxial cable, and filled with Polytetrafluoroethylene (PTFE) to reduce its physical length. The PTFE-loaded choke performance is shown through both numerical simulations and measurements on prototypes, in the 200-400 MHz frequency range. Finally, a numerical parametric analysis is performed to get some design criteria for more complex multiple-choke arrangements.

Synthesis of nonuniformly spaced linear array of parallel and collinear dipole with minimum standing wave ratio using evolutionary optimization techniques

In this paper, the author proposes a method based on two recent evolutionary algorithms (EAS): particle swarm optimization (PSO) and differential evolution (DE) to design nonuniformly placed linear arrays of half-wavelength long dipoles. The objective of the work is to generate pencil beam in horizontal (for parallel array) and vertical (for collinear array) plane with minimum standing wave ratio (SWR) and fixed side lobe level (SLL). Dynamic range ratio (DRR) of current amplitude distribution is kept at a fixed value. Two different examples have been presented having different array alignments. For both the configurations parallel and collinear, the excitation distribution and geometry of individual array elements are perturbed to accomplish the designing goal. Coupling effect between the elements is analyzed using induced electromotive force (EMF) method and minimized in terms of SWR. Numerical results obtained from both the algorithms are statistically compared to present a comprehensive overview. Beside this, the article also efficiently computes the trade-off curves between SLL, beam width, and number of array elements for nonuniformly spaced parallel array. It featured the average element spacing versus SWR curve for nonuniformly separated arrays. Furthermore, minimum achievable SLL performances of uniformly and nonuniformly spaced parallel arrays are compared for same average spacing in the proposed work.

Zero tilt omnidirectional collinear array antenna with coplanar feed

An innovative approach to the design of a centre-fed omnidirectional collinear array for use in the 900 MHz band is presented. The coplanar printed circuit realisation using a combination of the CPW and coplanar strips is shown to be very effective in eliminating beam tilt with change in frequency. Both measured and simulated results confirm less than 1.5° of beam tilt in the omnidirectional pattern with an azimuth ripple of approximately +/−0.7 dB, over an impedance bandwidth of greater than 10%.

The Van der Pauw method for sheet resistance measurements of polypyrrole‐coated para‐aramide woven fabrics

AbstractIn this article, it is shown that the Van der Pauw (VDP) method, generally known in microelectronics, can be successfully adapted to sheet resistance measurements of electroconductive fabrics. We prepared two polypyrrole‐coated woven para‐aramide fabrics and used a simple setup to measure their sheet resistances. The results were then compared with those obtained using a sophisticated commercial collinear array probe. The measurements were done in a 1 month interval, to investigate the influence of the coating aging on the sheet resistance of the samples. The influence of the contact positioning on the accuracy of the VDP measurement was investigated. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Pb, Sr and Nd isotope systematics of metavolcanic rocks of the Hutti greenstone belt, Eastern Dharwar craton: Constraints on age, duration of volcanism and evolution of mantle sources during Late Archean

The Hutti greenstone belt, hosting major gold mines, is made up of tholeiitic basalts, felsic volcanic rocks and sediments metamorphosed to amphibolite facies and surrounded by granitoid rocks, predominantly of granodiorite in composition. The granitoid rocks show intrusive contact relationship at places along the eastern and northern margins of the belt while such relationships could not be observed along the western margin as it is covered by soil. The tholeiitic basalts have flat to moderately LREE-enriched chondrite normalized REE patterns and show depletion in Nb relative to MORB. The Hutti metabasalts define a collinear array in the Rb–Sr isotope evolution diagram with a slope corresponding to an age of 2706 ± 130 Ma. The higher uncertainty is due to scatter caused by mobility of Rb and Sr during metamorphism and low temperature hydrothermal alteration. In the 206Pb/ 204Pb vs. 207Pb/ 204Pb diagram the metabasalts define a collinear array corresponding to an age of 2637 ± 150 Ma with significant scatter indicating that Pb was also mobilized by the post-crystallization alteration processes. The Sm–Nd isotope system in the Hutti metabasalts has been least disturbed giving an isochron age of 2662 ± 81 Ma which is suggested as the age of formation of their precursors. Combined with the published U–Pb SHRIMP ages on zircons from the felsic volcanic rocks it is inferred that the Hutti greenstone belt formed over a period of ⩾86 Ma. The major greenstone belts of the eastern Dharwar craton have evolved coevally at ca. 2700 Ma ago and are older than the surrounding granitoid rocks. The metabasalts have ε Nd values of +1.4 to +3.0 and ε Sr values of −23.4 to +2.0 and plot close to the mantle array. They were derived from long-term LREE depleted mantle source. The felsic volcanic rocks have ε Nd values of −1.3 and −1.4 and ε Sr values of −30.6 and +89.3, respectively. Their magmas were derived from older continental crustal sources.