Omnidirectional Array Research Articles

Self‐Feedback Sensing Properties of Self‐Powered Multi‐Parameter Meteorological Sensor with Omnidirectional Array Structure

AbstractFrequent meteorological disasters pose more and more extensive threats to human life and property. However, the traditional meteorological sensors based on external power supply, for natural disaster monitoring and early warning, are severely limited in remote and unattended areas. Herein, a self‐powered multi‐parameter meteorological sensor (SMPM‐sensor) for various weather monitoring is proposed, which can monitor the weather through the feedback of electrical energy output while collecting natural energy. The designed 360° omnidirectional array structure facilitates efficient collection of all‐weather solar energy and rain energy in different directions and monitoring the light intensity without the influence of solar azimuth. Based on the four‐segmented disc‐shaped structure and the introduced Ecoflex transition layer, the frequency and amplitude of the wind electrical output can be effectively improved. Owing to structure and material optimizations, a good linearity of 0.9746 between the current and the solar illuminance is exhibited, a wide monitoring range of rainfall intensity changes from 0.1 to 11.9 mm min−1, and the linearity between wind speed and voltage frequency can be as high as 0.9986. Therefore, based on excellent sensing performances, good stability, and real‐time characteristic, the fabricated SMPM sensor provides a potential technological strategy for the field of meteorological disaster monitoring.

Compact, Broadband, and Omnidirectional Antenna Array for Millimeter-Wave Communication Systems

In this paper, a millimeter-wave printed quadrupole antenna is proposed. It consists of two symmetric printed dipoles that make the quadrupole radiating power omnidirectionally. Such an arrangement eliminates the influence of the ground as reflector. Simulation results show that the quadrupole antenna exhibits a broad impedance bandwidth and an enhanced gain compared to conventional dipoles. More interestingly, the configuration of the quadrupole includes an integrated feed network, making the design compact. Next, a novel omnidirectional array was designed, simulated, fabricated, and measured, exhibiting enhanced features like compactness, broad bandwidth, high gain, high efficiency, low cross-polarization, low cross-polarization level, low cost, and low profile.

A novel wideband planar Ku‐band array antenna for omnidirectional radar

AbstractThis aticle presents a new wideband omnidirectional array antenna that operates at Ku‐band. Each element of the array antenna consists of a modified planar bow‐tie dipoles radiator, a pair of parasitic strips, and a pair of directors. The parasitic strips and directors are designed to enhance the antenna omnidirectional radiating performance. All elements are combined through a double‐sided parallel strip‐line feeding network. A wideband semicircular balun is employed at the feeding port to broaden the impedance bandwidth. Finally, a 2 × 2 prototype is designed, fabricated, and measured. The measured results demonstrate that the proposed array antenna provides 47.3% (11.3‐18.4 GHz) relative impedance bandwidth with 4.1 dBi maximum gain, around 44.8° half‐power beamwidth at 15.0 GHz and less than 2.5 dB unroundness over the whole operating band in xoy plane.

A Horizontal Azimuth Pattern-Reconfigurable Antenna Using Omnidirectional Microstrip Arrays for WLAN Application

A horizontal azimuth pattern-reconfigurable antenna with configurable parasitic element arrays for WLAN applications is proposed in this paper. It consists of a control board, a central series-fed omnidirectional microstrip array, four configurable parasitic elements, a bottom conducting plate, and a top supporting plate. The omnidirectional microstrip array is adopted as an exciter, around which the four same parasitic element arrays are arranged at four corners. The p-i-n diodes as switches are placed between the parasitic element arrays and the conducting plate to control the fifteen radiation patterns of the proposed antenna. The parasitic element arrays are configured as reflectors or directors by switching the p-i-n diodes on or off. The bandwidth achieved ranges from 5.00 GHz to 5.27 GHz. A gain of 8.52 dBi is obtained when the antenna reaches the maximum gain in the H-plane at 5.2 GHz. Good agreements between the simulated and measured results were observed. The proposed parasitic structure which has the same structure with the driven element can enhance the horizontal azimuth gain of the antenna. Only 4 p-i-n diodes are used to produce up to 15 useful beam configurations with a gain range of 4.56-8.52 dBi at the horizontal azimuth.

Masked beamforming in frequency domain for hybrid acoustic vector sensor array

A masked beamforming algorithm for a hybrid acoustic vector sensor array (AVSA) is presented. In the general literature, a full-rank AVSA, comprised entirely of an acoustic vector sensor (AVS), is known to be capable of left–right ambiguity elimination. However, a full-rank AVSA has disadvantages including rotation perturbation of sensor directivity, complexity of electrical loading, and high cost. To alleviate these disadvantages, a hybrid AVSA consisting of only a single AVS in an array of omni-directional sensors is reported in the patent with a limited performance in left–right ambiguity elimination. A masked beamforming algorithm is proposed to achieve good left–right ambiguity elimination performance in a hybrid AVSA by masking the beam output spectrum of the omni-directional sensor array with the beam output spectrum of an AVS in the frequency domain. Simulation results that validate the performance of the proposed method are also presented.

Mechanical Properties of AlSi12-Based Metal Matrix Composites with Layered Metallic Glass Ribbons

During the last years, several studies proved the high potential of metallic glasses to be used as reinforcements in lightweight alloys. Thereby, focus was mostly on particle reinforced composites or three-dimensional and omnidirectional glass arrays within the composite. Using a specific layered structure of the entire ribbons as reinforcement to design direction-dependent tailored properties is a novel approach. The composites in this study were produced by gas pressure infiltration of a layered stack of metallic glass ribbons. Ribbons of the metallic glass Ni60Nb20Ta20 were used as reinforcements and aluminum alloy AlSi12 as matrix. Mechanical tests like four point bending and tensile tests as well as elastic analysis using ultrasound phase spectroscopy (UPS) were performed to classify composite’s properties. Further, micro computed tomography (µCT) analysis and metallographic investigations were carried out on the four point bending samples after testing to reveal occurring damage mechanisms.

A Compact Dual-Polarized 3:1 Bandwidth Omnidirectional Array of Spiral Antennas

A circularly polarized wideband omnidirectional array of spiral antennas is presented. It covers the frequency band from 1.2 up to 3.6 GHz while keeping a good $S_{11}$ and an omnidirectional coverage. This array achieved a dual polarization using left- and right-hand Archimedean spiral antennas. The gain of the array is enhanced using a unique cavity for the entire array, and the realized gain is above the maximum theoretical gain of a single spiral antenna.

Centre-fed dual band omnidirectional array antenna with electrical down tilt

A centre-fed dual band (3.5GHz/5.8GHz) omnidirectional microstrip array antenna for using in wimax applications is presented. Two distinct series fed back-to-back subarrays separated by a power divider are designated for these two bands. The proposed centre-fed structure reduces interference of two subarrays and provides a flexible progressive phase and so independent tilt angle control in dual bands. In addition, it is shown that compared to edge-fed dual band structure, the centre-fed structure makes the use of low permittivity substrates possible which are more appropriate for antenna radiation. The fabricated antenna can cover 3–3.7GHz and 5.4–6.4GHz frequency bands with S11<−10dB. It also shows about 10° down tilt in both frequency bands.

Consciousness displaced: Art and technology education/collaboration for an aesthetic of liberation

Abstract Modernity’s grand plans were designed far from where we stand today. The prerogative of progress as an ideological imperative that defined colonialism as a natural balance between the ‘developed’ societies’ moral duty to rescue ‘underdeveloped’ peoples from their fate of myth and superstition created education. Education that functions as an instrument that is used to facilitate the integration of generations into the logic and aesthetics of the status quo and to bring about conformity to the hegemonic cultural form of western technological consumer capitalism. This article explores whose education and for whom was it created by the imperial ideologies, not of nineteenth- or twentieth-century colonialism but for twenty-first-century western technological consumer neo-colonialism. From South Africa’s Apartheid era Liberation before education to Paulo Freire’s practice of freedom, this article questions the practices of new technologies, art and technology education at the edge of the disenfranchised. The traditional frameworks of education are on an ideological and methodological crisis worldwide. The hegemony of knowledge has ruptured away from academia. The linearity of thought has burst open as an omni-directional array. The hierarchy of authorship is contested and the audiences are becoming users and participants. As the ubiquity of information technologies, the emergence of connectedness, cheap chips and the presage of the Internet of things permeates every aspect of a particular section of people clustered in specific cities and spread out around the globe, a unique consciousness is evolving where a new collaboration paradigm is gaining a place of balance between us, nature and our technologies, our positions on social justice, and is evolving a symbiotic outlook at other cultures and societies.

Experimental Investigations of Cochannel Interference Reduction Effect at High Elevation Base Station Using Beam Tilt and Orthogonal Polarization

This paper addresses the problem of cochannel interference (CCI) generated in a mixed cell architecture in microcellular systems. In this type of microcellular systems in which both microcells and macrocells coexist in the same geographical urban area, the base station antennas mounted on the rooftops of buildings to cover wide circular radio zones suffer severe CCI from the surrounding low base stations. A dielectric-loaded slotted-cylinder antenna (DSCA) is applied to horizontally polarized omnidirectional array antennas in a height-diversity configuration with the high gain of 8 dBi, which is comparable to that of a collinear antenna, to reduce the CCI. The measurements conducted in a suburban area clarify the reduction in the CCI for three techniques. The beam-tilt technique reduces the CCI level by approximately 10 dB for both collinear antennas and the DSCA array antennas. The use of horizontal polarization reduces the CCI level by approximately 13 dB for the DSCA array antennas with and without beam tilt. The combination of the beam tilt and horizontal polarization or the DSCA array antennas with beam tilt significantly reduces the CCI level by approximately 23 dB.

Geographic mapping model for underground structural deformation monitoring

Underground structural deformation occurs because of the complex effects of the internal and external environments and it needs to undergo regional coverage deformation monitoring to realize the early warning of natural hazards. This issue remains a challenge for current deformation monitoring techniques. We present a geographic mapping model based on an ultrasonic omnidirectional array for deformation monitoring. First, an ultrasonic spherical array is established to achieve all-around monitoring for underground structural deformation. Second, an earth longitude–latitude mapping method is adopted to visually manage the spatial monitoring information. Third, the initial working time for the sensor node is allocated by considering a variety of environmental factors and using an intelligent clustering algorithm. The proposed method automatically detects, localizes, and tracks deformations by analysing the monitoring information, which is displayed on the earth longitude–latitude map. Lastly, experimental data are used to illustrate the application techniques as well as demonstrate the validity of the approach.

Path-Loss Model Including LOS-NLOS Transition Regions for Indoor Corridors at 5 GHz [Wireless Corner

Wideband indoor channel measurements were carried out by using dipole and omnidirectional arrays in two different office buildings. The carrier frequency was 5.25 GHz with 100 MHz RF bandwidth. In this paper, a d <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> -and- d <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> path-loss model is developed based on thirteen measurements routes in two different buildings. The model can continuously predict path loss when a mobile is turning indoor corners from line-of-sight (LOS) to non-line-of-sight (NLOS), or vice versa. By comparisons with the measured data, it was found that the path-loss model developed in this paper is more accurate than the ITU-R and WINNER I models. It is useful for indoor WLAN and B3G P2P (peer-to-peer) network simulations, planning, and optimization.

Individual Variability in Benefit from Fixed and Adaptive Directional Microphones

This study aimed to document improvements in speech recognition when listening through fixed or adaptive directional microphone arrays relative to listening through omnidirectional microphone arrays in a variety of near-field noise conditions. Twelve participants with mild to severe hearing loss were recruited. Data were analyzed in a manner to facilitate discussion of both group and individual performance. The activation of directional microphones significantly improved speech recognition in all listening conditions when compared to omnidirectional listening conditions. Significant differences in speech recognition performance were not observed between fixed and adaptive directional microphone conditions. Analysis of individual outcomes shows a wide range of both absolute speech recognition scores and directional benefit across treatment conditions.

WIDEBAND OMNIDIRECTIONAL PRINTED DIPOLE ANTENNA WITH COUPLING FEED FOR WIRELESS COMMUNICATION APPLICATIONS

The wideband and omnidirectional performance of a printed dipole antenna with a novel coupling feed structure is presented. Besides using printed dipole for omnidirectional radiation patterns, the coupling feed structure, which includes the transmission line coupling to a slot line to efiectively improve the impedance matching, can be used for bandwidth enhancement. A wideband impedance characteristic of about 45.6% for VSWR • 2 ranging from 1.54 to 2.45GHz is obtained. The omnidirectional radiation patterns in the whole operation bands are achieved which the un-roundness in H-plane is less than 1.6dB. It is su-cient for accommodating recent wireless communication services such as DCS1800, PCS1900, UMTS, IMT2000, Wibro, etc. Furthermore, the proposed antenna should be a good candidate as a unit of the omnidirectional array. A prototype has been fabricated and tested, and the experimental results validate the design procedure.

2A2-B02 32ch低サイドローブ設計マイクロホンアレイの開発と屋外での音源定位評価

2A2-B02 32ch低サイドローブ設計マイクロホンアレイの開発と屋外での音源定位評価

MILLIMETER WAVE OMNIDIRECTIONAL QUASI-YAGI ARRAY

A novel planar omnidirectional array based on Quasi-Yagi antenna is proposed in this paper. The modeling of this antenna and design method based on equivalent circuits have been developed. An eight-unit planar array has been designed, fabricated and measured. Measured results exhibit good performance of the return loss and radiation pattern in horizontal plane. The gain of the array in horizontal plane was about 0 dBi. The un-roundness of the radiation pattern in horizontal plane was about 5 dB.

A wideband 8‐element omnidirectional array for wireless system

AbstractA smart broad‐band planar antenna for wireless system is presented. The simple modeling of this antenna and design method based on equivalent circuits has been developed. An eight‐element planar array has been designed, fabricated and measured. Measured results exhibit good performance of the return loss and horizontal plane radiation pattern. The measured 10‐dB return loss bandwidth of the broad‐band planar array is demonstrated to be 62.5% and the un‐roundness of its horizontal plane pattern is less than 4.5 dB. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 2944–2946, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22925

Beamformer performance with acoustic vector sensors in air

For some time, compact acoustic vector sensors (AVSs) capable of sensing particle velocity in three orthogonal directions have been used in underwater acoustic sensing applications. Potential advantages of using AVSs in air include substantial noise reduction with a very small aperture and few channels. For this study, a four-microphone array approximating a small (1 cm3) AVS in air was constructed using three gradient microphones and one omnidirectional microphone. This study evaluates the signal extraction performance of one nonadaptive and four adaptive beamforming algorithms. Test signals, consisting of two to five speech sources, were processed with each algorithm, and the signal extraction performance was quantified by calculating the signal-to-noise ratio (SNR) of the output. For a three-microphone array, robust and nonrobust versions of a frequency-domain minimum-variance (FMV) distortionless-response beamformer produced SNR improvements of 11 to 14 dB, and a generalized sidelobe canceller (GSC) produced improvements of 5.5 to 8.5 dB. In comparison, a two-microphone omnidirectional array with a spacing of 15 cm yielded slightly lower SNR improvements for similar multi-interferer speech signals.

Radiation Characteristics of Hexagonal Transducer Array

A staggered transducer array such as a hexagonal transducer array is one of structures used to effectively suppress grating lobes. Some advantages of hexagonal array are outlined. The directivity of a hexagonal array consisting of circular sound sources is derived and compared with that of a conventional square array. Due to the suppression of grating lobes, a hexagonal array can use a larger sound source element than a square array and therefore the number of elements can be reduced. The hexagonal array emits a greater effective radiation power than the square array. In the case where an omnidirectional array is required, the hexagonal array is more effective than the conventional square array.

Theory and design of broadband sensor arrays with frequency invariant far-field beam patterns

The theory and design of a broadband array of sensors with a frequency invariant far-field beam pattern over an arbitrarily wide design bandwidth is presented. The frequency invariant beam pattern property is defined in terms of a continuously distributed sensor, and the problem of designing a practical sensor array is then treated as an approximation to this continuous sensor using a discrete set of filtered broadband omnidirectional array elements. The design methodology is suitable for one-, two-, and three-dimensional sensor arrays; it imposes no restrictions on the desired aperture distribution (beam shape), and can cope with arbitrarily wide bandwidths. An important consequence of the results is that the frequency response of the filter applied to the output of each sensor can be factored into two components: One component is related to a slice of the desired aperture distribution, and the other is sensor independent. The results also indicate that the locations of the sensors are not a crucial design consideration, although it is shown that nonuniform spacings simultaneously avoid spatial aliasing and minimize the number of sensors. An example design which covers a 10:1 frequency range (which is suitable for speech acquisition using a microphone array) illustrates the utility of the method. Finally, the theory is generalized to cover a parameterized class of arrays in which the frequency dependence of the beam pattern can be controlled in a continuous manner from a classical single-frequency design to a frequency invariant design.