Omnidirectional Beam Research Articles

Generation of Circularly Polarized Conical Beam Pattern Using Torus Knot Antenna

A wideband circularly polarized antenna with a conical beam radiation pattern is presented. It consists of a torus knot as a radiator and a feeding probe to excite it. The proposed feeding mechanism is simple and does not use power divider network to generate circular polarization (CP). Characteristic mode analysis of a knot shows that a particular kind of knot, with a suitable excitation, can radiate omnidirectional beam with CP. To validate the design, a prototype of torus knot antenna is realized using additive manufacturing technology. The return loss, radiation pattern, and axial ratio (AR) are measured. A parametric study is carried out to understand the effect of various geometric parameters on the performance of the antenna. The fabricated torus knot antenna has a usable bandwidth of 51.8% and the measured AR bandwidth is 66%.

Omnidirectional 2-D Leaky-Wave Antennas With Reconfigurable Polarization

Fabry-Perot cavity two-dimensional leaky-wave antennas with polarization-reconfigurable omnidirectional conical beam are proposed. The antenna cavity is bounded by an annular, locally periodic metal partially reflective surface, and is loaded by a dielectric or a wire-medium slab in order to suppress undesired radiation from the fundamental quasi-TEM mode. A suitable design of the partially reflective surface and of the loading slab, based on a dispersion analysis of the linearized structure, allows for equalizing the phase and attenuation constants of the first higher order TM 1 and TE 1 leaky modes around a given frequency. Omnidirectional beams with full polarization reconfigurability are then achieved through independent excitation of such modes with a pair of azimuthally independent sources. Preliminary designs, aimed at producing a conical beam with circular polarization, are presented and optimized with state-of-art simulation software.

Directionality of nose-emitted echolocation calls from bats without a nose leaf (Plecotus auritus).

All echolocating bats and whales measured to date emit a directional bio-sonar beam that affords them a number of advantages over an omni-directional beam, i.e. reduced clutter, increased source level and inherent directional information. In this study, we investigated the importance of directional sound emission for navigation through echolocation by measuring the sonar beam of brown long-eared bats, Plecotus auritusPlecotus auritus emits sound through the nostrils but has no external appendages to readily facilitate a directional sound emission as found in most nose emitters. The study shows that P. auritus, despite lacking an external focusing apparatus, emits a directional echolocation beam (directivity index=13 dB) and that the beam is more directional vertically (-6 dB angle at 22deg) than horizontally (-6 dB angle at 35deg). Using a simple numerical model, we found that the recorded emission pattern is achievable if P. auritus emits sound through the nostrils as well as the mouth. The study thus supports the hypothesis that a directional echolocation beam is important for perception through echolocation and we propose that animals with similarly non-directional emitter characteristics may facilitate a directional sound emission by emitting sound through both the nostrils and the mouth.

Design of books inventory with RFID antenna in library management system

A 915 MHz printed radio-frequency-identification (RFID) antennas with the characteristics of good gain and omnidirectional beam wave is constructed and evaluated in this study. The objective is to find out their best reading rates for providing effective wireless communications among RFID antenna during the library book inventory process. And an optimal library inventory system which is based on electromagnetic identification (EMID) technology is proposed, which is constructed to find the optimal tag location for a book, test the tag readability for bookshelves, and connect a couple of multi-layer bookshelves with multiplexers and updat the tag reading status in the database of the computer terminal. The fabricated antenna reader and the proposed system are embedded into different locations of bookshelves and tested at the library of Cheng Shiu University in Taiwan. According to the experimental results, the designed prototype of the antenna reader has the characteristics of the directional radiation pattern, good gain, simple shape, low cost and is easy to be integrated into the bookshelf. And the designed library inventory system can authenticate the location of a book automatically. They can benefit administrating librarians with the capabilities of decreasing the library inventory processing time and reducing the possibility of the books being misplaced.

Multimodal and omnidirectional beam splitters for Lamb modes in elastic plates

Omnidirectional beam splitters for the simultaneous control of the three fundamental Lamb modes in an elastic plate are designed and numerically studied. Beam splitters consist in radially symmetric and inhomogeneous lenses designed to redirect the incoming energy towards a given angle. In this work, these devices are designed by means of graded phononic crystals combined with thickness variations of the plate. Numerical simulations are presented to show the performance of the designed devices.

Dual-band pattern reconfigurable antenna for wireless MIMO applications

In this study, a dual-band pattern reconfigurable antenna is proposed for 2.4 and 5.8 GHz wireless multiple-input multiple-output (MIMO) applications. The proposed antenna comprises four pairs of active elements and parasitic elements loaded on PIN diodes. By switching PIN diodes, the parasitic element acts as a director or reflector, and the radiation patterns of the antenna are optimized. The antenna offers three modes with nine radiation beam patterns in a 5.8 GHz band. The measured peak gain of all the beam patterns ranges from 5.6 to 10.4 dBi. At a 2.4 GHz band, omnidirectional beam patterns with a measured peak gain of approximately 4.5 dBi are generated.

Miniaturized Dual-band V-Shaped Monopole Antenna fed by V-Stub

A miniaturized dual-band v-shaped monopole antenna fed by v-stub is presented. The proposed antenna performs two resonant modes covering dual-band of wireless standards, for operating in the IEEE 802.11 a,g,n WLAN (5.15-5.35GHz and 5.725-5.825GHz) and IEEE 802.16e WiMAX (3.3-3.69GHz and 5.25-5.85GHz) bands. The antenna is printed on a 1.6-mm thick FR-4 substrate and the relative permittivity of 4.4, is fed by cross v-strip line a 50Ω with SMA connector. The antenna size is 18mm × 26mm × 1.6mm in dimensions. The measured results show that the miniaturized size antenna achieves a broad operating bandwidth of 3.24–3.71GHz and 4.85-5.87GHz for |S11| < -10dB and omnidirectional beam. The measured gains of the antenna at 3.5GHz and 5.5GHz frequencies are 1.51 dBi and 2.34 dBi, respectively.

Steering electromagnetic beams with conical curvature singularities.

We describe how the transformation-optics technique can be used to design an effective medium mimicking the conical curvature singularity. Anholonomic coordinate transformation gives rise to linear topological defects that break the rotational symmetry. The bending and splitting of the optical beams are found analytically and numerically, depending on the incident direction and the topological charge. Beyond their practical applications to omnidirectional beam steering for photonics, our findings set forth an attractive realm to simulate the relevant physical phenomena in the optical laboratory.

Dipole transducer enhancement from a passive resonator.

A passive resonator model for enhancing the low frequency performance of dipole transducers is presented using a spherical wave function model. It is shown that because the near field response of a dipole has the same on-axis low frequency dependence as an equivalent monopole, it can effectively excite a nearby monopole passive resonator and do this with enough strength to significantly modify the response of the system. Sample results are presented to demonstrate the performance enhancement and to illustrate the conversion of the dipole beam pattern to a nearly omni-directional beam pattern.

The effects of an adaptive directional BEAM microphone on the mismatch negativity responses of cochlear implant users in noise

To investigate the effects of noise on mismatch negativity (MMN) responses and the possible benefits of an adaptive directional BEAM microphone in noise during MMN recordings, and to compare the cochlear implant-evoked potential results with normal hearing subjects. Materials and methods: /da/ and /di/ speech stimuli were used to elicit MMN responses in 11 Freedom cochlear implant users and in 11 normal hearing subjects. Speech noise was delivered at 80 dB sound pressure level (-10 dB signal-to-noise ratio). All subjects were tested in quiet and noisy conditions. To compare the microphone effects, MMN responses for the cochlear implant group were recorded with an omnidirectional and adaptive directional BEAM microphone mode in noise. Results: The MMN responses of the cochlear implantees and the normal hearing group were remarkably similar in terms of latency, amplitude, and morphology in both quiet and noisy conditions. MMN peak latencies were significantly prolonged in the noisy conditions compared to the quiet conditions for both groups. There was a significant decrease in MMN latencies when using an adaptive directional microphone in noise. Conclusion: MMN could be a useful tool to evaluate postoperative cortical auditory performance. BEAM technology provides an ease of discrimination similar to quiet settings for cochlear implant recipients in noisy environments (BEAM and Freedom are trademarks of Cochlear Limited).

지능형 빔 재구성 시스템을 위한 3-D 빔 조향 안테나

Abstract In this paper we propose two types of reconfigurable 3-D beam steering antenna for intelligent or smart antenna system. Proposed antennas are composed of triangular(structure1.) or circuler(structure2.) loop structure and bended dipole antenna structure. This antenna can steer beam pattern of 6 direction at xy-plane state (0, 1, 2) and xz-plane state (3, 4, 5) by 4 switch motion with one antenna element. Antenna structure1. is symmetric equilibrium structures based on feeding point. There is no grounding point. As a result, designed antenna's gain is similar to dipole antenna. Also, As unbalanced structure by using CPWG in the form of a semicircular, structure2. is enhanced directivity. The operation frequency of antenna are 2.5 GHz(Structure1.) and 2.55 GHz(Structure2.), maximum gain is 1.04 ~ 2.06 dBi(Structure1. : Omni-directional beam), 1.6 ~ 4 dBi(structure2. : Directional beam). The overall HPBW is about over 160° in the both of the xy-plane and xz-plane at structure1. and over 125° at structure2.

Series-Fed Microstrip Antenna Arrays and Their Application to Omni-Directional Antennas

The analysis of a series feed approach for N-element slot-coupled microstrip antenna arrays is presented. A cylindrical arrangement of six four-element arrays using this feeding mechanism is shown to achieve optimum omni-directional beam characteristics and exhibit pattern stability over frequency in the C-band. The cylindrical arrangement is measured to have a gain of 6 dB over 750 MHz of bandwidth. A closed-form omni-directional pattern analysis is also developed.

Design and Implementation of an Omni-Directional Underwater Acoustic Micro-Modem Based on a Low-Power Micro-Controller Unit

For decades, underwater acoustic communication has been restricted to the point-to-point long distance applications such as deep sea probes and offshore oil fields. For this reason, previous acoustic modems were typically characterized by high data rates and long working ranges at the expense of large size and high power consumption. Recently, as the need for underwater wireless sensor networks (UWSNs) has increased, the research and development of compact and low-power consuming communication devices has become the focus. From the consideration that the requisites of acoustic modems for UWSNs are low power consumption, omni-directional beam pattern, low cost and so on, in this paper, we design and implement an omni-directional underwater acoustic micro-modem satisfying these requirements. In order to execute fast digital domain signal processing and support flexible interfaces with other peripherals, an ARM Cortex-M3 is embedded in the micro-modem. Also, for the realization of small and omni-directional properties, a spherical transducer having a resonant frequency of 70 kHz and a diameter of 34 mm is utilized for the implementation. Physical layer frame format and symbol structure for efficient packet-based underwater communication systems are also investigated. The developed acoustic micro-modem is verified analytically and experimentally in indoor and outdoor environments in terms of functionality and performance. Since the modem satisfies the requirements for use in UWSNs, it could be deployed in a wide range of applications requiring underwater acoustic communication.

광대역 수중 스피커 시스템의 설계 및 성능 특성

An underwater speaker was developed for use as an acoustic deterrent device that transmits acoustic energy through the water omnidirectionally over a broadband frequency range to eliminate marine mammal attacks and to prevent physical damage to the inshore and coastal fishing grounds of Korea. The underwater speaker was constructed of two vibration caps machined from 6061-T6 aluminum alloy and a stack of PZ 26 piezoelectric ceramic rings (Ferroperm Piezoceramics A/S) connected mechanically in series and electrically in parallel. The performance characteristics of the underwater speaker were measured and analyzed in an experimental water tank of <TEX>$5\;m{\times}5\;m{\times}6\;m$</TEX>. The peak transmitting voltage response (TVR) was measured at 11.16 kHz with 163.45 dB re <TEX>$1\;{\mu}Pa$</TEX>/V at 1m. The underwater speaker showed a near omnidirectional beam pattern at the peak TVR resonance frequency. The usable frequency range was 4-25 kHz with a lower TVR limit of approximately 140 dB. We conclude that this underwater speaker could be satisfactorily used as an acoustic deterrent device against marine mammals, particularly the bottlenose dolphin, to protect catches and fishing grounds as well as the mammals themselves, for example, by keeping them away from fishing gear and/or vessels.

GA-Based Design of Multi-Ring Arrays With Omnidirectional Conical Beam Pattern

The optimal design is presented of single- and multi-ring arrays with an omnidirectional conical beam by using a genetic algorithm (GA). The design parameters to be optimized are ring radii, excitation phases and amplitudes, requiring that the excitations of all elements in the same ring have the same amplitude and periodic phase for minimal azimuth-dependence in beam pattern. Parametric studies of the beam pattern were conducted and the theoretical radiation pattern was also validated from the experimental result with a single ring array antenna. As examples of GA-based design, two types of conical beam pattern were considered, illuminating a significant circular zone for satellite communications on moving vehicles. All results gave an omnidirectional conical beam pattern, in good agreement with the desired mask pattern.

The design of a wideband and widebeam piston transducer in a finite closed circular baffle

The design of a high power piezoelectric underwater transducer operating at frequency range 45kHz‐85kHz with acoustic power capability in excess of 150W is described. The transducer consists of two back‐to‐back elements. Each element is formed by stacked PZT‐4 ceramic rings, a matching and a steel backing layer, and placed in a finite rigid circular baffle. We investigate the dependence of bandwidth and beamwidth to the combination of piston and baffle radii, a and b, respectively. With a ka of 2.45 (k:wave number) and b/a ratio of 2, the transducer resonates at 65kHz with 70% bandwidth and has a beamwidth of 60° at each half space. We show that when two transducers are placed at right angles spatially and driven in parallel, we can obtain an omnidirectional beam pattern horizontally in the lower frequency band. The beam pattern exhibits two dips in each quadrant at the higher end of the frequency band, which are within 7 dB. We also investigated power handling capability of the transducer from thermal point of view using finite element analysis. The input impedance measurements agree well with the numerical results within the pass band.

Modal Propagation and Excitation on a Wire-Medium Slab

A grounded wire-medium slab has recently been shown to support leaky modes with azimuthally independent propagation wavenumbers capable of radiating directive omnidirectional beams. In this paper, the analysis is generalized to wire-medium slabs in air, extending the omnidirectionality properties to even modes, performing a parametric analysis of leaky modes by varying the geometrical parameters of the wire-medium lattice, and showing that, in the long-wavelength regime, surface modes cannot be excited at the interface between the air and wire medium. The electric field excited at the air/wire-medium interface by a horizontal electric dipole parallel to the wires is also studied by deriving the relevant Green's function for the homogenized slab model. When the near field is dominated by a leaky mode, it is found to be azimuthally independent and almost perfectly linearly polarized. This result, which has not been previously observed in any other leaky-wave structure for a single leaky mode, is validated through full-wave moment-method simulations of an actual wire-medium slab with a finite size.

Planar multilateral disc monopole antenna for UWB application

AbstractA planar multilateral disc monopole antenna for ultrawideband (UWB) application is proposed and experimentally studied. The proposed antenna has wide impedance bandwidth from 2.85 GHz to more than 15 GHz with better than −10 dB return loss. Moreover, the proposed antenna is simple in structure and easy to fabricate. The design is demonstrated assuming FR4 substrate with a relative dielectric constant of 4.4 and thickness of 1.6 mm. The size of the antenna is 40 mm × 50 mm. Experimental patterns are showing the behavior of omnidirectional beam pattern in H‐plane. Details of the proposed antenna design and simulation results for UWB operations are presented and discussed. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1101–1103, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22353

Four-sector cross-shaped urban microcellular systems with intelligent switched-beam antennas

A four-sector cross-shaped urban microcellular system with intelligent switched-beam antennas is proposed. Each sector covers a street block with a base station located at an intersection, and an intelligent beam-switching scheme is used to locate mobile users in the most suitable beam coverage. Due to directional narrow-beam patterns and waveguide effects of tall buildings, radio signals along vertical and horizontal streets do not interfere with each other. Therefore, a channel can be reused simultaneously in multiple neighboring cells as long as cochannels do not encounter each other along the line of sight. The proposed scheme has a channel reuse efficiency of 0.95 for a traffic load of 0.02 [new-call arrivals/s/cell]. The system also increases system capacity more than three times with a blocking probability of 1% and considerably reduces handoff traffic when compared with a conventional cross-shaped microcellular system with an omnidirectional beam pattern.

Omnidirectional Beam Formation Using Spiral Antennas above a Conducting Cylinder

An N-spiral array antenna mounted on a finite-length conducting cylinder of length 2L yc and radius rcy is numerically analyzed using the method of moments (MoM). The analysis is performed with 2L y