Bidirectional Radiation Pattern Research Articles

FREQUENCY RECONFIGURABLE MICROSTRIP PATCH-SLOT ANTENNA WITH DIRECTIONAL RADIATION PATTERN

In this paper, frequency reconfigurable slot-patch antenna with reflector at the back of an antenna is presented. The proposed antenna consists of a microstrip patch antenna and a microstrip slot antenna where the slot antenna is positioned at the ground plane underneath the patch. Three switches are placed in the slot. The antenna is capable to reconfigure up to six different frequency bands from 1.7 GHz to 3.5 GHz. The microstrip patch antenna produces three different frequency bands with directional radiation pattern while the microstrip slot antenna produces another three frequency bands with bidirectional radiation pattern. Due to the reflector placed at the back of the antenna, the radiation pattern is directional at all frequency bands. Simulated and measured results are used to demonstrate the performance of the antenna. The simulated and measured reflection coefficients and radiation patterns are presented and compared.

BANDWIDTH ENHANCEMENT OF PLANAR INVERTED CONE ANTENNA

In this paper, initially a Planar Inverted Cone Metal Antenna (PICMA) is optimized for wideband wireless communication. Finally, a compact Shorted Planar Inverted Cone Metal Antenna (SPICMA) is developed by introducing a shorting strip on the radiating element of optimized PICMA. The PICMA is optimized to operate from 1.7GHz to more than 20GHz, and the SPICMA is optimized to extend the operating band from 1.05GHz to more than 20GHz resulting in size reduction of 38%. The proposed antenna yields bidirectional radiation pattern in E and H planes. Various characteristics of the antenna have been analyzed using Finite Integration Technique (FIT) based commercial software CST studio. The measured re∞ection coe-cient agrees with the simulated result for the optimized SPICMA.

Design of A CPW‐FED C‐Shaped Slot Array Antenna for Coal Mine/Tunnel Applications

ABSTRACTThis article proposes a C‐shaped slot array antenna for coal mine or tunnel communications fed by a coplanar waveguide slot line. Each antenna element has a short‐ended C‐shaped slot pair. Instead of working at the basic mode, in the way that traditional half‐wavelength straight slots do, the proposed C‐shaped slot pair of each element operates at the first high‐order mode to realize maximum bidirectional radiation at boresight. The design procedure is generalized, and some influential parameters are studied. A four‐element C‐shaped slot array antenna sample is designed, fabricated, and measured. The measured impedance bandwidth for |S11| ≤ −10 dB is 230 MHz (2.37 GHz to 2.60 GHz), and the measured in‐band maximum gains lie in the range of 9.0–11.1 dBi. The measured bidirectional radiation patterns remain stable without main beam tilting across the 2.4‐GHz WLAN band. The measured and the simulated results show good agreement. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1784–1789, 2013

Design of an Extremely Wideband Planar Elliptical Metal Antenna

In this letter, a planar elliptical metal antenna (PEMA) is proposed for wideband applications. To predict the lower cutoff frequency of the antenna, a modified formula is reported. A shorting strip is introduced as a top inductive load to reduce the size of the antenna. Also, a modified coplanar waveguide (CPW) line is designed to feed the antenna. The impedance bandwidth for |S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> | <; 10 dB of the shorted PEMA exhibits from 0.81 to 40 GHz. The proposed antenna yields bidirectional radiation pattern in E- and H-plane. Various characteristics of the proposed antenna are studied using commercial software CST Studio. The simulated and measured reflection coefficients are in good agreement.

A novel design of compact wideband hexagonal antenna

A novel design of planar hexagonal antenna (PHA) fed by a coplanar waveguide has been presented for wideband applications. The semicircular base to upper and lower side of hexagonal radiator increases the impedance bandwidth. A shorting strip is introduced as a top load to the antenna to achieve compactness. The proposed shorted PHA (SPHA) yields bidirectional radiation pattern in both elevation and azimuth plane. The � 10 dB return loss of SPHA exhibits from 1.24 to 20 GHz. The simulated results for various characteristics of the antenna have been shown using finite integration technique based commercial software CST MICROWAVE STUDIO. The simulated and measured return loss characteristics of SPHA are in good agreement. V C 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1-4, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/ mop.27276

Very‐low‐frequency saucers observed on DEMETER

Observations of very‐low‐frequency saucers by the electric field instrument (Instrument Champ Electrique, ICE) aboard the DEMETER spacecraft have added new evidence about the nature of the highly localized source of this radiation. DEMETER orbited sun‐synchronously at altitudes around 660 km, significantly below those at which earlier spacecraft detected saucers. Also, DEMETER data establish the existence of saucer sources in the dayside ionosphere. Frequency‐time slopes of saucers in DEMETER spectrograms have been analyzed with two‐dimensional ray tracing. To produce such slopes requires long vertical separations between the source and the spacecraft, in some cases much greater than the height of the spacecraft above ground. It is concluded that the sources lie above the satellite and radiate downward. Bidirectional radiation patterns and the broadband quasielectrostatic whistler mode energy spectrum are consistent with the published results of simulations of nonlinear two‐stream instabilities.

A Bidirectional Endfire Array With Compact Antenna Elements for Coal Mine/Tunnel Communication

A six-element endfire array is proposed for coal mine or tunnel communication in this letter. To further decrease the end cross section, which has adverse effect on air ventilation, meander-line folded dipoles are used as antenna elements. By the antenna itself, the cross section toward the ventilation direction is only 100 × 1 mm2. A prototype array is fabricated and tested. Bidirectional endfire radiation patterns with low cross-polarization levels in the azimuth and elevation plane are achieved. The measured - 10-dB bandwidth is approximately 7.5% (834-899 MHz), and the corresponding peak gain is 8.05-9.05 dBi.

Wideband and Low Sidelobe Slot Antenna Fed by Series-Fed Printed Array

A combination of slots and series-fed patch antenna array is introduced leading to an array antenna with wide bandwidth, low sidelobe level (SLL), and high front-to-back ratio (F/B). Three structures are analyzed. The first, the reference structure, is the conventional series-fed microstrip antenna array that operates at 16.26 GHz with a bandwidth of 3%, SLL of -24 dB, and F/B of 23 dB. The second is similar to the reference structure, but a large slot that covers the patch array is removed from the ground plane. This results in a wide operating bandwidth of over 72% for , with a 3 dB gain bandwidth of over 15.9%. The SLL of this structure is improved to more than at 16.26 GHz, and stable SLL of over 15.5-16.4 GHz band is also exhibited. This structure has a bi-directional radiation pattern. To make the pattern uni-directional and increase the F/B, a third structure is analyzed. In this structure, rather than one single large slot, an array of slots is used and a reflector is placed above the series-fed patch array. This increases the F/B to 40 dB. The simulated and measured results are presented and discussed.

Planar ultrawideband antenna array for short‐range wireless communications

AbstractIn this article, novel 2‐element and 4‐element planar ultrawideband (UWB) antenna arrays with bidirectional radiation patterns based on identical UWB antenna elements for UWB communications applications have been proposed, simulated and experimentally investigated. Each array is constructed by means of feeding omni‐directional printed UWB monopole antennas with a UWB power divider. The proposed 2‐element antenna array yields an impedance bandwidth of 110% (3.1–10.6 GHz) covering the whole UWB frequency bandwidth while the impedance bandwidth is multi‐band in case of the 4‐element antenna array because of the increasing effect of mutual coupling among antenna elements. The calculated gain of the 2‐element and 4‐element array is quite stable with about 3 and 6 dB higher than that of the single element, respectively. Both measured and calculated E‐plane radiation patterns of the array and the single element are almost the same while the H‐plane radiation patterns of the array are distinctively bidirectional compared to the omni‐directional pattern of the single element. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1061–1066, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25140

TWO-PROBE EXCITED CIRCULAR RING ANTENNA FOR MIMO APPLICATION

This paper presents the analysis and design of a two-probe excited circular ring antenna. The analysis is conducted by using induced emf method and transmission line model. The design process is to choose a suitable radius of the ring for a single probe antenna. Then, the suitable probe length and ring length are determined for the two- probe antenna. Finally, isolation between the two probes is enhanced by insertion of an inductor coil between the probes. The operational characteristics of the prototype antenna at the frequency of 5.2GHz are measured and compared with calculation results. It is evident that these results are in good agreement. The antenna achieved isolation in excess of 20dB and VSWR less than 2 : 1 over the desired bandwidth and a bidirectional radiation pattern with 4dBi gain. This antenna is suitable for Multiple-Input Multiple-Output (MIMO) system covering a long and narrow environment.

A BIDIRECTIONAL MULTIBAND ANTENNA WITH MODIFIED FRACTAL SLOT FED BY CPW

This paper presents a multiband slot antenna with modifying fractal geometry fed by coplanar waveguide (CPW) transmission line. The presented antenna has been designed by modifying an inner fractal patch of the antenna to operate at multiple resonant frequencies, which efiectively supports the digital communication system (DCS 1.71{1.88GHz), worldwide interoperability for microwave access (WiMAX 3.30{3.80GHz), IMT advanced system or forth generation mobile communication system (3.40{4.2GHz), and wireless local area network (WLAN 5.15{ 5.35GHz). Manifestly, it has been found that the radiation patterns of the presented antenna are still similarly to the bidirectional radiation pattern at all operating frequencies. The properties of the antennas, for instance, return losses, radiation patterns and gain are determined via numerical simulation and measurement.

UWB antenna array for wireless transmission along corridors

AbstractA 2‐element elliptical patch antenna array with a bidirectional radiation pattern has been developed for ultra wideband indoor wireless communications. The array is constructed by means of feeding two omni‐directional elliptical patch elements with a 3‐section hybrid power divider. Experimental results show that the array has a stable radiation pattern and low return loss over a broad bandwidth of 64% (3.1–6 GHz). © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 886–890, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23232

An ultra‐wideband microstrip elliptical slot antenna excited by a circular patch

AbstractA novel ultra‐wide band printed slot antenna is presented. By using the novel feeding structure of a circular patch with a tapered microstrip line, the bandwidth of the elliptical slot antenna is greatly enhanced. The impedance bandwidth (VSWR &lt; 2) reaches 174%, covering 1.90–27.7 GHz with bandwidth ratio of 14.6:1. This novel structure also features a bidirectional radiation pattern and a thin profile, making it promising in various wideband applications. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 845–846, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23240

2×2 etched slot array with corporate slotline feed network

Measured and simulated results for a planar 2×2 slot array corporately fed by a slotline feed network are presented. The antenna array has a coplanar-waveguide input port and the slots are etched on the finite ground plane of a single substrate. The coplanar-waveguide transmission line is transitioned into a four-way slotline feed network, which directly feeds the four half-wavelength slots from the narrow edges of the slots. An experimental array achieved an impedance bandwidth of more than 12%, stable bidirectional radiation patterns with low cross-polarisation, and a maximum gain of more than 8 dBi.

A Double Square Loop Antenna with Modified Minkowski Fractal Geometry for Multiband Operation

A double square loop antenna with fractal geometry that supports for multiband operation is proposed. The antenna has multiband operation in that the generator model, which is an initial model to create a fractal loop antenna to operate at the first and second resonant frequencies, is inserted at each center side of a big square loop antenna. It also has a small square loop to operate at the third resonant frequency. The proposed antenna is implemented and shown to effectively support the global system for mobile communication (880-960 MHz), digital communication system (1710-1880MHz), personal communication system (1850-1990 MHz), universal mobile telecommunication system (1920-2170 MHz), and wireless local area network (2400-2483 MHz) bands. The radiation patterns of the proposed antenna are still similar to a bidirectional radiation pattern. The properties of the antenna such as return losses, radiation patterns and gain are determined via numerical simulation and measurement.

CPW-fed bow-tie slot antenna for ultra-wideband communications

A modified coplanar waveguide (CPW)-fed bow-tie slot antenna is proposed to have a wider impedance bandwidth than that of the conventional CPW-fed bow-tie slot antenna. The antenna structure remains simple and has better impedance matching for ultra-wideband communications obtained through the adjustment of bow-tie flare angle and stem width. The in-band antenna gains varied from 3.5 to 7.1 dBi and broadside bidirectional radiation patterns are measured and presented.

CLIP antenna for wireless bluetooth applications

In this paper, a novel design for a coplanar waveguide antenna is developed that consists of two U-shaped slots. The antenna is named CLIP. The antenna was designed for a central frequency of 2.4 GHz, with an input impedance of 50 /spl Omega/. The antenna dimensions represent a 72% size reduction compared to a conventional microstrip rectangular-patch antenna. The measured antenna bandwidth was about 11%, while its gain was about 17 dB. These values are fairly acceptable in all wireless communication systems. The antenna configuration has a bidirectional radiation pattern, while a unidirectional radiation pattern was achieved by using a /spl lambda//sub 0//4 reflector with a metal plate. A 2/spl times/2 multi-element sub array was implemented to widen the application area. The mutual coupling between adjacent elements was low. Orthogonal-plane coupling between adjacent elements was introduced to increase the reduction in the mutual coupling. The mutual coupling level was reduced to less than -23 dB in all coupling planes. The CLIP antenna element and arrays were fabricated. Experimental measurements showed very good performance, which agreed well with simulation results.

Computer-aided design of a CPW-fed slot antenna for MM-wave applications

This article presents a comprehensive parametric study with experimental characterization of an inductively coupled CPW-fed slot antenna on a GaAs substrate for MMIC applications. The length, width, and feed inset of the antenna are varied and their influences on the input impedance, bandwidth, and gain are investigated. The parametric study reveals that the slot length is the prime factor for determining the resonant frequency, while the width is used for fine-tuning of resonant frequency and gain-bandwidth product. For the fixed slot dimensions, the feed inset tremendously affects both resonant frequency and input match. The manufactured antenna resonates at 22.4 GHz with a 6.1% impedance bandwidth, 2% gain bandwidth, 2.5-dBi boresight gain, and 5-dB front-to-back (F/B) radiation level. The antenna exhibits bidirectional radiation patterns with almost omnidirectional patterns in the E-plane and a wide beamwidth of 84° 3-dB beam width in the H-plane. © 2003 Wiley Periodicals, Inc. Int J RF and Microwave CAE 14, 4–14, 2004

Slot-coupled back-to-back microstrip antenna with an omni- or a bi-directional radiation pattern

A new slot-coupled back-to-back microstrip antenna is proposed. Two rectangular patches are arranged relative to a slot on the ground plane. The proposed microstrip antenna has an omnidirectional or a bi-directional radiation pattern in the horizontal plane. The characteristics of the proposed antenna were clarified by experiments. The input impedances and radiation patterns were measured as a parameter of the length of various slots. Good input impedances and radiation patterns were obtained. The mechanism to realise these radiation patterns was clarified by using an electromagnetic simulator. The application of the proposed antenna to obtain a circularly polarised bi-directional radiation pattern is also described.

Microstrip antenna with back-to-back configurationrelative to a slot on a ground plane

A new microstrip antenna with a back-to-back configuration relative to a slot on a ground plane is proposed. The proposed antenna has an omnidirectional or bidirectional radiation pattern in a horizontal plane. The characteristics of the proposed antenna were clarified by experiments. The input impedances and radiation patterns were measured as parameters of the slot length. Good input impedances and radiation patterns have been obtained. The proposed antenna is suitable as a base station in many wireless communications, and as a portable telephone.