Use Of Antennas Research Articles

Miniature microwave applicator for murine bladder hyperthermia studies

Purpose: Novel combinations of heat with chemotherapeutic agents are often studied in murine tumour models. Currently, no device exists to selectively heat small tumours at depth in mice. In this project we modelled, built and tested a miniature microwave heat applicator, the physical dimensions of which can be scaled to adjust the volume and depth of heating to focus on the tumour volume. Of particular interest is a device that can selectively heat murine bladder.Materials and methods: Using Avizo® segmentation software, we created a numerical mouse model based on micro-MRI scan data. The model was imported into HFSS™ (Ansys) simulation software and parametric studies were performed to optimise the dimensions of a water-loaded circular waveguide for selective power deposition inside a 0.15 mL bladder. A working prototype was constructed operating at 2.45 GHz. Heating performance was characterised by mapping fibre-optic temperature sensors along catheters inserted at depths of 0–1 mm (subcutaneous), 2–3 mm (vaginal), and 4–5 mm (rectal) below the abdominal wall, with the mid depth catheter adjacent to the bladder. Core temperature was monitored orally.Results: Thermal measurements confirm the simulations which demonstrate that this applicator can provide local heating at depth in small animals. Measured temperatures in murine pelvis show well-localised bladder heating to 42–43°C while maintaining normothermic skin and core temperatures.Conclusions: Simulation techniques facilitate the design optimisation of microwave antennas for use in pre-clinical applications such as localised tumour heating in small animals. Laboratory measurements demonstrate the effectiveness of a new miniature water-coupled microwave applicator for localised heating of murine bladder.

UWB Omnidirectional Square Monopole Antenna for Use in Circular Cylindrical Microwave Imaging Systems

In this letter, a novel ultrawideband (UWB) printed monopole antenna (PMA) for use in a circular cylindrical microwave imaging system is presented. The proposed antenna consists of a square radiating patch and a ground plane with a pair of E-shaped slots and a rectangular slot with a pair of horizontal T-shaped strips protruded inside the slot, which provides a wide usable fractional bandwidth of more than 120% (2.97-12.83 GHz). By cutting two modified E-shaped slots with variable dimensions on the ground plane corners and also by inserting two T-shaped strips inside the rectangular slot located in the ground plane center, additional resonances are excited, and hence much wider impedance bandwidth can be produced, especially at the higher band. The proposed antenna has an ordinary square radiating patch, therefore displays a good omnidirectional radiation pattern even at higher frequencies, and also its radiation efficiency is greater than 86% across the entire radiating band. The designed antenna has a small size of 12 ×18 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . Simulated and measured results are presented to validate the usefulness of the proposed antenna structure for circular cylindrical microwave imaging system.

MODIFIED DIRECTIONAL WIDE BAND PRINTED MONOPOLE ANTENNA FOR USE IN RADAR AND MICROWAVE IMAGING APPLICATIONS

This paper presents a modifled design of directional monopole antenna with parabolic-shaped ground plane. To increase the directivity, axis of parabola in the ground plane is rotated 45 degrees (in comparison with the previous antenna) to extend throughout the direction of the substrate's diagonal. Consequently, vertex of the parabola is placed at the optimum point in the corner of the substrate. The aim of this attempt is to design an extended and symmetrical ground plane around the patch, with more clarity, to maximize its capability as a re∞ector. Directivity is further improved by inserting parabolic-shaped slots at the corners of the ground plane. Simulation and measurements show that the proposed antenna has stable directional radiation pattern and higher gain compared to the previous directional monopole antennas. Impedance bandwidth of the antenna covers the frequency range of 4{9GHz. Measured HPBW is among the degrees 54{22 between 4 and 9GHz. Gain and HPBW of the antenna are improved 1.3{3.1dB and 5{15 degrees, respectively among the bandwidth in comparison with previous antenna. Results conflrm the good characteristics of the antenna for use in microwave imaging, where high resolution is required.

Evaluation of the Quality Factor, Q, of Electrically Small Microstrip-Patch Antennas [Wireless Corner

The quality factor, Q, for a number of configurations of a microstrip antenna is evaluated using exact and approximate quality-factor formulas found in the literature. A number of slits parallel to the radiating edges are used to miniaturize the microstrip antenna's size. The microstrip antenna in use is considered to be electrically small according to Wheeler's electrically small antenna definition. The Q for each configuration is numerically evaluated using the given expressions, for simulated and measured data, and is compared to the Chu lower bound. There is good agreement between the results, while the Q lower fundamental limitation is not violated. Despite the size reduction, satisfying radiation efficiency is achieved, and the radiation pattern remains unchanged.

The Design of an Economical Antenna-Gain and Radiation-Pattern Measurement System

The design of a system capable of making antenna-gain and radiation-pattern measurements at 2.4 GHz is presented. System performance based on component specifications is summarized and compared to measured data. Antenna measurements taken using the system were compared to those obtained using commercially available test equipment in an anechoic test chamber. The accuracy of the system was found to be ±0.5 dB within a dynamic range of 13 dB plus the gains of the antennas in use. The system was shown to be capable of making high quality antenna radiation-pattern measurements in an anechoic test chamber. For a total cost of less than $1300, the system presents an economical alternative to more-sophisticated microwave measurement systems, and is well suited for use in a learning environment.

Lateralization in the Invertebrate Brain: Left-Right Asymmetry of Olfaction in Bumble Bee, Bombus terrestris

Brain and behavioural lateralization at the population level has been recently hypothesized to have evolved under social selective pressures as a strategy to optimize coordination among asymmetrical individuals. Evidence for this hypothesis have been collected in Hymenoptera: eusocial honey bees showed olfactory lateralization at the population level, whereas solitary mason bees only showed individual-level olfactory lateralization. Here we investigated lateralization of odour detection and learning in the bumble bee, Bombus terrestris L., an annual eusocial species of Hymenoptera. By training bumble bees on the proboscis extension reflex paradigm with only one antenna in use, we provided the very first evidence of asymmetrical performance favouring the right antenna in responding to learned odours in this species. Electroantennographic responses did not reveal significant antennal asymmetries in odour detection, whereas morphological counting of olfactory sensilla showed a predominance in the number of olfactory sensilla trichodea type A in the right antenna. The occurrence of a population level asymmetry in olfactory learning of bumble bee provides new information on the relationship between social behaviour and the evolution of population-level asymmetries in animals.

Plasmonic beaming and active control over fluorescent emission

Nanometallic optical antennas are rapidly gaining popularity in applications that require exquisite control over light concentration and emission processes. The search is on for high-performance antennas that offer facile integration on chips. Here we demonstrate a new, easily fabricated optical antenna design that achieves an unprecedented level of control over fluorescent emission by combining concepts from plasmonics, radiative decay engineering and optical beaming. The antenna consists of a nanoscale plasmonic cavity filled with quantum dots coupled to a miniature grating structure that can be engineered to produce one or more highly collimated beams. Electromagnetic simulations and confocal microscopy were used to visualize the beaming process. The metals defining the plasmonic cavity can be utilized to electrically control the emission intensity and wavelength. These findings facilitate the realization of a new class of active optical antennas for use in new optical sources and a wide range of nanoscale optical spectroscopy applications.

Design of an Internal Antenna with Near-Omnidirectional H-Plane Radiation Pattern over Ultra-wide Bandwidth

In this paper, an ultra-wideband internal antenna for use in mobile applications is proposed. The proposed antenna has symmetrical bi-arm structures printed on the top and bottom of the substrate, and it occupies a compact area of 10 mm × 10 mm × 1 mm. The designed antenna has an impedance bandwidth from 3 GHz to 12 GHz and near omnidirectional radiation patterns over the frequency band of interest. The group delay between two antennas fabricated using the proposed design is less than 0.8 ns, and the maximum gain variation is about 3.16 dB.

Design of an Ultrawideband Monopole Antenna for Portable Radio Transceiver

This letter describes the design of a compact monopole antenna for use in a portable transceiver to access almost all modern wireless services from 850 MHz to 6 GHz. Initially, a microstrip-fed planar monopole of quarter-elliptical shape accompanied by a ground plane of 60 × 90 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> on FR-4 substrate is designed. To generate an ultrawide impedance bandwidth, this radiating element is accompanied by a parasitic microstrip stub and a ground plane cut. To reduce its projection area, the planar monopole is folded to occupy a volume of 13 × 60 × 5.6 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> . This antenna is then fabricated and experimentally tested. Both simulation and experimental results show its operational band from 0.85 to 6 GHz, with reference to the 6-dB return loss (VSWR 3:1). Its radiation patterns are omnidirectional in the lower band and become directional at higher frequencies, with the gain varying between 1 and 7 dBi.

Design of a small antenna for wideband mobile direction finding systems

In this study, the authors propose a novel small antenna for use in mobile direction finding (DF) systems covering the range 20-1300 MHz. The proposed antenna has a multiconical sleeve to increase the input resistance at low frequencies while reducing the antenna size. A skirt-shaped disk on top of the antenna body maintains the omnidirectional radiation pattern over a wide frequency band without radiation nulls in the broadside direction. The detailed design parameters of the proposed antenna were optimised using a Pareto genetic algorithm (GA) with the FEKO EM software package. Below 200 MHz, the proposed antenna shows a receiving performance comparable to a 60-cm conventional dipole but at only half the size. Above 200 MHz, the antenna maintains an omnidirectional radiation pattern up to 1300 MHz with a stable realised gain, whereas the 60-cm dipole has a broadside radiation null at about 850 MHz.

Design and Development of a Novel 3-D Cubic Antenna for Wireless Sensor Networks (WSNs) and RFID Applications

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> A novel miniaturized 3-D cubic antenna for use in a wireless sensor network (WSN) and RFIDs for environmental sensing is introduced. The antenna produces a truly omnidirectional pattern in both E-plane and H-plane, which allows for non-intermittent communication that is orientation independent. The frequency of operation lies in the UHF RFID band, 902 MHz–928 MHz (centered at 915 MHz). The ultra-compact cubic antenna has dimensions of <formula formulatype="inline"><tex Notation="TeX">$3\ {\hbox {cm}}\times 3\ {\hbox {cm}}\times 3\ {\hbox {cm}}$</tex></formula> (27 <formula formulatype="inline"> <tex Notation="TeX">${\hbox {cm}}^{3}$</tex></formula>), which features a length dimension of <formula formulatype="inline"><tex Notation="TeX">$\lambda/11$</tex> </formula>. The cubic shape of the antenna allows for “smart” packaging, as sensor equipment may be easily integrated inside the cube's hollow (or Styrofoam-filled) interior. The prototype fabrication was performed on six (planar) sides on liquid crystal polymer (LCP) substrate, and then folded into the cubic structure. The geometry of the design is inspired by the RFID inductively coupled meander line structures, which are folded around the sides of the cube. Due to the large number of freedom degrees, this antenna concept may be easily reconfigured for many values of impedances and design parameters. Experimental data verify the simulation results. </para>

A Compact Ultrawideband Monopole Antenna for Wireless Communication Application

An internal ultrawideband monopole antenna for use in the portable wireless communication applications is presented. The proposed antenna had compact dimensions of 12 mm ×16 mm × 4.5 mm. It consisted of a radiating patch, a matching stub, and a ground plane. The designed antenna was fabricated with a case and had a wide bandwidth of more than 8.7 GHz (2.3-11 GHz) for a return loss of less than 10 dB. With this ultrawideband capability, the antenna could cover the wireless-broadband (2.3-2.39 GHz), Bluetooth (2.4-2.4835 GHz), S-DMB (2.605-2.655 GHz), and UWB (3.1-10.6 GHz) bands. The performances of the proposed antenna as installed on a laptop computer was investigated and discussed.

A Modified Quasi-Yagi Antenna With a New Compact Microstrip-to-Coplanar Strip Transition Using Artificial Transmission Lines

We present a modified quasi-Yagi antenna for use in WLAN access points. The antenna uses a new microstrip-to-coplanar strip (CPS) transition, consisting of a tapered microstrip input, T-junction, conventional 50-ohm microstrip line, and three artificial transmission line (ATL) sections. The design concept, mode conversion scheme, and simulated and experimental <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">S</i> -parameters of the transition are discussed first. It features a compact size, and a 3dB-insertion loss bandwidth of 78.6%. Based on the transition, a modified quasi-Yagi antenna is demonstrated. In addition to the new transition, the antenna consists of a CPS feed line, a meandered dipole, and a parasitic element. The meandered dipole can substantially increase to the front-to-back ratio of the antenna without sacrificing the operating bandwidth. The parasitic element is placed in close proximity to the driven element to improve impedance bandwidth and radiation characteristics. The antenna exhibits excellent end-fire radiation with a front-to-back ratio of greater than 15 dB. It features a moderate gain around 4 dBi, and a fractional bandwidth of 38.3%. We carefully investigate the concept, methodology, and experimental results of the proposed antenna.

후면 패치를 갖는 광대역 사다리꼴 모노폴 안테나의 설계

본 논문에서는 PCS/WCDMA/WiBro/S-DMB(1.750<TEX>${\sim}$</TEX>2.655 GHz) 공용 모노폴 안테나로서 사용 가능한 광대역 모노폴 안테나를 제안한다. 제안된 안테나는 FR-4 기판에 제작된 사다리꼴 모노폴 안테나의 후면에 패치를 추가하여 대역폭을 개선시킨다 제안된 안테나의 광대역 특성과 복사 패턴을 확인하기 위하여 설계된 안테나를 제작하고 복사 특성을 측정하여 계산된 결과와 비교하였다. 측정 결과는 계산 결과와 비슷하게 나타났으며, 사용대역 내에서 2 dBi 이상의 이득을 가지며, 1.73<TEX>${\sim}$</TEX>3.48 GHz 대역(중심 주파수 기준 67.2 %)에서 1.5:1 이하의 VSWR을 갖는 것으로 나타났다. 본 논문에서 설계된 모노폴 안테나는 PCS/WCDMA/WiBro/S-DMB 공용 실내용 안테나로 사용할 수 있을 것으로 생각된다. In this paper, a wide-band monopole antenna for use in PCS/WDCMA/Wivro/S-DMB(1.750<TEX>${\sim}$</TEX>2.655 GHz) band is presented. The presented antenna is a trapezoidal monopole antenna which has back-side patch and improves the bandwidth. To confirm the wide-band characteristics and radiation pattern of presented antenna, the experimental antenna is fabricated and its radiation characteristics are measured, compared with calculated results. It is shown that the designed antenna has VSWR less than 1.5, gain over 2 dBi in 1.73<TEX>${\sim}$</TEX>3.48 GHz. The measured results show good agreement with calculated results. From the result, we confirm that the designed antenna can be used indoor antenna for PCS/WCDMA/WiBro/S-DMB.

Design of a Compact Semi-Elliptic Monopole Slot Antenna for UWB Systems

A printed semi-elliptic monopole slot antenna for use in ultrawideband (UWB) communication systems is presented. The antenna features a coplanar waveguide signal strip terminated with a semi-elliptic stub and a modified ground plane to achieve wide bandwidth from 2.85-20 GHz. An exhaustive study of the radiation characteristics of this antenna in the frequency and time domains are presented. Design equations are derived and experimentally validated. Transient analysis indicates linear phase response and minimum dispersion to the transmitted pulse. The proposed radiator is omnidirectional with appreciable gain throughout the band.

Electrically Small Spheroidal Loops Wound on Hollow Ferrite Cores

The complete electrical properties of a small loop wound on a hollow spheroidal ferrite core are calculated using quasistatic theory. Closed-form expressions are derived for all of the elements of an equivalent circuit. It is shown that not only may the bandwidth be increased by the use of a ferrite core, but also that by redistributing the same volume of ferrite over a slightly larger spheroid as a thin layer, the bandwidth may be increased even more. Core losses are computed for a typical ferrite. Although the primary objective is to simplify the design of a transmitting antenna for use in the lower part of the HF band, 2 to 8 MHz, the theory presented is equally valid for the design of receiving antennas and for other frequencies.

Comparison of simulated and experimental results from helical antennas within a muscle-equivalent phantom

Miniature microwave helical antennas for use in thermal therapy applications are usually investigated using muscle-equivalent phantoms. In this paper, an alternative method using an electromagnetic solver based on the finite integration technique is used to simulate a range of 915 MHz helical antennas within a medium with the dielectric properties of muscle. By avoiding the stair-casing effect associated with many solvers, this method enables accurate simulations of non-orthogonal geometric objects such as helical antennas to be achieved. The effects of coil-spacing and insertion depth on the SAR distribution produced by the antennas were characterized and showed good agreement with previously published results obtained using a muscle phantom and a thermographic camera. The simulations confirm that the performance of helical antennas depends on insertion depth. Modification of the coil density demonstrated improvement of the return loss characteristics and changes to the resulting SAR profile.

A Wide-band Circular Polarization Stacked Patch Antenna for the Wireless Communication Applications

A wide-band 'corners-truncated rectangular' stacked patch antenna for use in the circular polarization applications was proposed. The antenna proposed in this paper an axial ratio of less than 3dB and a VSWR of less than 2:1 were shown to be achievable over a 25% bandwidth for use in the wireless communication applications, and this antenna can achieves higher gain, lower side lobes and wider bandwidth compared to the traditional microstrip patch antenna.

The Electrically Small Elliptical Loop with an Oblate Spheroidal Core

The fundamental properties of an electrically small elliptical loop wound on an oblate spheroidal core are calculated using quasi-static theory. Closed-form expressions are derived for the elements of a complete equivalent circuit, including the inductance and capacitance, and radiation, conductor, and core-loss resistances. It is shown that the bandwidth and efficiency are greatly increased by the use of a ferrite core. Losses in the core are computed for two low-loss ferrites. Although the primary objective is to simplify the design of a transmitting antenna for use in the lower part of the HF band, 2-4 MHz, the theory presented is equally valid for the design of receiving antennas and for other frequencies.

V‐band corrugated metal antenna for Giga‐bit wireless applications

AbstractIn this article we describe the design and performance of a waveguide‐fed corrugated surface wave antenna for use in the 57–62 GHz V‐band wireless communication band for HD video hook‐up. The antenna dimensions are calculated using standard closed form leaky‐wave formulae for infinitely wide corrugations. The actual structure which has finite corrugations is simulated using HFSS with good agreement to measurement. The final structure has a mid‐band return loss of −8 dB and the antenna, exhibits ∼4.2‐dB gain at 60° above the horizontal plane. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 2953–2956, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22940