Radiation Characteristics Of Antenna Research Articles

Comparison of performance of compact ring printed monopole and loop antennas for wireless‐implantable body area network applications

ABSTRACTHuman bodies have a variety of tissues and organs, and so it needs to be characterized as a radio‐wave propagation medium to create a reliable wireless communication link. The radiation characteristics of printed monopole antenna and printed loop antenna for wireless‐implantable body area network (WiBAN) applications are presented in this article. The two antennas are submerged into canola oil to mimic an implanted antenna in the human tissue. The tissue is considered a lossy environment and hence, it adversely degrades radiation characteristics of both antennas. Therefore, the RF transmission attenuation, dB can be used for characterizing the propagating wave from the submerged antennas to the free‐air surface. The measured results show satisfactory performance and are in good agreement with the simulation. As indicated in the results, the attenuation rate from a lossy environment to the free space for the printed loop antenna (0.1 dB/mm) is smaller compared to that of printed monopole antenna (0.1–0.3 dB/mm). More so, the printed loop antenna is smaller in size (about 56%) compared to the printed monopole antenna, which suggests that the loop antenna is more suitable than the monopole for the WiBAN applications. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:1270–1274, 2014

Effects of an ordinary adhesive material on radiation characteristics of a dielectric resonator antenna

ABSTRACTThis article reports the impact of using an ordinary adhesive material to bond a dielectric resonator antenna (DRA) to the ground plane to predict the potential variations in resonant frequency and impedance bandwidth of DRA. A set of aperture fed and monopole fed cylindrical DRAs have been analyzed at resonant frequencies of 2.4 and 8.9 GHz. For DRAs resonating at 2.4 GHz, an upward resonance frequency shift of 6.2% along with increase of 1.4 to 2% in impedance bandwidth have been observed. However, a significant shift of 12% in the resonant frequency and 17–20% increase in impedance bandwidth have been observed for DRAs operating at 8.9 GHz. End‐fire TM01 mode has been excited in the DRAs, and it has been observed that the adhesive material has not affected the operating resonant mode. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:1502–1506, 2014

Investigation of Multiwall Carbon Nanotubes as Antennas in the Subterahertz Range

In this paper, we investigate the performance of a multiwall Carbon Nanotube (MWCNT) as an antenna in the subterahertz range. To this end, a circuit model for the transverse structure is proposed and derived for the MWCNT, which is valid as long as the applied wavelength is much longer than the diameter of the MWCNT. Using this model, the modal equation of the axial propagation constant is derived, and the antenna radiation characteristics are obtained. In addition we study a bundle of MWCNT's as an antenna with higher radiation efficiency. Numerical examples show that the radiation resistance of a λ/2 antenna can be comparable to normal metallic antenna.

An experimental verification of metamaterial coupled enhanced transmission for antenna applications

Inspired by the work of Bethe on electromagnetic transmission through subwavelength hole, there has been immense interest on the extraordinary transmission through subwavelength slot/slit on metal plates. The invention of metamaterials has boosted the extra ordinary transmission through subwavelength slots. We examine computationally and experimentally the concept of metamaterial cover using an array of split ring resonators (SRRs), for enhancing the transmission in a stacked dipole antenna working in the S band. The front to back ratio is considerably improved by enhancing the magnetic resonant strength in close proximity of the slit of the upper parasitic dipole. The effect of stacking height of the SRR monolayer on the resonant characteristics of the split ring resonators and its effect on antenna radiation characteristics has been studied.

Radiation Characteristics of a Square Pyramidal Horn Antenna with Tapered DielectricE-Plane Boundary Walls Loaded With Periodic Conducting Strips

A rectangular pyramidal horn antenna fabricated with tapered dielectric E-plane boundary walls whose inner surface is periodically loaded with thin conducting strips is investigated. For better impedance matching, at the throat region of the horn antenna, 3 cm portion is metallised. The radiation characteristics of this horn antenna are compared with that of an identical conventional horn antenna with conducting E-plane boundary walls. Considerable improvement in the E-plane radiation characteristics is observed. As H-plane boundary walls are not modified, no change in the H-plane radiation characteristics is observed. However,the conventional horn antenna shows slightly better impedance matching than the test horn antenna.

Response to “Comments on “Planar Artificial Transmission Lines Loading for Miniturization of RFID Printed Quasi-Yagi Antenna””

The He et al. comment that claimed the ATL segments contribute little in the antenna radiation characteristics has been investigated and rejected with different clear reasons such as current distribution, radiation pattern, and input impedance.

Research on radiation characteristic of plasma antenna through FDTD method.

The radiation characteristic of plasma antenna is investigated by using the finite-difference time-domain (FDTD) approach in this paper. Through using FDTD method, we study the propagation of electromagnetic wave in free space in stretched coordinate. And the iterative equations of Maxwell equation are derived. In order to validate the correctness of this method, we simulate the process of electromagnetic wave propagating in free space. Results show that electromagnetic wave spreads out around the signal source and can be absorbed by the perfectly matched layer (PML). Otherwise, we study the propagation of electromagnetic wave in plasma by using the Boltzmann-Maxwell theory. In order to verify this theory, the whole process of electromagnetic wave propagating in plasma under one-dimension case is simulated. Results show that Boltzmann-Maxwell theory can be used to explain the phenomenon of electromagnetic wave propagating in plasma. Finally, the two-dimensional simulation model of plasma antenna is established under the cylindrical coordinate. And the near-field and far-field radiation pattern of plasma antenna are obtained. The experiments show that the variation of electron density can introduce the change of radiation characteristic.

Analysis of E- Plane Radiation Patterns of a Simulated Scalar Feed Horn Antenna

Simulated scalar feed horn antennas are found to be exhibiting identical radiation characteristics of metallic corrugated feed horn antennas of same dimensions. Hence, in this paper, the E-plane radiation characteristics of a simulated scalar feed horn antenna is analysed theoretically by extending the theory of metallic corrugated horn antennas. The theoretical E-plane radiation patterns at different frequencies in X- band are compared with that of experimentally obtained E-plane radiation patterns. Even though the nulls of of the radiation patterns are not fully realised by the theory, the main beam characteristics are well explained. Losses that may occur in the dielectric substrate of the E-plane walls are not considered in the theoretical explanation. This may be the reason for slight discrepancies observed in the experimental and theoretical 3-dB and 10 dB beam widths.

Radiation Characteristics of 3D Resonant Cavity Antenna with Grid-Oscillator Integrated Inside

A three-dimensional (3D) rectangular cavity antenna with an aperture size of 80 mm×80 mm and a length of 16 mm, integrated with a four-MESFET transistor grid-oscillator, is designed and studied experimentally. It is found that the use of 3D antenna resonant cavity in case of small or medium gain microwave active cavity antenna leads to effective and stable power combining and radiation. The lack of lateral cavity diffraction and radiation helps in producing a directive gain of about 17 dB and radiation aperture efficiency bigger than 75% at a resonance frequency of 8.62 GHz. Good DC to RF oscillator efficiency of 26%, effective isotropic radiated power (EIRP) of 5.2 W, and SSB spectral power density of −82 dBc/Hz are found from the measured data. The 3D antenna cavity serves also as a strong metal container for the solid-state oscillator circuitry.

Predicting the Performance of Pyramidal and Corrugated Horn Antennas Using ANFIS

This letter presents the development of an adaptive neuro fuzzy inference system (ANFIS)-based model for predicting the performance of a pyramidal and a conical corrugated horn antennas. Different ANFIS-based models were developed. Using these models, horn return-loss characteristics and radiation patterns (copolarization and cross-polarization) can be obtained with great accuracy for any combination of design parameters. The results obtained using ANFIS models were compared to that of the commercial horn antenna design software and found in close agreement. The advantage of the proposed method lies with the fact that, with less time and minimum computational resources, the return-loss and radiation characteristics of a horn antenna under test can be obtained with high degree of accuracy.

DESIGN OF A COMPACT ULTRA-WIDE BAND BOW-TIE SLOT ANTENNA SYSTEM FOR THE EVALUATION OF STRUCTURAL CHANGES IN CIVIL ENGINEERING WORKS

A compact UWB bowtie-slot antenna (36 £ 23cm 2 ) fed by a CPW transition is proposed for an improved ground-coupling radar. The antenna has an operating frequency band in the range (0:46;4)GHz. Full-wave modeling using the FDTD approach has allowed to study in details the antenna radiation characteristics in air and in the presence of a soil. Afterwards, a radar system made of a pair of independent shielded bowtie antennas has been considered to probe the sub-surface very close to the air-soil interface. The polarization diversity in the E and H-planes is an important aspect which has been studied in order to further detect the orientation of damages (cracks, delaminations ...) in civil engineering structures. Measurements in a dry and wet sand in difierent system conflgurations have allowed to flrst characterize the GPR system and to draw comparisons with numerical results. The ability of the radar to detect small buried objects has been investigated.

OPTIMIZING THE BOWTIE NANO-ANTENNA FOR ENHANCED PURCELL FACTOR AND ELECTRIC FIELD

With the development of nano-optic technology, the optical nano-antenna has been widely used in the flelds of novel light sources, high-sensitive biological sensors, nanometer lithography, and nano-optical imaging. The relationship between the structural parameters of the antenna and the Purcell factor is very important for engineering applications. The electric near fleld proflle of the antenna was calculated and analyzed by using the flnite-difierence time-domain (FDTD) method, and the in∞uence of the structural parameters on the Purcell factor and the electric fleld was thoroughly investigated. A careful comparison of bowtie antenna radiation characteristics with difierent structural parameters was carried out. The results show that the thickness, the length and the curvature radius have great efiects on the Purcell factor and the optical antenna's electric near fleld. These flndings are promising for improving the performance of the optical bowtie nano-antenna.

Radiation characteristics improvement of aperture coupled antennas using double reflector structure

The radiation characteristics of aperture stacked patch antenna, namely, front-to-back (F/B) ratio, gain, and gain bandwidth are improved. The results show that the gain bandwidth of the proposed antenna is up to 72% (6.09–12.87 GHz) with F/B ratio better than 8 dB across the band of operation which is a considerable improvement compared to the available microstrip antennas.

Mechanically reconfigurable antennas using an anisotropic carbon‐fibre composite ground

The authors present reconfigurable antennas based on anisotropic reinforced continuous carbon fibre composite (RCCFC) material. By the rotation of the anisotropic RCCFC ground plane, the current distribution can be changed to select a desirable mode of resonance and suppress unwanted modes. Hence, the RCCFC ground plane behaves as a mode filter in the proposed reconfigurable antennas. Several types of probe-fed reconfigurable microstrip-patch antennas are presented, including the RCCFC conductivity characteristics, the principle of reconfigurable operation and the simulated and measured performance. The outstanding mechanical strength of RCCFC materials along with the promising radiation characteristics of these reconfigurable antennas make them good candidates for radio cognitive and military applications.

대칭형 인공자기도체 구조를 이용한 메타물질 특성의 고임피던스 표면 구현 및 SAR 특성 분석

In this paper, we proposed new type of an artificial magnetic conductor(AMC) structure, which has a high impedance surface for realizing the meta-material characteristics. The designed AMC structure set a goal of 3.2GHz, and the reflector, which consists of periodically arrayed AMCs is fabricated and measured. The high impedance improves the reflection coefficient, decreases the system size and interference, and increases the antenna performance. The structure has embodied the high impedance by the thickness and relative permitivity of the dielectric substrate and the design configuration without the metallic via hole which connects the AMC to the GND. The bandwidth is 150% broader than the similar AMC structures. Also, the distance between the antenna and the AMC reflector is decreased by as working as the metal(PEC) reflectors. The antenna radiation characteristics are 3dB increased at 10mm away from reflector by measurement. The proposed reflector could be inserted in the portable mobile devices, and the antenna`s performance has improved by the reflector. The specific absorption rate is dramatically decreased over 94% because the back radiation of the antenna is shielded.

Directional Pattern Measuring System Research of a TT&C Antenna

Directional pattern is a clear visual representation form of antenna radiation characteristics. Taking a certain kind of shipborne radar as example, the basic principle of the directional pattern measurement was analyzed, the basic methods and execution scheme were introduced in detail. A directional pattern automatic testing system which was based on Lavbiew was researched on the basis of existed testing techniques, and finally the directional pattern automatic measurement was realized through the use of virtual instrument GPIB and serial interface techniques.

Millimeter-Wave EBG-Based Aperture-Coupled Dielectric Resonator Antenna

Design, fabrication and testing of millimeter-wave (MMW) dielectric resonator antenna (DRA) surrounded by electromagnetic band-gap (EBG) structure are presented. For this purpose, MMW mushroom-like, circular patch EBG (CP-EBG) cell is designed and fabricated. The propagation characteristics of the proposed CP-EBG structure are measured using the asymmetric microstrip line method. A cylindrical DRA incorporating the developed CP-EBG structure is then designed and its performance is evaluated with and without the CP-EBG around the 60 GHz bandwidth. Measurements show a significant improvement in the antenna radiation characteristics when it is surrounded by CP-EBG structure. A gain increase of up to 3.2 dBi is obtained while preserving the gain flatness over the suggested bandwidth ( ± 0.7 dB). An additional backlobe suppression of up to 6.5 dBi is achieved. Moreover, radiation toward substrate edges is significantly reduced.

A Reconfigurable SIW Cavity-Backed Slot Antenna With One Octave Tuning Range

A reconfigurable Substrate Integrated Waveguide Cavity-Backed Slot (SIW-CBS) antenna is presented with one octave tuning range and six different tuning states using a new tuning method. The method is based on loading the SIW cavity with shortening posts and manipulating the field distribution within the cavity. This tuning method shifts up the operating frequency of the antenna. Based on the number of the posts and their location, this frequency shift can be controlled. Benefiting from a two-layer structure and therefore being totally isolated from the biasing circuit, the CBS antenna can be easily tuned by switching the posts using p-i-n diodes. Using this technique a frequency tuning ratio <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$(f_{TR}=f_{up}/f_{low})$</tex> </formula> as high as an octave (1.1–2.2 GHz) is achieved. The impedance and radiation characteristics of the CBS antenna are presented and discussed. The antenna shows similar radiation patterns with low cross-polarization levels and high front to back ratio for all six states. To the authors' knowledge this is the first presentation of a SIW-CBS tunable antenna with one octave tuning and also the technique used for antenna tuning.

Inductive loaded 마이크로스트립 패치 안테나를 이용한 E-평면 선형 배열 안테나의 방사 특성

Inductive loaded 패치 안테나를 단위 안테나로 이용하는 E-평면 선형 배열 안테나의 방사 특성에 대하여 연구하였다. 유전상수가 크고 두꺼운 기판을 이용하여 설계한 inductive loaded 패치 선형 배열 안테나의 방사 특성은 인접 안테나 간 상호결합이 작기 때문에 일반적인 사각 패치 선형 배열 안테나의 방사 특성에 비해 크게 향상되었다. 5 소자 E-평면 inductive loaded 패치 선형 배열 안테나의 방사 특성이 가장 향상되는 단위 5×2 inductive loaded 패치 안테나의 패치 길이를 도출하였다.

A fully probe corrected near-field far-field transformation technique employing plane-wave synthesis

Abstract. The far-field behavior of an antenna under test (AUT) can be obtained by exciting the AUT with a plane wave. In a measurement, it is sufficient if the plane wave is artificially generated in the vicinity of the AUT. This can be achieved by using a virtual antenna array formed by a probe antenna which is sequentially sampling the radiating near-field of the AUT at different positions. For this purpose, an optimal filter for the virtual antenna array is computed in a preprocessing step. Applying this filter to the near-field measurements, the far-field of the AUT is obtained according to the propagation direction and polarization of the synthesized plane wave. This means that the near-field far-field transformation (NFFFT) is achieved simply by filtering the near-field measurement data. Taking the radiation characteristic of the probe antenna into account during the synthesis process, its influence on the NFFFT is compensated. The principle of the plane-wave synthesis and its application to the NFFFT is presented in detail in this paper. Furthermore, the method is verified by performing transformations of simulated near-field measurement data and of near-field data measured in an anechoic chamber.