Aidin Mehdipour

Compact Multiband Planar Antenna for 2.4/3.5/5.2/5.8-GHz Wireless Applications

A low-profile planar monopole antenna is proposed to operate within WLAN and WiMAX frequency bands. The antenna is composed of three radiating elements together with an additional strip to control the antenna performance. An electromagnetic (EM) model of the proposed antenna is developed in CST Microwave Studio for numerical analysis and optimization. The principle of operation and parametric study on the antenna performance are provided. Two dual-band and triple-band antennas are fabricated, and experimental results are presented.

COMPLETE DISPERSION ANALYSIS OF VIVALDI ANTENNA FOR ULTRA WIDEBAND APPLICATIONS

Besides the return loss and radiation pattern, dispersion characteristic of the antenna is one of the most important factors which should be considered in ultra wideband applications. In this paper, dispersion behavior of two specific Vivaldi antennas has been fully investigated in both frequency and time domains. All simulations are carried out by CST MS software. Moreover, by fabricating the antennas, the simulation results are verified by experimental data.

Carbon Nanotube Composites for Wideband Millimeter-Wave Antenna Applications

In this paper, we explore using carbon nanotube (CNT) composite material for wideband millimeter-wave antenna applications. An accurate electromagnetic model of the composite antenna is developed using Microwave Studio for numerical analysis. Good agreement between computed and measured results is shown for both copper and CNT antennas, and their performance is compared. The CNT antenna shows stable gain and radiation patterns over the 24 to 34 GHz frequency range. The dispersion characteristics of the CNT antenna show its suitability for wideband communication systems. Using a quarter-wave matched T-junction as feed network, a two-element CNT antenna array is realized and the performance is compared with a copper antenna. The housing effect on the performance of the CNT antenna is shown to be much lower than for the copper antenna.

Multi-Band Miniaturized Antenna Loaded by ZOR and CSRR Metamaterial Structures With Monopolar Radiation Pattern

Miniaturized low-profile monopole antennas loaded by metamaterial (MTM) structures are presented. The antenna is loaded by zeroth-order resonator (ZOR) and complimentary split-ring resonator (CSSR) units, resonating over three frequency bands so that they can be tuned by changing the geometrical parameters of the MTM structures. Surface current distribution and equivalent circuit models are provided to describe the principle of operation. The experimental results are presented to validate the numerical results. Showing the monopole-shape radiation pattern characteristics at all resonant frequencies, the proposed MTM antennas are suitable for vehicular wireless applications.

Full-Composite Fractal Antenna Using Carbon Nanotubes for Multiband Wireless Applications

In this letter, single-wall carbon nanotube (CNT) composite materials are explored for the design of multiband antennas. An accurate electromagnetic (EM) model of the modified Sierpinski fractal composite antenna is developed using Microwave Studio for numerical analysis. For antenna fabrication, we printed CNT on both sides of a substrate and then cut out the desired antenna pattern using a high-precision milling machine. The CNT material was hardened by resin infiltration in order to be processed on the milling machine. The CNT antenna shows satisfactory gain and radiation patterns for UHF-RFID (900 MHz), Bluetooth (2.4 GHz), and WLAN (5.5 GHz) applications. Good agreement between computed and measured results is observed.

A Novel Coplanar Waveguide-Fed Slot Antenna for Ultrawideband Applications

A new coplanar waveguide-fed slot antenna for ultrawideband (UWB) applications is presented. The proposed X-shape antenna is analyzed both numerically and experimentally. The UWB characteristics of the antenna are achieved through the electromagnetic coupling between two adjacent slot arms. All the design procedures are performed by using CST MS software. The antenna operates with VSWR lower than 2.2 (S11< -8.5 dB) over the whole frequency band from 3.1 GHz to 10.6 GHz. In addition to the return loss, dispersion characteristic of the antenna is considered in the design procedure. A parametric study is presented to investigate the effect of the antenna geometrical parameters on its performance. The antenna shows fairly stable radiation pattern over the frequency range of interest. Furthermore, to analyze the dispersion behavior of the antenna, the frequency-domain and time domain characteristics of the antenna are investigated by means of the antenna transfer function.

Reinforced Continuous Carbon-Fiber Composites Using Multi-Wall Carbon Nanotubes for Wideband Antenna Applications

We explore using reinforced continuous carbon fiber (RCCF) composite for wideband antennas in wireless applications. We use composite material as the radiating element for a wireless applications. An electromagnetic (EM) model of the composite antenna is developed using Microwave Studio for numerical analysis. An RCCF composite sample is prepared including up to 2% multiwall carbon nanotube (MWCNT) to enhance the conductivity. The anisotropic conductivity of the resulting material is determined by measurement using standard waveguide setups. The reflection coefficient, radiation pattern and gain of the composite antenna are investigated. The frequency- and time-domain dispersions are found for the composite antenna to show its suitability for ultrawideband (UWB) communication systems. It is observed that RCCF/MWCNT composite is an effectively alternative to metal for the antenna structure.

Carbon-fiber composite T-match folded bow-tie antenna for RFID applications

In this paper, we explore using advanced carbon-fiber composites in RFID antenna systems. For this purpose, the T-match folded bow-tie RFID antenna is considered for study and two different kinds of composites, braided-tissue of carbon-fibers and reinforced long carbon-fiber composites, are used as a material for the radiating element. Since braided-tissue of carbon-fiber composite shows isotropic behavior, the composite antenna has almost the same resonant frequency of 950 MHz as the metal antenna. However, the radiation efficiency degrades due to the low conductivity of composites compared to metals. By using anisotropic reinforced carbon-fiber composite as a material for the radiating element, the behavior of the antenna changes and the resonant frequency increases to 2.45 GHz. The anisotropic conductivity allows the antenna designer to largely restrict current flow to one direction, and this may lead to novel antenna designs.

A Novel Electrically Small Spherical Wire Antenna With Almost Isotropic Radiation Pattern

Two new electrically small spherical antennas are presented in this letter. The antennas have perpendicular arms to reduce radiation cancellation. While having low resonant frequency and high radiation efficiency, the radiation patterns of the antennas are almost isotropic. The proposed folded spherical wire antenna (SWA) shows approximately 50-Omega radiation resistance which eliminates the need for using a matching circuit for antenna feeding. Moreover, the proposed folded SWA is fabricated to verify simulation results. An attempt has been made to approach the fundamental limitations of small antennas for better characteristics while keeping the size as small as possible.

Multiwall Carbon Nanotube–Epoxy Composites With High Shielding Effectiveness for Aeronautic Applications

Using mass-produced multiwall carbon nanotubes (MWCNTs) from different providers, we have fabricated nanocomposites with high and nearly constant shielding effectiveness (SE) over a wide frequency range up to 26.5 GHz. The MWCNT weight fraction and sample thickness were lower than 10% and 2 mm, respectively. The fabrication process and percolation curves are described. A high dc conductivity of 239.1 S/m was achieved at an MWCNT loading of only 8% by weight. The effect of aspect ratio on shielding performance is addressed. By comparing the measured SE of the composite with predictions from a model of the measurement setup using Microwave Studio, the effective conductivity of the nanocomposite was determined. Since the thickness is very important for shielding analysis, the SE/unit thickness diagram was calculated by using the effective parameters of samples. The results were verified experimentally by measuring the SE of samples with different thicknesses.