Huda A. Majid

Log Periodic Fractal Koch Antenna for UHF Band Applications

In this paper, the design of Log Periodic Fractal Koch Antennas (LPFKA) is proposed for Ultra High Frequency (UHF) band applications. The procedure to design the LPFKA with three different numbers of iterations in order to reduce the antenna size is discussed. The Computer Simulation Technology (CST) software has been used to analyze the performances of the designed antennas such as return loss, radiation patterns, current distribution and gain. The antennas have been fabricated using FR4 laminate board with wet etching technique. Using fractal Koch technique, the size of the antenna can be reduced up to 27% when the series iteration is applied to the antennas without degrading the overall performances. Both simulated and measured results are compared, analyzed and presented in this paper.

A Compact Frequency-Reconfigurable Narrowband Microstrip Slot Antenna

A frequency-reconfigurable microstrip slot antenna is proposed. The antenna is capable of frequency switching at six different frequency bands between 2.2 and 4.75 GHz. Five RF p-i-n diode switches are positioned in the slot to achieve frequency reconfigurability. The feed line and the slot are bended to reduce 33% of the original size of the antenna. The biasing circuit is integrated into the ground plane to minimize the parasitic effects toward the performance of the antenna. Simulated and measured results are used to demonstrate the performance of the antenna. The simulated and measured return losses, together with the radiation patterns, are presented and compared.

Frequency-Reconfigurable Microstrip Patch-Slot Antenna

A frequency-reconfigurable microstrip patch switchable to slot antenna is proposed. The antenna is capable of frequency switching at nine different frequency bands between 1.98 and 3.59 GHz. The patch is resonating at 3.59 GHz, while the slot produces eight different operating frequencies between 1.98 and 3.41 GHz. Five RF p-i-n diode switches are positioned in the slot to achieve frequency reconfigurability. Simulated and measured results are used to demonstrate the performance of the antenna. The simulated and measured return losses, together with the radiation patterns, are presented.

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.

FRACTAL KOCH MULTIBAND TEXTILE ANTENNA PERFORMANCE WITH BENDING, WET CONDITIONS AND ON THE HUMAN BODY

A multiband Fractal Koch dipole textile antenna is proposed for wearable applications. The antenna is designed to operate at 0.9GHz, 2.45GHz and 5.8GHz. Denim materials as the substrate are selected aiming to obtain robustness, ∞exibility and a lightweight textile antenna. The antenna model is designed, simulated, optimized and analyzed using Microwave Studio CST software. Two types of multiband antenna prototypes are fabricated and evaluated with difierent conducting elements (Shield It fabric and copper foil tape). Antenna performance is observed in terms of return loss, bandwidth, radiation pattern and realized gain. Three difierent comprehensive analyses are taken into consideration: measurement antenna with difierent bending sizes, on-body measurement and under wet conditions. The antenna performances are evaluated based on resonant frequency (fo) and bandwidth (BW). The antennas performance with bending on the human body (arm & forearm) is compared and investigated. A suitable placement on the body has been discovered between the chest and backside. The antennas have also been tested under wet conditions to ensure a stable characteristic under the in∞uence of water.

Design and Analysis of Microstrip Reflectarray Antenna with Minkowski Shape Radiating Element

This paper describes the design and analysis of a Microstrip Re∞ectarray Antenna (MRA) with Minkowski shape radiating element at frequency of 11GHz. This structure has been analyzed and compared with the traditional re∞ectarray element (square element patch). It is found that this antenna array has lower sidelobe level (SLL) characteristic which is down to i25dB. This MRA has maximum realized gain of 29.6dB with half-power beamwidth (HPBW) of 3.7 - . The validation for the proposed MRA is done by comparing the simulated and measured E-plane radiation pattern. A very good agreement is found from the comparison between simulation and measurement.

Frequency and pattern reconfigurable slot antenna

A novel frequency and pattern reconfigurable slot antenna is proposed. Slot antenna produces a bidirectional radiation pattern, thus a reflector is positioned behind of the antenna to generate a directional radiation pattern. Two switches are placed in the slot to produce three reconfigurable frequency bands: at 1.82 GHz, 1.93 GHz and 2.10 GHz. The introduction of four slits at the edge of the ground plane offers pattern reconfigurability. To tune the beam angles, three switches are inserted into each slit. By manipulating the phase of upper and lower slits in the ground plane, the proposed antenna is capable of reconfiguring its beam to three different angles at 0°, -15° and +15°. The simulated and measured results of reflection coefficient and radiation patterns are presented and compared.

FREQUENCY AND PATTERN RECONFIGURABLE YAGI ANTENNA

A novel frequency and pattern reconfigurable Yagi antenna is proposed. The antenna is formed by a driver, a reflector and two directors. The introduction of switches using a PIN diode at the arms of the driver element produces three switchable frequencies at 1.25 GHz, 1.85 GHz and 2.45 GHz. By controlling the switches at the directors and reflector, the radiation pattern can be configured to near omni-directional pattern or directional pattern at those three frequencies. Simulated and measured results are used to demonstrate the performance of the antenna. The simulated and measured return losses and the radiation patterns, are presented and compared. It was found that the gain of the antenna increases from 3.3 dB to 5 dB in a directional pattern, when compared to the near omni-directional pattern.

Frequency reconfigurable wide to narrow band monopole with slotted ground plane antenna

A frequency reconfigurable wide to narrow band antenna is presented. The proposed antenna is a combination of a monopole antenna (MA) and a microstrip slot antenna (MSA). The MA produces a wide frequency band from 1.66 to 4.93 GHz, and the MSA produces three different frequency bands resonating at 3.02, 3.89, and 4.56 GHz. Simulated and measured results are used to validate the performance of the antenna. The effects of using copper strip and PIN diode as switches in the simulation and measurement are demonstrated. The simulated and measured return losses, together with the radiation patterns, are presented and compared.

Compact Dual-Port Polarization-Reconfigurable Antenna With High Isolations for MIMO Application

This letter proposes the design of a dual-port microstrip patch antenna with polarization reconfigurability features. The reconfigurability is realized through the modification of the feed network. The antenna consists of a circular-shaped patch on the upper substrate as a radiating element, and a coplanar-waveguide (CPW) slotline transmission located in the ground plane. To obtain a good impedance matching, the CPW slotline is terminated with a tapered impedance transformer. Dual ports are constructed by utilizing the CPW feeding structure and the odd and even feedline modes of the CPW. Four p-i-n diodes are used as switches to alter the flow of the current. The p-i-n diodes are placed on the CPW transmission slotline interjunction. Consequently, the excited polarization can be altered and determined, depending on the switch configurations. This antenna demonstrates good port-to-port isolation and a compact structure and is suitable to be used in systems that operate in a wireless local area network (WLAN) frequency band.