Ahmad Rashidy Razali

Coplanar Inverted-F Antenna With Open-End Ground Slots for Multiband Operation

This letter reports on a new idea to achieve multiband operation of a coplanar inverted-F antenna (CIFA). In the proposed approach, a microstripline is used to feed the primary CIFA radiator. This feeding arrangement allows for a flexible coupling of the feed to open-end slots in the finite-size ground to launch new resonant frequencies. Two configurations of meandered-tail CIFA with ground slots for WLAN and WiMAX applications are designed, fabricated, and experimentally tested to validate the proposed technique. Good agreement between the simulated and experimental results confirms the practical feasibility of the proposed multiband antenna design.

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 mm2 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 mm3. 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.

Reconfigurable coplanar inverted-F antenna with electronically controlled ground slot

In this article, a coplanar inverted-F antenna with an electronically controlled ground slot enabling reconflgurability is proposed. Initially a quarter wavelength coplanar inverted-F radiator is designed to operate at 900MHz. To minimize its size, the radiator is folded to occupy an area of about 10 £ 40mm 2 . Next, a ground slot is introduced to excite another resonance at around 1850MHz without afiecting the 900MHz operation. The slot is loaded with three pairs of PIN diode switches with simple biasing circuits to vary its resonant frequency. The proposed reconflgurable antenna is fabricated and experimentally tested. A good agreement is achieved between the simulated and measured return loss of the antenna showing the experimental impedance bandwidth covering GSM900, PCS1900 and UMTS2100 services. In these frequency bands, the antenna ofiers nearly omni-directional radiation patterns with measured peak gain between 1.4dBi to 3.45dBi.

Design of a dual-band microstrip-fed meandered-tail PIFA for WLAN applications

The design of a novel dual-band PIFA of compact size for WLAN application has been presented. This new miniaturized PIFA is capable to operate in dual-band that cover 2.4–2.4835 GHz band for 802.11/b/g and 5.15–5.825 GHz band for 802.11a (indoor and outdoor) for application. The operation in the upper band is achieved by the introduction of a ground slot which is excited by the same feed used for launching the lower band. The proper choice of dimensions and location of the slot not only introduces new operational band. It also improves the bandwidth and quality of return loss. Using the meandered structure accompanied by a ground slot reduces the overall size of the primary PIFA element to almost 50% of its original size given in [2]. The attributes of reduced size and improved bandwidth are welcome with respect to the intended WLAN application.

Compact Planar Multiband Antennas for Mobile Applications

This chapter focuses on the design of compact planar multiband antennas intended for exist‐ ing wireless services including LTE, GPS, GSM, PCS, DCS, GPS, UMTS, WLAN and Wi‐ MAX bands. The present techniques available in the open literature include the modification of the main radiator via bending, folding, meandering and wrapping. Each approach offers different advantages, depending on the required application. The constraint for the lower band generation is the main challenge in radiator miniaturization. The quarter wavelength radiator that is subjected to miniaturization may suffer from limited bandwidth and low ra‐ diation efficiency. An alternative approach which relies on modifications to the ground plane is a promising technique, which often has been previously overlooked by antenna de‐ signers. The introduction of a ground slot in a finite antenna ground plane can be further extended to include reconfigurable features. Thus, such antennas that are compact and have multiband capability can be promising candidates for many wireless applications.

Miniaturization techniques of multiband antennas for portable transceivers

This paper describes various miniaturization techniques of multiband antennas for portable transceivers. The considered techniques include folding, meandering and wrapping of the primary radiator. In addition, utilization of ground slots to widen the existing or generate new bands is described. These techniques are illustrated through design examples. Finally, a wideband antenna created by wrapping a quarter-elliptical monopole and a quarter-elliptical antenna with a complimentary slot are presented. These antennas cover all the popular wireless frequency bands in the 850MHz to 6GHz frequency spectrum with respect to the 6dB return loss reference. Full-wave EM simulations and experimental results for these compact multiband antennas are given.

A folded quarter-elliptical wideband antenna for portable devices

In the last decade, compact low-profile antennas featuring multiband operation have drawn a considerable interest from designers of portable wireless devices. The demand for these antennas stems from the fact that modern portable devices have to access an increased number of wireless services across the frequency spectrum from approximately 880MHz to 5850MHz. These services include GSM, GPS, DCS, PCS, UMTS, WLAN and WiMAX. There is a considerable challenge to design an embedded antenna, which would fulfill this multiband operation, using a limited space offered by modern portable RF transceivers. With respect to designing wideband antennas, which by default offer multiband performance, many of the published works have been devoted to the UWB frequency range of 3.1 to 10.6 GHz. The number of wideband antenna designs capable to operate in a lower microwave region to support portable wireless services steadily increase. In [1], a wideband antenna with an impedance bandwidth from 800MHz to 3.85GHz at 9.5dB return loss was proposed. However the designed CPW-fed antenna is 90mm × 110mm in size and thus cannot be used in typical portable devices such as cellular phone or personal assistant. An approach proposed in [2] to generate a wideband performance has a more practical value because the designed quarter elliptical resonator antenna is 20mm × 18mm and requires only a 50mm × 60mm ground plane to achieve operation between 1.9GHz to 3GHz at a 10dB return loss level. This paper is a logical continuation of the work described in [2]. It presents the design of a folded quarter-elliptical antenna that can cover the frequency bands between 850MHz to 6GHz at 6dB return loss or VSWR 3:1.

Characteristic Evaluation of Multiple Layers Microwave Absorber Coated with Biomass Composite

Radiation Absorbing Material (RAM) is used to absorb radiations of electromagnetic wave surrounding us. Thus, the multiple layers’ microwave absorber using biomass composite materials could be one of the solutions to address the problem. In order to effectively absorb the radiation of electromagnetic wave, the multiple layers’ absorber is characterized to optimize the performance of the absorber. The characterization is made by varying biomass composite material contents, thickness and other possible considerations. CST Microwave Studio software is first used to design and simulate the multiple layers’ absorber to estimate its performance. Development of multiple layers’ prototype is carried out to test its performance at free space environment. Free space dielectric measurement method is used to determine the value of multiple layers’ absorber dielectric. The dielectric value is then used in CST software in order to make the simulation more precise. Free space arch which is connected to Agilent Analyzer is used to measure absorption of multiple layers’ microwave absorber.

A compact multiband NRI-TL metamaterial-loaded planar antenna for heart failure monitoring

A compact, planar antenna is proposed, which uses negative-refractive-index transmission-line (NRI-TL) metamaterial loading in order to achieve multiband operation with orthogonal pattern diversity in different bands. The antenna occupies a small footprint, which is a key requirement for its future use in a heart failure monitoring system. It is shown that by employing two metamaterial unit cells as the main radiators, this produces a dipolar mode at 1.43 GHz and 1.92 GHz and an orthogonal folded monopole mode at 4.18 GHz. The associated -10 dB bandwidths around each of these frequencies are 24 MHz, 57 MHz and 372 MHz, while the corresponding gain and radiation efficiency are 0.82 dBi (71%), 1.27 dBi (75%) and 2.13 dBi (90%), respectively. The total size of the antenna is 30 × 36 × 1.59 mm3, while the height of each radiating arm is only 5 mm.

Slotted triangle on hollow pyramidal microwave absorber characteristics

This paper presents the performance effect of hollow pyramidal microwave absorber that had been applied with slotted array principle. The Sierpinski triangle was used as the slotted on the hollow pyramidal microwave absorber. This paper includes the theories, simulation and measurement result. The simulation using CST Microwave Studio Suite used to predict the Sierpinski triangle design of microwave absorber performance. Measurement had been done successfully via an arch method at 8 GHz till 12 GHz. From the increasing iteration in Sierpinski triangle principle leads to stable the impedance of absorber and resulting high absorption at frequency range between 11 GHz till 12 GHz.