Investigation into a folded wideband monopole antenna for use in portable devices

This paper presents investigations into a compact antenna for use in portable devices to access almost all modern wireless services from about 800MHz to 6GHz. Initially, a microstrip-fed planar monopole of quarter-elliptical shape on FR-4 substrate is designed to generate a wide impedance bandwidth. This radiating element is augmented with a parasitic microstrip stub and a ground-plane cut to improve wideband performance. To reduce its projection area, the planar monopole is folded. The folded antenna occupies a volume of 13mm × 50mm × 5.6mm. It operates over two wide bands between 0.85 and 3.8GHz, and 4.9 and 6GHz, with reference to 6dB return loss (VSWR 3:1). Its radiation patterns are omnidirectional in the lower band and deteriorate at higher frequencies. The corresponding gain varies between 1.5 and 7dBi

Dielectric properties assessment of honey by using non-destructive dielectric spectroscopy

In this research the dielectric constant of three types of Malaysian honey has been investigated using a non-destructive measurement technique. The objective of this research is to assess the dielectric constant of the three types of honey in Malaysia using a non-destructive measurement technique known as an open-ended coaxial probe in the frequency range from 100 MHz to 10 GHz frequency. Analysis on the effect water concentration in honey on the dielectric constant and the effect of temperature on dielectric constant of honey has been conducted. The three types of honey that have been chosen to be investigated in this project are stingless bee honey, wild honey and commercial (organic) honey and together their water adulterated samples. For this research, the probe had been set up by setting a range of frequency from 100 MHz to 10 GHz and needs to be calibrated with three calibration methods namely open, short and reference water. From the result it was found that the higher the temperature of the honey and the higher percentage of water content in the honey, the dielectric constant is increased. The dielectric constants of all honeys decreased with increasing frequency in the measured frequency range and increased with increase percentage of water content and temperature

Wireless Power Transfer via Inductive Coupling

Various types of wireless power transfer method have been developed in recent years. This technology has eventually impacted the human life, especially the way they harvest the electrical energy resources. The most common and the first technology of wireless power created are known as inductive coupling method, which transfers power using magnetism process. This paper proposes the design of an oscillator that produces oscillation frequency at 1MHz for nearfield wireless power transfer, and it is applicable for a short range wireless power transmission only. In conjunction to that, this paper also presents a design of the resonator of an antenna using copper wire in transmitting and receiving the energy transfer for short range transmission of wireless power transfer. The proposed design uses the concept of pad charger where the coil is designed from a pancake coil properties known as flat circular coil. The coil acts as an antenna and magnetic coupled or electromagnetic induced such that when there are changes of current occur in one coil, it will induce the voltage at the other end of the coil, in which the wireless power is transferred between the transmitter and the receive. It can be concluded in this proposed method has the ability to successfully transfer the power between the transmitter and the receiver, even when some obstacles are placed between the coil antennas. Then, a rectifier was used at the receiver to convert the alternating received current to the direct current. The received power is measured to observe the variations at several distances

Performance Study of Egg Tray Microwave Absorber

This paper proposes the physical models of a threelayer egg tray microwave absorber that contains biomass material as the design. The absorbing materials were prepared in three layers: carbon, palm ash and a mixture of coconut shell granular with carbon. To verify the performance of the absorber, it was modeled and measured by free space arch reflectivity measurement to determine the absorption level in a frequency range of 8 GHz to 12 GHz. The absorption level resulting from this investigation were then analyzed and discussed. The investigation shows that palm ash granular with carbon can increase the absorption level performance. Thus, the material has the potential to be used in electromagnetic absorption

Performance Evaluation of Flat Shape Absorbers Coated with Multi-Layer Biomass Composite

Microwave absorber is one of the main components used widely in anechoic chambers for antenna measurement. It is also used to absorb unwanted radiations in electronic products and other applications. This paper presents an investigation on the performance of flat shape microwave absorbers coated with biomass composite namely sawdust carbon and palm ash composite. The layer of biomass composite applied on the surface of this flat shape absorbers was found to contribute significant impact on the performance. This study is also looking at the impact of using two different board materials that is cardboard and plywood as the base of the absorbers. The wave frequency ranging from 8GHz to 12 GHz was chosen for the purpose of this study

Design of Compact Multiband Antennas for Portable Wireless Transceivers

In recent years, the rapid expansion of wireless communications and the consequent introduction of new frequency bands have increased the demand for multiband transceivers. For manufacturers, the multiband transceivers have to feature compact sizes and low fabrication costs. In addition, from the technical point of view, the RF front-end module of the receivers has to be easily integrated with embedded antennas that should be unobtrusive in appearance. To fulfil all these requirements, considerable attention is given to planar or microstrip patch antennas because they are easy to manufacture, and offer considerable flexibility with regards to the space constraints in RF front-end circuitry, which is primarily fabricated on Printed Circuit Boards (PCB). However, as the transceiver modules become more compact, this type of antenna faces a number of challenges. It has to achieve a multiband operation in the smaller volume that is available in modern compact wireless transceivers. To meet these goals, a suitable design methodology has to be used. This thesis work focuses on compact multi-band patch antennas which are designed for existing wireless services including GSM, PCS, DCS, GPS, UMTS, WLAN and WiMAX 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 and disadvantages depending on the required application. The constraint for the lower band generation is the main challenge in radiator miniaturization. The quarter wavelength radiator subjected to miniaturization may suffer from limited bandwidth and low radiation efficiency. Alternative approaches using modifications of the ground plane are a promising technique, which were often previously overlooked by antenna designers. It is shown herein that the introduction of a ground slot at its quarter wavelength electrical dimension excites new resonances. Proper dimension and configuration design results in a minimal usage of ground plane area, which is traditionally dedicated for electronic circuitry in the transceiver module. The introduction of a ground slot in a finite antenna ground plane can be further extended to include reconfigurable features. With easily available electrical switches such as MEMS, varactors or PIN diodes, ground slots can be turned into a frequency-tuneable element. Thus, such antennas offering compact size with multiband capability can be promising candidates for wireless antenna design. This thesis presents a viable solution and a promising approach to address these challenging scenarios in antenna design. As compared to the previously published antennas in the literatures, the reported antennas present several multiband solutions by utilizing the ground slot, slit and cut instead of the conventional radiator modifications. In addition, the antennas are modified using several novel techniques to miniaturize the main radiator, such as a meandered-tail and folded quarter ellipse configurations. Finally, the thesis proposed a novel reconfigurable ground slot which eliminates the need to have a complicated bias network commonly faced in designing reconfigurable radiators. Five novel antenna designs are presented in the thesis. Initially, a compact 6 x 13 mm coplanar inverted-F antenna (CIFA) with ground slots is developed to produce a multiband operation for WLAN 2.4 GHz, 5.2 GHz and 5.8 GHz services. The antenna is the first in the literature to utilize the coupling configuration between ground slot and microstrip feedline to introduce a new resonant frequency, and thus to achieve a multiband operation. In addition, a compact 13 x 60 x 5.6 mm antenna based on a novel quarter-ellipse monopole design is also presented. In the design, the modification of the ground plane involves the use of a ground cut and a parasitic element. The resulting antenna has ultra-wideband coverage for all wireless services ranging from the GSM 850 MHz up to WLAN 5.8 GHz, the first planar antenna within 5 mm height to achieve this coverage performance. The design of a 3 mm inverted-F antenna to cover GSM, DCS and PCS operation is also proposed. This 3 mm antenna height is the slimmest dual band PIFA ever proposed in the literature. This compact 40 x 10 mm antenna radiator makes use of less than 5% of its ground plane area for the modification needed to achieve the desired operational bandwidth. In the final part, the thesis presents a reconfigurable CIFA with the first ever tunable ground slot configuration in the literature. The novel tunable ground slot utilizes PIN diodes as a switching device to produce an antenna that is compact and covers the GSM, DCS, PCS and UMTS bands. The performance of all the designed antennas has been verified through experimental investigations. The obtained radiation characteristics for all the presented antennas are close to the omni-directional pattern, a feature which is needed for portable transceivers. Also, the achieved antenna gains and efficiencies are within the feasible range of 0 to 7 dBi that is suitable for most of the portable wireless applications. The presented novel antenna design methods provide potential solutions to the compact and multiband requirement of modern portable antenna designs. With the presented antenna design methods, the solutions to the compact and multiband requirement of modern portable antenna design are addressed

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 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. 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

Planar antennas for compact multiband transceivers using a microstrip feedline and multiple open-ended ground slots

Two planar antennas for compact multiband transceivers are presented, that employ an open-ended microstrip feedline that couples to multiple open-ended ground slots. The effect of separately introducing each of the slots on the antenna performance is outlined, and it is shown that the resonant frequencies of the antennas can be independently controlled by adjusting the dimensions of the ground slots. Antenna 1, consisting of an open-ended microstrip feedline that couples to three open-ended ground slots, exhibits a measured vertical bar S-11 vertical bar < -6 dB in the frequency ranges of 1.64-3.50 GHz, and 5.22-6.81 GHz, covering the standards of DCS, PCS, UMTS, Wibro, Bluetooth, WiMAX, HiperLAN 2 and WLAN with a measured gain that varies between 1.85 and 3.98 dBi, and with radiation efficiencies in excess of 80%. Antenna 2, consisting of an open-ended microstrip feedline that couples to four open-ended ground slots, exhibits a measured vertical bar S-11 vertical bar < -6 dB in the entire frequency range of 2.74-6.71 GHz, covering the standards of WiMAX, HiperLAN 2 and WLAN with a measured gain that varies between 4.98 and 5.28 dBi, and with radiation efficiencies in excess of 80%. Both antennas occupy a total size of only 40 x 30 x 1.6 mm(3)