UTHM water quality classification based on sub index

River or stream at their source is unpolluted, but as water flow downstream, the river or lake is receiving point and non-point pollutant source. Ammoniacal nitrogen (NH3- N) and suspended solids (SS) strongly influences the dynamics of the dissolved oxygen in the water. Studies on monitoring this parameter were conducted for a river or lake but limited to the small man-made lake. This study is initiate to determine the changes in water quality of UTHM watershed as the water flows from upstream to downstream. The monitoring of NH3-N and TSS were monitored at two sampling schemes, 1) at the two-week interval and, 2) at a daily basis followed by the determination of the water quality sub-index particularly SIAN and SISS. The results showed that the two lakes in UTHM watershed were classified as polluted. In conclusion, the remedial action should be implemented to improve the water quality to meet the requirements at least to meet the recreational purpose

Planar Ultra-Thin Small Beam-Switching Antenna

A novel planar ultrathin electronically steerable parasitic array radiator (ESPAR) is presented in this paper. Through theoretical analysis of the electric fields of orthogonally crossed dipoles in phase quadrature, it is found that the crossed dipoles radiate linearly polarized wave with a rotational electric field in the azimuth plane. This characteristic is then utilized to design a planar crossed dipole ESPAR, termed as “CD-ESPAR.” Furthermore, a simple but effective impedance matching method is also proposed and analyzed. To verify these concepts, a prototype with compact size and very low profile (0.42 ?0 × 0.42 ?0 ×0.006 ?0) resonating at 2.3 GHz is designed, fabricated, and measured. The measured results indicate that the proposed antenna achieves more than 17.8% impedance bandwidth and can produce four directional beams, covering the whole azimuth plane. Owing to its planar ultrathin structure, compact size, electronically beam-switching ability, low power, and low cost characteristics, it is promising for applications in wireless communication

Parasitic Layer-Based Reconfigurable Antenna and Array For Wireless Applications

Antenna is one of the most important components in wireless systems since signal transmission and reception are conducted through the antenna interface. Therefore, the signal quality is highly affected by the properties of the antenna. Traditional antennas integrated in devices such as laptops or cell phones have fixed radiation properties and can not be changed to adapt to different environments. Thus the performance of thefwhole system will be negatively affected since the antenna will not operate in the optimum status in different environments. To solve this problem, reconfigurable antenna, which can dynamically change its operation frequency, radiation pattern, and polarization, has gained a significant interest recently. Recongurable antennas are considered smart antennas, and can maximize the capacity of the wireless system. This dissertation focuses upon the theoretical analysis and design of smart antennas with recongurable radiation properties. The presented multi-functional reconfigurable antennas (MRAs) are aimed to applications in WLAN (wireless local area network) systems. The theoretical analysis of the MRA was rst investigated to validate the design concept, and then applied for practical applications. The multi-functional recongurable antenna array (MRAA), which is a new class of antenna array, is also created as a linear formation (4 1) of MRA, with theoretical analysis and design of the MRAA fully described. This work developed three MRA(A)s for practical implementation in WLAN systems. The rst design is the MRA operating in 802.11 b/g band (2.4-2.5 GHz), with nine beam steering directions in a parasitic layer-based MRA structure. The second is a MRA operating in 802.11ac band (5.17-5.83 GHz) with three beam steering directions in a simplied parasitic layer-based MRA structure. The third is a MRAA extension of the second design. The design process of these MRA(A)s is realized with the joint utilization of electromagnetic (EM) full-wave analysis and multi-objective genetic algorithm. All three MRA(A) designs have been fabricated and measured. The measured and simulated results agree well for both impedance and radiation characteristics. These prototypes can be directly employed in a WLAN system since practical limits have been taken into account with real switches and components implemented. Finally, this dissertation work concludes with plans for future work, which will focus on development of MRA(A)s with dual-frequency operation

Reconfigurable microstrip antennas with tunable radiation pattern characteristics

Reconfigurable beam antenna systems are capable of changing their radiation characteristics in real time, such as beam direction, beam shape, beamwidth, etc. Such antenna system is desired for various wireless applications because of many reasons among them; it helps to enhance signal strength received from an intended target, mitigates interference, and accommodates sudden changes in traffic demand of wireless networks. It might also help to reduce the deployment cost of wireless networks infrastructures. In this dissertation, designs for reconfigurable beam microstrip antennas with tunable radiation characteristics have been proposed. The method to achieve these designs is the reconfigurable parasitic element (s) of tunable electrical size, placed in close proximity to the driven patch. A tuning mechanism with the aid of Varactor diodes is introduced for the parasitic patch that effectively allows for controlling its electrical size. This (these) reconfigurable parasitic patch (es) is (are) then applied in different fashions to devise several antenna designs with dynamic electronic control over certain radiation specifications. The accomplished antenna designs in the dissertation are: * Circularly polarized (CP) beam scanning antenna, where two elements microstrip Yagi-Uda antenna is used. The first element is a square patch driven with two probe feeds of quadrature phase for CP excitation. The second element is a parasitic square patch with narrow square-shaped slot carved on its surface. The parasitic patch is adjacent to the driven patch with a small separation distance. Four varactor diodes are placed on the middle of each side of the square slot to facilitate tuning of its electrical size. The parasitic patch electrical size is alloto be effectively tuned by varying the applied reverse biasing DC voltage to the varactors (capacitance value). The CP beam direction is scanned from -36° to 32° with gain variation from 5.7 to 8.2 dBic, and efficiency from 54% to 75.58% along the scanning range. * Two-dimensional beam scanning antenna, where two orthogonal crossed Yagi-Uda antenna configuration is utilized. The driven element is a square patch excited with a probe coaxial feed. The other two parasitic patches are closely placed along the E & H planes of the driven patch. Each parasitic patch has a narrow rectangular slit at its center, where a varactor diode is placed to allow for tuning its electrical size. The beam direction is permitted to be scanned in both the elevation and azimuth planes. The achieved scan range in the elevation plane is from 0° to 32°, whereas in azimuth plan is from 0° to 90°. Along the scanning range, the attained gain changes from 8.1 to 8.9 dBi, and efficiency changes from 86% to 93%. * Tunable beamwidth antenna, with a dynamic control over the radiation beam focusing is proposed. The antenna consists of a square patch excited by a coaxial probe feed, and other two square parasitic patches placed on both sides of the driven along its H-plane. Each parasitic patch has a narrow slit at its center loaded with lumped varactor diode to tune its electrical size. Upon changing the parasitic patches size, the antenna effective aperture is altered, and hence the beamwidth in the H-plane is controlled. The achieved beamwidth tuning range is from 52° to 108°, whereas the gain changes from 6.5 to 8.1 dBi. Throughout the dissertation, 2.45 GHz is chosen, as an example, to be the target frequency. All the designs are validated through experimental measurements for fabricated prototypes, and good agreement is observed between the predicted and measured results

Recon gurable Antennas Based on Varactor-Loaded Stubs

The term “reconfigurable” is typically used for devices which exhibit some flexibility of functionalities and agility in their operation characteristics, with the aim of achieving high performance in various conditions. In antenna technology, the reconfiguration can be fulfilled through several techniques that provide an ability to modify the electrical current on the antenna’s structure, primarily to accomplish a physically realised new response. The main key to the reconfigurable antenna application is their potential to avoid the use of multiple antennas for multi-functionality, thus facilitating miniaturisation of the antenna system configuration. In this context, several novel reconfigurable antennas with a wide performance range are proposed in this thesis. Varactor-loaded stubs are used as tuning mechanism for these microwave antenna designs with improved performance throughout this thesis. Two types of electromagnetic structures are studied in this work, namely reconfigurable antennas and reconfigurable periodic structures, with these two main topics building the two main major parts of this thesis. In its first main part, the thesis proposes reconfigurable antenna designs with combined frequency and pattern reconfigurable characteristics. The main focus is first on the manipulation of near-resonant current distributions in a two-element array antenna as well as the optimisation of their feeding through T-junction power dividers. Each element has a controllable active component that allows the antenna to be tuned to different operating frequencies, while the concurrent adaption of the two elements is the basis of continuous beam scanning characteristics. Next, the thesis examines the exploitation of a single-element antenna structure based on the same operation principle. An optimisation procedure including a study of relevant design parameters is also presented. The core contribution for the two-element array and the single-element antenna is that they combine frequency-reconfigurability with effective beam scanning. The main difference between the two designs however is that they scan in the H-plane and the E-plane, respectively. In the second main part, the thesis focuses on a reconfigurable reflectarray antenna design. Potential applications of this advanced antenna design include the development of high gain antennas with various controllable reflection beam directions throughout a wide range of operation frequencies. The proposed reflectarray antenna unit cell is firstly proposed, together with an opimisation of the antenna characteristics in terms of reflection loss and phase range performance. It is further shown that the proposed antenna provides an excellent performance compared to the state-of-the-art. Performance measures include a near full phase tuning range of about 300 to 320 with a reflection loss of magnitude better than 3 dB within a fractional frequency range of operation of 18%. In contrast, most reflectarray antenna designs in the literature provide a limited phase range at a fixed operating frequency or within a narrower frequency tuning range. Experimental validation is provided with a 12-element linear reflectarray tested in twodimensional settings, for which the experimental challenges are also discussed in detail. The capability of reflected beam scanning is verified and successfully demonstrated.Thesis (Ph.D.) -- University of Adelaide, School of Electrical & Electronic Engineering, 201

RF choke based methodology for flange effect mitigation and antenna isolation improvement in bistatic radars of aerospace vehicles

This paper presents a novel technique for mitigation of flange effect and antenna transmit to receive isolation improvement methodology using RF choke for the bistatic radars of aerospace vehicles. The presence of flange causes variation in antenna radiation pattern, by an increase in sidelobe level, decrease in gain and dip in roll pattern, thereby degradation in the performance of the antenna. An RF choke adjacent to the waveguide wall is introduced to nullify the undesirable effects of the flange. This Paper demonstrates through simulation and experimentation that this choke effectively suppresses the surface wave and can be applied in many types of antennas to improve the radiation pattern deteriorated by parasitic elements. It is also demonstrated through measurements that the isolation from transmit to receive antenna is improved by introducing choke, with this technique antenna isolation is enhanced by 23 dB with 11 dB antenna gain. The gain and sidelobe improvement of the antenna with RF choke is 2 dB, and 6 dB, respectively. The proposed array antenna is fabricated with and without choke, measurements are performed and test results are presented. The isolation test between transmit & receive antenna is performed in an anechoic chamber and test results are presented

Wideband Circularly Polarized Elements and Arrays for Wireless Systems

Circularly polarized (CP) antennas have received increasing interest during recent decades due to their unique features such as the mitigation of multi-path fading, reduction of the "Faraday rotation" effect when signals propagate through the ionosphere and immunity of the polarization mismatching between transmitting and receiving antennas. Due to the requirements of high date rate and large system capacity, CP antennas deployed in various wireless systems are always demanded to have wide bandwidth. Furthermore, other system requirements such as polarization diversity, wide-angle beam scanning and low power consumption impose additional requirements to CP antennas. Therefore, it is becoming a more stringent requirement to design wideband CP antennas with diverse features to fulfil the requirements of various wireless systems. In this thesis, six different types of wideband CP antenna elements and arrays are designed, fabricated and characterized to meet the different demands of wireless systems. Chapters 3-5 investigate three different types of wideband CP antenna elements while Chapters 6-8 investigate three different kinds of wideband CP array antennas. In Chapter 3, an ultra-wideband CP element with a bandwidth of 100% (3:1) is proposed. It over-comes the problem of limited 3 dB axial ratio (AR) bandwidth for single-feed CP antennas and achieves high front-to-back ratio (FBR) by using a novel ground plane with simple configuration, which makes it a good candidate for high-performance Global Navigation Satellite System (GNSS) receivers. Chapter 4 presents a wideband loop antenna with electronically switchable circular polarizations. It solves the issue of narrow overlapped bandwidth under different polarization states for a polarization reconfigurable CP antenna. Because of the available orthogonal polarizations across a wide bandwidth, this antenna can be deployed in wireless communications which implement polarization diversity. The third antenna element investigated in Chapter 5 tackles the difficulty of designing wide-band wide AR beamwidth CP antennas. It achieves wide AR beamwidth within a 42% bandwidth, which is suitable for wideband wide-angle CP beam-scanning applications. The second main part of this thesis focuses on the investigation of wideband CP arrays. In Chapter 6, a dual-CP beam-scanning array is investigated, which can scan its beam independently in right-hand circular polarization (RHCP) and left-hand polarization (LHCP) from 27 GHz to 30 GHz. It tackles the problem of low isolation between the two orthogonally polarized ports across a wide bandwidth at Ka-band. A single-layer high-efficiency CP reflectarray is proposed in the following Chapter. The proposed design solves the issues of bandwidth limitation and low aperture efficiency for single-layer CP reflectarrays. It achieves the widest bandwidth compared with other CP reflectarrays reported in terms of 3 dB AR bandwidth, 3 dB gain bandwidth, larger than 50% aperture efficiency and undistorted radiation pattern bandwidth. In Chapter 8, we investigate the first application of tightly coupled array (TCA) concept into ultra-wideband arrays with CP radiation. Instead of trying to reduce the mutual coupling among the elements, it exploits the strong mutual coupling to improve the bandwidth of a CP array. By using the strong coupling in a constructive way, it overcomes the bandwidth limitation of CP arrays which are constituted by narrow-band elements

Radiation characteristics of a conical monopole antenna with a partially corrugated ground plane.

In order to preserve broadband performance, the conical monopole antenna is ideally mounted on a semi-infinite ground plane. Practical finite ground planes can introduce unwanted effects in the radiation patterns such as significant back lobes. Periodic surfaces such as rotationally symmetric corrugated structures have been proven capable of improving the radiation characteristics of a variety of antennas. In this paper, the radiation patterns of a conical antenna with a PEC reflector are initially presented. The PEC reflector is then replaced with a partially corrugated reflector surface. The effects of the partially corrugated reflector on the radiation patterns and electric field distribution along the reflector surface are investigated. The simulation results reveal that the radiation patterns of a conical antenna with a partially corrugated reflector are more stable over a wide frequency band than that for the PEC reflector

A Review: Substrate Integrated Waveguide Antennas and Arrays

This study aims to provide an overview and deployment of Substrate-Integrated Waveguide (SIW) based antenna and arrays, with different configurations, feeding mechanisms, and performances. Their performance improvement methods, including bandwidth enhancement, size reduction, and gain improvement are also discussed based on available literature. SIW technology, which acts as a bridge between planar and non-planar technology, is a very favorable candidate for the development of components operating at microwave and millimeter wave band. Due to this, SIW antennas and array take the advantages of both classical metallic waveguide, which includes high gain, high power capacity, low cross polarization, and high selectivity, and that of planar antennas which comprises low profile, light weight, low fabrication cost, conformability to planar or bent surfaces, and easy integration with planar circuits