Simulation of co-planar waveguide liquid crystal based phase shifter

This paper discussed the design and performances of a liquid crystal phase shifter that can be used in tuning devices. Tuning devices growth with the demand in the emerging in telecommunication system. Tuning devices with smooth continuous phase shifting at low cost and compact size would be an advantage. This paper proposed a phase shifter using 5CB liquid crystal material. The advantages of using the material is the smoothness and continuity of the transitions in the phase shift. It is done by having a structure with cavity filled with the liquid crystal and applied with certain voltage that can be changed. The changes in voltage would change the applied electric field, and thus would change the permittivity of the material. The changes would affect the wave propagation and thus contribute to the phase shifting. The performance of the phase shifter was tested by means of simulation using CST Suite 2014 software. The results show that the higher the frequency, the higher the phase shift would occur. The highest FoM achieved is 68 (deg/dB) at 8 GHz. A phase shifter with smooth and continuous phase shift can be used as the feeding network in an array scanning antennas systems

Keberkesanan penggunaan edubase dalam kalangan pelajar teknikal yang berbeza gaya kognitif, afektif dan psikomotor di Politeknik Malaysia

Bahan bantu pengajaran yang digunakan secara bersesuaian dengan pelajar menyumbang kepada perkembangan pembelajaran mereka. Dalam dunia pendidikan teknikal, aspek kognitif dan psikomotor turut memberi kesan kepada kualiti pembelajaran pelajar. Kajian ini membincangkan tentang kesan penggunaan EDUBASE terhadap pencapaian dan minat pelajar yang mempunyai gaya kognitif, afektif dan psikomotor yang berbeza dalam topik Electromagnetism. Seramai 70 orang pelajar politeknik yang terdiri daripada 33 pelajar kumpulan rawatan dan 37 pelajar kumpulan kawalan telah terlibat dalam kajian yang menggunakan kaedah kuasi-ekperimen ini. Ujian kognitif, psikomotor, ujian pra-pasca dan kaji selidik telah diagihkan untuk memantau kesan penggunaan EDUBASE terhadap pelajar. Dapatan kajian ini telah dianalisis dengan menggunakan statistik MANCOVA, korelasi Pearson dan skor min. Hasil dapatan dalam kajian ini menunjukkan bahawa terdapat perbezaan yang tidak signifikan secara statistik bagi skor pelajar kumpulan kawalan dan kumpulan rawatan. Namun, skor min menunjukkan kumpulan rawatan memberikan skor yang lebih cemerlang dan minat mereka juga turut meningkat dalam topik pembelajaran tersebut berbanding pelajar yang mengaplikasikan pembelajaran secara konvensional. Selain itu, hasil dapatan kajian juga menunjukkan terdapat hubungan yang signifikan terhadap minat dan pencapaian. Di samping itu, EDUBASE yang diaplikasikan telah memenuhi keperluan dan minat pelajar. Secara ringkasnya, hasil kajian ini menunjukkan bahawa penggunaan EDUBASE sebagai alat bahan bantu mengajar dilihat berkesan dalam memberikan kecemerlangan pencapaian dan meningkatkan minat pelajar politeknik terhadap topik Electromagnetism

Floral structure for textile-based metamaterial absorber

Based on an annulled circle structure metamaterial absorber (MMAb), a floral structure MMAb design is proposed for performance improvement especially on absorptivity. Since the initial purpose of designing the MMAb is for hiding one’s existence from electromagnetic motion detector, it is expected that the MMAb will has flexibility as one of its characteristics. The MMAb composes of textile-based substrate in between floral structure at the top and ground plane at the bottom, based on metallic plate. The targeted center frequency is 10.525 GHz and through series of simulation done in CST Microwave Software, the MMAb can reach up to 97.03% of absorptivity. The operating angle can be extended at least 68o before its absorptivity deteriorated below 80%. In addition, the proposed MMAb has a high absorptivity regardless of the polarization angle of the electromagnetic waves

High capacity and miniaturized flexible chipless RFID tag using modified complementary split ring resonator

This paper aims to produce a high data capacity and miniaturized flexible chipless RFID tag based on the frequency signature using the Modified Complementary Split Ring Resonator (MCSRR). The proposed 19 bits chipless RFID tag using the frequency shifting technique consists of five slotted overlaying MCSRR with Different Width (MCSRR with DW) structures and the dimension of 48 mm x 48 mm. The structure is designed by using a flexible (Polyethylene Terephthalate ) PET substrate with permittivity of 0.2. The operating frequency is between 0.9 GHz and 2.7 GHz. The advancement of slotted overlaying MCSRR with DW structures has successfully miniaturized the chipless RFID tag structure to about 107 mm2/ bit, 0.02/2 mid =bit and 0.09 GHz/bit by maximizing the number of resonators in a limited space and minimizing the frequency separation between the resonators. The omnidirectional tag antenna is incorporated with the proposed MCSRR structure using the retransmission measurement method. The log-periodic antenna with a gain of 5-7 dBi is used for this measurement to improve the range distance between tag and reader system. Based on the retransmission measurement involving the antenna tag, the 19 bits chipless RFID tag which consists of five MCSRR with DW structures can be detected with a maximum range distance of 30 cm and a power transmitted level of 30 dBm

Low loss waveguide-based Butler matrix with iris coupling control method for millimeterwave applications

This paper proposes a low loss 4×4 Butler matrix based on rectangular waveguide cavity resonators technology for millimeterwave beamforming network using iris coupling method. This method has the advantage of controlling the electrical fields and the coupling factor inside a complex medium such as waveguide cavity resonators. The coupling factor of 6 dB for 4×4 Butler matrix is achieved by tuning the iris coupling k-value between the waveguide cavity resonators. Thus, avoiding a higher phase difference losses and component losses at upper millimeterwave bands. To validate the proposed method, CST software simulations are performed under several iris coupling k-values to achieve a 6 dB coupling factor. Then, the proposed 4×4 Butler matrix is 3D metal printed using selective laser melting (SLM) technique. The measured reflection and isolation coefficients are observed below −10 dB, with coupling coefficients ranging between −6 and −7 dB. The phase differences of −42.02°, 42.02°, −130.95°, and 133.3° are achieved at the outputs. It confirmed that using this proposed method has the superiority over the conventional microstrip and waveguide coupling methods by a 1 dB coupling factor loss and a 3° phase difference error

IoT-based intelligent irrigation management and monitoring system using arduino

Plants, flowers and crops are living things around us that makes our earth more productive and beautiful. In order to growth healthy, they need water, light and nutrition from the soil in order to effect cleaning air naturally and produce oxygen to the world. Therefore, a technology that manage to brilliantly control plants watering rate according to its soil moisture and user requirement is proposed in this paper. The developed system included an Internet of Things (IoT) in Wireless Sensor Network (WSN) environment where it manages and monitors the irrigation system either manually or automatically, depending on the user requirement. This proposed system applied Arduino technology and NRF24L01 as the microprocessor and transceiver for the communication channel, respectively. Smart agriculture and smart lifestyle can be developed by implementing this technology for the future work. It will save the budget for hiring employees and prevent from water wastage in daily necessities

Wideband antenna with reconfigurable band notched using EBG structure

A wideband antenna with band notch function using electromagnetic bandgap (EBG) structure is proposed. The antenna is capable of reconfiguring up to three band notch operation. Three EBGs are aligned underneath the feed line of the wideband antenna. The transmission lines over EBGs unit cells perform as a band stop filter. A switch is placed on each of the EBG structure, which enables the reconfigurable band stop operation. The simulated and measured reflection coefficients, together with the radiation patterns, are shown to demonstrate the performance of the antenna

Implantable slot antenna with substrate integrated waveguide for biomedical applications

This work presents a new design of capsule slot antenna with substrate integrated waveguide (SIW) for wireless body area networks (WBANs) operating at the range of (2.5-4 GHz) which is located in the body area networks (BAN) standard in IEEE802.15.6. The proposed antenna was designed for WBANs. The substrate is assumed to be from Rogers 5880 with relative permittivity of 2.2, and thickness of 0.787 mm. The ground and the patch are created from annealed copper while the capsule is assumed to be a plastic material of medical grade polycarbonate. The antenna designed and summited using computer simulation technology (CST) software. A CST voxel model was used to study the performance of SIW capsule antenna and the ability of the band (2.5-4 GHz). Results indicated a wide bandwidth of 1.5 GHz between the range of (2.5-4) GHz at 3.3 GHz as center frequency, with return loss with more than -24.52 dB, a gain of -18.2 dB, voltage standing wave ratio (VSWR) of 1.17, and front-to-back ratio (FBR) of 10.07 dB. Through simulation, all considerable parameters associated with the proposed antenna including return loss, bandwidth, operating frequency, VSWR less than 2, radiation pattern were examined. Regarding size, gain, and frequency band, the proposed antenna is located with the standards of implantable medical devices (IMDs)

Micromachined millimeter wave circuits

This thesis presents the design and characterisation of millimetre-wave Butler matrix beamforming circuits at 63 GHz. A micromachining technique is used to fabricate the tiny structures. The ability to manufacture the circuits at this frequency may benefit to the development of intelligent transport system (ITS) communication and sensing systems. All components that build the Butler matrix beamformer are designed to fit the thick SU-8 photoresist micromachining technology, where structures are built by bonding together five layers of metal coated SU-8. The matrix is constructed using air filled rectangular coaxial lines. The dielectric losses are avoided by having air filled structure, however the suspended lines need supporting system. Therefore, stubs are placed in the circuits to hold the suspended lines. In order to transfer signal from the Butler matrix to the antenna, a transition is necessary. A rectangular coaxial line to ridge waveguide transition is designed to feed the H-plane horn antenna and the ridge waveguide slot antenna. The novelty of this work is in both the design of new microwave structure and also in the demonstration of millimetre wave structures in micromachined form using SU8 resist. Four new microwave structures are (1) a back to back rectangular coaxial line to ridge waveguide transition, (2) an H-plane horn antenna, (3) a ridge waveguide slot antenna, and (4) a Butler matrix with a patch antenna array. These and other structures have been built and tested and finally the selection put together to form a new type of Butler matrix. The compatibility of the designs to the fabrication method has been demonstrated. The transition return loss is better than -12 dB from 60 GHz to 90 GHz and has been proven to work with integration to the horn and the waveguide slot antenna. The Butler matrix with a patch antenna array exhibits the forming of the beams at $\pm$17$\circ$ as expected from the theoretical calculation