Direct integration of push-pull amplifier and aperture coupled antenna

The work described in this thesis concerns the integration of push-pull class B amplifier and antenna modules. Push-pull class B is well-known with its fruitful advantages of using differential feeding technique, resulting in low distortion, reasonably high efficiency and high output power. Meanwhile, the antenna module in this work is adapted from the aperture-coupled antenna structure due to its degree of freedom to control the variables which provide the best possible topology that could be realised in system on chip or system in package. More generally, the variables allow good coverage of the Smith Chart so that a wide range of odd-mode matching requirements could be met, for different devices and bias condition of a given transistor. The approach also offers additional filtering up to 3rd harmonic in that it comprises identical harmonic traps on both sides of the aperture using resonant stubs to form bandstop filters, which reduce the ripples at the output waveforms, giving them a significant advantage of neat and tight integration of a push-pull transmitting amplifier

A comparison of various double loops frequency selective surfaces in terms of angular stability

This paper presents the comparison of Frequency Selective Surfaces (FSS) structure performance based on three different double loops: square, circular and hexagonal structures. The simulation process of the double loops FFS structures are carried out by using the Computer Simulation Technology (CST) Microwave Studio software. The dielectric substrate used in the simulation is the FR-4 lossy substrate

Design of Triple-band Dipole-type Antenna with Dual-band Artificial Magnetic Conductor Structure

A design of dual-band high-impedance surface called Artificial Magnetic Conductor (AMC) is presented. The AMC is designed to resonate at 0.92GHz and 2.45GHz. In this paper also, the design parameters that influence the AMC frequencies are discussed. The designed AMC then is incorporated with the designed triple-band printed dipole antenna (operating at 0.92GHz, 2.45GHz and 5.8GHz). Here, the performance of the dipole antenna with 2 and 4 unit cells of 0.92GHz and 2.45GHz AMC ground plane are presented. The reported results show that, by applying the AMC structure as a ground plane for the printed dipole antenna, the gain of the dipole antenna can be increased due to the attracting feature of the AMC surface that provide in-phase reflected waves with the incident waves

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

UHF RFID antenna tag design and analysis for antenna miniaturization

This paper proposes four designs of UHF RFID antenna tag with two different radiating element, copper and aluminum, for antenna miniaturization. The main contribution of this work is the unique design that involves a meander line traced in a variety shape of a bowtie antenna. The UHF RFID band is achieved by reshaping a 900 MHz straight line dipole antenna into the form of a bowtie, thus reducing the size of the antenna significantly while maintaining the operating frequency. The effectiveness of the method is tested in multiple steps. First, the antenna tag designs are run through CST software simulations and optimized to achieve desired outcome. Next, the designs are transferred to Silhouette Studio software to be fabricated using a cutting machine, and finally measured using a vector network analyzer. The comparison between the measurement result of the reflection coefficient and the radiation pattern to their respective simulation results shows that they have a good agreement between each other. With further research and improvements, the size of the antenna tag could be further reduced while maintaining or even improving the performance of the antenna tag

Millimeter wave fifth generation (5G) antenna for smartphone application

In this paper, a single element antenna is designed at millimeter-wave frequency bands for future 5G smartphone applications. The configuration of proposed antenna is multiple L-slots on the ground plane which is designed on a low cost FR4 board. The antenna covers a frequency range between 28 to 35 GHz with a higher bandwidth 4.7 GHz. The antenna shows an excellent performance when integrated with the mobile phone application. The single element antenna exhibits a maximum radiation pattern around 5.945 dBi

Multiband hairpin-line bandpass filters by using metamaterial complimentary split ring resonator

Telecommunication systems for the new generation have greatly stimulated the demand for multi-band bandpass filters with compact dimensions, low insertion loss, robust, low cost and less complex design. In this paper, a compact multi-band bandpass filter, with the fractional bandwidth of 40% and 20% at resonant frequency 3.5 and 5.5 GHz respectively with the response of Chebyshev passband ripple of 0.1 dB is presented. This bandpass filter is suitable for WiMAX application. The design is based on the hairpin-line configuration and metamaterial of complementary split ring resonator structure. The hairpin-line is used for the compact structure design and easy to fabricate because it has open-circuited ends that require no grounding. While the complementary split ring resonator structure is easy to design and can provide multi-band without affecting of size and performance of the filter. The simulated results show the dual-band bandpass response with the insertion loss is 0 dB and high attenuation at stopband. The proposed filter provides a compact, low insertion loss, and less complex structure design that are promising candidates in order to meet the demands of the new generation of communication systems

Design of Miniaturized Multiband Patch Antenna Using CSRR for WLAN/WiMAX Applications

A novel miniaturized multiband, single-feed microstrip patch antenna is presented in this paper for WLAN and WiMAX applications. Both size reduction and multiband are obtained by etching the Multiple Complementary Split Ring Resonators (MC-SRR) on the ground plane of the normal patch antenna. At first, the normal patch antenna produces a single band of 5.15 GHz; 200 MHz (5.0500~5.2499). Subsequently, a Single Circular Split Ring Resonator (SC-SRR) is etched on the ground plane and produces a triple band of: 3.25 GHz; 288 MHz (3.1085~3.3964), 4.5 GHz; 101.3 MHz (4.4488~4.5501), and 5.22 GHz; 220 MHz (5.1191~5.3400) and Double Single Circular Split Ring Resonator (DC-MCSRR) with: 2.99 GHz; 60.7 MHz (2.9574~3.0181), 3.57 GHz; 324.7 MHz (3.4065~3.7312), and 5.1413 GHz; 115.4 MHz (5.0817~5.1971). The working bandwidths cover the desired frequency bands of WLAN 5.2 GHz and WiMAX 3.3/3.5 GHz. The proposed (MC-SRR) antenna can be employed to wireless communication systems due to its simplicity in design, compactness and miniaturization

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

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