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The aim of the study is to practically implement the Defected Ground Structure (DGS) based microstrip bandpass filter in an energy harvester circuit. DGS is widely used to bring about an enhancement in the characteristics of microwave circuits. The study of DGS is derived from the concept of Photonic/electromagnetic Band Gap (PBG) structures but it is easier to design and fabricate and has an easier equivalent LC resonator circuit. In this study, DGS has been reviewed from all aspects such as comparing it with PBG, discussing in detail its unit, its structure and property according to various shapes and designs and its several advantages in microstrip filters. Although DGS has various advantages in the area of microwave power amplifier, Wilkinson power divider, microwave antennas, couplers, etc., it is extensively used in the design of microwave filter to achieve stopband effects, slow-wave effects, frequency adjustment etc. Finally a DGS based bandpass filter working at 900 MHz has been designed, fabricated and tested for implementation in an Energy Harvester circuit.

Modern communication systems are required to be compact in size; hence devices building up the system face the challenge to be miniaturized. An iterative designed Bowtie shaped two pole planar bandpass filters utilizing triangular substrate integrated waveguide (SIW) resonators are presented. The triangular cavity design structure is presented; and the coupling of two cavities forms the first iteration of the bowtie shaped filter. The second iteration with reduced interresonator coupling area is also designed, simulated and fabricated for the center frequency of 7 GHz. The bandpass filter maintains high quality factor. The filter's responses reveal that along with miniaturization a better performance in terms of filter's insertion loss being better than 0.2 dB and return loss presented to be less than 30 dB is achieved.

This paper presents the design, modeling, and simulation of a multiple resonant MEMS vibration energy harvester (VEH) suitable for wireless sensor network (WSN) applications. Since ambient vibration has a frequency of 100 Hz and below, a multiple resonant harvester will be an advantage to increase the vibration frequency and hence the output voltage produced by the device. The high frequency harvester is designed using CMOS technology capable of monolithically integration with any CMOS circuits. For a standard button battery size (16 × 16 × 5 mm3) harvester, simulation result shows that the harvester can provide peak voltage of 3.0 Volts at 20 Hz and 1 g vibration with a single high frequency oscillator. The series configuration of high frequency structures can provide multiple of 3.0 Volts output voltage.

A tunable bandpass filter based on a technique that utilizes substrate integrated waveguide (SIW) and double coupling is presented. The SIW based bandpass filter is implemented using a bowtie shaped resonator structure. The bowtie shaped filter exhibits similar performance as found in rectangular and circular shaped SIW based bandpass filters. This concept reduces the circuit foot print of SIW; along with miniaturization high quality factor is maintained by the structure. The design methodology for single-pole triangular resonator structure is presented. Two different inter-resonator couplings of the resonators are incorporated in the design of the two-pole bowtie shaped SIW bandpass filter, and switching between the two couplings using a packaged RF MEMS switch delivers the tunable filter. A tunning of 1 GHz is achieved for two frequency states of 6.3 and 7.3 GHz. The total size of the circuit is 70mm x 36mm x 0.787 mm (LxWxH).

Wireless power transfer (WPT) system has got significant attention in recent years due to its applications in consumer electronics, medical implants and electric vehicles etc. WPT is a promising choice in situations, where the physical connectors can be unreliable and susceptible to failure. The efficiency of WPT system decreasing rapidly with increasing air-gap. Many circuit topologies have been employed to enhance the efficiency of the WPT system. This paper presents the modelling and performance analysis of resonant wireless power transfer (RWPT) system using series-parallel-mixed topology. The power transfer efficiency analysis of the model is investigated via circuit theory. S-parameters have been used for measuring power transfer efficiency. Transient analysis is performed to realize the behavior of voltage and current waveforms using advanced design system (ADS) software. The proposed model is tested with two amplitudes i.e. 100 V peak-to-peak and 110 V peak-to-peak at the same frequency of 365.1 kHz. The overall result shows that the series-parallel-mixed topology model has higher efficiency at low coupling factor (K) for both voltage amplitudes.

An end-coupled line bandpass filter (BPF) is proposed and designed by placing defected ground structure (DGS) in the ground plane. DGS is used for its property of miniaturizing the size of microwave filter and also improving the mutual coupling between the resonators. The proposed dumbbell shaped DGS is used to tune the bandpass filter to 2.4 GHz with dimension of 44 mm × 18 mm. A wide tuning range of 0.64 GHz is achieved by tuning the height, length and width dimension of DGS unit cell. This filter gives an insertion loss of -0.42 dB, a return loss of -12.31 dB and -3 dB bandwidth of 0.92 GHz. The effect of DGS structure parameters on the frequency of bandpass filter is discussed here. The discussion is concerned over the change in R, L and C parameters of the bandpass filter when defected ground structure is etched in its ground plane. The results conclude that the DGS brings a change in effective inductance and capacitance of a transmission line.

A single element circular slot aperture coupled Cylindrical Dielectric Resonator Antenna (CDRA) with a parabolic reflector is simulated and presented. The measured bandwidth of the single element CDRA is about 1.8 % (5.32 - 5.52) while the simulated bandwidth is 1.11% (5.32 - 5.44 GHz). A comprehensive parametric study has been conducted to realize the effects of reflector parameters to increase the directivity of the designed antenna. The simulation of the antenna with parabolic reflector shows that it can enhance the gain about 240% as compared to the single element CDRA without reflector. The experimental results show that the antenna covers 5 GHz band, which satisfies the basic requirement of the WLAN application IEEE 802.11a.

In this paper, theoretical and experimental study on cylindrical dielectric resonator antenna (CDRA) made of CCTO material is reported. The CDRA with high dielectric constant (eΓ = 55) is fed with aperture coupled 50 ς microstrip transmission line. The TE011+S mode of CDRA is excited to operate at 5.15-5.35 GHz for wireless local area network (WLAN) application. The electrical model of the aperture coupled CDRA is built to verify the antenna feasibility. The validity of the electrical model is confirmed by comparing the values of the return losses obtained through an electrical model using Agilent Advanced Design System (ADS) against those obtained through antenna geometry using computer simulation technology (CST) and fabricated prototype.

With the fast development in the ubiquitous computing and wireless sensing technologies, a new era of smart cities is evolving. Future smart cities will gather sensory data, needed for effective management of the city, using wireless sensor networks. Exhaustive power sources such as batteries need periodic replacement and hence increase the cost of ownership of wireless sensor network. On the other hand, renewable vibration energy is found in abundance in many target environments of wireless sensor network, which can be harvested to power up the sensor node. The average power of a vibration energy harvester strongly depends on the frequency of vibration and quality factor of the harvester. Unfortunately, most of the environmental vibrations occur in a low frequency range of few tens of Hz. This paper analytically investigates the challenges in designing a low frequency energy harvester with a high quality factor.

Defected ground structures (DGS) have known to be serving for the improvement in characteristics of many microwave circuits. Not only DGS has various advantages in the area of microwave power amplifier, Wilkinson power divider, microwave antennas, couplers etc, it is also used in the design of microwave filter to achieve stopband effects, slow-wave effects, frequency adjustment etc. A bandpass filter based on Dumbbell-shaped DGS unit is presented here. This unit provides two transmission zeros near the passband edges. The center frequency has been tuned to 2.4 GHz using different dimensions of DGS. This filter gives an insertion loss of -0.42 dB, a return loss of -12.31 dB and -3 dB bandwidth of 0.92 GHz. The tuning of end-coupled line bandpass filter, using dumbbell DGS structure parameters is discussed here. The measurements show a close agreement with simulation results.

The concept of Substrate integrated waveguide (SIW) has emerged to be a good replacement of rectangular waveguides in low-cost and high-volume microwave and millimeter wave band applications. A number of bandpass filters have been developed since the advent of the SIW technology. However, its various forms have also been introduced in order to bring about further reduction in the footprint of these filters. This paper presents a review on the technological implementation of Substrate integrated waveguide bandpass filters and its variant miniaturization techniques developed so far. It also covers the SIW technology applied in tunable filters.

This paper presents some recent developments in microwave reflector antenna technology. The main focus of this research is on novel reflector antenna designs to overcome the challenges caused by the rising communication systems. Prototype implementation will be described in this paper; published microwave reflector antenna frequency range, low profile and compact designs, wideband reflector antennas, low sidelobe level, low cross polarization and enhanced gain microwave reflector antenna's review is brought up.

In this paper an experimental study on a directional cylindrical dielectric resonator antenna (CDRA) at 5.8 GHz is discussed and presented. Dielectric resonator (DR) ceramic-base material is investigated in the design and it is found that it improves the antenna performance. The dielectric constant of dielectric resonator palette is 55 and it is fed with a 50 Ω microstrip transmission line. The aperture coupling technique is highlighted in order to improve the performance of the CDRA in terms of their tuning frequencies, impedance bandwidth, radiation pattern and gain. The CDRA measured results are compared with the simulation, by using the 3D microwave simulator, Computer Simulation Technology (CST).

A compact dual band cylindrical dielectric resonator antenna (CDRA) is designed and presented. The CDRA is excited by E-shaped aperture, which is located below the microstrip line feed on the ground plane. The defected ground plane has a conducting strip under the Dielectric Resonator Antenna (DRA) that causes the upper resonance at 5 GHz. The lower band at 2.45 GHz is achieved by applying a metallic top-loaded cylindrical dielectric antenna (CDRA). The experimental results show the antenna covers 2.45 GHz and 5 GHz with −10dB return loss, satisfying the desired standards of WLAN applications.

Electricity supply to Universiti Teknologi PETRONAS (UTP) is provided by two generating units at gas district cooling (GDC) plant located in the campus. Under normal operation, UTP power system is operating in island mode and during emergency, it will be connected to utility grid of Tenaga Nasional Berhad (TNB). Each generating unit is grounded through neutral earthing resistor (NER). It has been observed that NER temperature become high when generator operating in parallel with the grid. Investigation reveals that triplen harmonics currents continuously flow through NER during island and parallel operation. Higher triplen harmonics currents are noticed during parallel operation as compared to island mode of operation. High NER temperature is caused by increase in triplen harmonics currents that flow through it. The above phenomena are described in this paper together with some proposed measures to overcome the problem.

A stepped impedance resonator bandpass filter (SIR BPF) is proposed and designed by placing defected ground structure (DGS) in the ground plane. DGS is used for its property of miniaturizing the size of microwave filter and also improving the mutual coupling between the resonators. The proposed dumbbell shaped DGS is used to tune the bandpass filter to 2.4 GHz with dimension of 28 mm × 30 mm. A wide tuning range of 0.64 GHz is achieved by tuning the height, length and width dimension of DGS unit cell. This filter gives an insertion loss of -0.23 dB, a return loss of -38.03 dB and -3 dB bandwidth of 0.56 GHz. The tuning of SIR bandpass filter, using DGS structure parameters is discussed here. Moreover, the effect of different parameters of DGS on center frequency is shown and discussed with results.