Search

Due to small size and lightweight properties, the development of microstrip (MS) patch antennas for wireless communication has become one of the mobile application devices in demand in recent years. This has helped to reduce reliance on wired cables. In this paper, a study has been performed on MS antenna by developing a quasi-Yagi structure on a fire retardant-4 (FR-4) substrate with a MS to coplanar strip line (CPS) transition feeding technique. The antenna is designed by using computer simulation technology (CST) to achieve the desired resonant frequency and bandwidth. The proposed dual band quasi-Yagi antenna has impedance bandwidths of approximately 0.3 GHz and 0.22 GHz resonating at 1.80 GHz and 2.60 GHz, respectively, which makes it suitable for long-term evolution (LTE) applications. Eight-director elements in four pairs are constructed to achieve directivity with magnitudes of 6 dB and 8.3 dBi at both resonant frequencies, 1.80 GHz and 2.60 GHz, respectively. Different parametric studies have also been performed to characterize the antenna radiation characteristics. The return loss, voltage standing wave ratio (VSWR), front to back (F/B) ratio and far-field radiation are analyzed and discussed.

In a fiber optic communication system, optical fiber is used as a transmission medium consisting of a flexible filament that guides the optical signal to be transmitted from the transmitter to the receiver or vice versa. Like any other communication medium, the optical fiber cable faces some losses that can be caused by the material and length of the fiber. One of the main reasons for losses in optical communication systems is misalignment during the fiber to fiber joining process. This type of loss is also known as coupling loss, which is caused by an imperfect physical connection between two fibers. The coupling losses are most often caused by three misalignment issues: end gap displacement, lateral displacement, and angular displacement. The main goal of this article is to investigate coupling loss caused by misalignment in optical fiber using the Modicom 6 module. Before we can find a way to reduce the coupling losses in the fiber optic system, we need to have a concrete idea about the nature of coupling losses due to misalignment. An ideal fiber coupler should not lose light and should be insensitive to light dispersion.

This research purposed the design of rectenna that it can convert the electromagnetic field source into the DC voltage output. The research is conducted in two steps, simulation and fabrication of antennas, and rectifier circuits. This research applies CST Studio Suite software to simulate the antenna and NI Multisim 14.0 to simulate the rectifier. The antenna has been designed and fabricated by utilizing the array antenna of the circular patch microstrip with adding of the insertion feeder with 7 mm of length and 1 mm of width to reach of the matching antenna. The rectifier has been created by using BAT 85 DO-35 Schottky diode where it can work at high frequency. The measurement result of the antenna is minimum with the return loss amount of 33.783686 dB, bandwidth is 100 MHz, and VSWR (Voltage Standing Wave Ratio) is 1.021669. The rectenna can receive a maximum voltage of 11 mV at a range of 1cm.

This research proposed microstrip circular patch antenna simulation at a working frequency 3500 MHz. The antenna has been designed using a Duroid RT5880 substrate with dielectric constant (εr) = 2.2, substrate thickness (h) = 1.575 mm, and tangent loss = 0.0009 with microstrip line feeding. The simulation result, return loss value obtained -26.385, VSWR value 1.09, gain value 7.64 dBi, total radiation efficiency value -0.6489 dB, and bandwidth value 72 MHz (3468.8 MHz – 3541.9 MHz).

Energy harvesting is a rapidly growing area in many scientific and engineering-related fields due to the demand for many applications. This paper focuses on the design and simulation of the voltage doubler rectifier circuit at 2.45 GHz operating frequency. The design of a rectifier is optimized based on the use of Schottky diode HSMS 286 B due to its low forward voltage at this frequency. 2 stages of the Schottky diode voltage doublers circuit are designed and simulated in this paper. The shunt capacitor and optimal load resistance are also introduced in the course to reduce signal loss. A multi-stage rectifier is used to produce maximum power conversion from AC to DC. The simulated results present that the maximum output voltage of 6.651 V with an input power of 25 dBm is produced, which presents a maximum power conversion efficiency of 73.13%, which applicable in small device applications.

Numerous works that have demonstrated the study and enhancement of switching properties of ZnO-based RRAM devices are discussed. Several native point defects that have a direct or indirect effect on ZnO are discussed. The use of doping elements, multi-layered structures, suitable bottom and top electrodes, controlling the deposition materials, and the impact of hybrid structure for enhancing the switching dynamics are discussed. The potentials of ZnO-based RRAM for invisible and bendable devices are also covered. ZnO-based RRAM has the potential for possible application in bio-inspired cognitive computational systems. Thus, the synapse capability of ZnO is presented. The sneak-path current issue also besets ZnO-based RRAM crossbar array architecture. Hence, various attempts to subdue the bottleneck have been shown and discussed in this article. Interestingly, ZnO provides not only helpful memory features. However, it demonstrates the ability to be used in nonvolatile multifunctional memory devices. Also, this review covers various issues like the effect of electrodes, interfacial layers, proper switching layers, appropriate fabrication techniques, and proper annealing settings. These may offer a valuable understanding of the study and development of ZnO-based RRAM and should be an avenue for overcoming RRAM challenges.

Resistive random access memory (RRAM) has two distinct processes, the SET and RESET processes, that control the formation and dissolution of conductive filament, respectively. The laws of thermodynamics state that these processes correspond to the lowest possible level of free energy. In an RRAM device, a high operating voltage causes device degradation, such as bends, cracks, or bubble-like patterns. In this work, we developed a statistical simulation of the switching mechanism in a ZnO-based RRAM. The model used field-driven ion migration and temperature effects to design a ZnO-based RRAM dynamic SET and RESET resistance transition process. We observed that heat transport within the conducting filament generated a great deal of heat energy due to the carrier transport of the constituent dielectric material. The model was implemented using the built-in COMSOL Multiphysics software to address heat transfer, electrostatic, and yield RRAM energy. The heat energy increased with the increase in the operating power. Hence, the reliability of a device with high power consumption cannot be assured. We obtained various carrier heat analyses in 2D images and concluded that developing RRAM devices with low operating currents through material and structure optimization is crucial.

Crowd behavior analysis has become one of the new areas of interest in the computer vision community due to the increasing demands from surveillance and security industries. It is important to meticulously understand crowd behavior to prevent any disaster and unwanted incidents such as thief, stampede and riots. For this purpose, crowd features such as density, motion and trajectory are analyzed to detect any abnormality in the crowd. Thus, this review is aimed to provide insight on several detection methods including Gaussian Mixture Model (GMM), Hidden Markov Model (HMM), Optical Flow method and Spatio-Temporal Technique (STT). Providing the latest development, the review presented the studies that are published in journals and conferences over the past 5 years.

Stress is a complex response that begins when people are exposed to various stressors, including psychological and environmental factors, which are associated with negative cognitive effects. However, little is known about their interactions within the brain. This research aimed to examine the influence of low and high noise levels in the workplace on changes in brain activity in the prefrontal cortex (PFC) during stressful psychological tasks by measuring synchronized functional near-infrared spectroscopy (fNIRS) and electroencephalogram (EEG). The results showed a decreased oxygenated haemoglobin (HbO) concentrations in the right dorsolateral PFC and part of the frontopolar area when exposed to higher noise levels compared to lower levels. Results also showed a higher correlation between fNIRS-HbO and EEG-alpha power under stress conditions compared to other EEG bands. We suggest that higher levels of noise in the workplace may be directly related to increased psychological stress.

Enhanced oil recovery (EOR) is the recovery of oil trapped in the reservoir after primary and secondary recovery processes through novel techniques. Viscosity is primarily a major cause of the high proportion of hydrocarbon fluid entrapped. Recently, emergence of nanotechnology has gained attention in oil industry. The major factor hindering the efficiency of nanoparticles is poor transport inside the reservoir due to high adsorption energy to grains surfaces, leading to their retention. Some studies have reported the effectiveness of nanoparticles on oil viscosity. However, report on the use of pristine graphene has been missing along with requisite transportation behaviour on sandstone surface. This work investigates the applicability of graphene in EOR. The effects of graphene concentrations (0.01, 0.05 & 0.1 wt%) on flowability of oil (50 cP and 0.85 cP), and its adsorption energy are reported. Experimentally, viscosity of the more viscous crude oil was reduced by 43–65%. Using molecular simulation, diffusion coefficient estimation indicate improvement in diffusivity of light decane by 112%. Furthermore, the adsorption energy of graphene is surprisingly found to be low (−9.11 kcal/mol). This study concluded that graphene is applicable, the oil sample is Newtonian and viscosity well reduced.

The residual stress is often due to a thermal mismatch in the thermal expansion coefficient (CTE) between the two materials. This phenomenon causes device failure such as curling, buckling, and also fracture upon releasing. Hence, strategies are needed to minimize the effect of residual stress on the induced beam bending upon release of the device. In this paper, four different geometrical structures are studied theoretically and simulated. The stress level is deduced by measuring the deflection of the beam. The result has shown that the beam with Al and SiO 2 strip arranged alternately as the top layer and SiO 2 as the bottom layer have the least downward deflection upon applied temperature. For T = 50 K, deflection of 0.8425 µm is measured. Simulation-based of varying thickness also show that having thicker SiO 2 (with a similar total thickness of the beam) contribute to smaller downward deflection and least percentage error between theoretical and simulation result. Surface stress analysis also shows that the stress measured is 107.86 MPa, which is lower than the yield strength of Al and SiO 2 materials.

Bypassing red light is a traffic offense contributing in many accidents in Malaysia. Having a monitoring system to capture such an incidence helps to provide evidence to convict the traffic offenders; hence, potentially reducing the number of accidents. This paper proposes a framework design of traffic light offense monitoring to improve traffic light signals adherence for drivers in Malaysia. The input, the process and the output of the monitoring are investigated to develop accurate framework design for better accuracy. Additional work is presented on hardware selection and software usage cost effectiveness. The challenges to design the framework are also identified. Contributions of this study to IR4.0 is briefly discussed.

Interdigitated Electrodes (IDEs) based sensor in comb-like electrodes structure is also an attractive candidate in gas sensor and biosensor applications, owing to its simple structural design. The sensitivity can be improved based on geometric parameters of the sensor. Hence, in this paper, we study the physical model of the IDEs-based sensor and concern with its geometrical parameters (gap sizes, number of fingers and width of fingers) based on the finite element simulations using COMSOL Multiphysics. The simulation results were used to show the electrical field that generated by the IDEs and compare to other to find the optimum design. Based on the results, the relationship between the geometric parameters and the IDEs performances are studied. The simulation results show that the higher electric fields are generated with the smaller gap size and smaller width of fingers. Besides that, the results show that the gap size and the width of fingers affect the IDEs performance significantly compared to the number of fingers. The IDE with the design 18 fingers, 0.1 mm gap size between fingers and 0.1 mm width of the finger is the optimum design which generates 30.6 kV/m average of electric field magnitude.

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.

Short-term load forecast plays an important role in planning and operation of power systems. The accuracy of the forecast value is necessary for economically efficient operation and effective control of the plant. This study describes the methods of Autoregressive (AR) Burg’s and Modified Covariance (MCOV) in solving the short term load forecast. Both algorithms are tested with power load data from Malaysian grid and New South Wales, Australia. The forecast accuracy is assessed in terms of their errors. For the comparison the algorithms are tested and benchmark with the previous successful proposed methods.

In recent years, active Radio Frequency Identiflcation (RFID) tags have crossed into ultra low power domain. With obvious advantages over passive tags, a setback for active tag growth is the need for battery replacement and limited operational life. Battery life could be extended by scavenging surrounding Wi-Fi signals using rectenna architecture which consists of a receiving antenna attached to a rectifying circuit. A seven stage Cockroft-Walton voltage multiplier optimized for low input power (below 0dBm) is proposed. Prototype was fabricated on RT/Duroid 5880 (RO5880) printed circuit board (PCB) substrate with dielectric constant and loss tangent of 2.2 and 0.0009 respectively. Experimental results show that 2V output voltage can be harvested from an operating frequency of 2.48GHz with i9dBm (0.13mW) sensitivity with 1.57mm board thickness.

In this paper, a design of wideband antenna by tuning the aperture slot parameters and using two dielectric pellets is investigated and discussed. The performance of the resonant frequencies, impedance bandwidth and radiation pattern of the DGS-CDRA (Defected Ground Structure Cylindrical Dielectric Resonator Antenna) are analyzed. The design achieved a wideband impedance bandwidth of 4.0 GHz (50.74 %) by using two slots aperture and thick substrate. Two dielectric pellets with the same type and size are coupled to a microstrip line through two rectangular slots. The slots positions are tuned along (below) microstrip line to a position where impedance bandwidth from both dielectric pellets are merged and form a wide impedance bandwidth. Subsequently, performance of the antenna is being analyzed based on the simulation results of return loss and radiation pattern. The design is fabricated and the measurement results of impedance bandwidth are compared with the simulation results.

A single element rectangular aperture coupled cylindrical dielectric resonator antenna (CDRA) with a plane reflector is proposed. A plane reflector is integrated at the back of the proposed CDRA to provide unidirectional radiation pattern with the improvement in gain and sidelobe level. The gain of the DRA is improved by reducing the back radiation caused by the aperture coupling. The peak gain of the antenna has been enhanced about 4.3 dB from 4.7 to 9.0 dBi at 5.18 GHz. The measured impedance bandwidth achieved for the proposed DRA is 0.2 GHz for S11 < −10 dB from 5.17 to 5.37 GHz. The radiation pattern with broadside radiation and low back radiation has been obtained. The experimental and measured results show that the antenna is high gain, small in size and satisfies the basic requirements of WLAN 802.11a.

In the presence of guard band sub-carriers, the existing correlation-based time-domain channel estimation schemes do not perform well and suffer from high computational complexity. Herein, we proposed an optimized time domain channel estimation scheme with high accuracy and low complexity. In proposed correlation error cancellation (CEC) solution, the larger part of actual channel estimation solution is estimated from no-guard band (without null sub-carriers) solution, which can be easily obtained by choosing appropriate pilot design. In order to estimate the complete actual solution, the correction term can be obtained from the difference in the actual transmitted pilot and the pilot used for no-guard-band solution. The theoretical analysis and simulation results show that the proposed CEC solution reduces the complexity up to 0(L2) in one-step of iteration and achieves accuracy close to Cramer Rao Bound (CRB).

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.

In this paper, four elements fractal shape antenna with non-uniform annular ring Photonic Band Gap (PBG) etched in the ground is presented. The impact of the PBG structure in removing the undesired harmonic frequencies of the proposed antenna is demonstrated. The proposed antenna is designed, fabricated and tested. The results show that the designed antenna is capable of resonating at three different frequencies of 915 MHz, 1.8 GHz and 2.45 GHz with high-efficiency performance in terms of return loss, gain and radiation pattern characteristics with compact size. Good agreement between the measured and the simulated results is observed.

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).

Many researchers continue to look for novel means to harvest energy and generate power using existing sources thus eradicating the need of batteries and power supplies which only add up to the cost of the system. A rectifier is the main component in energy harvesting circuits as it converts RF energy from available sources to DC power. This article aimed at developing a novel rectifying circuit to be used in harvesting applications at a frequency of 900 MHz. Besides, it is also aimed to enhance the output voltage of Cockcroft Walton rectifier circuit and Dickson rectifier. The design is built by integrating the Cockcroft Walton rectifier, arranged in series, with the Dickson rectifier, arranged in parallel. A Schottky diode HSMS 285C is selected for designing the rectifiers circuit. A simulation of the circuit was optimized utilizing ADS 2009. The rectifiers had been fabricated on an RT/Duroid 5880 (RO5880) printed circuit board (PCB) substrate with a dielectric constant and loss tangent of 2.2 and 0.0009, respectively. Simulation and experimental results show great output thresholds for the three models. The novel rectifier had the highest efficiency and output voltage.

In this contribution, a simple but highly sensitive biosensor based on microstrip ring-resonator is presented for tissues moisture evaluation. By incorporating high impedance ring, tight and enhanced coupling mechanism the proposed 1 GHz ring-resonator demonstrates significant change in the resonance frequency than normal resonator. Simulated and measured results are in good agreement. The proposed resonator gives 37% better performance than the conventional resonator.

With vast benefits across various market segments, active RFID tags have shown great potential in the healthcare sector. Battery replacement remains a deterrent towards mass implementation of active RFID tag technology. Within this context, rectenna architecture has been investigated as the RF power transfer mechanism for ultra low power on-body communication. A working prototype consisting of 7-stage Cockroft-Walton voltage multiplier integrated with band pass filter and lowpass filter has successfully been developed on 1.57 mm RT/Duroid 5880 laminate with the goal of prolonging battery lifespan. A qualitative assessment is proposed as means of evaluating rectenna performance with various antenna designs connected to optimized rectifier. Under non-controlled environment, powering an LED from a Wireless Access Point transmitter source can be used to gauge robustness of rectenna system. Antenna with 5 dBi gain was capable of powering LED at 10 cm distance from RF source.

A planar bandpass filter based on a technique that utilizes substrate integrated waveguide (SIW) 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 for single-pole resonator structure is presented; and by coupling the resonators a two-pole bowtie shaped SIW bandpass filter is achieved for the frequency of 7 GHz. The simulation result reveals that the filter’s insertion loss is better than 1 dB and return loss is less than 30 dB.

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.

Channel impairments degrade the performance of accurate data signal detection and decoding. The said problem becomes further severe in low SNR environment. As a result it reduces the performance of channel estimation. To alleviate this problem we develop a pilot based Pre FFT (time domain) channel estimation technique in the presence of Rayleigh fading channel. A novel time domain channel estimation technique is proposed that accurately measure the channel impulse response by using cross correlation between received signal and pilot carriers, especially at low SNR. In addition, the proposed technique enhances robustness in Orthogonal Frequency Division Multiplexing (OFDM) channel estimation by reducing Mean Square Error (MSE). Simulation results show that proposed method provides better accuracy in term of MSE over conventional techniques (LS and MMSE) that estimate the channel impulse response in frequency domain.

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, electrical models of single element cylindrical dielectric resonator antenna (CDRA) and two element CDRA array made of Calcium Copper Titanium Oxide (CCTO) material are presented. The 50 Δ microstrip transmission line is used to excite the CDRAs through coupling slots etched on the ground plane. The electric models of single element CDRA and two element CDRA array are designed by using Advanced Design System (ADS). The electrical circuits are used to validate the CST design feasibility. The validity of RLC model is verified by comparing the return loss of the ADS model against those obtained through computer simulation technology (CST) and fabricated prototype. The results obtained through simulated (CST and ADS) designs and fabricated prototype of single element CDRA (0.20 GHz and 0.23 GHz) and two elements CDRA array (0.375 GHz and 0.510 GHz) are in good agreement.

A planar bandpass filter based on a technique that utilizes quarter mode of substrate integrated waveguide (SIW) is presented. This concept reduces the circuit foot print of SIW to a quarter of its size, along with miniaturization good performance and high quality factor is maintained by the structure. The design concept for single-pole resonator structure is presented; and by coupling the resonators a two-pole substrate integrated waveguide bandpass filter is achieved for the frequency of 5.9 GHz. The results show that the filter insertion losses are better than 2 dB and return losses are less than 20 dB. The measured frequency response is in good agreement with the simulated response in the region of interest.

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.

Preserving inter-actor connectivity is essential in most wireless sensor and actor network (WSAN) applications as nodes have to collaborate and coordinate their actions against the events reported by the sensors. However, failure of a critical (i.e., cut-vertex) node partitions inter-actor network into disjoint segments and thus hinder network operation. The prime objective of this paper is to analyze the performance of reactive connectivity restoration algorithms for delay-tolerant WSAN applications. First, we provide insights to the state-of-the-art reactive connectivity restoration algorithms. Then, we present a Nearest Non-critical Neighbor (NNN) algorithm; a localized and distributed reactive approach for reconnecting network partitions. In NNN, each actor periodically determine its criticality (i.e., cut-vertex or not) based on 2-hop information and exchange with its neighbors. In case of a critical actor failure, the neighbors detect and trigger a connectivity restoration procedure that involves controlled and coordinated node relocation. NNN prefer to displace non-critical nodes during relocation in order to minimize recovery overhead in terms of distance movement and message coordination. We analyze the performance of reactive schemes through theoretical analysis and simulations.

In this paper channel estimation techniques for Digital Video Broadcasting Terrestrial (DVB-T) based OFDM transmission and reception are investigated. Channel estimation based on comb type pilot arrangement is studied through Discrete Fourier Transform (DFT) algorithm. The estimation of channel at pilot frequencies is based on Least Squares (LS) and Minimum Mean Square Error (MMSE) estimators while interpolation is done using linear and spline cubic interpolation. Existing channel estimation usually addresses the scattered and continual pilot arrangement for DVB-T based OFDM systems. Pilot based channel estimator presented here differs from previous methods in a way that it is based on comb type pilot arrangement, which accurately estimates the MSE in the presence of COST 207 Typical Urban Reception (TU6) channel model. This paper shows that DFT-based algorithm can improved the MSE of conventional LS and MMSE estimators by removing the impact of noise outside the maximum channel delay length.

A single element circular slot aperture coupled Cylindrical Dielectric Resonator Antenna (CDRA) with a box shaped reflector is designed and presented. The simulated bandwidth achieved for the designed antenna is about 1.11% (5.32 GHz-5.44 GHz) while the measured bandwidth is about 1.8% (5.32 GHz-5.52 GHz). This method enhances the directivity of the CDRA upto 53% i.e from 5 dBi to 7.5 dBi. The analysis of the effects of changing the slot size, slot position and different parameters of the reflector to increase the directivity and to reduce the backlobe level has been carried out. The experimental results illustrate that the designed antenna works over 5 GHz band, therefore it can be used in WLAN application IEEE 802.11a.

A 1 × 3 element linear array of cylindrical dielectric resonator antenna (CDRA) is designed and presented for 802.11a WLAN system applications. The two elements of CDRA array are excited by rectangular shaped aperture slots placed on the ground plane, while the slots themselves are excited through the microstrip line. The third element (i.e., central CDRA) is excited through the mutual coupling of two radiating elements by its sides; this mechanism enhances the bandwidth of the array by 10%. Designed antenna array is fabricated and tested. Using the CST microwave studio and fabricated prototype, directivity of 10.5 and 10.8 dBi respectively has been achieved for operating frequency of 5.6 GHz. Good agreement is achieved between the simulated and measured results. The comparison between the proposed and previous work is also reported in this article.

In this paper, the experimental study on cylindrical dielectric resonator antenna (CDRA) with an aperture coupled dielectric image line (DIL) is presented using a CCTO material. The CDRA is fed by a 50Ω dielectric image line at a frequency around 2.45 GHz. High permittivity (er = 55) DIL samples with different heights are employed. The CST microwave studio is used to analyze the different results in term of return loss, bandwidth and radiation pattern. The DIL feeding technique has shown a better directivity for CDRA as compared to microstrip line coupling.

A single element circular slot aperture coupled Cylindrical Dielectric Resonator Antenna (CDRA) with a flat reflector is designed and presented. The measured bandwidth of the antenna 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 slot size, slot position and reflector parameters to increase the directivity of the designed antenna. The experimental results show that the antenna covers 5 GHz band, which satisfies the basic requirement of the WLAN application IEEE 802.11a.

Whilst a normal inverter converts the DC voltage into AC voltage, an off grid inverter occupies input from either solar panel or wind turbine. This paper is about the design and simulation of a bi-input inverter using PV and Wind power system. The overall design will result in a regulated AC output load for AC grid connected system. This paper also discusses on two circuits which is charge controller and inverter. It is found that regulated output AC voltage level of 110 V and current 13 A have been successfully simulated using MULTISIM Power Pro Edition 12.0 which is applicable for national 50-Hz transmission grid line.

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.

In this paper, the tuning technique of 3-elements cylindrical dielectric resonator antenna (CDRA) array for wireless LAN 802.11 a/b/g standard applications is studied experimentally. The rectangular shaped aperture slots are used to excite the first and last radiating element. The aperture slots etched on the ground plane are excited by using the 50Ω microstrip transmission line. The electromagnetic coupling technique is used to excite the middle radiating element to enhance the antenna bandwidth as well as gain. The effects of changing the dimensions of slot width on the resonance frequency are also analyzed using a CST microwave studio. The simulated and measured results have successfully given the resonance at 2.45 and 5.0 GHz. The 2-D and 3-D radiation patterns of the proposed dual band antenna are addressed in this paper.

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.

Wideband and high gain linear 3-element cylindrical dielectric resonator (CDR) array antenna is designed and proposed for 802.11a wireless local area network (WLAN) system applications. The mutual coupling mechanism is used to excite the middle element of the CDRA array which enhances the 10% bandwidth and reduces the back lobe level of the proposed antenna without using reflector. The other two neighboring elements are excited by rectangular shaped aperture slots placed on the ground plane, while the slots themselves are excited through the microstrip line. The designed array antenna performance is analyzed using a CST microwave studio. The maximum directivity of 9.6 dBi has been achieved at operating frequency of 5.5 GHz. 2-D and 3-D radiation pattern results are also reported in this paper. Designed antenna array is fabricated and tested. The comparison between the proposed and previous work is also tabulated in this paper.