Zahriladha Zakaria

Design of reconfigurable defected ground structure (DGS) for UWB application

This paper presents the design of reconfigurable defected ground structure (DGS) resonator that can be integrated with ultrawide-band (UWB) microwave filter to produce bandpass and bandstop response simultaneously. The reconfigurable DGS is designed based upon coplanar waveguide (CPW) technology to exhibit bandstop characteristic at 3.5 GHz and 5.5 GHz using FR-4 on a 1.6 mm dielectric substrate thick with dielectric constant εr = 4.6. The simulation performance shows promising results that could be further validated during the experimental works. This topology of reconfigurable DGS is useful for applications when the undesired signals need to be removed such as in wideband systems.

Investigation of dual and triple meander slot to microstrip patch antenna

A dual and triple microstrip meander slot antenna is presented for Wireless Local Area Network (WLAN) application. The antenna also has the potential to be used as the receiving antenna in an energy harvesting system. The proposed antenna comprises a rectangular microstrip patch element embedded with meander slots. The parametric study is performed to investigate the characteristic of microstrip patch antenna with double meandered slots compared to the same microstrip patch antenna with triple meandered slots. Microstrip patch antenna with dual meander slot can achieve return loss until -24.54dB. However the gain of the antenna, 1.46 dBi is lower than microstrip patch antenna with triple meander slot which is 4.28 dBi. Other antenna parameters are also investigated such as bandwidth, radiation patterns and directivity have been observed and simulated. Measurement results are also recorded in this paper.

Dual-band monopole antenna for energy harvesting system

A planar dual-band monopole antenna is presented for Global System for Mobile Communications (GSM) band applications, which also have the potential to be used for energy harvesting system. The proposed antenna comprises of a ground plane at the back of the FR4 substrate and three microstrip lines which are physically connected with each other at the top surface of the substrate. The monopole antenna achieves good return loss at resonance frequencies of 915 MHz and 1800 MHz with a bandwidth value of 124.2 MHz and 196.9 MHz respectively. The antenna gains of 1.97 dB and 3.05 dB are achieved at resonance frequencies of 900 MHz and 1800 MHz. Experimental results show good agreement with simulated performance. The output from the receiving antenna is also observed in order to analyze the relationship of the power level and the distance between transmitting and receiving antenna. This study is an early investigation in designing the RF energy harvesting system to support green technology and sustainable development particularly for Wireless Sensor Network (WSN) applications.

Rectangular microstrip patch antenna based on resonant circuit approach

This paper presents the investigation based upon the resonant circuit approach to characterize the rectangular microstrip patch antenna from the low-pass prototype lumped element. The physical layout of the rectangular microstrip patch antenna based on single-mode and dual-mode will be established. An improvement on bandwidth of the antenna can be achieved by increasing the number of modes. In the paper, the understanding of microwave filter synthesis technique is applied in order to obtain the resonance at 2 GHz. A notch technique is used in the design to produce dual-mode frequencies on the microstrip patch antenna. The prototype circuit and proposed physical layout of the single and dual-mode microstrip patch antennas are demonstrated through the analysis of circuit and EM simulations in order to proof the proposed concept. This study would be useful to realize antenna for broadband applications as well as to investigate the appropriate technique for integrating antenna and microwave filter.

Isolation improvement of SPDT discrete switch with single switchable open stub resonator at 2 GHz band

Generally, if using single low performance discrete PIN diode, it is difficult to get high isolation of Single Pole Double Throw (SPDT) switch at 2 GHz band. The PIN diodes are usually packaged in a standard package such as SOT23, SOT323, SOD323 or SOD523. Therefore, this paper proposed single switchable open stub resonator for isolation improvement of shunt SPDT discrete PIN diode switch for Time Division Duplex switching of wireless communication system at 2 GHz band. The discussion of the conceptual and operation of the resonator are included in this paper. The circuit has been simulated for further analysis in simulation software where parameters of microstrip line and FR4 substrate have been taken into account. Result in simulation has shown high isolation between 25 to 28 dB at frequency of 2 to 3 GHz compared to conventional shunt SPDT switch and has been verified with measurement.

Design of SIW bandpass filter with 6 dB offset

This paper presents a novel design of SIW bandpass filter based on even- and odd-mode predistortion technique. This technique allows for the realization of lossy filter responses equivalent to lossless filter responses, although at an increased insertion and return loss. Hence, the filter can be designed with low Qu resonators, which will significantly contribute to the reduction of its physical size and weight. An experimental third-degree filter with Chebyshev characteristic demonstrated good measured results, which were in-line with the simulated results.

Robust Nonlinear H∞ State Feedback Control of Polynomial Discrete-Time Systems: An Integrator Approach

This paper investigates the problem of designing a nonlinear H∞ state feedback controller for polynomial discrete-time systems with norm-bounded uncertainties. In general, the problem of designing a controller for polynomial discrete-time systems is difficult, because it is a nonconvex problem. More precisely, in general, its Lyapunov function and control input are not jointly convex. Hence, it cannot be solved by semidefinite programming. In this paper, a novel approach is proposed, where an integrator is incorporated into the controller structure. In doing so, a convex formulation of the controller design problem can be rendered in a less conservative way than the available approaches. Furthermore, we establish the interconnection between robust H∞ control of polynomial discrete-time systems with norm-bounded uncertainties and H∞ control of scaled polynomial discrete-time systems. This establishment allows us to convert the robust H∞ control problems to H∞ control problems. Then, based on the sum of squares (SOS) approach, sufficient conditions for the existence of a nonlinear H∞ state feedback controller are given in terms of solvability of polynomial matrix inequalities (PMIs), which can be solved by the recently developed SOS solvers. A tunnel diode circuit is used to demonstrate the validity of this integrator approach.

Microwave filter and antenna for wireless communication systems

This paper presents the investigation and characterization of integrated microwave filter and antenna to reduce the overall physical volume for RF/ microwave front-end subsystems. This study focuses on the integrating of rectangular Substrate Integrated Waveguide (SIW) filter with rectangular microstrip patch antenna to produce filtering and radiating element in a single device. To proof the concept, the integrated microwave filter and antenna at center frequency of 2 GHz is demonstrated and validated through simulation and analysis. This class of microwave filters and antenna integration would be useful in microwave systems where the reduction of size and weight as well as cost is very important such as in base stations and multiplexer in any communication systems.

Simulation of virtual MIMO base stations for mobile location in IMT-Advanced networks

The conventional Location and Positioning (L&P) methods rely on availability of base station (BS) locations as well as mitigation of propagation effects. It is known that the location estimation accuracy suffers from poor geometric dilution of precision (GDOP) caused by BS location as the conventional location algorithms which result in large GDOP values correspond to poor geometrical topology. In addition, NLOS effects cause a large error in time of arrival (TOA) reading; thus affecting mobile station (MS) estimation accuracy. In this paper a novel concept of virtual BS (VirBS) utilizing multiple input multiple output (MIMO) technology has been introduced and applied for improving L&P accuracy. The performance of the proposed algorithm has been evaluated via computer simulations. The simulation results demonstrate that the proposed algorithm allows up to 30 percent improvement in L&P accuracy without additional expenditure on network architecture.

Transformation of generalized chebyshev lowpass filter prototype to Suspended Stripline Structure highpass filter for wideband communication systems

This paper presents the transformation of generalized Chebyshev lowpass filter prototype to highpass filter using Suspended Stripline Structure (SSS) technology. The study involves circuit analysis to determine generalized Chebyshev responses with a transmission zero at finite frequency. The transformation of the highpass filter from the lowpass filter prototype provides a cutoff frequency of 3.1 GHz with a return loss better than -20 dB. The design is simulated on a Roger Duroid RO4350 with a dielectric constant, εr of 3.48 and a thickness of 0.168 mm. The simulation performance results show promising results that could be further examined during the experimental works. This class of generalized Chebyshev highpass filter with finite transmission zero would be useful in any RF/ microwave communication systems particularly in wideband applications where the reduction of overall physical volume and weight as well as cost very important, while maintaining its excellent performance.