Koo Voon Chet

A novel wideband antenna for dual band WLAN application

A novel dual band antenna for Wireless Local Area Network (WLAN) applications is presented. The dual band characteristic is achieved by feeding two different length resonant paths with a 50 Ω microstrip line. The compact antenna only occupies 5.3 × 16 mm2 and promotes wideband characteristic. The bandwidth for lower resonance spans from 2.03 GHz to 2.80 GHz (30.3%) and 4.86 GHz to 6.44 GHz (31.6%) at higher band, effectively fulfilling the bandwidth requirement of IEEE 802.11b/g and IEEE 802.11a. The return loss, gain and radiation patterns of the proposed dual band antenna are depicted in this paper. Gain of 6.15 dB and 2.12 dB is obtained at lower resonant frequency 2.44 GHz and higher resonant frequency 5.21 GHz, respectively.

Analysis of slotted waveguide structure using MoM techniques

A number of approaches has been suggested for analyzing the performance of slotted waveguide antenna. In this study, a well-known technique namely, the method of moment (MoM) is used to design slotted waveguide antenna arrays. Two types of slotted waveguide structure namely centerline slot with tuning screw and shunt slot are presented. Generally, the performance of the slotted arrays depends on the choice of physical dimension, slot displacement, number of slots and their overall arrangements. A comparison on their effects using numerical simulation is presented and discussed.

Design and development of a scatterometer system for environmental monitoring

A ground-based C-band Scatterometer System has been constructed at the Universiti Multimedia Telekom, Malaysia. The system is a full polarimetric FM-CW radar which has the capability to determine the complete backscattering matrix of a natural target. The system is to be used to conduct in situ backscatter measurement on Earth terrain such as vegetation fields, forest and soil surfaces. In this paper, a summarized report on the design and development of the system is presented.

Development of a semi-automated SAR test-bed

Observation of the Earth from aerial and spaceborne platforms using synthetic aperture radar (SAR) has provided scientists and researchers with a deeper knowledge of the physical surface information of the planet. With the aim of launching our own SAR sensor into orbit for the purpose of remote sensing, we have a program to test our systems in an airborne platform. Prior to that, we need to first test all related on-board subsystems of SAR sensor on the ground. A semi-automated rail enabled ground-based SAR imaging test-bed was developed and is able to function carrying our L-band SAR systems. Part of the challenge in this project is the scale, as related L-band SAR system is relatively larger than systems of higher bands. The target and scan area covered in the ground measurement is also large, leading to a rail design that need to be extendable yet still mobile. This paper explains our systems radio frequency (RF) subsystem, which generates, transmits and receives the electromagnetic waves and also the rail-based Positioner Subsystem. In addition, the paper also shows the SAR system design specifications, how they are applied into the RF subsystem, and its implementation with the moving platform of the Positioner Subsystem in a field test.

Kalman Filtering and Its Real‐Time Applications

Kalman filter was pioneered by Rudolf Emil Kalman in 1960, originally designed and developed to solve the navigation problem in Apollo Project. Since then, numerous applications were developed with the implementation of Kalman filter, such as applications in the fields of navigation and computer visions object tracking. Kalman filter consists of two separate processes, namely the prediction process and the measure‐ ment process, which work in a recursive manner. Both processes are modeled by groups of equations in the state space model to achieve optimal estimation outputs. Prior knowledge on the state space model is needed, and it differs between different systems. In this chapter, the authors outlined and explained the fundamental Kalman filtering model in real‐time discrete form and devised two real‐time applications that implement‐ ed Kalman filter. The first application involved using vision camera to perform real‐ time image processing for vehicle tracking, whereas the second application discussed the real‐time Global Positioning System (GPS)‐aided Strapdown Inertial Navigation Unit (SINU) system implementation using Kalman filter. Detail descriptions, model derivations, and results are outlined in both applications.

Development of circularly polarized Synthetic Aperture Radar onboard unmanned aerial vehicle

Synthetic Aperture Radar (SAR) is well-known as a multi-purpose sensor in all-weather and day-night time. In this research, we are developing Circularly Polarized Synthetic Aperture Radar (CP-SAR) onboard microsatellite to observe land deformation on Earth surface under Japanese Ministry of Education and Technology (MEXT) program etc. The CP-SAR employs elliptical wave propagation and scattering phenomenon by radiating and receiving the elliptically polarized wave, including the specific polarization as circular and linear polarizations. The sensor is designed as a low cost, light, low profile of configuration to transmit and receive left-handed circular polarization (LHCP) and right-handed circular polarization (RHCP). Then these circularly polarized waves are employed to investigate relationship of physical information of scatterer and axial ratio, ellipticity, tilt angle etc. This sensor is also considered to reduce the effect of ionospheres Faraday rotation. For ground experiment of CP-SAR, we also develop the CP-SAR onboard unmanned aerial vehicle (UAV CP-SAR) that is discussed in this paper.

Ku-band ground-based SAR experiments for surface deformation monitoring

Continuous monitoring of ground deformation on high-risk areas is of great importance for the study of landslide mechanisms as well as to serve as an early warning system before the triggers of hazardous events. A new ground-based synthetic aperture radar (GBSAR) has been developed and installed at selected landslide-prone areas in Malaysia. The proposed system operates at 17.2 GHz with high resolution change detection capability using interferometry technique. This paper presents the experimental results of the GBSAR in surface deformation monitoring.

A PC-based orientation sensing using 9-DOF strapdown inertial measurement unit

This paper presents the design and development of a PC-based orientation sensing system using strapdown inertial measurement unit (SIMU). A 9-DOF (degree of freedom) SIMU, which consists of 3-DOF gyroscopes, 3-DOF accelerometers, and 3-DOF magnetometers, are used to estimate the orientation. Data fusion is performed to improve measurement accuracy. In this paper, the orientation measurements are compared and discussed using three different approaches, known as the conventional accelerometer/gyroscope approach, the Kalman filter based 9-DOF SIMU approach, and the gradient decent algorithm based 9-DOF SIMU approach. The derivation of each approach together with the design of the PC-based orientation sensing system is outlined in this paper.

Interfacing of Biped KHR-1 with DSP Board TMS320F2812

This paper describes the interfacing of the biped robot KHR-1 with DSP board TMS320F2812. In this study, the KHR-1 is modeled as a seven-link biped, with each joint connected with a servomotor KRS-784 ICS. The I/O port of the DSP board provides PWM signals to the biped joints for joint control. TMS320F2812 is chosen due to its high PWM resolution as well as its flexibility in PWM frequency setting. The computed joint trajectories of the biped robot are based on the zero moment point (ZMP) model. Walking trajectories are constructed and tested, and the results are beneficial to both biped research as well as mechatronics education for undergraduates

Analysis of novel slotted waveguide structure for antenna arrays application

Summary form only given. A number of approaches have been suggested for analyzing the performance of slotted waveguide antennas. In this study, a well-known technique called the method of moments (MoM) is used to design slotted waveguide antenna arrays. Novel types of slotted waveguide structure namely centerline slot with tuning screw are presented. Generally, the performance of the slotted arrays depends on the choice of physical dimension, width, and displacement of the tuning screw, number of slots and their overall arrangements. The results from the numerical simulation are compared to the widely used finite element code (high frequency structure simulator) HFSS.