B.Y. Toh

Bio: B.Y. Toh is an academic researcher from Queen's University Belfast. The author has contributed to research in topics: Attendance & Computer science. The author has an hindex of 1, co-authored 1 publications receiving 384 citations.

Understanding and measuring circular polarization

Abstract: Many modern satellite and terrestrial point-to-point communications systems use circular polarization (CP) wave propagation in order to maximize the polarization efficiency component of the link budget. Therefore, in an undergraduate electromagnetics syllabus, an introduction to the topic of circular polarization is necessary to promote an understanding of the propagation aspects of modern communications system design. Students new to the antennas and propagation discipline often have difficulty in grasping the concept of CP; therefore, in this paper, the essential aspects of this topic are reinforced by a tutorial description of CP in terms of wave propagation, antenna properties, and measurement techniques. A simple laboratory-based project is described that requires the design, fabrication, and measurement of a crossed dipole antenna. The measured input impedance and radiation patterns are correlated with theory to highlight the conditions necessary to support CP wave propagation. By combining basic electromagnetic concepts with a series of simple intuitive laboratory experiments, the students can more easily visualize, and hence understand, CP wave propagation and its use in communications systems design.

Challenging the beliefs that synchronous online lecture attendance correlates to students’ overall grade

Abstract: CHALLENGING THE BELIEFS THAT SYNCHRONOUS ONLINE LECTURE ATTENDANCE CORRELATES TO STUDENTS’ OVERALL GRADE

Investigating the Effects of Synchronous versus Asynchronous Online Engagement on Performance of a Large Class

Abstract: This study examined the effects of online engagement in live lectures versus offline studies on students’ performance of an undergraduate Databases module with a large class size of over 400 students. We have discovered that attendance at synchronous (live) online-lectures has very little correlation to students’ performance. Our view is that the change to online learning has caused a considerable shift in study habits. In fact, a significant number of students who had hardly attended any live online-lectures still performed extremely well in the summative assessments, indicating that they were still engaging asynchronously.

Antennas and Propagation in UHF RFID Systems

Abstract: In this paper, we discuss antennas and propagation aspects in current passive UHF RFID systems. We consider a "reader-tag-reader" link and concentrate on each part of it: reader antennas, propagation channel, and tags. We include channel modeling equations and support our discussion with experimental measurements of tag performance in various conditions. We also provide a comprehensive literature review.

Single antenna full duplex communications using a common carrier

Abstract: Recently there has been much interest in systems capable of full duplex communications operating with a common RF carrier frequency in both the transmit and receive channels. All the reported systems require transceivers with multiple transmit and receive antennas in order to achieve sufficient isolation between the transmit and receive channels. The technique detailed in this paper is the first reported system to achieve full duplex communication using a common carrier operating with a single antenna resulting in high transmit to receive isolation and low insertion loss. The technique provides over 40 dB isolation between the transmitter and receiver channels and 0.75dB insertion loss for the transmitter-to-antenna and antenna-to-receiver paths.

Axial Ratio Bandwidth Enhancement of 60-GHz Substrate Integrated Waveguide-Fed Circularly Polarized LTCC Antenna Array

Abstract: A substrate integrated waveguide (SIW)-fed circularly polarized (CP) antenna array with a broad bandwidth of axial ratio (AR) is presented for 60-GHz wireless personal area networks (WPAN) applications. The widened AR bandwidth of an antenna element is achieved by positioning a slot-coupled rotated strip above a slot cut onto the broadwall of an SIW. A 4 × 4 antenna array is designed and fabricated using low temperature cofired ceramic (LTCC) technology. A metal-topped via fence is introduced around the strip to reduce the mutual coupling between the elements of the array. The measured results show that the AR bandwidth is more than 7 GHz. A stable boresight gain is greater than 12.5 dBic across the desired bandwidth of 57-64 GHz.

Single-Fed Microstrip Patch Antenna With Switchable Polarization

Abstract: A single-fed reconfigurable microstrip antenna that can provide various polarization diversities is presented in this paper. The antenna is excited by a microstrip feed line through aperture coupling. When two PIN diodes are used to respectively reconfigure the coupling slot and the open stub of the feed line, the polarization of the microstrip antenna can be switched between vertical and horizontal polarizations. For the reconfigurable antenna with the linear polarization diversity, it can be converted to a circularly-polarized antenna with switchable polarization sense by introducing a perturbation segment. Moreover, an antenna with the quadri-polarization diversity, including dual orthogonal linear polarizations and two circular polarizations, is also developed from the structure of the switchable circular polarization microstrip antenna, and only three diodes are required. Details of the antenna design are shown, and the measured results for the constructed prototype are also exhibited and discussed.

Bandwidth Enhancement of a Single-Feed Circularly Polarized Antenna Using a Metasurface: Metamaterial-based wideband CP rectangular microstrip antenna.

Abstract: Wireless systems manufacturers desire a low-profile, wideband, circularly polarized (CP) antenna. Generally, a single-feed CP microstrip antenna (CPMA) has a simple configuration but is hindered by a narrow, 3-dB axial ratio (AR) bandwidth. The bandwidth of a multiple-feed CPMA can be enhanced but requires a complicated and larger feeding network. Many techniques have been employed to improve AR bandwidth, such as using dual-feed, network-based structures [1], stacked patches [2]?[3], array antennas with sequential feeding network [4], and multilayered structures [5]. However, these CP antennas are based on multiradiating patches or complicated feeding structures.