Lecture videos to supplement electromagnetic classes at Cal Poly San Luis Obispo

Electromagnetics and Transmission Lines is a fundamental, yet difficult subject in the Electrical Engineering (EE) field. To help improve information retention, a series of lecture videos was created to supplement traditional lectures, to facilitate in-class discussions, and to improve students’ proficiency and interest in electromagnetics. Engineering electromagnetics classes at California Polytechnic State University, San Luis Obispo cover fundamentals to understand and analyze cell phone communications, radar systems (air traffic control, law enforcement), and biomedical imaging (MRI). However, this subject also requires considerable mathematics preparation in vector calculus, differential equations, linear algebra, and background in both physics and EE. Lecture videos were created on the Camtasia software to produce MP4 audio-visual files. All videos include a topic outline, stationary and animated visual displays of lecture topic applications, and a detailed discussion using outlines and handwritten notes. Example calculations and real-world applications, Smith Chart graphical analysis, and Matlab computations and visual animations (standing and traveling waves, dynamic vector field and scalar contour diagrams) augment theoretical discussions and help visualize course concepts. Real-world applications including the Large Hadron Collider (CERN), RF test equipment (network analyzers), cell phone tower antennas, and radar imaging systems are introduced in the videos and related to course topics. A total of 36 videos were recorded for EE 335 (junior-level electromagnetics); average video length is 20 to 25 minutes for each 50 minute lecture. All lecture videos were stored online (dropbox.com) and made available one week prior to each class session. A student survey was conducted to assess perceived video effectiveness, to compare to traditional lectures, and to estimate video usage (how often watched, how many hours per week). Questions also include overall suggestions for video improvement, favorite (and not so favorite) parts of the class, and overall impressions. Most students appeared to value the new videos: 55% agreed with the statement “the lecture videos helped me learn course concepts.” Video length (20 – 25 minute average) was between too long (43%) and just right (29%). The most common negative comment mentioned the additional time required to view the videos over a traditional lecture class. Future efforts toward a flipped (inverted) classroom format include the development of topic videos and post-video quizzes to encourage pre-lecture viewing, as suggested in [1]. Video production improvements including minimized length and enhanced information organization will be applied to future lecture videos. Practical lab projects [2] will also be explored and added as another method of enhancing student interest in electromagnetics. Finally, information retention between traditional and flipped classroom formats will be compared to determine the relative effectiveness of both approaches

Absorber Foam Characterization for Predicting Overall Anechoic Chamber Performance

A new rectangular anechoic chamber (20’L x 10’W x 9’7”H) has been established at California Polytechnic State University (Cal Poly) through donations and financial support from industry and Cal Poly departments and programs. The chamber was designed and constructed by three graduate students as part of their thesis studies to explore and further their understanding of chamber design and antenna measurements. The chamber project has included RF absorber characterization, overall chamber performance assessment, and software development for the coordination of a positioner with a vector network analyzer. This paper presents absorber characterization as a function of incidence angle and orientation to enable an overall chamber performance analysis. Test data at low incidence angles (\u3c 30o) are compared to manufacturer performance curves at normal incidence. The mean response of the measured data indicates a correlation with manufacturer curves. Through ray tracing analysis, the ripple encountered in the test data is used to identify two effective reflection planes indicative of the foam geometry. The measured data are subsequently used to predict overall anechoic chamber performance to within 1dB for a majority of the actual scan data. Details of this analysis and comparisons to actual chamber performance are presented in a companion paper

A Laboratory Course on Antenna Measurement

This paper presents background information and experiment procedures for an antenna measurement laboratory course to be held in a new anechoic chamber at California Polytechnic State University. The lab consists of five experiments and one design project intended to give students practical experience with antenna measurement techniques and to creatively apply analytical skills to design, construct, and test antennas that meet given specifications. The experiments reinforce antenna principles including E-field polarization, antenna gain, radiation patterns, image theory, and frequency response. In addition to the experiment procedures, this paper presents the design and characterization of Helical Beam (RHCP and LHCP) and Discone antennas, a Dipole Antenna near Planar and Corner Reflectors, and Dipoles with and without a balun. These antennas demonstrate polarization, antenna gain, broadband matching characteristics, image theory, and feedline radiation due to unbalanced currents. Measured radiation patterns, gain, and axial ratio (helical only) show excellent correlation to theoretical predictions

Design and Assembly of an Antenna Demonstration System

This paper describes the design, assembly, and operation of a self-contained wireless demonstration system that required only dc power supplies. The system demonstrated polarization effects, radiation patterns, gain, directivity, and signal interference from environmental barriers from dipole, corner reflector (simulated antenna array), Quagi, and embedded patch antennas. The system included an RF oscillator, high-frequency amplifiers,RF bandpass filters, a signal-strength indicator, and multiple adjustable antenna-mounting platforms

Reflectivity Characterization and Identification of Primary Reflection Path in Anechoic Chamber Analysis

This paper presents an analysis of the reflectivity performance of the anechoic chamber. Measurements indicating the performance of the chamber-installed foam absorbers (described in a companion paper) are used to complete this analysis. This is followed by a comparison of the analysis results to chamber measurements taken in accordance with the free-space VSWR procedure [1]. Agreement between the analysis results and worst-case VSWR test measurements is within 1dB for a majority of reflection angles. In addition to chamber performance predictions, this paper describes a method of identifying primary reflection paths through interferometer calculations that compare all single bounce reflection path lengths to the direct path length. The angular spacing between interferometer nulls is used to identify the primary reflection direction. This information can be used to improve the overall chamber reflectivity by identifying areas of significant reflections and enhancing absorber treatments in these areas

Magnetosome Formation in Prokaryotes

Magnetotactic bacteria were discovered almost 30 years ago, and for many years and many different reasons, the number of researchers working in this field was few and progress was slow. Recently, however, thanks to the isolation of new strains and the development of new techniques for manipulating these strains, researchers from several laboratories have made significant progress in elucidating the molecular, biochemical, chemical and genetic bases of magnetosome formation and understanding how these unique intracellular organelles function. We focus here on this progress