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Courseware Sample Telecommunications Courseware Sample 85756-F0 A TELECOMMUNICATIONS COURSEWARE SAMPLE by the Staff of Lab-Volt Ltd. Copyright © 2008 Lab-Volt Ltd. All rights reserved. No part of this publication may be reproduced, in any form or by any means, without the prior written permission of Lab-Volt Ltd. Printed in Canada February 2009 Table of Contents Introduction ................................................... V Courseware Outline Microwave Fundamentals ..................................... VII Sample Exercise Extracted from Microwave Fundamentals Exercise 7 Standing Waves .....................................3 Instructor Guide Sample Exercise Extracted from Microwave Fundamentals Exercise 7 Standing Waves ....................................31 Bibliography III IV Introduction The Lab-Volt Computer-Assisted Microwave Technology Training System, Model 8091, is a complete, state-of-the-art microwave training system, including data acquisition and instrumentation. Specifically designed for hands-on training, this integrated package of software, hardware, and courseware comes with all power supplies, high-quality microwave components, and accessories required to perform the experiments. The courseware experiments are performed by using the Lab-Volt software Data Acquisition and Management for Microwave systems (LVDAM-MW®). This modern software is built around a Data Acquisition Interface (DAI), that performs 12-bit A/D acquisition on four channels. The software uses the acquired data received from the interface to calculate and display the values of power and SWR measurements on a computer screen. The software also features an oscilloscope, a Smith Chart displaying the values of the transmission line parameters and used to perform impedance matching, and a data table used to record, save, and graph all the measured parameters. The microwave components and accessories include: • A Gunn diode oscillator running at 10.5 GHz in continuous wave (CW) mode or modulated by a 1-kHz square wave. • A crystal detector, a thermistor, and a slotted line used with the LVDAM--MW software to detect microwave signals and power and to take SWR measurements. The Gunn Oscillator Power Supply provides power to the Data Acquisition Interface through a connector that aligns when this interface is stacked on top of the power supply. • An antenna azimuth indicator for accurate plotting of antenna field patterns. • Inductive and capacitive irises used to measure reactive impedance. • Three lenses, a metal plate, and a dielectric plate for microwave optics experiments. • A PIN diode to teach microwave switching, variable attenuation, and amplitude modulation of microwave signals. • A hybrid tee to teach microwave signals' splitting and coupling. V VI Courseware Outline MICROWAVE FUNDAMENTALS Exercise 1 Familiarization with Microwave Equipment Identifying the basic components of a microwave setup. Assembling a typical microwave setup and measuring power. Learning how to use the Power Meter of the LVDAM-MW Software. Exercise 2 Power Measurements Familiarization with the operating principles of a microwave power meter. Performing power calculation and measurements. Exercise 3 The Gunn Oscillator Familiarization with the basic operating principles of a Gunn oscillator. Characterizing a Gunn oscillator by plotting the following curves: the current-versus-voltage curve, the delivered power-versus-voltage curve, and the efficiency-versus-voltage curve. Exercise 4 Calibration of the Variable Attenuator Familiarization with the concepts of attenuation and insertion losses. Characterizing a variable attenuator by plotting its attenuation-versus- blade position curve. Exercise 5 Detection of Microwave Signals Familiarization with a crystal detector operating in the square-law region. Plotting the sensitivity curve of a crystal detector and evaluating its tangential sensitivity. Exercise 6 Attenuation Measurements Using the SWR Meter of LVDAM-MW and the Crystal Detector to measure attenuation. Measuring attenuation with the RF substitution method. Exercise 7 Standing Waves Creation of standing waves in waveguides. Performing microwave frequency measurements and standing wave measurements with the Slotted Line and the SWR Meter. VII Courseware Outline MICROWAVE FUNDAMENTALS Exercise 8 The Directional Coupler Familiarization with the operating principles of a directional coupler. Defining and measuring the coupling factor and the directivity of a directional coupler. Exercise 9 Reflection Coefficient Measurements Familiarization with the concepts of reflection coefficient and return loss. Measuring the reflection coefficient of a load. Determining the power absorbed by a load based on its reflection coefficient. Exercise 10 SWR Measurements Familiarization with the concept of standing-wave ratio (SWR). Using the SWR Meter and the Slotted Line to measure the SWR. Exercise 11 Impedance Measurements Relationship between the reflection coefficient at the load and the load impedance. The Smith Chart. Plotting a normalized impedance on the Smith Chart. Determining the SWR produced by a given load. Determining the magnitude and phase of the reflection coefficient produced by a given load. Determining the impedance of a load with a slotted line (short-circuit minima-shift method). Exercise 12 Reactive Impedances Effect of discontinuities in the relationship between the electric field and the magnetic field. Familiarization with the following discontinuities: the capacitive iris, the inductive iris, and the screw tuner. Determining the reactance produced by an iris or a screw tuner in a waveguide. Converting impedances to admittances, and vice versa, using the Smith Chart. Determining the admittance and the impedance of an iris with the Smith Chart. Exercise 13 Impedance Matching Reflection coefficient along a waveguide. Measuring an impedance along a waveguide, using the Smith Chart. Determining the impedance and the location of the matching device required to match a load, using the Smith Chart. Using a slide-screw tuner. VIII Courseware Outline MICROWAVE FUNDAMENTALS Exercise 14 Antennas and Propagation Propagation in free space. Propagation loss due to the separation between the antennas. Isotropic radiators. Attenuation of a transmitted signal as a function of the distance between the transmitting and receiving antennas. Power received by an antenna as a function of its orientation with respect to the transmitting antenna. Plotting a radiation pattern. Characterization of an antenna with two radiation patterns (E- and H-plane patterns). Methods used to measure the gain of an antenna. Exercise 15 Microwave Optics Phenomena usually encountered in optics. Index of refraction of a material as a function of the frequency. The reflection coefficient and the coefficient of transmission. The Snell's Law. Lenses and parabolic antennas. Exercise 16 A Microwave Transmission Demonstration (Requires Optional Equipment) A simple demonstration to show how a microwave signal can be used to carry information along a line of sight from one point to another. Exercise 17 PIN Diodes Construction of PIN diodes. Operation of a PIN diode when forward and reverse biased. Typical resistance-versus-bias current response of a forward biased PIN diode. Equivalent RF circuit of a forward biased PIN diode. Attenuation of a reverse biased PIN diode as a function of frequency. Typical applications of PIN diodes. Exercise 18 Wireless Video Transmission System (Requires Optional Equipment) Implementation and testing of a wireless video transmission system that uses a PIN diode as a microwave AM modulator. Effects that constructive and destructive interference has on the strength of the signal received and on the image displayed by the video/TV receiver. Exercise 19 Hybrid Tees Introduction to waveguide tees. The hybrid (magic) tee. Using a hybrid tee as a power splitter or a power combiner. Attenuation between the H- and E-plane arms of the tee and each of its lateral arms. Typical applications of hybrid tees. IX Courseware Outline MICROWAVE FUNDAMENTALS Appendices A Common Symbols B Module Front Panels C Answers to Procedure Step Questions D Answers to Review Questions E New Terms and Words F Equipment Utilization Chart Bibliography X Sample Exercise Extracted from Microwave Fundamentals Exercise 7 Standing Waves EXERCISE OBJECTIVES When you have completed this exercise, you will know how standing waves are created in waveguides. You will be able to perform microwave frequency measurements and standing wave measurements with the Slotted Line and the SWR Meter of LVDAM-MW. DISCUSSION Creation of Standing Waves When a sinusoidal microwave source is connected to a waveguide, sinusoidal waves of voltage and current propagate along it. Note: In fact, we could also say that both an electric field wave and a magnetic field wave propagate inside the waveguide. Considering voltages and currents instead of electric and magnetic fields is simply a different way of viewing things. The voltage is present between the top and the bottom of the waveguide, whereas the current flows in the side walls. Throughout this exercise, we will deal with voltages and currents to facilitate the understanding. The amplitude of the voltage and the current depend on the characteristic impedance of the waveguide and on the impedance of the terminating load. When the impedance of the load is equal to the characteristic impedance of the waveguide, the load continually absorbs all the received energy. No energy is reflected back toward the
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