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28 DESIGN007 MAGAZINE I FEBRUARY 2023 the current flow in a transmission line. e magic here is the displacement current flowing through the dielectric at the wave-front, along the transmission line. • e laws of physics apply to everything in the universe. DESIGN007 References 1. "Beyond Design: Forget What You Were Taught," by Barry Olney, PCBDesign007 Magazine, Nov. 2022. 2. "Electromagnetic Fields for Normal Folks," pre- sentation by Dan Beeker at AltiumLive 2017, Oct. 3, 2017. 3. "Laws of Physics," by Ralph Morrison, reprinted in Printed Circuit Design & Fab Circuits Assembly Magazine, April 2021. Resources • "How Does a Transformer Work: 9 Answers You Should Know," by Sneha Panda, LambdaGeeks.com, 2023. • "Waveguide," Wikipedia.org, Dec. 5, 2022. • "Displacement current," Wikipedia.org, Nov. 4, 2022. • "Short-Slot Waveguide Hybrid," Micowaves101.com, 2008. • "Basics of waveguide theory," by Christian Wolff, RadarTutorial.eu. Barry Olney is managing direc- tor of In-Circuit Design Pty Ltd (iCD), Australia, a PCB design service bureau that specializes in board-level simulation. The company developed the iCD Design Integrity software incorporating the iCD Stackup, PDN, and CPW Planner. The software can be downloaded at www.icd.com.au. To read past columns, click here. Rick Hartley is the principal engineer at R Hartley Enter- prises and has been in the industry for over 50 years. He is one of the primary consultants for PCB manu- facturing and design compa- nies. Rick has also conducted classes worldwide on EMI, signal integrity, and various other electrical topics for the last 30 years. electromagnetic fields carry energy in space, it must be true at all frequencies in all media. at is the law. If it is true for light, it must also be true for high-speed transmission lines, 60 Hz power, and at DC 3 ." Key Points • e propagation of electromagnetic energy can be controlled in a number of ways depending on the medium the energy is traveling in. • e propagation of electromagnetic energy does not require electron current flow for the transfer of energy. • Waveguides act like conduits for high frequency displacement currents. • Transformers transfer the electric energy into magnetic energy (primary windings) and then back to electric energy (secondary winding). • Capacitors block electron flow. However, displacement current flows in the dielec- tric and this current produces the mag- netic field in the region between the plates. • e displacement current term is now seen as a crucial addition that completed Maxwell's equations and is necessary to explain many phenomena, most particularly the existence of electro- magnetic waves. • Displacement current plays a vital role in the propagation of electromagnetic radiation. • A traveling, varying magnetic field is associated with a periodically changing electric field that may be conceived in terms of a displacement current. • Electromagnetic waves are propagated through space completely detached from electric currents in conductors. • Displacement current is not an electric current of moving charges, but rather a time-varying electric field. • ere are two types of current: Conduc- tion current and displacement current. • Field energy moving through a space is