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22 DESIGN007 MAGAZINE I FEBRUARY 2023 e propagation of electromagnetic energy can be controlled in several ways depending on the medium the energy is traveling in. How- ever, electromagnetic waves do not require a medium to propagate. is means that elec- tromagnetic waves can travel not only through liquids, solids, and air, but also through the vacuum of space. What's more, they do not require electron current flow for the transfer of energy. Electromagnetic energy can be guided in the following ways: 1. Direct Current: Conductors guide the energy flow. 2. Alternating Current: Conductors, coplanar and substrate integrated waveguides at high frequencies control the energy. 3. Radio and Microwave Frequencies: Waveguides and antennae guide the energy. Displacement Current: The Key to Electromagnetic Energy Propagation 4. Light Frequency: Optical fiber channels, lenses/mirrors, and gravitational lensing control the energy path. Continuing on from my previous column, "Forget What You Were Taught," let's take a closer look at how electromagnetic energy propagates at different frequencies 1 . Waveguides A waveguide is a form of transmission line used to connect microwave transmitters and receivers to their antennas. ey are metal tubes made of high-quality copper and brass. A waveguide can have a rectangular, circular, or elliptical cross-section. e rectangular section is most used for relatively short connections. Figure 1 depicts a plot in QWED soware of the electric and magnetic field distribution along a rectangular waveguide. A transverse electromagnetic wave travels perpendicular to both the electric and magnetic fields. Beyond Design Feature Column by Barry Olney, IN-CIRCUIT DESIGN PTY LTD / AUSTRALIA with Special Advisor Rick Hartley, R HARTLEY ENTERPRISES Figure 1: Electric field (left) and magnetic field (right) distribution along a rectangular waveguide. (Source: QWED)