What is the primary limitation of waveguides at lower frequencies?

The primary limitation of waveguides at lower frequencies is related to physical size. As frequency decreases, the wavelength of the signal increases. Waveguides are designed to operate efficiently at specific frequency ranges, and their dimensions must be a fraction of the wavelength of the signal being transmitted. At lower frequencies, the wavelengths can become very long, requiring larger physical dimensions for the waveguide to function properly. This presents practical challenges in terms of installation, cost, and size constraints when designing systems for lower frequency applications, making it less feasible to use standard waveguide structures.

In contrast, impedance matching, signal loss, and skin depth tend to have different implications in the realm of waveguide theory and application. Impedance matching issues typically arise at high frequencies or in specific transmission line scenarios. Signal loss can occur in various mediums, including waveguides, but it's not the primary issue with lower frequencies, as this usually becomes a more significant concern at higher frequencies or with longer distances. Skin depth refers to the depth at which a signal can penetrate a conductor and is more critical in the context of high-frequency signals where losses from the skin effect become significant.