Figure 3 plots load power (red curve) vs. First, given a source with a fixed impedance (50 Ω in Figure 1), the maximum power transfer theorem states that the maximum amount of power transfers to a load if the load impedance matches the source impedance. Figure 2: Use a distributed-impedance model when a signal’s wavelength approaches the length of the conductor carrying it. The Smith chart simplifies calculations involving complex numbers in the form of x + j y, which come up frequently in RF/microwave designs that involve transmission lines and require impedance matching. With RF signals, think instead of a transmission line consisting of an infinite series of distributed impedances ( Figure 2). When a signal’s wavelength (λ) approaches the lengths of the conductors carrying it, you can no longer rely on the lumped-element impedance model represented in Figure 1, in which perfect conductors carry currents traveling at infinite speeds.
With a lumped-element impedance model, perfect conductors carry currents at infinite speeds.
Even if you work primarily with low-speed analog and mixed-signal designs, you could benefit from familiarity with the Smith chart as wireless products proliferate and as high-speed-serial data signals exhibit microwave-like effects. A Smith chart provides insight into RF/microwave designs.
