In waveguides, what does the term "cutoff frequency" refer to?

The term "cutoff frequency" in the context of waveguides specifically refers to the lowest frequency that can propagate through the waveguide. Below this frequency, the waveguide will not support the propagation of the electromagnetic wave, leading to significant attenuation and potential total reflection. Each waveguide mode has its own cutoff frequency, determined by the physical dimensions and shape of the waveguide.

At frequencies above the cutoff frequency, the waveguide can effectively transmit signals, allowing energy to propagate through it. This is fundamental for waveguide design, as engineers must ensure that the intended communication or signal frequency operates well above the cutoff to maintain efficiency and minimize signal loss. Thus, knowing the cutoff frequency is essential for properly utilizing waveguides in various applications, especially in microwave and RF technologies.