Slot Line Overview
A slot line is a type of transmission line used in microwave and RF circuits. It consists of a narrow slot cut into a metal ground plane on one side of a dielectric substrate. The other side of the substrate has no conductor at all.
This simple structure supports a quasi-TEM wave that travels along the slot. The electromagnetic field is concentrated in and around the gap, which makes slot lines behave differently from microstrip lines.
Slot lines are commonly used in balanced circuits, antenna feed networks, and broadband components. They work well in millimeter-wave designs where compact, planar structures are needed.
The two most important parameters in slot line design are characteristic impedance (Zo) and guided wavelength (λg). Zo tells you how the line resists the flow of electrical energy. λg tells you the actual wavelength of the signal traveling inside the structure — it is shorter than the free-space wavelength because of the substrate material.
This calculator uses established models to compute both values based on your substrate permittivity (εr), substrate height (h), and slot width (W). Enter your parameters, click Calculate, and get your results instantly.