 Hey everybody, I'm Tossus with RF Elements and in today's episode of Inside Wireless we'll learn about waveguides. A waveguide is a type of transmission line like a coaxial cable. It allows electromagnetic energy to travel through it and transport from point A to point B. Essentially a waveguide is a hollow metallic tube that can have various shapes. The most common ones are circular, single ridge, double ridge, elliptical, or rectangular. Like coaxial cables, waveguides work as low pass filters. They don't let low frequency electromagnetic waves travel through below what's called the cutoff frequency. Above this frequency signal travels freely in what's known as the first transverse electric mode, commonly abbreviated as TE10 mode. In this mode of operation the electric fields are always perpendicular to the walls of the waveguide and energy can flow freely from one aperture to the other. The upper frequency at which a waveguide is practically usable is given by the cutoff frequency when the next higher order modes start to propagate. At this frequency the field inside the waveguide starts to behave in a complex way and energy transfer is no longer optimal. This is why waveguides are mainly used in the band between these two frequencies called single mode bandwidth. The frequency we want to use determines the size of the waveguide. The lower the frequency the larger the waveguide is. For example at 300 MHz the size of a rectangular waveguide is 58 by 29 cm, while at 18 GHz its size is 1 by 0.4 cm. Waveguide diameter of a symmetrical horn is 36 mm. Waveguides are particularly useful in high power applications or where very low loss is beneficial. Other transmission lines such as coaxial cables always suffer from higher losses than waveguides. Additionally, they are also immune to external noise and have high mechanical durability. Waveguides are used in a variety of applications such as communication systems, radar systems and of course microwave ovens. For more interesting topics from the RF world, don't forget to subscribe, give us a like or comment below. See you next time.