Frequencies involved
Passive microwave circuits - Metal waveguides

Microwaves are frequency bands for which the geometric dimensions of the devices involved are of the order of magnitude of the wavelength associated with the electromagnetic wave. The frequency f of an electromagnetic wave is related to its wavelength λ in vacuum (air) by the relation :

where c = 3 · 10⁸ m/s

The usual geometric dimensions range from millimeters to meters. The term "microwave" therefore encompasses all frequencies from approximately 300 MHz to 300 GHz. The word "microwave" is a literal translation of the English microwave, the French term being hyperfréquences [3].