Generally, the working frequency of waveguide is in the microwave range. At such a high frequency as microwave, the voltage and current at low frequency have not only lost their original meaning, but also can't be directly measured, so they can't be used as basic parameters of waveguide components. From the measurement point of view, the basic parameters of waveguide elements are power and frequency, while other parameters such as impedance, admittance, gain, attenuation, quality factor, etc. can generally be derived from the measured basic parameters.
Waveguides can be distinguished according to the number of "paths" of equivalent circuits (i.e. the number of branches or "end pairs" of elements); It can also be distinguished according to the nature of the substance filled in the element; It can also be distinguished according to the purpose of the components. The main waveguide components are listed in the table. However, from the use point of view, many of these components often have several purposes, so it is difficult to distinguish them completely.
Generally, the waveguide has more than two ports, and the electromagnetic wave is controlled by some kind of inhomogeneity or some kind of coupling mechanism, that is, the electromagnetic wave is transformed. Commonly used inhomogeneities include waveguide ladder (waveguide cross-section size changes suddenly), diaphragm, pin and resonant window, etc. Commonly used coupling mechanisms include coupling holes, cracks and coupling rings welded on the end faces of waveguides, which are used to extend or insert elements to connect waveguides or waveguide elements to each other. There are two kinds of flanges: flat flange and anti-flow flange.
① Flat flange: connected by mechanical contact of smooth surfaces of two flanges;
② Anti-flow flange; Cut out a quarter-wavelength anti-flow groove on the end face, and the notch is also a quarter-wavelength away from the inner wall of the waveguide, that is, the groove bottom is half-wavelength away from the inner surface of the waveguide. In this way, the current node can be caused at the mechanical contact. Even if there is a slight gap or twist between the two waveguide end faces, there will still be short-circuit reactance between them, so as to achieve microwave coupling for DC open circuit and RF short circuit.