In microwave, that is, circuit analysis, signal system, electromagnetic wave transmission and so on. Many operations can be handled in this way, which not only ensures the convenience of operation, but also highlights the essential significance of physical quantities.
For example, after each frequency value in the filter is normalized by the cutoff frequency, the frequency is the relative value of the cutoff frequency, and there is no dimension. After the impedance is normalized by the internal resistance of the power supply, each impedance becomes a relative impedance value, and the dimension of "ohm" is gone. After various operations are completed, everything is restored by denormalization. Nyquist frequency is often used in signal processing toolbox, which is defined as half the sampling frequency. Nyquist frequency is used to normalize the cut-off frequency in filter order selection and design. For example, for a system with a sampling frequency of 1000hz, the normalized frequency of 400hz is 400/500 = 0.8. The normalized frequency range is between [0, 1]. If the normalized frequency is converted into angular frequency, the normalized frequency is multiplied by 2 * π; If the normalized frequency is converted to hz, the normalized frequency is multiplied by half the sampling frequency.