The power filter is a filter circuit composed of a capacitor, an inductor, and a resistor. The filter can effectively filter out the frequency of a specific frequency in the power line or a frequency other than the frequency to obtain a power signal of a specific frequency or eliminate the power signal after a specific frequency.
Waves, as the name suggests, are devices that filter waves. "Wave" is a very broad physics concept. In the field of electronic technology, "wave" is narrowly limited to the process of describing the fluctuations of various physical quantities over time.
This process is converted into a time function of voltage or current by the action of various types of sensors, which is called a time waveform of various physical quantities, or a signal. Because the independent variable time 'is continuous value, it is called continuous time signal, and is used to call it analog signal.
With the development and rapid development of digital electronic computers (referred to as computer) technology, in order to facilitate the computer to process the signals, a complete theory and method for transforming continuous time signals into discrete time signals under the guidance of the sampling theorem is generated.