In layman's terms. Filtering refers to the processing of a signal to change the spectral characteristics of a signal by selectively transmitting or suppressing a signal of a specific frequency.
Think of a filter as a frequency selector that retains components in certain frequency ranges of the signal and eliminates components in other frequency ranges.
Its purpose is to remove noise, smooth the signal, extract useful information, etc.
The term filtering originates from the theory of communication, which is a technique for extracting useful signals from received signals that contain interference. The received signal is equivalent to the observed random process, and the useful signal is equivalent to the estimated random process. For example, when an aircraft is tracked by radar, the measured position of the aircraft contains measurement errors and other random interference.
Filtering is an important concept in signal processing, and is divided into classical filtering and modern filtering!
1. Classical filtering
The concept of classical filtering is an engineering concept based on Fourier analysis and transformation. According to higher mathematical theory, any signal that satisfies certain conditions can be regarded as the superposition of an infinite number of sine waves. In other words, the engineering signal is a sine of different frequencies.
The sine waves of different frequencies that make up the signal are called the frequency component of the signal or the harmonic component of the signal formed by the linear superposition of waves.
2. Modern filtering
It uses analog electronic circuits to filter analog signals, and its basic principle is to use the frequency of the circuit.
Characteristics enable the selection of frequency components in the signal. In frequency filtering, the signal is regarded as an analog signal composed of sine waves of different frequencies, and the signal is filtered by selecting different frequency components.
In the field of electronic engineering, filtering is commonly used in signal processing, circuit design, and communication. This can be done by changing the parameters of the components in the circuit or by adding specific circuits. In addition, in digital signal processing, filtering functions can also be implemented using software.
Filtering is the operation of filtering the frequency of a specific frequency band in a signal, which is an important measure to suppress and prevent interference. Filtration is divided into classic filtration and modern filtration.
Filtering is the operation of filtering a specific bandwidth frequency in a signal, which is an important measure to suppress and prevent interference. It is a probability theory and method for evaluating other related stochastic processes based on observations of the outcomes of stochastic processes.
The ideal DC voltage source does not need to be filtered at the output of the power supply?
Indeed, filter capacitors can reduce the AC resistance of a power supply. Add a capacitor to the output of the power supply so that the current that rises and is maintained immediately in a short period of time can be provided by the capacitor, the capacitor is immediately reduced, and the current that is held for a short time is reversed to the other side to charge the capacitor. Most of these instantaneous currents are exchanged directly on the capacitor without passing through the internal resistance of the power supply, so the AC resistance of the power supply can be reduced.
In fact, this is the function, because the power supply has internal resistance, and the transmission line also has impedance, so the modular capacitor can allow part of the instantaneous change current to be directly exchanged on the capacitor, reducing the size of the current change on the line, on the one hand, it helps the power supply of this IC.
From this point of view, for an ideal power supply, the separation power cannot be ignored, because the wires are not perfect.
In fact, all power sources have propulsion capacity, and as long as the driving capacity is met, the output power will remain relatively stable. The output power requirement is also to some extent a requirement for internal resistance, which is indeed different, the internal resistance must produce a voltage drop, whereas a regulated power supply can theoretically provide a constant output power over the output power range by using a closed control loop.
The so-called AC resistance reduction ability is mainly aimed at high-frequency AC resistance, because even if the power supply is turned off, there are requirements for response speed and response, and the load current change cannot be tracked immediately, resulting in small voltage fluctuations. By adding capacitors, it is possible to reduce the instantaneous change in the current inside the power supply, thereby changing the nature of the power supply.
In the case of filtered power supplies, we just talked about reducing AC resistance, but in fact it is more important to reduce ripple at the output. For dry batteries, the output does not produce ripple and no filtering is required.
However, in terms of reducing AC resistance, it is necessary to increase capacitors for complex circuits, especially near the IC power supply pins.
Because the alternating current is obtained after the rectification is pulsating DC, such a DC power supply can not be directly used as the power supply of the electronic circuit due to the large AC ripple contained in it, and the filter circuit can greatly reduce the AC ripple component, so that the voltage waveform after rectification becomes relatively smooth.