Filter principle

Filter 18.432M

Guide: A filter is a device that filters “waves”. It filters out the desired band signal and attenuates other signals. It is usually divided into low-pass, high-pass, band-pass, and band according to the desired band signal. Block four, then what is their principle? Please see below for details~~

First, the principle of the filter - - Introduction

A filter is a filter circuit consisting of a capacitor, an inductor, and a resistor. It filters out signals in the desired frequency band and attenuates other signals. The basis of the filter is a resonant circuit, so that a filter circuit can be combined as long as it can constitute a resonant circuit.

Second, the filter principle - - classification

The filter divides the processed signal into an analog filter and a digital filter depending on whether the signal is analog or digital. The analog filter is used to filter the analog signal, and the digital filter is used to filter the digital signal.

The filter can be divided into four types: low-pass filter, high-pass filter, band-pass filter and band-stop filter according to the frequency band of the signal passed. The low-pass filter only allows low-frequency signals or DC components in the signal to pass (suppress high-frequency components, interference, noise), and the high-pass filter only allows high-frequency components in the signal to pass (suppress low-frequency components, DC components), bandpass The filter only allows signals in a certain frequency band to pass (suppress signals, interference, and noise outside the band), and the band-stop filter only allows signals outside a certain frequency band to pass (suppress signals in the band).

The filter can be divided into active filter and passive filter according to the components used. The active filter is composed of a passive component and an active component, and the passive filter is composed only of passive components, and does not require a DC power supply during operation.

Filters can be divided into on-board filters and panel filters depending on where they are placed. The on-board filter is mounted on the circuit board, and the panel filter is mounted on the metal panel of the shielded chassis.

Third, the filter principle

The classification of filters has been described in detail above. In our usual use, the most common classification method is to divide it into four types: low pass, high pass, band pass and band stop. The principle of these four filters.

The low-pass filter usually refers to a circuit in an on-board power amplifier that allows only low frequencies to pass through without passing the medium and high frequencies, and enhances the bass to drive the woofer of the speaker. Generally, the class AB amplification design is adopted, and the power loss is relatively large. Different low-pass filters have different degrees of attenuation for the same frequency signal.

The high-pass filter is opposite to the low-pass filter, which means that the low-band signal is blocked, and the signal above a certain frequency band is passed. Like the low-pass filter, different high-pass filters have different degrees of attenuation for the same frequency band. .

The bandpass filter should have a completely flat passband, and the signal at the passband frequency is completely attenuated, but this is only ideal. In real life, the bandpass filter does not filter out all unwanted signals as expected. There is a small frequency conversion, which is often referred to as the roll-off phenomenon of the filter.

The band-stop filter is opposite to the band-pass filter, and refers to a signal that blocks a certain frequency band, and passes a signal higher or lower than the frequency band. Like the band-pass filter, there is also a roll-off phenomenon.

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Filter principle