How to choose the filter by circuit form and loss parameter
Information sources：本站 | Release date：
2017-12-04
| Browse volume：122
The size of the installation and use space, the installation method of the filter, the installation size, and even the consideration of the filter outline structure during the installation process, the consideration of the magnitude of the voltage and current can be used as the reference standard for the selected filter. In addition to referencing these commonly used reference data standards, it is also possible to find the filter that meets the requirements of use by installing the circuit form and the filter insertion loss parameter.
First, the circuit form
According to the principle of impedance mismatch, the greater the filter impedance and the impedance mismatch between the two ports, the more effective the attenuation of the electromagnetic interference energy is. The filter should consider the low impedance end of the high impedance termination filter of the circuit. The low-impedance termination of the circuit is based on the principle of the high-impedance end of the filter, and the filter circuit is selected according to the filtering requirements.
Second, the filter insertion loss parameter
The main parameter of the filter is the insertion loss, which reflects the filter's ability to suppress the interference signal. Various EMI filters have their own corresponding attenuation and frequency curves. When selecting a filter, the insertion loss should be determined according to the frequency of the interference signal and the degree of attenuation and cutoff frequency. It is worth noting that the manufacturer gives the insertion. The loss is measured in the 50 ohm system without load (no load condition), but the input/output impedance in the actual circuit is not exactly 50 ohms, so the actual insertion loss of the filter in the line and the product standard The weighing is often different. For the measurement of the filter performance, there are approximation measurement and online measurement in the application, in order to be closer to the actual situation.
