4 Lines 3a Emi Signal Filter For Air Conditioning Signal Line Anechoic Chamber
There are two basic methods used to suppress noise: filters and shields. These have a mutually supportive relationship; although both are generally needed, either may be simplified if there is little noise. Shields are generally made of metal. Since they must cover the entire electronic device they tend to be large. This means that they also tend to increase the cost and weight of the device. Filters are electronic components, and making skillful use of them can allow you to simplify shields, and can help reduce the cost and weight of electronic devices.
This chapter gives a brief overview of filter operating principles and explains a typical circuit configuration in order to provide a good base of knowledge for making skillful use of filters. Filter circuits used to eliminate electromagnetic noise are typically called EMI suppression filters, but they will be referred to simply as "filters" here.
| Type |
Target noise |
Information used to separate noise |
Difference in signal/noise |
Implementation method |
Major applications |
| EMI suppression filter |
Radio noise in general |
Deviation in frequency distribution |
Signal |
Low frequency |
Low-pass filter |
Electric circuits in general |
| Noise |
High frequency |
| Common mode choke coil |
Common mode noise |
Difference in transmission mode |
Signal |
Normal |
Coupling coil |
Power supplies (AC/DC)
Differential signal |
| Noise |
Common |
| Surge absorber |
High voltage surges |
Difference in voltage |
Signal |
Low voltage |
Non-linear resistance
Discharge gap, etc. |
Electronic devices in general
(surge entry point) |
