There are several different types of EMI control devices that may be placed in a conducted path (either signal or power lines) to selectively pass intended signals and reject unintended EMI signals. The rejection is provided on the basis of some characteristics of the EMI signal, which differs from the intended signal. Thus, these EMI control devices provide a means of suppressing conducted interfering signals that have certain characteristics. Filters, which are discussed in Section 8.1, discriminate between desired and interfering signals on the basis of frequency. Ferrites may also be used to provide frequency selectivity, and these devices are discussed in Section 8.2. Isolators, which are discussed in Section 8.3, discriminate between common-mode and differential-mode signals existing in the conducted path. Transient suppressors, which are discussed in Section 8.4, discriminate between signals on the basis of signal level. All four of these device types are very important in system applications, because they can usually be used at equipment inputs or outputs to control EMI problems that occur as a result of integrating the equipment into a system.

Chapter Contents:

• 8.1 Filters
• 8.1.1 Power Line Filters
• 8.1.2 Signal Filters
• 8.2 Ferrites
• 8.3 Isolators
• 8.3.1 Isolation Transformers
• 8.3.2 Optical Isolators
• 8.4 Transient Suppressors
• 8.4.1 Crowbar Devices
• 8.4.2 Voltage-Clamping Devices
• 8.4.3 Hybrid Transient Suppressors
• Suggested Readings: Filters, Ferrites, Isolators, and Transient Suppressors
• Web Addresses for Companies that Provide EMI Mitigation Devices

Inspec keywords: interference suppression; microwave isolators; electromagnetic interference; ferrite devices; filters

Other keywords: filters; isolators; conducted path; common-mode signals; conducted interfering signal suppression; frequency selectivity; transient suppressors; unintended EMI signal rejection; EMI control devices; ferrites; differential-mode signals

Subjects: Magnetic material applications and devices; Filters and other networks; Electromagnetic compatibility and interference; Waveguide and microwave transmission line components