RF interference source: Electronic system clock frequency for several hundred megahertz, the pulse along in the before and after ns range. Network interface data rate is 10 0Mbit / s and 155 and 622Mbit / s (ATM-asynchronous transfer mode). The high-quality video circuitry for the sub-nanosecond pixel rate. These higher processing speed, said the project has been a constant challenge. This challenge is one of the radio frequency (RF) interference, which is caused by rapid changes in the electromagnetic energy. The oscillation rate of the circuit becomes faster (rise / fall time), the magnitude of the voltage / current becomes larger, the problem becomes more. Therefore, today the same than before, to solve the electromagnetic compatibility (EMC) more difficult. Prior to the two-wave section of the circuit, the pulse current of the rapidly changing, indicating that the so-called differential mode noise source, the circuit around the electromagnetic field can be coupled to other components and invasive connections. Inductive or capacitive coupling noise is common mode interference.

Radio frequency interference currents are identical to each other, the system can be modeled as: noise sources, the victim circuit "or" recipient "and loop (backplane). To describe the size of the interference on several factors: "the intensity of the noise source " interference current surround area the size of the rate of change is so, although in the circuit is likely to produce unwanted interference, noise is almost always a total model. Once the input / output (I / O) access cable between the connector and the chassis or ground plane, when some of the RF voltage, leading to a few mA RF current will be enough to exceed the allowable emission level. Noise coupling and propagation of common mode noise is due to the unreasonable design. Some typical reasons for the different lines on the individual wires of different length, or distance to the power plane or chassis. Another reason is that the defects of the components, such as magnetic induction coils and transformers, capacitors and active devices (such as application specific integrated circuit (ASIC).) Magnetic components, especially the so-called "core chokes" the energy storage inductor, is used in the power converter being always generate electromagnetic fields. The air gap in the magnetic circuit is equivalent to a large resistor in series circuit, where you want to consume more power. Thus, the iron core chokes wound on a ferrite rod, stick around a strong electromagnetic field, the strongest field strength near the electrode. Retrace the structure of the switching power supply, the transformer must have a gap, during which there is a strong magnetic field. In which to maintain the most appropriate components of the magnetic field is a spiral, so that the electromagnetic field distribution along the length direction of the die. This is preferred in the high-frequency magnetic components one of the reasons of the helix.