cable news: talk about the radiation of cable-非凡电子娱乐

it can be said that wire and cable since the invention of the existence of radiation problems. this is the physical property of the wire, which can be avoided but not eliminated. people use many ways to avoid it, such as the installation of shielding. and away from equipment. however, the effect is not ideal for common mode current is how to generate many people often confused. to understand this problem, first of all, it is clear that the common mode voltage is the root cause of the common mode current, and the common mode voltage is the voltage between the cable and the earth (or any other large conductor nearby). starting from the common mode voltage, it is easy to find the cause of the common mode current, and it is difficult to solve the problem once the cause of the problem is clear. the reason of common mode current on the cable from the following points: differential mode current leakage current caused by common mode. even if the cable contains a signal loop, can not guarantee the signal current 100% return signal source from the loop, especially in the high frequency of the occasion, the space of various stray parameters for signal current provides third or more. the return path. although the proportion of this common mode current is very small, but due to the large area of the radiation loop, radiation is not to be ignored.

common mode current caused by ground noise of circuit board. return line, the signal ground signal is therefore inevitable voltage between two ground, for the high frequency circuit, the voltage is high frequency noise, as a common mode voltage driver common mode current on the cable, the common mode radiation. a variety of methods to reduce the ground impedance are provided in the chapter of circuit board design. a recommended method is to set up a "clean"". what is called clean is that there is no circuit that can produce noise on the ground, so the local potential on the ground is almost equal. if the case is a metal case, connect the piece to the metal cabinet. common mode current induced by space induced electromagnetic wave in a case. shielded cable is able to effectively prevent radiation, there is a layer of shielding. therefore, the cost is increased, and the production step to increase the difficulty, but the use is still very wide.