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 In very much high frequency emissive equipment, the emissive power that a directional coupler inserts to measure emissive equipment in the access that often is put to emissive antenna in end course result or the reflection power that measure aerial, I introduce the working principle of this kind of directional coupler below.
If graph X is the principle graph of directional coupler, among them A, B is advocate of feed cable inside conductor, be close to inside L3 of a coil is put in conductor, among them C is L3 is mixed inside the distributinging capacitance between conductor. Should radio frequency signal sends fashionable, a, B has voltaic I to had flowed, among them E is the radio frequency voltage between conductor of inside and outside, as a result of the existence of distributinging capacitance C, so inside there is one electric current to shed outer conductor through C, R1 in conductor, this electric current produces EL3 of voltage of a mutual inductance in R1 admiral, apparent, the output voltage E=ER1+EL3 of two end of A-b, in make we choose L3 and R1 appropriately and C and M of coefficient of mutual inductance are changed in debug, make on a direction output voltage E is maximum (although get ER1 and EL3 to be in phasic going up is additional) , and on another direction E outputs dinky minimum (although get ER1 and EL3 to be in phasic going up is decrease) , such effect that we achieved directional coupling, output voltage E comes through BG1 demodulation evacuation demonstrative system, such we can go up in demonstrative system numerate the real power that the machine delivers Xiang Tian line.
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