| Base station Antenna PIM (Passive intermodulation measurements) it happened onhigh power conditions, due to the two non-linear (contact and material nonlinearity)generated intermodulation interference. The multiband internal RET antenna is animportant part of modern base station, but if multiband simultaneously exist in receivingand transmitting device, and at the same in the system also exist an open RET, it lead thePIM issue more serious in this kinds of antenna.This paper introduces the relevant knowledge base station antennas and PIM andcurrent research for PIM. Then introduced the basic theory of PIM and the importanceofthird-order PIM in passive. Then focus on recently prevalent multiband internal RETantenna PIM issue to discuss, the designed antenna is in order to meet China Mobile Orderrequired performance. This antenna structure is the representative of such antenna. In thispaper it starting from its structural features, in the firstly do the analysis for the PIM rootcause: during the antenna working, the antenna radiating elements at the front of theantenna but the back radiation will reach the RET, the RET on the back of the antenna.Considering there is non-linear material, so it will bring PIM, and the PIM also willradiation back to dipole, thereby define the experimental direction on how to reduce oreliminate these kinds of passive intermodulation interference signal coupling. Thendesigned choke and install them on the two side of the reflector, it can optimize the antennaF/B and then to improve antenna PIM, on the other hand we found make the RET flexiblecable coupling to ground, the cable will lose the ability to transmit or radiate signals. It alsocan improve antenna PIM performance. Finally we measured by sampling experimentsvalidate the feasibility of the program.This paper improved meaningful information to Antenna industrial production for how to improve multiband internal RET antenna PIM. |
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