Design Of Combiner/Divider Unit Of Passive Intermodulation Analyzer In Mobile Communication Systems

Passive intermodulation (referred to as PIM) is due to nonlinear characteristics of varieties of passive components in Communication Systems. In the high-power multiple-channel system, these passive devices will have higher harmonics that will be mixed to generate new frequencies,and they fall into receive Channel to influence the communication quality. Mobile communications are booming, that is about to spend more and more frequency resource. Once the frequency planning have been identified, each kind of passive intermodulation interference is determined.Thus, the main work is concentrated in devices manufacturing and systems measurement.The thesis mainly based on that the generation mechanism and mitigation measures of PIM are studied, combined with filter design theory, to design the Combiner/divider unit of passive intermodulation analyzer in mobile communication systems.This thesis analyzes the design requirements of the demultiplexer and combiner unit of passive intermodulation analyzer,and then analysis and studies the filter theory and passive intermodulations mechanism and reduction measures. The main work carried out the following:First of all,we introduced the types of microwave filters, filter's major technique Parameter, low-pass prototype and frequency transformation,then analysis of the coupled resonator band pass filter theory. Second, This thesis research the passive intermodulation interference mechanism and the general nature of intermodulation products, Including passive nonlinearities types and the complexity of intermodulation products. Further, This thesis analyzes on the influence of antinoise performance of passive intermodulation interference on communication system.And I establish discussed the Passive intermodulation mitigation measures. Through the experiment, This thesis discovered to passive intermodulations the contribution quite big key region. Finally, through to the test method research which passive intermodulations,I give the overall construction and the index allocation of passive intermodulation analyzer. Based on the above theory analysis,I choose coaxial resonators to achieve the combiner/divider unit of the low insertion, high inhibition, low intermodulation requirements. Through the circuit and microwave structure simulation, This thesis designed a combiner/divider unit of passive intermodulation analyzer.This combiner/divider unit is analyzed and designed by high frequency simulation software HFSS and Desinger. Then the combiner/divider unit is fabricated, debuged and measured. The measured results show that the 3-order, 5-order, and 7-order passive intermodulation can achieve 165dBc above, segregation degree achieve 60dB above.The combiner/divider unit can satisfy the requirements of passive intermodulation tester system.