基于混沌理论的无源互调功率预测研究

Prediction of Passive Intermodulation Level Based on Chaos Method

该文以通信系统中常用的典型微波部件——同轴连接器为研究对象,基于混沌理论对获得的同轴连接器的无源互调(PIM)功率时间序列进行分析,验证了使用混沌理论预测无源互调的有效性。首先通过实验系统获得同轴连接器的3阶无源互调功率时间序列,并对得到的实验数据进行相空间重构,确定该时间序列的最佳嵌入维数m和延迟时间τ。然后,结合最佳嵌入维数和延迟时间,分别构建相图和使用小数据量法计算该时间序列的最大Lyapunov指数,从而从定性和定量角度验证了该无源互调功率时间序列具有混沌特性。在此基础上,基于获得的最大Lyapunov指数对该无源互调功率时间序列进行混沌预测,在最大可预测尺度范围内,理论预测值与实验值最大误差为2.61%,表明采用混沌方法预测无源互调功率效果较好。该文提出的使用混沌理论预测通信系统中微波部件无源互调功率的方法,为开展无源互调抑制技术研究,提高通信系统的性能提供了新思路。

Passive InterModulation(PIM)products are spurious frequency signals which occur in microwave and radio frequency communication system.And it is noticed that PIM levels have the characteristic of changing with time.In order to find out the relationship between PIM level and time,as the typical microwave component which more often causes PIM in communication system,coaxial connector is chosen and analyzed using chaotic method.Firstly,the third order PIM level time series of coaxial connector is obtained by PIM measurement system.Based on the experimental data,the phase space is reconstructed and the optimal embedding dimension m and delay timeτare confirmed.Secondly,the largest Lyapunov exponent is calculated by the method named the small data sets with embedding dimension m and delay timeτ.And from the qualitative and quantitative perspective,it is verified that the passive intermodulation level time series have the characteristic of chaos.Lastly,the prediction of PIM level with chaotic method is performed on the basis of the largest Lyapunov exponent.And the maximum error between the theoretical prediction value and the experimental value is 2.61%within the maximum predictable scale,indicating that the chaotic prediction is an effective way.The method that predicts the PIM level of microwave components in the communication system discussed in this paper provides a new way of studying the PIM mitigation technique for communication system and provides a new idea for improving the performance of the communication system.