| Passive intermodulation refers the phenomenon that when a signal with two or more frequency components passes through passive components(such as loads,antennas,coax,duplexers,etc.),it can produce new frequencies besides harmonics due to the nonlinearity of the device.In wireless communication systems,the development trend of high power,multi-carrier and broadband causes the problem of passive intermodulation interference in communication systems to become more and more serious.When passive intermodulation interference falls into the receive passband,the receiver's sensitivity will decrease,thus affecting the receiving performance.However,there are few researches on the impact of passive intermodulation on the performance of communication systems,which is still in its infancy.Based on the performance of the communication system,this paper mainly studies the numerical analysis models of the impact of passive intermodulation interference on the performance of two performance indexes: the bit error rate and the capture probability of frame synchronization.The specific works are as follows:1.This paper first analyzes the factors that affect the communication system,including the non-linear characteristics of passive components,the characteristics of downlink signal,such as number of downlink signal multiplexing,bandwidth,power and so on.2.A new distribution model,ie,the modified Cauchy distribution is proposed for passive intermodulation statistical property.In view of the influence of passive intermodulation on bit error rate(BER)performance,the numerical analysis models of bit error rate are deduced respectively in the Gaussian channel and Rayleigh channel with BPSK modulation.Compared with the simulation results,the error is less than 2d B under the same bit error rate,which verifies the correctness of the numerical analysis model of bit error rate under the interference of passive intermodulation.3.To study the effect of passive intermodulation on frame synchronization performance,this paper takes OFDM as an example and adopts the improved Schmidl&Cox algorithm to analyze the statistical properties of the time metric functions which fall into and do not fall into the cyclic prefix respectively.According to the predefined decision threshold,we complete the analysis of the numerical simulation model about the impact of passive intermodulation interference on the frame capture probability in OFDM system.And the correctness of the numerical analysis model is verified by the simulation.Through the analysis of the performance of communication system under the condition of passive intermodulation in this paper,it can provide certain reference value and practical value for the design and development of modern communication system such as high power satellite payload,mobile communication system and civil radio communication system. |
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