Study On EMC Problems During Smart Mobile Phone Research And Design Stage

The EMC problems during the smart mobile phone design and research stage are comprehensively, systematically, deeply and creatively studied in this dissertation by the first time, and the studying results must be as good reference to analyzing, resolving and suppressing the EMC problems in smart mobile phone. Firstly, the mechanical structure, hardware block diagram and operation theory of the smart phone, and the noise or interference source existing or potentially existing in smart mobile phone is introduced. Then, the electromagnetic topology of smart mobile phone is established, and based on the topology all the EMC problems are preliminarily categorized, analyzed and concluded. Moreover, the EMC problems such as CSE(Continuous Spurious Emission), RSE(Radiated Spurious Emission) and Desense(Sensitivity Degradation) those are unique to smart mobile phone are further analyzed, and their flow charts for experiment analysis and root causes fixing are figured out, and the EMC problems requiring further study are found, which are totally 7 kinds:They are the study on improving the receiver’s ability to suppress the interference, the study on suppressing the interference from the transmitter, the study on co-existence problems, the study on the conducted coupling of interference in smart mobile phone circuits, the study on transmission line model and on its use for analyzing and resolving the EMC problem in smart mobile phone, the study on the unintentional radiation mechanism and control and the study on the problems induced by shielding can. Finally, all of the 7 kinds of the research directions are studied respectively in 7 chapters:firstly, the progress of each research direction is concluded, and the new researching points such as the work or study which requires complementary work or which remains unfinished are found out; secondly, the study work and efforts on the new points are performed, and the novel results are gotten; at last, the instructions or guidelines for the EMC design work are concluded, and are used to design, analyze and resolve the real EMC problems.The main novel points in this dissertation are as follows.The elecromagnetic topology of the smart mobile phone is established.The influnce of baseband signal processing such channel coding, modulation and spreading, and the influnce of the RF link circuits to the wireless receiver’s ability to suppress the interference in smart mobile phone is analyzed and studied by mehods of theory analysis, simulation and experiment.The verificaiton of the feasibility and precision of X paramter’s pridiction to th smart mobile phone’s high power amplifier’s distortion to the signal quality and its out band spurious generation is performed and finished.The essence and mechanism of the co-existence problem is concluded. The co-existence problems in the Inter-band LTE (FDD LTE B1 and B3) in mobile phone are anlyzed. The analysis and degin of co-existence problems for a real designing SGLTE(Simultaneous GSM and TDD-LTE) mobile phone is finished, and then the design is verifed by performing test on engineering samples.The transmission line equation is derived for the two-condcutor or multi-conductor systems’reaction to the stimulation of the radiation interference along the conductors by the methods of electrostatic analogy and by using the KVL and KCL(circuits thoery) alogn the conductors. The method to equate the coupling between two PCB traces with unequal length with the coupling between two transmission lines with equal length is abtained, and the steps of this method are specified. The general analytical expression of the voltage and current along the vitim PCB(Printed Circuit Board) trace due to the weakly coupling from the interference PCB trace, which parallels the victim trace and is shorter than victim trace, is abtained; moreover, the analytical expression of ports’voltage, current and power of the victim trace with special port’s impedacne is abtained, the factors that decide the ports’coupling power are listed and further analyzed, and the methods and guidlines for PCB traces design are worked out.The equivalent circuit model, which can be as good equivalence to real current loop circuits, and can clearly figure out the mechanisms of the common mode current generating, of unintenatianal radiating from the real current loop and the inteference receiving by the real current loop, is found out.The CSE problem induced by the shielding can in a real moble phone design is experimentally analyzed, and the feasible solution is recommended. By method of simulation, the design reference and guidelines for suppressing the shielding cans’ influence to microstrip line are proposed.