Investigation On Radiation From Microstrip On Printed Circuit Board

As the increasing applications of the electronic devices and the household appliances, the spectrum band becomes wider and wider, the operating frequency becomes higher and higher, which lead to that electromagnetic interference is greatly serious, and that electromagnetic environment is quite formidable. The electromagnetic interference has been regarded as a big obstacle for modern electronic technologic development. The electromagnetic compatibility of printed circuit board (PCB), which is the necessary for the electronic devices, can influence on the performance of the devices directly. Therefore, it is inevitable to investigate the electromagnetic compatibility on PCB and to control the electromagnetic interference between the electronic equipments.In this paper, we studied several EMC problems, such as the antenna effectiveness of PCB traces and the electromagnetic interference suppression effectiveness of guard lines for signal lines. Moreover, we proposed an optimization method of suppression on multilayer PCB.The main contributions of this paper are listed as follows:1. A closed-form spatial domain Green's functions of basic microstrip geometry is proposed, and a high-efficient moment of method (MOM) algorithm is developed. The proposed approach can be used to calculate the radiating and scattering fields of large size microstrip geometry. Compare to the complex image method and FDTD, the proposed method quickens computing speed and enhances computational efficiency.2. An MOM algorithm which includes closed-form spatial domain Green's functions of multilayer PCB geometry is proposed. Based on the multilayer PCB, the radiated interference field from a signal line to adjacent layer together with Faraday fence is calculated, and the relationship between the electromagnetic interference field and multiple parameters is researched. The numerical results show that the closer length to resonant lengths, the bigger mismatched loads, the smaller loss and the thicker thickness of substrate, the larger the radiated interference field.3. For the model of the electromagnetic interference from a signal line and a shielding line placed nearby the signal line to adjacent layer, a modified algorithm of computing radiation for a shielding line on multilayer PCB geometry is proposed. The radiation effectiveness of the model is studied. Furthermore, the radiated suppression effectiveness of line length, termination loads, loss and thickness of the substrate, separation between shielding line and signal line, width and length of shielding line is analyzed. The results show that the geometry of a shielding line is suitable for interference reduction. The closer length to resonant lengths, the bigger mismatched loads, the thinner thickness of substrate, the shorter separation between shielding line and signal line, and the wider width of shielding line, the lower the electromagnetic interference field. In addition, the loss of substrate and the length of shielding line have little influence on the interference suppression.4. For the model of the electromagnetic interference from a signal line and two shielding lines laid nearby both sides of the signal line to adjacent layer, a modified algorithm of computing radiation for two shielding lines is proposed. The radiation effectiveness of the model is investigated. Moreover, the electromagnetic interference field from a signal line and two shielding lines to adjacent layer is calculated, and the relationship between the electromagnetic field and correlative parameters is discussed. The results show that the interference reduction by two shielding lines is much stronger than that by the single shielding line.