Effect of Layer Spacing and Line Width of PCB Coil on Resonant Frequency Shen WANG, Zhi-qiang WEI, Yan-ping CONG * and Hao-kun CHI

Transcription

1 2016 International Conerence on Sustainable Energy, Environment and Inormation Engineering (SEEIE 2016) ISBN: Eect o Layer Spacing and Line Width o PCB Coil on Resonant Frequency Shen WANG, Zhi-qiang WEI, Yan-ping CONG * and Hao-kun CHI Ocean University o China, No.238, Songling Road, Laoshan District, Qingdao City, Shandong Province, China *Corresponding author Keywords: Wireless power transmission, PCB, Line width, Resonant requency, Layer spacing, HFSS. Abstract. With the development o electronic science and technology, people have entered the inormation society, a variety o portable electronic products enter people s lives. A large number o miniature human implantable medical devices applied to clinical ields. The traditional human implantable medical device power supply is implanted battery, its biggest drawback is the treatment problem ater the battery power consumption. Whether it is taken to replace the new battery, or deep into the body, there is a huge risk. Thereore, the portable external wireless charging, it becomes the best choice or human implantable medical devices. Because some o the implanted device volume is very small, they can't accommodate bulky solenoid coil, which seriously restrict the application o wireless charging technology in implantable medical devices. Printed circuit board (PCB) coil has the advantages o high wiring density, small volume, light weight, beneicial to the miniaturization o electronic equipment, they can replace traditional solenoid coil, and applied to the wireless charging technology. In this paper, HFSS sotware is used to simulate, a large number o simulation experiments are carried out on the PCB with 2 layers coils. At the same time, the electrical parameters such as layer spacing, line width and resonant requency are analyzed. Finally, the conclusion is: in the case o ixed layer spacing, with the increasing o the line width, the resonance requency is gradually reduced; but the resonance requency is reduced to a certain extent, it is not changed. When line width is ixed, with the growing layer spacing, the resonance requency value is constantly increasing, the resonant requency o the growth is also more and more slow. Introduction In recent years, the rapid development o resonant coupled radio transmission technology. In the energy transer system, the transmitting coil and the receiving coil are sel resonant coils with the same resonant requency, and they are the key parts o the system. For a coil, in the design must meet to ensure sel resonant requency accuracy, as ar as possible to improve the coil s quality actor and other requirements. In its design stage, it can accurately simulate and calculate or its characteristics (resonant requency, quality actor, etc). In the course o the study there are many kinds o coil structure can be selected, which is based on the PCB lat coil due to high precision, high stability, easy to manuacture, and so on. Especially suitable or the human body implantable medical devices, such as a variety o small power occasions. PCB coil has its own electrical parameters, line width, layer spacing, line center distance and so on. No matter which indicators occur change, will have an impact on the resonant requency and quality actor. The resonant requency o the system is related to the 1 transmission eiciency. Resonant requency o a resonant circuit is, the resonant 2 LC requency o the system changes, which aects the transmission eiciency o the whole system. Thereore, the study o the relationship between the PCB coil line width, layer spacing and the resonant requency o the system or the study o energy transer eiciency has very important signiicance. 81

2 [1],[2] introduces the S Wang and Wong C. Ho, they analyzed the inductance value o dual layer and multilayer PCB coil; [3] describes the relationship between inductance value and operating requency o rectangular spiral inductor based on wire grid method; [4] introduced the straight conductor inductance s calculation ormula, and propose a method o computing the rectangular spiral inductor; [5] introduced a K. Ram Rakh yani, who analyzed the multi-turn solenoidal coil inductance and other key electrical parameters, and the parameters are analyzed and veriied. The inluence or the eiciency o wireless energy transer system is obtained. Above literature, only studied PCB inductance coil, and no studied the characteristic o resonance requency. [6] introduced the distribution capacitance o planar spiral coil is changed with the change o requency; [7] points out that there is a mutual restraint relationship between the system s requency wavelength(λ), the transmission distance (D) and the coil radius(r). It is a matter o design wireless power transmission system that must be considered; [8] introduced when the resonance occurs, the resonance requency o the helical antenna and the geometrical parameters empirical ormula; [9] introduced or the requency splitting caused by the change o the transmission distance, ultimately lead to drastic changes in transmission eiciency, and proposed an automatic requency tracking method; [10],[11] use the mutual inductance circuit model, studied the causes o requency splitting and the general rules. And the requency tracking method is used to improve the transmission eiciency. Although the above literature has carried on the research and the analysis to the wireless energy transmission technology s characteristic o resonance requency, but they are not based on the rectangular plane spiral PCB coil.it is ound that the research on the relationship between the electrical parameters and the resonant requency o the rectangular spiral coils is still very little. The Equivalent Circuit Model o PCB Coil Design Figure 1. Equivalent circuit or PCB board design model. The equivalent circuit o the PCB board design model is shown in igure 1.The resonance requency() is related to the inductance(l) and capacitance(c).when inductance and capacitance changes, the resonant requency will change. Between inductance and capacitance will produce mutual inductance. And with the change o the coil layer spacing, mutual inductance will change, also shows that when the inductance and capacitance change, so that the resonance requency change. Speciic Design o PCB Rectangular Coil HFSS (Frequency Structure Simulator High) is the world's irst commercial 3D electromagnetic ield simulation sotware, the industry recognized the three-dimensional electromagnetic ield design and analysis o industrial standards. HFSS simulation with high precision and high reliability, ast simulation speed, user-riendly operation interace,stable and mature adaptive meshing techniques, etc, making it the tool o choice or high-requency design and industry standards, it has been widely used in many ields o aviation, aerospace, electronics, semiconductor, computer, communications and so on. In this paper, HFSS sotware is used to carry out simulation experiment.pcb coil design, as 82

3 shown in igures 2 and 3.The plane spiral coil is a square structure, and the bottom layer is a coil bracket which is composed o FR4 material, and a spiral coil is attached to the surace o the medium plate, a total o 8 turns. Figure 2. Plane graph. Figure 3. Graphic model. PCB electrical coil design parameters with letters: w is width; s is center distance o adjacent coils; l is rectangular coil side; h_ is a layer spacing; n is the total number o turns o the coil; h_c is the thickness o the copper; h_ is the thickness o the substrate FR4. The dimensions shown in igure 4. Figure 4. Dimensioning. Its speciic electrical parameter settings are shown in table 1: Table 1. Electrical parameter settings. Electrical parameter n s l h h_ h_c w Set value 8 turns 80mil 40mm 0.1mm-0.5mm 0.33mm 0.035mm 5-65mil 83

4 Result Analysis Ater setting, the sotware will automatically be simulated. In this paper, the experimental results are based on a large number o simulation experiments. The simulation data shown in table 2.The data in this table indicates that h is 0.1mm-1mm, the corresponding s is 5mil to 65mil, the value o each resonance requency. Table 2. Simulation data. w h The inal result will be in the orm o a chart. In the ten groups o simulation experiments, we choose when h is 0.2mm, the results obtained are analyzed, the simulation results shown in igure 5. Figure 5. Simulation results. 84

5 As shown in the igure, X represents the value o the resonant requency. Between 5mil and 65mil, a total o 13 times were analyzed. So there will be 13 peaks, the resonant requency o each group simulation experiments are clearly displayed. According to the measured data, can draw the igure 6, it shows that the relationship between the line width, layer spacing and resonant requency. (MHz) w(mil) Figure 6. Relationship between line width, layer spacing and the resonance requency. According to igure 6, the conclusion is: In the case o ixed layer spacing, with the increasing o the line width, the resonance requency is gradually reduced; but the resonance requency is reduced to a certain extent, it is not changed. For "reduced to a certain extent", urther analysis. To set up a unction: i i 1 ( i) i i 1 is the dierence between the irst and last two resonant requencies, this unction represents the rate o change o the resonance requency. By observing relationship diagram, taking the numerical point seemingly no change in the region on each curve, into the unction, taking h=0.2mm as an example. Through observation, when the line width is 40mil to 50mil, resonance requency is almost constant. The numerical point between this: =15.7MHz and =15.46MHz. the calculation result is: <1.5%.According to the above algorithm, or or the rest o nine 15.7 i j curve, the same algorithm analysis. We can be ound in the condition: < 1.5%,the resonant requencies o the each curve is almost does not change. Which can determine this analysis can be applied to all situations. Meanwhile in the diagram can be ound, ater keeping the resonant requency constant, in the 60mil-65mil there will be a little rising trend. In the layer spacing unchanged, this trend is one o the relationship between the line widths and the resonance requency. By longitudinal observation igure 6, and or example, draw the relationship diagram: line width w=5mil and w=10mil. As shown in igure 7 and igure 8: i i 85

6 (MHz) h(mm) Figure 7. w=5mil, the relationship between the layer spacing and the resonant requency. (MHz) h(mm) Figure 8. w=10mil, the relationship between the layer spacing and the resonant requency. Observation o igure 7 and igure 8, it can be concluded: when line width is ixed, with the growing layer spacing, the resonance requency value is constantly increasing. But the dierence between the two resonant requency values is getting smaller and smaller. It shows that the growth trend is becoming more and more slow. Also in igure 6, it can be seen in the increase o the resonant requency at the same time. With the increase o the layer spacing distance value, the vertical spacing o each curve is shrinking. This shows that the resonant requency o the growth is also more and more slow. Summary This paper mainly studies the PCB coil used in the human implantable wireless charging system. By using HFSS simulation sotware, using the method o observation and analysis, ocus on the relationship between the PCB coil line width, layer spacing, and the resonant requencies were analyzed and summarized. Finally, the conclusion is: in the case o ixed layer spacing, with the increasing o the width, the resonance requency is gradually reduced; but the resonance requency is reduced to a certain extent, it is not changed. When line width is ixed, with the growing layer spacing, the resonance requency value is constantly increasing, the resonant requency o the growth is also more and more slow. This understanding on the development o the human implantable wireless charging system o our uture is very helpul. Acknowledgements This paper received unding o China International Scientiic and Technological Cooperation Special (2013DFA10490) and Qingdao innovation and entrepreneurship leading talent project (13-cx-2). 86

7 Reerences [1] S. C. Tang, S. Y. Hui, and H. S.-H. Chung, Characterization o coreless printed circuit board (PCB)\ transormers, IEEE Trans. Power Electron., vol. 15, no. 6, pp , [2] W. C. Ho and M. H. Pong, Analysis and design o printed windings o power transormers using partial inductance method, Proc. IECON 95-21st Annu. Con. IEEE Ind. Electron., vol. 1, pp , [3] Modiied inductance calculation with current redistribution in spiral inductors. Microwaves, Antennas and Propagation, IEEE Proceedings, 2003, 150(6): [4] H.M. Greenhouse. Design o Planar Rectangular Microelectronic Inductors. IEEE Trans. on Parts, Hybirds, and Packaging, PHP-1974,10(2): [5] A. K. Ramrakhyani, S.Mirabbasi, Mu Chiao, and C.M, Design and optimization o resonance-based eicient wireless power delivery systems or biomedical implants, IEEE Trans. Biomed. Circuits Syst.vol.5, no.1, pp , [6] WANG Xin, WANG Zong-xin, YUAN Xiao-jun. Calculation o Sel-inductance and Distributed Capacitance o Spiral Inductor[J]. Research & Progress o SSE, 2000, 20(4): (WANG Xin, WANG Zhong-xin, YUAN Xiao-jun. Circular helical coil inductance and distributed capacitance calculations[j]. Research & Progress o Solid State Electronics, 2000,2 0(4): ) [7] LIN Yong. Great power wireless transmission technology[j]. Electronic Design & Application, 2007(6): [8] CAO Zhi-yu. Pocket communications antenna design and production[j]. Modern communications technology, 1991(12):26 [9] Kim K Y, Kim K Y, Kim C W. Automated requency tracking system or eicient mid-range magnetic resonance wireless power transer[j]. MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, 2012,54(6): [10] ZHANG Xian, YANG Qing-xin, CHEN Hai-yan. Study on requency splitting characteristics o electromagnetic coupling resonant energy transer system[j]. China Electrical Engineering, 2012, 21(9): [11] LIN Yang, YANG Qing-xin, YAN Zhuo. Resonant requency characteristics o the magnetic coupling wireless power transmission system[j]. Electric Machines and Control,2012,16(7):