Research On Complex Permittivity Test Technology Of High Frequency PCB Material

With the rapidly development of signal transmission to the high frequencydirection，the electromagnetic properties of the printed circuit board whose role is thesignal carrier becomes more important in the entire circuit system. The conventionalFR4substrate has been not applicable in the design and product of microwave PCB.High frequency dielectric substrate represented by PTFE becomes more useful，and iswidely used in high performance computers、radar communications、telemetry andremote sensing technology.In the electromagnetic parameters of high frequency PCB material，the mostimportant parameter is the complex permittivity，which directly affects the data rateand dielectric loss of the signal carried by the PCB. Therefore，accurately informedthe complex permittivity of the dielectric material has an important significance，either for materials manufactures or engineers.The complex permittivity measurement method of dielectric material wasstudied in detail. Considering material characteristics of high frequency PCBmaterial，the test scheme combines the strip line method and the split cylinderresonant method.Based on strip line resonator theory， a simulation of strip line resonator wasmade. And by theoretical calculation， the value of Lwhich is the effectiveamount of growth caused by fringing field effects was analyzed. Strip line test fixturewas designed. With the network analyzer、high frequency coupling probe and otherrelated auxiliary equipment， a strip line test system was built and the automatic testsoftware was designed. In addition，the preparation of sample was discussedemphatically.The split cylinder resonator method was studied in detail，and the formulas ofcomplex dielectric constant were deduced. Based on model purification theory， thesize of TE011mode split cylinder resonator was optimized. And combined with testrequirements，the split cylinder resonator and coupling adjustable device weredesigned. In addition，with the network analyze the split cylinder resonator testsystem was built.Through the actual measurement of typical materials，the test system was calibrated. The measurement errors were analyzed. The future researched direction ofthe test system was talked.Finally the strip line test system has been developed for measuring the complexpermittivity of high frequency PCB material from2GHz to14GHz. The split cylinderresonator test system has been developed for measuring the complex permittivity ofhigh frequency PCB material at10GHz，and the test result of loss tangent is veryaccurate.The test system can cover the test requirement of high frequency PCB substratecommonly used and provide important reference datas for theoretical research andmanufacture of national high frequency PCB material. So it is extraordinarypractical.