A Research And Design Of Wideband Compact High Performance Balun

With the rapid development of modern wireless communication technology,various terminal and network equipment have put forward higher requirements on radio frequency microwave modules and radio frequency components.Onchip passive components,especially baluns,are indispensable in applications that require single ended and differential circuit conversion,and play an important role in improving circuit performance.Therefore,the balun with wide operaion bandwidth,compact size,high balance and easy integration become a research hotspot in the world.This dissertation takes broadband compact high performance balun as the research topic,focusing on the research of miniaturization design methods under different processes,bandwidth extension technologies,and balance compensation within a wide bandwidth.The main content is divided into the following four parts:The first part introduces the coupling structure and explains the coupling principle through the electromagnetic field distribution of the coupling structure.Then the main characteristics of the electromagnetic field propagation mode in the coupling structure are discussed.In addition,the generalized capacitance representation method of the coupled line is explained,and the equivalent circuit is analyzed using the odd and even mode.At the same time,the composition and principle of the capacitor are carefully introduced by taking the microstrip line and the coupled microstrip line as examples.Finally,the main performance indicators of the balun and the commonly used balun structure are introduced.The second part analyzes the working principle and network analysis of Marchand balun,and analyzes the influence of physical parameters on the balun bandwidth,insertion loss,standing wave performance and amplitude phase balance.In addition,a coupling line modeling method based on the network model and the distribution model is deduced,and the model parameters are extracted using simulation software,the calculation results match the simulation results well.Through this modeling method,the dependence of the design process on electromagnetic field simulation can be reduced,and the design efficiency can be improved.Finally,based on the analysis of the balun and the proposed two modeling method,the design process of the broadband balun is summarized,and a broadband balun with pattern ground structure is designed.The simulated results shows good performance in terms of bandwidth and in band balance.The third part theoretically analyzes the influence of the coupling line mismatch on the balance performance of the balun,and proposes a new type of asymmetric slot line coupled microstrip line structure and derives the related formulas.Simulated results of the structure verifies the accuracy of the formula.Finally,a miniaturized broadband balun with shield compensation was designed and fabricated.The simulation results show that the introduction of an asymmetric slot line coupled microstrip line improves the amplitude phase balance performance of the Marchand Balun within wide bandwidth,which verifies the effectiveness of the compensation method.The fourth part analyzes the influence of the connecting line between the coupled lines on the balance performance of the balun,and theoretically derives a method to compensate the balance by adding a short circuit stub to the ground terminal of the coupled line.Then,the equivalent method of multilayer dielectric is proposed to reduce the design difficulty,and the source of loss of on chip metal traces are analyzed.Finally,a short circuit stub compensation balun with a floating shield on the chip is designed and simulated.The simulation results show that the balun has excellent bandwidth and balance performance,which verifies the effectiveness of the short circuit stub compensation method.