Research On Miniaturized Wilkinson Power Divider Based On Open Stub Structure

With the rapid development of radio frequency and microwave communication technology,the application of microwave devices has become more and more extensive.As an important component for signal integration and distribution,the power divider plays a vital role in the development of the radio frequency industry,which is widely used in radio frequency channels and wireless communications such as antenna arrays,power amplifiers,and modems.The traditional Wilkinson power divider has been widely used due to its good matching and isolation characteristics since it was proposed.The traditional Wilkinson power divider is composed of two quarter-wavelength transmission lines at the design frequency,which occupies a large plane area at low frequencies.Therefore,it is crucial to achieve the miniaturization of the power divider.On the other hand,due to the small size of the isolation resistor,the distance between the transmission lines is very close,which will cause parasitic effects and additional coupling effects.The problem becomes more pressing as the frequency becomes higher.Fortunately,adding transmission lines between the isolation resistor and two output ports can reduce the impact of parasitic effects by means of the Wilkinson power divider.In addition,T-shaped structures and radial stubs can not only reduce the circuit size,but also suppress higher harmonics.In order to realize the miniaturization,this paper proposes a miniaturized Wilkinson power divider based on the open stub.The specific research content is as follows:First of all,starting from the theory of transmission lines,this paper separately studies the input impedance equation of transmission lines and the matching principle of two-port network.It also introduces the common even and odd mode analysis methods of power dividers.Based on the equivalent relationship,the quarter-wavelength transmission line at the set frequency is transformed into a T-shaped structure.Then the circuit matching is realized through the analysis of odd and even mode circuit.Finally,the impedance expression of the transmission line is obtained.Secondly,in order to further realize the miniaturization,the open-circuit transmission line is replaced with a radial stub.According to the Bessel function,the formula for calculating the input impedance of the radial stub is derived.On the basis of the equivalent conditions,the angle,arc length,and radius are obtained depending on the input impedance and the actual size of the radial stub is also determined.To build the final circuit structure,the open-circuit transmission lines will be replaced by radial stubs.Finally,considering the influence of the electromagnetic field and the coupling of the transmission lines,the final circuit model is built in SONNET.We solder the isolation resistor after printing and making the actual circuit.The result will be measured with a vector network analyzer.Through the comparison between the simulation results and the measurement results,the matching effect at the set frequency is wonderful which is accord with the expectation.Good suppression of high-order harmonics is achieved.This proves the accuracy and practicability of the miniaturized Wilkinson power divider based on the open stub.In this paper,the final miniaturized circuit is determined through the steps of replacing quarter-wavelength transmission lines with T-shaped structures and replacing open-circuit transmission lines with radial stubs.The simulation and measurement results confirm the feasibility of the miniaturized design of the power divider.It also provides a solution for the miniaturization of power dividers.On the other hand,the radial stubs introduced in this paper enhance the suppression of higher harmonics.It can be seen from the measurement results that compared with the Horst-type power divider,this paper not only reduces the circuit size by 64 %,but also has obvious suppression effects on the third and fifth harmonics.