Study And Design On DGS And Reconfigurable Filtering Power Divider

With the rapid development of modern wireless communication system,the demands of high integration,miniaturization,low cost and high performance of microwave radio frequency circuit are increasing.To meet the strict demands of wireless communication system,reconfigurable filter power divider and Defected Ground Structure(DGS)have become a hot topic.Among them,the reconfigurable filtering power divider can concentrate multiple functions on one circuit,which can reduce the occupation of system space and the insertion loss,and DGS uses the ground effectively,overcomes the limitation of circuit plane technology,which can be widely used in the design and optimization of miniaturized circuits.The specific work of this thesis is as follows:1.A new type of nested U-shaped defected ground structure(DGS)is proposed.By compared with the traditional DGS,the etching area of the nested U-shaped DGS decreases by 68.26%,the steepness factor increases by 11.6%,and the selectivity characteristic factor increases by 40.3%.Then,the nested U-DGS is used to design a compact low-pass filter,the low-pass filter has the advantages of compact circuit structure,low passband insertion loss and wide stopband width.Aiming at the constraints of manufacturing process on the ratio of Wilkinson power divider,the Wilkinson power divier with U-shaped DGS is proposed.The nested U-shaped DGS can be used to improve the characteristic impedance of the microstrip,based on this,the Wilkinson power dividers with ratio of 1:5 and 1:10 are designed respectively.2.In this thesis,a ratio reconfigurable filter power divider is studied.The varactor loaded three line coupled microstrip structure and the shorted two line coupled microstrip structure are theoretically analyzed.Based on this theory,a ratio tunable high-selectivity wideband filtering power divider which has simple circuit structure is designed.The simulation results show that the reconfigurable range of the ratio of the filtering power divider is 1:1 to 1:2.3,the fractional bandwidth is 80%,the cut off rate is 0.22,the return loss is greater than 10 d B and the isolation is greater than 13 d B.Then,the stopband performance of the filtering power divider is optimized by using nested U-DGS.The simulation results show that the nested UDGS suppresses the third harmonic of the circuit and effectively improves its stopband width and depth.3.In this thesis,a frequency tunable dual-band bandpass filtering power divider is studied.A stub-loaded stepped-impedance resonators is designed,and the three resonant frequency points can be reconfigured by using the loaded varactors.Through the optimization algorithm,the appropriate coupling structure between the three mode resonator and the input and output microstrips is realized,and the design of the frequency-tunable dual-band bandpass filtering power divider is finally completed.The simulation results show that the initial passband center frequency of the filtering power divider is 0.84 GHz and 1.55 GHz respectively,the reconfigurable range of the center frequency is 9.5% and 12.9% respectively,the fractional bandwidth of the passband is 6% and 8% respectively,and the return loss and isolation are greater than 10 d B.