Design Of Differential Power Dividers Based On Slotline Structure

With the rapid development of modern wireless communication system,the external electromagnetic environment of electronic system gets more and more complex.On the other hand,with the increasing speed of data transmission,the problem of electromagnetic crosstalk and electromagnetic interference becomes more and more serious.Both of these phenomena will cause interference signals to enter into the signal link and affect the normal signals,which will cause confusion in the working state of the equipment.The application of the differential transmission technique can effectively suppress the common mode noise in the transmission link and improve the system sensitivity.The main contents of this thesis paper are as follows: Firstly,the basic theory of differential circuit and slotline are introduced primarily,and the technical indicators of power divider is introduced briefly.On that basis,the transmission resonance characteristics of slotlines are studied in detail,and the power division structure of slotline T-junction is proposed.After that,a balanced-to-balanced filtering power divider(FPD)with high selectivity is designed.The impedance bandwidth of the designed balanced-to-balanced FPD is from 2.54 GHz to 2.98 GHz(FBW = 15.9%).The measured differential mode(DM)insertion loss is less than 0.6 dB and a high suppression(greater than 45 dB)are achieved.Moreover,a novel isolation structure based on slotline is designed to improve the isolation between two output ports and solved the poor isolation introduced by slotline T-junction.Good DM isolation(>18 dB)around the DM passband can be achieved.Then,considering the practical application,a new balanced-to-single-ended FPD with two center frequencies is proposed based on the balanced-to-balanced FPD.The center frequencies of the balanced-to-single-ended FPD are located at 3.1 GHz and 4.78 GHz,respectively.The corresponding measured minimum insertion loss is 1.8 dB and 1.3 dB,respectively.And the CM suppression is better than 30 dB.The new dumbbell-shaped isolation structure based on slotline is adopted to realize the improvement of the isolation,and the isolation is better than 12 dB around the passband.Finally,based on the three-line coupling theory,a parallel coupling slotline structure is proposed,which can achieve a good power division response.Based on this structure,a balanced-to-balanced ultra-wide band(UWB)equal PD is designed.The DM passband of the fabricated balanced PD covers from 2.8 to 9.4 GHz,achieving a fractional bandwidth(FBW)of 108.2%.The measured minimum DM insertion loss is less than 1.4 dB and the CM suppression is better than 30 dB.Moreover,the DM isolation between the two output ports is better than 14 dB by the adoption of two new methods.In this thesis,three balanced power dividers have been designed,fabricated and measured.The measured results are in good agreement with the simulated results,which verifies the correctness of the design methods.