Research On Broadband Filter And Power Divider Based On Coupling Structure

With the advent of the Internet of Everything,there is an increasing demand in wireless communication systems with large capacity,high speed,small size and low power consumption.Filters and power dividers,as the core hardware in wireless communication systems,therir performance improvement is significant.This thesis studies the high performance broadband filters and power dividers based on the planar/multi-layer coupling structure.The main contents of this paper are as follows:Firstly,based on the multi-layer octagonal coupling structure with octagonal defects,two new kinds of ultra wide band(UWB)filters are proposed.Moreover,the scattering parameters of the coupled structure and the design formulas of the proposed filter are deduced.The first filter adopts single multi-layer octagonal coupling structure to achieve more than 140%3dB bandwidth,less than 0.3dB passband ripple.Further,parallel short/open-circuit branches are also used to realize two adjustable transmission zeros to improve the outband rejection performance.The second filter,based on a two-stage cascaded multi-layer octagonal coupling structure,achieves over 110%3dB bandwidth and 20dB super-wide stop band over 4.5 times the center frequency.Both filters are validated by processing and testing.Then,based on the isolation network,a broadband high isolation power divider is designed.Compared with the traditional power splitter,this structure can achieve better isolation performance and wider bandwidth.Moreover,since no isolation resistance is required,a power splitter based on this structure can be easily applied to a high-power applications.The simulation results show that in 3 GHz-9 GHz band,the return loss S11 and S22 are less than-18 dB and the isolation S23 is less than-20 dB.In 4GHz-8GHz band,the insertion loss S21 and S31 are both greater than-3.8dB.And the amplitude variation is less than 0.2dB.Finally,a wide isolation bandwidth power divider with bandpass filter response based on periodic time-varying isolation network is proposed.The power divider obtains a band-pass response by replacing the conventional Wilkinson power divider quarter-wavelength impedance transformer with parallel coupling lines.In addition,in order to improve the isolation bandwidth,a periodic and time-varying isolation network composed of RLC series resonant circuit and parallel short-circuit coupled line is proposed based on the theoretical analysis.The measurement proves the isolation bandwidth of the poewer divider can be increased by 1.5 times by using the isolation network.It can effectively improve the working bandwidth and the practicability of the filter power divider...