Research Of Microwave Filters Based On Grounded Suspended Coplanar Waveguide

Modern communication systems are developing rapidly,and the requirements for devices are getting higher and higher.Filters are an important class of devices in communication systems,and the development of communication systems complements each other.Nowadays,the requirements for miniaturization,high performance and easy integration of filters are increasing.Compared with other transmission line structures,coplanar waveguides have the advantages of easy integration,good electromagnetic shielding performance,good dispersion and simple processing.In addition,the suspension structure can reduce the insertion loss of the circuit and increase the mechanical strength,and at the same time,the integrated circuit can be designed to realize self-packaging.In this paper,a new type of grounded suspended coplanar waveguide structure is proposed,and several filters are designed based on this.This paper presents a new type of grounded suspended coplanar waveguide structure based on self-packaging.Firstly,it is designed into a 3-layer model to study the basic characteristics of the structure.Then it is changed into a 5-layer model with hollowed-out inner side of the dielectric plate and copper on the outer sidewall,which is gradually approached to the structure that can be processed.The transition zone is then added to close the air cavity to improve performance,and a large number of simulations are performed again to study the effect of each variable on the transmission characteristics and determine the final structure.Comparing the propagation constant of the final structure with the conventional planar structure,it is confirmed that the grounded suspended coplanar waveguide structure improves the transmission line performance.Based on the proposed new grounded suspended coplanar waveguide structure,two bandpass filters are designed.Firstly,a two-passband filter based on a bent T-shaped uniform impedance resonator is proposed.The resonant frequency of the filter is calculated by the odd-even mode analysis method and the calculation results are verified by simulation software.This filter improves the out-of-band rejection of the filter by loading the open stub;and uses the magnetic coupling of the resonator to ground connection,the electrical coupling between the resonators,and the source and load coupling to produce four transmission zeros.In this paper,the variables affecting several transmission zeros are analyzed in detail.The final processing test results are in good agreement with the simulation results.Secondly,this paper also proposes a single passband filter based on a T-shaped stepped impedance resonator.The filter bends the three ends of the T-shaped resonator,one end is connected to the feed line,and etches the defect on the feed line,and a part of the feed line is extended to form a coupling with the resonator to affect the transmission zero point;the other end forms a hook-like structure,coupling with the other side of the resonator to form a transmission path,generating electrical coupling,controlling the filter bandwidth and affecting the transmission zero point;and one end is connected to the ground to form another transmission path,generating magnetic coupling and affecting the transmission zero and the filter Bandwidth,etc.Finally,a stepped impedance band-stop filter based on a novel grounded suspended coplanar waveguide structure is proposed.The phase difference of the two paths of the resonator is used to form the stopband characteristic.The passband and stopband performance of the filter is affected by changing the impedance ratio control.The adapter of this suspension structure filter was also changed from the original SMA adapter to the 2.92 mm End Launch adapter,the lowermost cover layer was thickened,and the number of rivets was increased to improve the structural closure and mechanical strength.