Design Of Lumped-Element RF Bandpass Filter Constructed On Multilayer Substrates

This thesis focuses on the design of lumped-element bandpass filter constructed on multilayer substrate.This kind of filter is widely studied in recent years because of its small size,high performance,and low cast.In this thesis,the stacked-plate capacitor,the LC resonator,the filter composed of LC resonator,and the cascade of filters are studied.Meanwhile,a fast design technique is also proposed and discussed.Several novel multilayered filters are proposed.The main research points and innovations of this thesis can be concluded as followed.1.A novel multilayered capacitor is proposed,which is called the stacked-plate capacitor.Both the equivalent circuits and electromagnetic simulations are used for analyzing.By vertically stacking different capacitors,the parasitic effects between capacitors and grounds can be obviously reduced.Meanwhile,less transmission lines are used because the adjacent capacitors share the same electrode.Both electromagnetic simulations and equivalent circuits show that the proposed capacitor outperforms the one designed with the technique from reference.These features make the proposed capacitor very suitable for multilayered filters design.Meanwhile,it can be used as a block in multilayered filters design.Based on the proposed capacitor,more structures are discussed.With the proposed capacitor,a novel multilayered filter is designed,fabricated,and measured.Compared with the filter from reference,the proposed filter shows better out-of-band suppression.2.The multilayered LC resonator is studied and two features are found to be very useful in multilayered filters design.(1)The frequency response of LC resonator is mainly determined by the product of capacitor and inductor.As long as the product of inductor and capacitor is kept unchanged,the response is almost not influenced by the change of inductor and capacitor.(2)According to the equivalent circuit of multilayered LC resonator,it is found that the parasitic components can be regarded as a part of the desired inductor and capacitor.This feature means that the parasitic effects can be made use of.As a result,the dimensions of multilayered components can be reduced.Based on these two features,a design technique for multilayered LC resonator is proposed and verified with an elliptic filter,which is composed of four LC resonators.A new multilayered elliptic filter is designed with the proposed technique and several experimental prototypes are fabricated.Because the influences of parasitic effects are reduced,the measured responses agree very well with the desired responses.No parasitic resonance is observed at second and third harmonic frequency.These results show the effectiveness of the proposed technique.3.The cascade of the second filters is studied.By introducing an additional impedance matching network,the matching can be improved.Meanwhile,the impedance matching network can introduce one or more controllable transmission zero(s).The equations for the impedance matching network are given.Several impedances matching networks are discussed and verified.A cascaded filter with five controllable transmission zeros is designed by cascading two second-order filters.The series LC resonator is used as the impedance matching network.Corresponding multilayered filter is designed and measured.The measured result shows that the out-of-band suppression at the second harmonic frequency is better than 50 d B while that at the third harmonic frequency is better than 40 d B.4.A fast design technique for multilayered filters is proposed,which shows two advantages.(1)It is based on the relationship between port impedance,component values,and the S-parameter.A ratio parameter is introduced,which represents the ratio of multilayered component values and theoretical component values.With this parameter,it is possible to reduce the number of design variables and simplify the design procedure.(2)By simply changing the port impedance in simulations,it is possible to fast preview the frequency responses of the filter when all component values are changed.The value of error variable can be estimated by the best frequency response and corresponding port impedance.Then,multilayered components can be tuned with a clear target.The flowchart of proposed technique is given and compared with the technique form references.Mathematical induction is used to prove the proposed technique.A filter from reference and an elliptic filter are used as examples to show the whole design procedures.It can be observed from the examples that,with the proposed technique,the number of simulations is obviously reduced and the design procedure for filters can be obviously simplified.