| The microstrip filter is a very important component of modern communication system.It is used to select useful signals and suppress interference and spurious signals.Modern electronic communication technology has been developing rapidly.The theoretical research and design of the microstrip filter are keeping pace with the times.In recent years,the research of miniaturized multiband microstrip filters has become a research hotspot,which can meet the requirements of the multi-band and integration of communication systems,improve the utilization of spectrum resources,and reduce the size,cost and power consumption.In this paper,my own research work has been carried out,which consists of how to design and implement the muti-band and miniature microstrip filters based on the theory of the generalized Chebyshew filters,multimode stepped impedance resonators(SIRs)and hybrid cross coupling technogy.The main contents and innovation points of this dissertation are listed as follows:1.A quad-band filter frequency transformation comprehensive theory based on the synthesis method of generalized Chebyshev filter function is presented,which builds on the detailed analysis of the comprehensive method of generalized Chebyshev filter function and coupling matrix of generalized Chebyshev filter and dual-band and tri-band filters'frequency transformation synthesis method.With the specific examples,the simulation curves of the dual-band and tri-band filters'transfer functions are given.The correctness of the theory and method is verified,and the comprehensive methods and steps of the frequency transformation of the multipass filter are summarized.2.A compact tri-band bandpass filter with high selectivity using novel modified?/4 wavelength tri-mode resonators and electromagnetic coupling technology is proposed.A 1.90/3.50/5.75 GHz tri-band experimental bandpass filter has been designed and fabricated to demonstrate the proposed method.Firstly,the analysis of the novel tri-mode modified?/4 stepped-impedance resonator with a closed rectangular loop and two loaded open stubs by selecting a resonant feeding position of input and output ports and stubs characteristic impedance,and secondly,selecting a resonable layout for the capacitive coupling and inductive coupling side length,a pair of transmission zeros are generated at the lower and upper stopband of each passband.The measured results show a compact,high selectivity and excellent band-to-band isolation tri-band experimental bandpass filter operated at 1.90/3.50/5.75 GHz;with fractional bandwidth of 6.1/6.7/7.8%;with six finite transmission zeros near the passbands located at 1.65/2.64/3.06/3.95/5.40/6.16 GHz,respectively.The circuit only occupies0.04?_g×0.07?_g,where?_g is the guided wavelength at the center frequency of the first passband.3.Based on the theoretical analysis of the odd-even mode resonant characteristics of the dual-section stepped impedance resonators and tri-section T shaped stubs loaded stepped impedance resonators,the relationships among the multi-band resonator center frequencies,the characteristic impedance ratios,the electric length ratios of these stubs are analyzed and explained rigorously and quantitatively.The application of capacitive coupling and 0 degree feed technology,a pair of tri-section T-shaped stubs loaded stepped impedance resonators are folded into dual split rings to cascade by capacitive coupling.A quad-band fiters is designed successfully,which operated at 1.3/2.2/3.3/4.5GHz;with 3dB fractional bandwidth of 5.2/3.63/4.2/9.6%;with seven finite transmission zeros near the passbands.The circuit only occupies0.32?_g×0.23?_g,where?_g is the guided wavelength at the center frequency of the first passband.The center frequencies of the quad-band filter can be adjusted flexibly by changing the characteristic impedance ratio and electric length ratio,and improved the filter selectivity and out-band rejection by introducing into multiple transmission zeros through electromagnetic coupling.4.An improved stepped impedance resonator and cross coupled technology are proposed to design narrowband bandpass filters with wide stopband characteristics and a T-shaped stubs loaded SIRs and cross coupled technology are proposed to design UWB filters.In order to make the design filter more miniaturized,the multi-layer planar microstrip circuits are applied.A compact third-order bandpass filter with high-frequency selectivity using novel dual-layer stepped-impedance resonators is presented.In the proposed novel dual-layer stepped-impedance resonator,the conventional low-impedance stub of the stepped-impedance resonator is replaced by a closed rectangular loop.The high-impedance stub is embedded in the closed loop for more compact structure.Multiple transmission zeros are introduced near the passband to improve the frequency selectivity and stopband performance.The proposed filter was designed,simulated,and fabricated to verify the validity of the proposed method.The measured results show that the center frequency is 2.83 GHz with a fractional bandwidth of 9.32%,and five transmission zeros were introduced near the passband.The circuit only occupies0.11?_g×0.08?_g,where?_g is the guided wavelength at the center frequency of the passband.A miniaturized multi-layered ultra-wideband bandpass(UWB)filter(BPF)Based on T-shaped short stub using the multilayer circuit board technology is proposed.The proposed filter consists of a T-shaped short stub and a pair of parallel transmission lines.Owing to the multi-path effect,multiple transmission zeros can be realized near the passband for enhanced selectivity.A wide-band filter from3.59 GHz to 8.21 GHz is designed,fabricated and measured.The measured results show that the center frequency is 6 GHz with a fractional bandwidth(FBW)of 74.8%.Three transmission zeros were introduced near the passband.The circuit size is only6.5 mm?3.4 mm.5.The design idea of the multi-band filter is introduced into the design of matching network of RF power amplifier,using parallel T–shaped open circuit and short-circuit stubs stepped impedance resonator to form dual-band resonance effect.The input and output resistance of single transistor RF power amplifier CGH40010F are complex impedance,to realize the impedance maching between the complex impedance and the50ohm real impdance using T-shaped open or shot adjusting stubs.A dual-band power amplifier operated at 0.9/2.6 GHz is designed successfully and the dual frequency characteristic of the power amplifier is good in selection performance and out of band suppression,compact in structure and small in size only 4.5 cm?3.2 cm. |
PDF Full Text Request