The Study Of Novel Microwave Waveguide Bandpass Filter On 3D Printing

Filters play important roles in many RF/microwave applications.They are used to separate or combine different frequencies.The electromagnetic spectrum is limited and has to be shared;filters are used to select or confine the RF/microwave signals within assigned spectral limits.Emerging applications,such as wireless communications,continue to challenge RF/microwave filters with ever more stringent requirements —higher performance,more functionalities such as tunable or reconfigurable,smaller size,lighter weight,and lower cost.Depending on the requirements and specifications,RF/microwave filters may be designed as lumped element or distributed element circuits,they may be realized in various transmission-line structures,such as waveguide,coaxial line,coplanar waveguide(CPW),slotline,and microstrip.BandPass Filter(BPF)is the essential components of all RF communication systems.Bandpass Filter(BPF)passes the frequency in pass band and provides attenuation for frequencies which lie outside pass band.Thus Bandpass Filter(BPF)acts as frequency selective circuit.Over the past two decades,there has been an increasing interest in the application of 3D printing(also known as additive manufacturing)to manufacture components with high geometrical complexity.Some of the 3D printing techniques have attracted a significant commercial interest and they are fused deposition modeling(FDM),stereolithography apparatus(SLA),and selective laser sintering(SLS).3D printing has offered a time and cost efficient pathway for fabricating geometrically complex microwave/millimeter-wave waveguide devices to adapt to the ever-increasing demands for multi-functional radio communication systems.In contrary to the conventional waveguide components made from metallic structural materials such as copper,brass,and aluminum using computer numerical control milling technology,these 3D printed parts are directly shaped,exhibiting much better flexibility in their structural designs with less need of either post fabrication assembly or tuning.With the evolution of commercial 3D printers in a scale from desktop to industrial level,many printing materials have been developed,such as photosensitive resins,engineering plastics,metal/alloy powders,and biopolymers.As the main process of this thesis,the advantages and disadvantages of 3D printing technology in the microwave/millimeter wave field and the difficulties that need to beovercome are discussed.Several band-pass filters are designed based on 3D printing technology.First of all,a set of design schemes is summarized from the principle of the filter,namely find n resonant cavities of the same physical structure,and then arrange them according to the appropriate topological structure.Based on this,a Ku-band interdigital band-pass filter is designed to analyze the out-of-band rejection of the bandpass filter from the perspective of transmission zero.Afterwards,three bandpass filters based on different topological structures of spherical resonators were designed.By comparing the influence of different topological structures on the out-of-band suppression of the band-pass filter,the out-of-band suppression of the band-pass filter is analyzed from the perspective of high-order modes.Finally,compared with other shapes,the high-Q characteristics of spherical resonators are discussed,thus embodying the advantages of 3D printing.