Research And Design Of Reconfigurable Bandpass Filter Based On Branch Loading

The rapid development of wireless communication technology in the 21 st century has led to the emergence of various communication protocols with obvious advantages and widespread applications,which has also promoted the rapid development of the field of radio frequency filters.As a key technical direction in filter research,reconfigurability has many highlights,such as improving frequency band compatibility,refining spectrum resources,and improving utilization,making filters based on this technology able to flexibly cope with complex communication environments.This thesis mainly focuses on the branch loaded reconfigurable microstrip passband filter based on varactor diode.With the idea of transition from single passband filter design to multi passband to achieve multi-mode reconfiguration.A simulation experiment was built using software,and ultimately,the physical processing and testing were carried out.This thesis mainly implements three reconstructed filters:1.Bandwidth reconfigurable filter based on axisymmetric structure: Using a single open-ring resonator as the basic structure,symmetrical open-circuited branches are loaded within the ring to introduce transmission zeros.By introducing capacitor tubes between the open-circuited branches to change the coupling strength,non-continuous reconstruction of the single-passband absolute bandwidth varies within the range of 90-380 MHz is achieved.And the relative bandwidth reconstruction amplitude is between 4.1% and 10.7%.The bandwidth reconstruction effect is significant,making it suitable for multi-band communication.2.Bandwidth reconfigurable filter based on centrosymmetric structure: Two electrically-coupled open-ring resonators are used as the basic structure,with single-section open-circuited transmission lines and fork-like structures loaded at the center of the rings to enhance coupling.A single varactor diode is loaded outside the ring axis to achieve 82.4%-117.6% continuous absolute bandwidth reconfiguration,with a tuning sensitivity of 5 MHz/0.1 pF,enabling high-precision adjustment suitable for applications that require fine frequency selection.3.Bandwidth and transmission-zero reconfigurable tri-band filter based on SIR branch loading:Using SIR structure as the basis for resonator construction,the odd-even mode circuit is changed by branch loading.By loading varactor diodes at different impedance levels of the open-loop resonator,a single module with dual-mode performance can be innovatively reconfigured.The first mode can reconfigure the position of independent transmission zeros,which can flexibly move in the range of5-10 GHz,achieve independent suppression effect of the tri-band,and change the number and filtering mode of the passbands.The second mode can change the bandwidth of the high-frequency passband,with a range of 78.4%-121.6%,and move the transmission-zero to suppress the lowfrequency passband and improve the filtering environment.