Design Of UWB Filter With Notch Bands

The research scope of this thesis is ultra-wideband filter with notched bands.The ultra-wideband technology research history can be traced back to the middle of the last century,but since 2002,the federal communications commission(FCC)formulate and publish the relevant technical standards,based on ultra-wideband communications because of its high rate of data communication,low transmission power,carrying large amount of information,such technical advantages make it received extensive attention of the academic circles and engineering,the importance of ultra-wideband filter for UWB communication system is self-evident,but in practical application,due to the ultra-wideband and mobile communication spectrum overlapping more and more serious,the signal interference problems stand out,also,need to be addressed,stopband,miniaturization,filter frequency selective flexibility,it force the filter designers to put forward higher requirements.Based on this situation,this paper designed three ultra-wideband microstrip filters(single notched band,double notched bands,notched bands can be switched).The main work in this thesis is:1.First,the multi-mode resonance theory is used to construct ultra-wideband filter based on Rogers5880 substrate.Through the analysis of "Gong" word resonant characteristics of resonator and the transmission zero position distribution,introduced the central loading side,based on the drawing of resonance characteristics choose to meet the need of admittance ratio,make the passband into three resonant modes resonance point location balanced distribution,thereby gaining flat passband,through CAD auxiliary tool calculates the impedance of the microstrip line,width and other parameters,and then a preliminary model is established in the software HFSS,by handing in refers to the back behind the open defect to enhance its coupling,satisfied passband range,low insertion loss of the UWB filter,and then,in the input line introduction of asymmetric coupling transmission path difference,produce WLAN(5.15 GHz to 5.15 GHz)spectrum of stopband,designed a single notch filter,finally based on the design of single notch filter,by grooving on T-shaped microstrip patch,makes resonance produced here a second signal X band(7.9 GHz to 7.9 GHz)spectrum of stopband,another double notch filter is designed.Finally,the single notch filter is tested.2.The design method of short circuit stubs load by transmission line was first used,Then,ultra-wideband filter model was constructed,the original design size is larger,so it is folded to reduce the size.Then the E shaped dual-mode resonator is designed,coupled with each other to produce doubled notched bands,on the basis of this design is: using PIN diode acts as a switch.The DC bias circuit is designed in the interior space of the filter,The reconfigurable filter designed through this processing,testing by incorporating conductive silver pulp,removaling of conductive silver pulp,analog switch diode on-off,through this,controling of the resonator working mode.When the switch is off,the filter stopband appears in the X-band,and when the switch is on,another WLAN band notch is presented,thus the reconfigurable ultra-wideband filter is realized.