Microwave Multi-band And Wideband Filter Design Based On DGS

With the continuous development of wireless communication technology,WLAN,Zigbee,Bluetooth,GSM,WCDMA,TD-LTE,LTE-FDD and other wireless communications services were derived.As a result,filter technology has been greatly promoted.In order to improve the utilization and the compatibility of frequency band,a large number of scholars have studied the multi band and broadband filters.This paper mainly focuses on the design of microwave multi band and broadband filter.The multiband and wide band filters with different frequency bands are designed,which are based on microstrip lines,defected ground structure(DGS),defected microstrip structure,multi-mode resonator and stepped impedance resonator.The main works are as following: firstly,analysis the basic theory of microstrip line,defected ground structure,stepped impedance shunt stub(SISS),defected microstrip structure(DMS),defected microstrip based on stepped impedance shunt stub structure(S-DMS).Then two broadband filters and three multi-band bandpass filters were designed based on these theories.Two broadband filters:(1)A wideband filter was designed using DGS and open loop coupling.The bandwidth of the wideband filter is 4.2 GHz ~ 11.5 GHz,the relative bandwidth is 93%,and the insertion loss is less than 0.54 dB.It is proud of its stopband rejection and low insertion loss in passband.(2)Using the step impedance resonator,combined with the DMS designed a broadband filter with excellent passband.The filter has a 3 dB bandwidth of 9.1 GHz,a relative bandwidth of 130%,an in-band insertion loss less than 0.6 dB,with an inner 11 S less than-10 dB.Three improved multi-band bandpass filters:(1)The S-DMS was used to design a harmonic suppression dual band bandpass filter.The center frequency is 3.5 GHz,8.5 GHz,respectively,insertion loss of 0.45 dB,2.7 dB,respectively,3 dB bandwidth of 550 MHz,260 MHz,respectively,with out-off-band maximum suppression less than-40 dB.(2)A compact three band bandpass filter with a rectangular resonator was designed Using a C-DGS.The size of the filter is 16 mm × 12 mm × 0.8 mm and the center frequency is 0.1 GHz,6.2 GHz,10.9 GHz,respectively,the insertion loss in the passband is-0.5 dB,-0.8 dB,-2.8 dB,respectively(3)A dual band bandpass filter with wide depth stopband was designed by Using the irregular DGS.The passband center frequency is 3.75 GHz,5.55 GHz,the insertion loss in the passband is 0.23 dB,0.31 dB.The low-frequency stopband attenuation is greater than 58 dB.