| In the past one hundred years,wireless technology has been developed rapidly.Since Maxwell integrated the experimental works of Coulomb,Ampere,Faraday,Hertz,and Tesla,he put forward Maxwell equations innovatively,relatively complete electromagnetic field theory have been built.Radio and satellite phone were also proposed,application of wireless communication in industry developed steadily.During World War II,radio application for the military field,and the wireless communication technology has been greatly improved on a short time.Since then,after several generations of development,communication industry developed from analogous signals systems of relatively small users and Low transmission rate to 2.5G and 3G Communication era,Cellular communication,array antenna,Cross-Polarization and other communication technologies have been developed in this period.Multi-band communication began to embark on the stage of history.At this time the wireless communication performance has been greatly improved compared to the previous generation.Communication systems are extraordinary complex such as GSM,CDMA,etc.These complex communication systems need to coexist,thus multi-band communication system is an inevitable trend.In order to reduce costs and space,Multi-band has become the mainstream at this stage.4G communication based on 3G and upcoming 5G communications are even especially true for this.Shannon theorem reveals relationship between upper bound on the rate of information transmission in the channel,noise-signal ratio and bandwidth.The wider the channel bandwidth,the faster the information transmission rate is.With the continuous improvement on people's living standards,people's demand for quality of life continues to improve,the requirements of communication capacity and information transmission speed are also increasing.Broadband technology is an effective solution to this trend.This paper proceed with the multi-band and wideband communications and other multi-mode communication RF front-end,studies on multi-band and wideband bandpass filter.The design of multimode resonator is the only way to construct multi band communication system.In the third chapter,through increasing of perturbation in the stub of resonator,improve the traditional stub loaded resonator to obtain an asymistry Y-shaped resonator with flexible control of three mode characteristics.A three pass band pass filter is constructed by using the asymmetric Y-shaped resonator with a class of 180 degree tap feed-in class – two.After deformation of resonator,the open-loaded stub resonator is closely related to the three frequency points.Thus the physical length of the stubs can be used to adjust the coupling of each pass band.In this way,separately controllable passbands achieved.We propose a novelwideband filter structure,which can be used to design a wideband filter with a bandwidth of66%.Finally,a single stage superconductive broadband filter is fabricated,which has a very low insertion loss,a flat group delay and other excellent properties of belt.According to the requirements of the wideband system,multi-loop resonator with low coupling coefficient and left-right hand composite transmission wire were used to design two superconductive notch filter with steep roll-off.We analysis and study the radiation loss of microstrip circuit,and improving the geometry of the resonator to reduce radiation loss.In this way,improved hairpin resonator is used to design a high quality factor filtering-antenna. |
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