Miniaturization Design And Key Technology Research Of RF/Microwave Filter

Due to the rapid development of communication technology,the filter becomes more and more important in microwave/millimeter wave system.Its function is to ensure the transmission of useful signals and block interference signals.In the emerging wireless communication system,such as 5G communication,all kinds of design requirements of filters are challenged unprecedentedly.High performance,miniaturization and low cost have become the basic requirements of current filter design.This paper takes miniaturized design as the core,a series of new filter structures are proposed,which are combined with transversal signal-interference technology and resonator self-coupling enhancement technology to improve the performance of the filter.The main contents of this thesis are as follows:1.A tripple-mode resonator and two four-mode resonator are proposed,and three ultra-wideband bandpass filters are formed by three parallel coupled-lines.The open-circuited and short-circuited stubs are loaded at the input/output feedline of these three filters to improve the selectivity and out-of-band suppression.The bandwidths of the proposed UWB bandoass filters with the return loss of-10dB can cover from3.1-10.6GHz.Meanwhile,a notch is introduced by the slot in the feedline for the third UWB filter.The position of the notch can be adjusted arbitrarily by adjusting the size of the slot.The 10-dB fractional bandwdith of the notched band with the centre frequency of 5.85GHz is about 2.01%.2.A novel resonator is constructed by a half-wavelength step-impedance resonator loaded two pairs of short-circuited stubs.Analyze resonance characteristics and generation mechanism of transmission zeros of the resonator,and then couple the two pairs of short-circuited stubs respectively to realize the miniaturization design of the filter.Two additional transmission paths are introduced by using the transverse signal interference technique to generate a transmission zero at the lower frequency of the passband to improve the filter selectivity.This filter has the compact size of 0.0955?_g~2with the centre frequency of 5GHz.The frequency range can cover from 3.4-6.5GHz.It is very suitable for satellite C-band television broadcast and small satellite ground station.3.A short circuit at one end of the parallel coupled transmission line and an open circuit at the other end bandpass response are used to construct the differential mode bandpass response of the three-mode resonator.The full-bandstop response of the open-circuit at both ends of the parallel coupled transmission line is used to construct the common mode suppression of the three-mode resonator.By introducing the coupling of source and load,a transmission zero is introduced to improve the selectivity and out-of-band suppression of the filter.4.A new type of quarter-wavelength step-impedance resonator is presented.The fundamental mode and the first order mode are analyzed.Then the short-circuited stub is loaded at the zero-voltage point of the first order mode for tuning the main mode,and the open-circuited stubs is loaded at the ventral-voltage point of the first order mode for tuning the first order mode.Finally,a closely proimate dual-band bandpass filter is constructed by means of reverse coupling.The wideband stopband suppression of the filter is realized by loading open stubs at the feedline.The centre frequencies of the proposed dual-band BPF are 1.24 and 1.53GHz,respectively while the 3dB-fractional bandwidths are 9.26%and 9.92%,respectively.This filter can be applied to the GPS application,whoes operate frequencies are 1227.60±1.023MHz?1575.42±1.023MHz.5.A lowpass filter with a pair of open-circuited parallel coupled line is proposed.The transmission characteristics of the lowpass filter are analyzed by using a lossless transmission line model and LC lumped circuit model.Then a tunable filter with a tuning range of up to 60.6%is constructed by loading a varactor diode at the end of the open–circuited stubs of the central symmetry plane.A bandstop filter with three transmission zeors is constructed by coupling a pair of open-circuited stubs with the main transmission path.The transmission characteristics of the bandstop filter are analyzed and three transmission zeros are extracted.Finally,the bandstop suppression depth of the band stop filter obtained is more than-35dB.6.Two millimeter-wave bandpass filters based on step impedance resonators are designed by using the 0.13-?m(Bi)-CMOS SiGe technology.The resonant characteristics of the resonator is analyzed by using LC lumped circuit model.Two transmission zeroes can be created By introducing the capacitance coupling and inductance coupling.Finally,the lumped circuit model is transformed into an on-chip EM filter structure.The first filter is miniaturized by extending the high-impedance line of the folded step impedance resonator with the centre frequency of 44.75GHz.The second filter spirals the high impedance line of the step impedance resonator with the centre frequency of 27.5GHz.Using the self-coupling inductance enhancement technology to move the central frequency of the filter to the low frequency to realize the miniaturization design of the filter.These two filters have potential application values in the future development of 5G millimeter-wave circuits.