Research On Multi-band And Wideband Circuit-reuse And Absorptive Microwave Circuits And Components

In view of development requirements of multi-mode,multi-frequency,wideband and high anti-interference performance of wireless communication systems,this thesis proposes a set of microwave circuits and components with circuit-reuse,functional-integration and absorption function expansion,and establishes a set of basic theories of microwave circuits.In terms of design concept,a novel multi-functional circuit-reuse dual-band coupler is proposed.In the aspect of functional-integration,the power divider and coupler with wideband filtering and absorption performance are proposed.In terms of performance improvement,a series of high-performance wideband and multi-band absorptive filters are designed to solve the key technical problems of absorption components design.In terms of practical application,a receiver equipped with absorptive filters is designed to verify the performance of absorptive filters.The work of this thesis includes the following aspects:1.A novel multi-functional dual-band coupler with circuit reuse,and the wideband filtering trans-directional(TRD)coupler and power divider with input-reflectionless performance:(1)The TRD coupler with wideband filtering and input reflectionless performance is designed,which has the advantages of wideband filtering performance and input reflectionless,as well as the function of DC blocking and miniaturized circuit size.Note that the input-reflectionless performance can be realized by the signal interference of reflection signals;(2)A novel multi-functional dual-band coupler with reuse of low-frequency TRD and high-frequency contra-directional(CTD)functions is proposed.Tight coupling is realized by loading capacitors between coupled-lines and two ports.The dual-band coupler can realize TRD coupler function and CTD coupler function at low frequency and high frequency respectively,thus realizing circuit function multiplexing and port function expansion,which greatly expands the application scenario of traditional four-port directional couplers;(3)A wide-band filtering power divider with all-frequency absorption and deep out-of-band suppression is designed.The relative bandwidth is 62.3%.The stopband suppression can reach 20 dB(2.64f0),and the all-band output isolation is better than 14.3 dB.By adding three simple absorptive stubs,the all-frequency absorptive performance is realized,which greatly reduces the reflected noise of the system.2.Single-band high-selectivity balanced absorptive bandpass filter:(1)Absorptive balanced bandpass filter with all-band CM suppression and in-band CM noise absorption performance is designed.The coupled-line resonator loaded with short-circuit branches can achieve wideband filtering performance with the relative bandwidth of 79.43%.By adding a grounded resistor and a quarter-wavelength branch in the central symmetry plane,all-band CM noise suppression and in-band absorption performance can be realized.The CM noise suppression is greater than 15 dB(0-8 GHz),The CM noise absorption is greater than 10 dB(2.41-4.63 GHz),and the absorption rate is greater than 90%(2.51-4.6 GHz);(2)The balanced bandpass filter with differential-mode(DM)and CM input-/two-port reflectionless performance is innovatively proposed.The detailed design theory and method is given.By adding absorptive branches at ends of the coupled ring resonator and two ports,wideband DM filtering performance,DM stopband noise reflectionless performance,broadband CM reflectionless performance,and all-band CM noise suppression are realized.The DM out-of-band noise absorption is greater than 10 dB(0-2.89f0).The CM noise suppression is greater than 14.5 dB(0-8 GHz).The CM noise absorption is greater than 10 dB(0-3.54f0),and the absorption rate is greater than 90%(0-3.8f0);(3)A series of input-/two-port DM and CM reflectionless balanced bandpass filters integrated with high-order filtering response are designed.Controllable absorption network and TZ control network are loaded at ends of the coupled ring resonator,which can achieve arbitrary high-order filtering response,and independently controllable number of TZs for the input-reflectionless type.In addition,the in-band flatness is optimized as the filtering order increases,and the stopband suppression can be improved by increasing TZs.Besides,the level of DM and CM reflectionless performance can be flexibly adjusted.3.Dual-band high-selectivity single-ended and balanced absorptive bandpass filters:(1)Novel complementary duplex structure is proposed to realize dual-band bandpass filter with input-/two-port reflectionless performance.The realization mechanism of absorption performance is discussed in detail,and a complete design method is proposed.The dual-band absorptive bandpass filter can realize in-band energy transmission in two operation bands,with the small in-band insertion loss(0.7 dB&1.35 dB).The reflected stopband signals can be absorbed by the complementary dual-band bandstop absorptive branches at all frequencies;(2)A high-selectivity dual-band balanced bandpass filter with broadband common-mode rejection and absorption performance is designed and implemented.The dual-band balanced bandpass filter is composed of cascaded coupled-lines and loaded stubs with controllable bandwidth and transmission zeros(TZs).Note that the balanced dual-band bandpass filter can realize all-band common-mode(CM)suppression and broadband CM noise absorption performance.The CM noise suppression is greater than 28 dB(0-2.69f0),the CM noise absorption is greater than 10 dB(0-2.45f0),and the CM noise absorption rate is greater than 90%(0-2.91f0),which can greatly improve the elimination of CM noise.4.A high-selectivity bandpass filter and a two-port reflectionless bandpass filter are proposed,and a superheterodyne receiver operating at 3.5 GHz is constructed to verify the impact of reflectionless bandpass filters on the performance of nonlinear devices.The influence of RF and IF reflectionless bandpass filters are tested respectively.The measured results indicate that the reflectionless bandpass filter can effectively reduce the reflected signals.Thus,the reflected signals at the input port of the mixer are easier to predict,and the frequency conversion loss of the mixer is close to its own performance.By carrying a reflectionless bandpass filter,the useless mixing signal and spurious interference in the system are greatly reduced,and the working performance of nonlinear components in the system is optimized.Finally,we test and analyze the overall performance of the receiver.