The Research On Key Technologies Of Microwave Millimeter Wave Filter And Its Module

With the rapid development of microwave and millimeter wave technology,the requirements for miniaturization,planarization and multi-functions are put forward to RF front-end system.Being as the indispensable component of microwave module,passive filter plays an important role in the design of the RF front-end system.Sometimes,its configuration and performance directly determines the structure and index of whole module.With appearance of the novel semi-conductor and PCB technique,microwave-millimeter wave filter and its module achieve a rapid development.The front-end system in microwave-millimeter wave field mainly contains T/R module,transmitting front end,receiving front end,mixing module and so on.With the development of the semi-conductor technique,multichip modules technology grows mature gradually.For the hot and difficult issues of the microwave-millimeter wave device and module today,three novel compact filters are designed with the realization of the planarization and miniaturization for millimeter wave filters and modules.The main contents can be summarized as below.1,Synthesis and application of the microstrip coupled filter:principles of a common bandpass filter with coupling structure are analyzed in the dissertation,with determination of the relation between the coupling coefficient and resonator size through a curve fitting method.And,the connection between S parameters and coupling matrixes is built through ADS equivalent model.Hence,knowing the indexes of filters,initial sizes of a filter can be obtained directly.Besides,the involved filter is applied in two different engineering cases.First,a novel multiplication module which satisfies the requirement for the planarization is designed based on interdigital and parallel coupling structures.Second,on the basis of the combline coupling form,a novel tunable bandpass filter is designed.The center frequency can be adjusted by the capacitor value of varactors,during which process the fractional bandwidth?FBW?or absolute bandwidth?ABW?can be fixed.These works has been sent to Journal of Electromagnetic Waves and Applications and are under review now.2,The design of a novel and compact series of bandpass filters:the gradually broadening of bandwidth of filter will result in too small a size of coupled line width and gap which is difficult to be processed with PCB technology sometimes.For this problem,a novel and compact series of bandpass filter is designed.a)The novel wideband filter design based on Stepped Impedance Resonator:Two transmission zeros locating at the passband edges which can be tuned by the characteristic impedance ratio of SIR are applied to improve sharp cut-off characteristics.The structure design is flexible due to the fact that it can be realized not only by a symmetrical coupled resonator,but also by an asymmetric coupled resonator.Two filters are fabricated based on two coupling structures with a good simulation and measurement.These works has been published in Journal of Electromagnetic Waves and Applications.b)The novel wideband filter design based on signal-interaction concept:a novel filter structure employing transversal signal interaction concept is presented.Two parallel transmission paths are applied to transmit signals.When the signal arriving at output port is out of phase,a stopband is formed because of out-of-phase cancellation.And a passband appears,when signal is in phase.When two parallel paths are substituted with two common transmission lines,the size of filter is too big,although the wideband response can be obtained.So,a novel 180°inverter is introduced to reduce the size,which can be realized by the structure of the Double-sided parallel strip line?DSPSL?and the microstrip line.Finally,a good measurement result is obtained.These works has been published in Journal of Electromagnetic Waves and Applications and Applied of Computational Electromagnetic Society.c)The wideband filter design and application based T shaped stub:a novel structure of filters is built on the basis of the substitution of the traditional transmission line with a T-shaped structure with an open-circuited stub.The adjustment of the position of the new produced transmission zero through the length of the open-circuited stub results in several filters of different performance.When the transmission zero is located at 4f₀,the upper stopband will be broadened.The location of the transmission zero at 4f₀ leads to the expansion of the stopband,while the location of the transmission zero at passband edge leads to the improvement of the rejection performance.A new active multiplier is designed based on the employment of the novel filter as the part of its output matching circuit.In this case,not only the size is reduced,also the first,third and fourth harmonics are suppressed.Besides,the novel filter is applied to a multiplication link circuit,in which each frequency doubler is followed by a newly designed filter.These works has been sent to Applied of Computational Electromagnetic Society and are agreed to publish.3,The design of a novel millimeter wave mixing module:A novel wideband up-converter module applied in millimeter wave is proposed.Due to the appearance of the multiplication and mixing in the module,the output spectrum contains not only useful signals,but also variable spurious and harmonics.To inhibit the interference signals,the variable kinds of filters and switching filtering components of different properties are integrated in the module,containing the planar wideband filter after multiplication,switching filtering module based on waveguide structure after mixing and compensation filter and lowpass filter after amplification.Finally,to reduce the size of module to a certain extent without deteriorating indexes of the mixing module,the thin film filter is designed whose size is only the half of that of waveguide filters.Finally,its performance is tested through experiment.These works has been published in 2016 international Radar conference.