Research On Multi-functional Microwave Passive Devices And Its Application In Antenna Feeding Systems

In recent years,with the explosive growth of data services and mobile communication technology,spectrum resources are becoming increasingly tight,which promotes the information transmission to be faster,more reliable and more flexible.Under this situation,the flexible application of multi-band,low-loss and multi-functional RF devices and systems has become the key of wireless communication technology.This thesis focuses on multi-functional microwave devices,and deeply explores their application in microwave signal processing system and wireless communication system,so as to integrate multiple functions and optimized performances in analog signal processing system and multi beam antenna array.There include two aspects of work.The first part aims to design and fabricate microwave devices with multi-function integration to realize such performances as broadband,low loss,miniaturization,filtering characteristics,flexible phase characteristics and so on.In the second part,the proposed microwave devices have been applied to several RF systems for theoretical verification and functional extension.In terms of signal processing,real-time Fourier and inverse Fourier transform systems with simplified topology are designed and analysised.While for communication and transmission,a variety of Butler matrices with flexible phase differences and multi-beam antenna arrays with beam expansion have been studied and processed.The work of this thesis can be summarized as follows:(1)Multi-Functional couplers with flexible phase characteristicsTunable couplers with dynamic elements loaded and flexible phase differences are proposed.The calculation formulas of transmission matrix and scattering matrix of coupler are deducted by even-and odd-mode analysis method,Design schemes and simulation characteristics of the tunable coupler are analyzed under different sets of frequencies and phase differences.Two kinds of tunable couplers are fabricated and measured,of which the working frequency can be tuned in the range of 1.88 to 2.2 GHz,and the phase differences vary arbitrarily within 52.6°～127.4°.Broadband/narrowband couplers with phase compensation are proposed.The relationship between the slope of phase difference and the circuit parameters of coupler is explored.Two kinds of coupler working at 2.2 GHz and 1.95 GHz have been fabricated respectively,possessing the bandwidths of 44.5%and 25.6%.Those couplers show the phase-difference slope of 32.4°/GHz and 88.8°/GHz.Measurement results show that the proposed coupler has smooth phase difference and accurate phase compensation,which brings greater flexibility to the application of RF front end.(2)Wideband phase shifters with flexible phase characteristicsA generalized broadband phase shifter based on coupled-line structure is proposed,which has stepped phase shift within the working frequency band.The theoretical value of its phase shift can be arbitrarily designed in the range of 0°～180°.Based on the theory of dual-band phase shifter,the phase control and reference units are designed and analyzed respectively.Four kinds of this stepped phase shifters have been fabricated,with the center frequencies of 2.2 GHz and relative bandwidth of 44%.Measurement results reveal that the phase shifting network has good transmission performance,with the phase difference deviation less than±12°.This structure brings about great convenience to wireless communication system,especially for phased array antenna and multi-beam array.A novel real-time Fourier and inverse Fourier transforming system is proposed,mapping the spectrum of the input signal into a waveform in time domain.The analytic relationship between the output waveform and the spectrum of the input signal is given.A section of non-uniform coupled-line structure is adopted to design the dispersion phase shifter.The relationship between odd and even mode impedance at different positions in the propagation direction and the slope of group delay is calculated for the non-uniform coupled line,and different parameter optimization schemes are discussed.For experimental demonstration,a real-time(inverse)Fourier transforming system operating at 6 GHz is build,with working band of 4～8 GHz and group delay slope of-0.5 ns/GHz.Two kinds of Fourier transformations are integrated within one system for the first time,reducing the number of dispersion phasers and filtering devices.This configuration possesses the characteristic of compact structure,simple design procedure,and good performance.This part of work is published in AEU International Journal of Electronics and Communications.(3)Wideband filtering coupler with arbitrary power division ratio based on Patterned Substrate Integrated Suspended LineA broadband filter-integrated coupler with arbitrary power division ratio is based on the substrate integrated suspended line structure.The transmission line is suspended in the air cavity by means of the multi-layer circuit construction,and the dielectric plate distributed in the middle layer is hollowed around the main circuit,greatly reducing the radiation loss of the electromagnetic wave.For further expansion of the coupler’s function,two wideband filtering couplers operating at different operating frequencies with equal/unequal power divisions are designed.The effect of circuit parameters on power division ratio are analyzed in detail,and different design cases are simulated and compared.A coupler with working frequency of 1.66 GHz and power division of 7 dB is fabricated and measured.The relative bandwidth is about 49.4%,with S11 less than-15 dB and loss less than 1dB.The coupler structure has the advantages of broadband,filter integration,arbitrary power division ratio,low loss,self-packaged and compact structure,which further extends the performance of the coupler.This part of work is published in Applied Computational Electronics Society Journal.(4)Butler matrix with flexible phase differences and multi-beam antenna array with beam expansionA wideband Butler matrix with flexible phase difference is proposed.The relationship between its phase response and circuit parameters is deduced,and simulated.A wideband 4×4 Butler matrix with a center frequency of 4.9 GHz is fabricated,possessing a relative bandwidth of about 44.8%when the measured parameter results of S11～S44 is lower than-15 dB.The phase differences have a flexible distribution,with error range less than±10°.Based on this Butler matrix,a wideband multi-beam antenna array is fabricated.The measured beam directions are around-12.0°,45.7°,33.9° and 18.7°,which has design flexibility.A Butler-like matrix integrating filtering and beam spreading functions is proposed.A group of parallel SPDT switches are placed at the output port to switch between different working states.The Butler-like matrix is constructed on three-layer circuits,with no crossover owing to the path distribution,leading to compact size and low loss.The general topology is given,with its design equation deduced and calculated.A filtering switchable 4×4 Butler-like matrix working at 4.9 GHz is designed and fabricated.The measurement results are consistent with the design parameters,with the phase differences under different switching modes coincident with the design of flexible phase differences.The theory of Butler matrix with unequal phase differences is proposed.The formula of radiation array pattern is calculated and design guidance is given.By using the designed phase compensated coupler structure,two kinds of Butler matrix topology have been designed with those proposed couplers with tunable phase differences and phase compensation.A wideband 4×4 Butler matrix with center frequency of 3.5 GHz is fabricated.When four input ports are excited respectively,the antenna array donates flexible beam pointings varying versus the working frequency during the range of 2.2～4.2 GHz.A tunable 2×4 Butler matrix centered at 1.9 GHz with flexible phase differences is proposed,which could realize tunable beam steering without altering either coupler or phase shifter,possessing fewer dynamic elements than traditional ones.The antenna array based on the fabricated 2×4 Butler matrix produces multiple beam pointing of {-13.2°,39.2°},｛-15.3°,36.1°},and {-10.1°,41.2°} in the band range of 1.8 to 2.2 GHz,the beam direction alters with the bias voltage of dynamic elements.Part of this work is published in IEEE Transactions on Circuits and Systems Ⅱ:Express Briefs.