Research On Multi-functional Microwave Devices And Concurrent Multiband Radar Front-end

With the rapid increase in the demand of communication and the increasing diversification of communication functions,wireless communication has undergone tremendous changes.Current wireless communications are evolving toward broadband,multi-band,multi-standard and multi-functional systems.For the development needs of low-cost,low-power,multi-functional and multi-standard systems,the multi-functional microwave devices with wideband or multi-band characteristics,and the concurrent multi-band radar front-end are studied in this thesis.The work of this thesis mainly includes the following aspects.(1)Two wideband bandpass filters are proposed.First,a three-mode resonator is designed based on stepped-impedance open-circuit stubs.Two interdigital coupled-lines are used to feed the resonator,which realizes a bandpass filter with wide passband,low insertion loss,high selectivity and deep stopband rejection.Then,a four-mode resonator with harmonic suppression is proposed,and a wideband filter with relative bandwidth of 89.9%and wide harmonic rejection bandwidth is designed using this four-mode resonator.The upper stopband rejection level of this filter greater than 30 dB from 4.2 GHz to 10.32 GHz.Some of this work is published in International Conference on Computational Electromagnetics.(2)Three wideband function-interated power dividers are proposed.First,the functional fusion design architecture of the filter and power divider is studied.A balanced wideband filtering-integrated planar power divider is designed,its transmission characteristics and filtering characteristics are analyzed using microwave transmission line theory and mixed mode analysis.This power divider shows 49%differential-mode filtering bandwidth with two additional transmission zeros introduced,and the common-mode transmission is suppressed below-12 dB over 141%frequency bandwidth.Then,a single conductor transmission line based on spoof surface plasmon polaritons(SSPPs)of bow-tie cells is proposed,which expands the design method of function-interated power dividers.A single-conductor planar quasi-symmetric unequal power divider with a working bandwidth of approximately 91%is realized based on this SSPPs transmission line.Finally,the performance of the double-sided parallel strip line and the double-sided parallel SSPPs transmission line are investigated.It combines the common advantages of traditional transmission line and SSPPs transmission line to achieve efficient impedance matching.A wideband power divider with ultra-wideband harmonic rejection is designed using a double-sided parallel SSPPs transformer.The bandwidth of this power divider is 146%,the upper stopband bandwidth is extended to 40 GHz(12.l f0),and the upper stopband is suppressed above 32 dB.This part of work is published in IEEE Access,AIP Advances and International Journal of RF and Microwave Computer-Aided Engineering.(3)The broadband,multi-band and multi-functional antenna is studied,a wideband polarization reconfigurable differential circularly polarized antenna and a tri-band array antenna with similar radiation patterns are proposed.First,the expansion of impedance and axial ratio bandwidth of the circularly polarized antenna is explored.A high-gain,wide impedance and axial ratio bandwidth four-feed antenna radiating element is proposed.The antenna-radiating element is then fed using a differential-to-single-ended sequential feeding network based on switches and stepped coupled line couplers to implement a polarization reconfigurable differential circularly polarized antenna.This antenna achieves an impedance bandwidth of 75.6%(81.8%)and an axial ratio of 66.7%(71.2%)for left-handed circular polarization(right-hand circular polarization).Then,a tri-band planar shared-aperture array antenna is proposed.The antenna structure includes two radiation patch layers,a ground layer and a feeding network layer.The three radiated frequencies with similarly shaped radiation patterns are generated by exciting the stacked radiation patches using a wideband feeding network.To verify the effectiveness of the proposed array antenna,a 4×4 array antenna prototype is simulated and measured.The measured impedance bandwidths are 0.48,0.66,and 1.35 GHz,and measured realized gains are 10.8,11,and 14.4 dB at 13.5,18,and 24 GHz.Some of this work is published in IEEE Access and Microwave and Optical Technology Letters.(4)The concurrent multi-band multi-functional radar front-end is studied,and a novel monostatic concurren multi-band radar front-end architecture that can work in several independent frequency bands is proposed.This multi-band radar has the characteristics of high measurement accuracy,strong anti-interference ability,easy multi-functional integration and low cost.It has the potential to support different modulation modes and multi-function integration in different frequency bands.To demonstrate the effectiveness of this multi-band radar front-end architecture,the corresponding dual-band radar operating at 13.5 GHz and 24 GHz,and two single-band radar prototypes operating at 13.5 GHz and 24 GHz are fabricated and measured.The good consistency of the dual-band and two single-band radar front ends verifies the effectiveness and reliability of the proposed new radar architecture.This part of work is published in AEU-International Journal of Electronics and Communications.