| With the rapid development of wireless communication,modern radar and electronic countermeasure,array antenna with low profile,wide operating bandwidth and high efficiency has been widely studied.Antennas based on waveguide structure have advantages of high radiation efficiency,low loss and high power capacity,so they have various applications in the design of array antenna.Among them,the slot array antenna based on the waveguide structure has characteristics of low sidelobe level and high gain.It can also realize arbitrary polarization and shaped-beam patterns,which is suited to the field of new generation satellite communication and radar detection very well.Besides,the CTS array antenna based on waveguide structure has characteristics of wide operating frequency bandwidth and beam scanning,which can meet the requirements of modern communication systems.In this dissertation,several kinds of slot array antennas and CTS array antennas based on waveguide structures are deeply investigated according to the requirements of current communication technology and related scientific research projects.The main research contributions are listed as follows.1.Based on the fundamental theory of slot antenna,three equations of Elliott's waveguide slot array antenna design process are introduced,which provides theoretical basis for antenna design and software development.The API function package is further expanded according to the basic principles of HFSS-MATLAB-API,and the automation of antenna design and optimization is realized.An independently-developed design software of waveguide slot array antenna is achieved based on the above-mentioned algorithms.The software controls HFSS to realize automatic modeling and simulation through Script interface,and calls Microsoft Word to record the simulation results.The automatic design module and the automatic optimization module are both included in this software,and these two modules are relatively independent.In order to optimize the sidelobe level of waveguide slot array antenna,an indirect optimization method of Equivalent Admittance Method(EAM)is proposed.With the help of self-developed automatic design software,waveguide slot array antenna is easily designed and optimized.It can be seen from the optimization results that the sidelobe level of the waveguide slot array antenna has been greatly improved in a short period of time.2.A line source is designed to feed the CTS array antenna by double layered parabolic cylindrical system.A high gain,broadband,one-dimensional beam-scanning parallel fed CTS array consisted of 64 stepped radiation branches is proposed.This antenna shows good matching characteristics over the required bandwidth(relative bandwidth=30%),and has great beam-scanning performance of ±27° which is very attractive for Ka-band applications.Furthermore,a VICTS array antenna with low profile,high radiation efficiency,broadband and continuous beam control capability is designed.The relationship between the radiation beam and the relative rotation angle between the CTS array and Line Source Generator(LSG)is accurately described through the analysis of array antenna.The radiation pattern of the array antenna is obtained by the integrated encryption sampling technique,which provides a theoretical basis for antenna design.The antenna is fabricated and measured in the microwave anechoic chamber to validate the performance of the VICTS antenna.The measured-10 d B relative impedance bandwidth is about 16%.Through the rotation of the CTS array(?=0°?50°),the designed antenna can realize great beam scanning performance of ±56°.3.Based on the radiation principle of slot,the circular polarized characteristic of the proposed antenna element is analyzed.Two circularly polarized mono-pulse waveguide array antennas for Ka-band wireless communication are designed.One of them uses a threedimensional waveguide folded section,so that there will be no seamless region when the two subarrays are terminated.A novel circular polarizer is also proposed.A great circularly polarized mono-pulse radiation mode is realized eventually.The antenna is fabricated and measured in the microwave anechoic chamber to validate its performance.The measured results show that the proposed antenna is well matched at 35 GHz with 3.7% relative bandwidth.The sum beam can maintain a gain of more than 20 dbic within the operating bandwidth.The peak gain is more than 23.3 d Bic.The axial ratio is less than 1.2 d B.The sidelobe level is less than-28 d B.In the difference beam pattern,the difference of the level between the two main lobes is less than 0.5 d B,and the zero depth is less than-30 d B.It is worth mentioning that the gain of the difference beam is higher than that of the sum beam over 95% of the angular range,except the ±5° interval area around the center of the pattern.Another millimeter wave circularly polarized mono-pulse antenna introduces a virtual PMC terminal,which makes the mono-pulse antenna more compact.It doesn't have complex three-dimensional structure,which is friendly to manufacturing process and mass production.According to the simulation results,the antenna has excellent circularly polarized monopulse radiation performance.The two subarrays in the mono-pulse radar system are no longer isolated due to the virtual PMC terminal.In the difference beam mode,the sidelobe level becomes lower,and the angle between the two main lobes becomes closer.The proposed array antenna has excellent circularly polarized mono-pulse radiation performance.In addition,the antenna structure is compact,which is very suitable for millimeter-wave circularly polarized mono-pulse radar system.4.Based on the superposition principle and Taylor synthesis theory,a beamforming synthesis method is proposed,and the design idea of pattern source calibration is introduced.This method can be actually used into the design of shaped-beam array antenna.A waveguide power divider based on evanescent mode principle is proposed to realize arbitrary power distribution ratio.A dielectric loaded ridge waveguide array antenna is designed,which achieves good beam-forming characteristic in the required frequency band.Moreover,the cost is reduced and the manufacturing is more convenient by using the method of dielectric loading,which provides a good candidate for the satellite communication terminal in mobile platform and radar system.In addition,based on the theory of waveguide resonator,a compact six-channel waveguide power divider is proposed.Through integrating the power divider and the ridge waveguide slot array on the same layer,the structure of antenna can be simplified,and the difficulty of mechanical processing can be reduced.Based on the improved array synthesis method,a array antenna with unequal element spacing is achieved which meet well with the beam forming requirement.The antenna is fabricated and measured in the microwave anechoic chamber to validate its performance.It reveals that the measurement result is in great consistency with the simulation result.The antenna operates well at the design frequency.The measured 3-d B beamwidths of E plane and H plane are52.72° and 3.15°,respectively.The corresponding sidelobe levels are-10 d B and-29.8 d B.The designed array antenna has good beamforming characteristic and compact structure.Besides,it can be used in a variety of environments because of its pure metal structure. |
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