| With the development of modern mobile communication technology,the evolution of radar and communication systems to the millimeter-wave frequency band has become a development trend.At the same time,it also faces greater challenges.The millimeter-wave space loss is large,and a broadband and high-gain array antenna is required.Under the same relative bandwidth,the millimeter wave frequency band can obtain a larger absolute bandwidth,which means that the communication system can achieve higher communication rate and greater throughput in the millimeter wave frequency band,and the radar system can obtain higher resolution.Frequency-modulated continuous wave(FMCW)radar has the advantages of miniaturization and low cost,and the large sweep bandwidth of the transmitted signal enables it to have highresolution imaging capabilities.This paper mainly focuses on the application of millimeter wave communication and imaging,and conducts research on active multi-beam arrays,including the design of antenna arrays and transceiver circuits.The details are as follows:1)For the fifth generation(5G)millimeter-wave broadband wireless communication and K-band and Ka-band satellite communications,a millimeter-wave broadband circularly polarized electromagnetic dipole antenna is proposed and designed.On the basis of the traditional linearly polarized electromagnetic dipole,the electric dipole and magnetic dipole parts are improved respectively,and additional magnetic dipoles are introduced,which not only increases the 3d B axial ratio bandwidth of the antenna unit,but also effectively The-10 d B impedance bandwidth of the antenna is broadened.At the same time,in order to improve the antenna gain,a 4 × 4 antenna array is jointly designed by using a broadband power distribution network and processed and tested.The test results are in good agreement with the simulation results,which verifies the correctness of the design.The antenna array has the advantages of wideband(impedance bandwidth,3d B axial ratio bandwidth,3d B gain bandwidth),low profile,low processing cost,simple structure,flexible design,etc.It is very suitable for applications such as millimeter wave broadband satellite communication systems.At the same time,a broadband low-profile circularly polarized microstrip antenna was designed based on this method.The related research results were published in the international core journal IEEE Trans.on AP and the international conference 2021 IEEE International Wireless Symposium(IWS).2)Aiming at the large insertion loss caused by cascaded filters in millimeter-wave RF transceivers,two filter antennas with different feeding forms are proposed.One is two millimeter-wave based single-mode and multi-mode resonator cavities.Filter antenna,under the excitation of feeding metal vias,the passband and stopband present different transfer forms to introduce radiation nulls;the other is based on short-circuit via loading,which drives the current distribution on the surface of the patch by perturbing the lower sideband and introduces additional nulls resulting in a filter response.Based on the single-mode resonator filter antenna,the effect of beam scanning on the filter characteristics is further studied.Both the single-mode resonator millimeter-wave filter antenna and the short-circuit via-loaded millimeter-wave filter antenna can cover the 24.25~29.5GHz 5G millimeter wave n257 and n258 frequency bands.At the same time,the actual antenna was processed for verification,and the measured results were basically consistent with the simulation.Not only did the in-band gain not reduce due to the introduction of the filter structure,but also the out-of-band spurious and noise power levels were effectively reduced.These three filter antennas have the characteristics of broadband,low profile,simple structure,and multiple radiation nulls,which are very suitable for 5G millimeterwave broadband communication applications.Some of the research results were published at the international conference 2021 13 th Global Symposium on Millimeter-Waves & Terahertz(GSMM)and 2021 IEEE International Workshop on Electromagnetics: Applications and Student Innovation Competition(i WEM).3)A phased array antenna array with wide bandwidth angle scanning in 24.25~29.5GHz is proposed.The antenna is based on the hybrid mode of monopole antenna and microstrip antenna,and a symmetrical monopole antenna is added around the traditional microstrip antenna.Extends the conventional ±45° scanning range to ±60°.In order to achieve miniaturization,on the basis of not affecting the antenna performance,the size of the antenna unit is set to 4×4mm2,and the polarization isolation under the same unit can reach 20 d B.At the same time,in order to further improve the isolation between units and avoid scanning blind spots Emergence,the use of defective ground(DGS)technology,effectively shifting the scanning blind spot within the band.As a verification,a phase-shifted 8×8 highly integrated phased array antenna array using a beamforming chip was designed and tested.The splitter achieves a wide operating bandwidth,ensuring uniformity of power reaching the chip,as well as high isolation between the two polarizations.The diameter of the entire antenna array is only 4×4cm~2 including surrounding dummy elements.The measured antenna scanning angle can reach ±60°,and it works in the 5G millimeter-wave frequency band,which is very suitable for broadband millimeter-wave communication systems such as small base stations.4)A highly integrated millimeter-wave radar imaging system based on L-shaped antenna array is proposed and implemented.The system is based on the phased array system of frequency modulated continuous wave,and consists of a frequency sweep source,a transmitting and receiving chain,and a beamforming antenna with the function of receiving and transmitting.Using a microstrip antenna,the unit has a wide beam,which is convenient for wide-angle scanning in the line array scanning process.When the radar system is working,firstly,the phase shifter of the transmit channel in the beamforming chip is used to deflect the beam by a specific angle,and then the receive link traverses the search target by scanning N beams.At this time,the echo data is 1×N In the matrix form,change the direction of the transmit beam until the entire imaging target is searched,and an N×N matrix data form can be formed,in which the received intermediate frequency frequency reflects the distance information of the imaging target.With the application of millimeter-wave beamforming chips,compared with the imaging system using the multi-beam system,too many radio frequency channels and baseband analogto-digital converters(ADCs)are omitted,which improves the overall integration level and ensures that a certain imaging accuracy at the same time,the cost is greatly reduced.Some of the research results will be published at the 2022 International Conference on Microwave and Millimeter Wave Technology(ICMMT). |
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