Research And Design Of Specific Beam Modulated Antennas

With the development of the Internet of Things to the Internet of Everything,the design of antennas is facing a variety of different and more application scenarios.Generally,in a specific scenario,the antenna of the wireless system needs to have different radiation patterns.In response to the above requirements,the research and design of specific beam modulated antennas has become increasingly important.A specific beam modulated antenna refers to an antenna that modulates and designs the far-field radiation characteristics of the antenna according to a specific scenario,and the principle of pattern multiplication is an effective means for the antenna to achieve a specific beam.At the same time,using the principle of pattern multiplication can improve the researchers'freedom of antenna beam control,and then realize the specific radiation pattern under the requirements of engineering applications and academic research.This article proposes three specific beam modulated antennas based on the beam control method for three application scenarios.(1)A circularly polarized,wide-beam antenna for electromagnetic energy harvesting scenarios is proposed.The proposed antenna is mainly used for electromagnetic energy harvesting in the 2G/3G/4G/5G and WIFI frequency bands,and has a good energy collection effect in the 2.45 GHz frequency band.The antenna introduces a radiation pattern similar to that of a monopole by coupling and exciting the surrounding parasitic structure,and then multiplies it with the radiation pattern of the main radiation patch to achieve wide beam characteristics and reduce in-band impedance fluctuations.At the same time,the antenna uses cut-angle radiation patches and asymmetrical feeding to introduce TM₁₀ and TM₀₁ modes with equal current amplitudes and orthogonal phases to achieve circular polarization radiation,and use coupled feeding to further increase the bandwidth of the antenna.The proposed antenna achieves an impedance bandwidth of 22.9%,an axial ratio bandwidth of 5.8%,a measured peak half-power beam width of 164°,and a measured paek 3dB axial ratio beam width of 156°while maintaining the low profile height around 0.11?_c(the free space wavelength corresponding to2.45GHz).(2)A sidelobe beam-enhancing antenna for wireless energy and information simultaneous transmission applications is proposed.Through beam control of the antenna,a high-gain main lobe(for energy transmission)is realized,while the remaining radiation energy is concentrated on the side lobe for information transmission.First,by loading parasitic loops and patch structures,the idelobe of the XoY plane,that is,the sidelobe of the main radiating patch,is extracted,so that the XoY plane has a certain gain,and its radiation pattern maintains good directivity.The measured peak gain of the antenna's main lobe is 7.5dBi,and the XoY plane gain is greater than 0dBi.Furthermore,in order to improve the XoY plane gain and front-to-back ratio of the antenna,the performance of the sidelobe beam-enhancing antenna for simultaneous transmission of energy information is improved by loading parasitic microstrips and defective ground structures.Among them,a new radiation pattern is introduced by loading a parasitic microstrip to improve the XoY plane's gain of the antenna,and a defective structure is introduced to change the current distribution on the metal reflecting surface to suppress backward radiation.The proposed antenna achieves an increase of more than 1dB in the simulated average gain of the XoY plane.Finally,in order to verify the feasibility of its application in green communication scenarios,experiments were performed on the ideal and actual scenarios where the proposed sidelobe beam-enhancing antenna is oriented to provide energy to nodes while transmitting information.(3)A filtering antenna unit with miniaturization and constant beamwidth characteristics of a multi-band shared-aperture antenna array that can be used for integrated shore-to-ship wireless communication scenarios is proposed.The proposed antenna introduces a radiation zero point by applying a filtering balun,and then realizes a low-pass filtering response.At the same time,the current path is extended by loading the parasitic patch on the antenna,and the bandwidth is expanded and the size is miniaturized.Furthermore,in order to compensate for the influence of the miniaturization of the antenna on the beam width.By introducing multiple parameters,including folding dipole arms and vertical metal walls,the degree of freedom for beam adjustment is improved,and a constant beam width is achieved.The proposed antenna achieves a constant half power beamwidth of 65±5°in a small size,while achieving high radiation efficiency in a wide frequency band(0.69GHz to 0.96GHz)and a wide stop band(1.7GHz to 4.0GHz)gain suppression exceeding 13dB.And its in-band radiation is stable,the in-band gain varies from 8.5dBi to 9.6dBi,and the in-band radiation efficiency exceeds 90%.