| As a RF front-end device,antenna plays an important role in mobile communication system,and radiation pattern is one of the most important indicators to measure antenna performance,which affects the performance of the whole wireless system.Therefore,more and more communication systems put forward more stringent requirements for antenna beam forming.There are many kinds of antennas,among which waveguide slot antenna has been widely studied and used since it was proposed.This is because the waveguide slot array antenna has many excellent characteristics,such as compact structure,light weight,high aperture efficiency,large power capacity and easy realization of low sidelobe and ultra-low sidelobe.It has been widely used in radar and communication fields.At the same time,the waveguide slot array antenna can realize the amplitude and phase control of the element,and it is easy to shape the pattern.Therefore,this paper focuses on the research of waveguide slot antenna beamforming.Based on the research of planar waveguide slot antenna beamforming,a method of proactive conformal beamforming is proposed.It mainly includes W-band double-sided low sidelobe waveguide slot array antenna and Ka-band waveguide slot array antenna with cosecant square beam based on the proactive conformal technology.1.W-band double-sided low sidelobe waveguide slot array antenna:1)The research is carried out on the integration and performance of the imaging radar system antenna on the W-band small airborne platform.On the premise of small size and weight,the antenna can achieve high gain,low profile,lightweight and accurate beamforming.By adjusting the resonance length,width and offset of the slot,the radiation ability of each slot can be controlled,so as to complete the low sidelobe design of Hplane.A delay line is used in the E-plane to compensate the phase difference caused by the unequal power division feeding network,and the low side lobe design of the E-plane is completed.Finally,the antenna is fabricated and tested based on Multilayer PCB technology.The sidelobe level of E-plane and H-plane of W-band double side low sidelobe waveguide slot array antenna developed in this paper is lower than-20 dB.2)On the basis of the above PCB version,in order to improve the efficiency and reduce the area,we need to give up the use of delay line,and choose to complete the phase compensation in the feeding network.Firstly,a novel E-plane unequal power divider is proposed to achieve the same phase and unequal amplitude output under small spacing,By properly adjusting the E-plane unequal power divider,better low sidelobe effect can be achieved in E-plane.At the same time,the H-plane pattern is shaped by adjusting the offset and harmonic length of the slot.Finally,a 16×16 waveguide slot array antenna was processed and tested based on MEMS silicon technology.In the bandwidth of 2GHz,the reflection coefficient is less than-12.5 dB,the beam widths of E-plane and H-plane are more than 4° and the average side lobe power of E-plane and H-plane is less than-26.7dB.2.Ka-band based on the proactive conformal waveguide slot antenna with cosecant square beam:Waveguide slot array antenna is widely used because of its excellent characteristics.However,the traditional planar slot array antenna has certain limitations,which limit its application in complex beamforming.For example,the phase distribution of a planar slot array antenna is limited and cannot be adjusted arbitrarily.In this paper,a proactive conformal waveguide slot array antenna with H-plane cosecant square pattern is designed.It can control the phase distribution by actively bending the array shape.The longitudinal position of the array antenna is fully utilized to break the limitation of phase control.Based on this,the proactive conformal waveguide slot array antenna can independently modulate the amplitude and phase distribution,then realizing a complex far-field pattern.Using 3D printing technology,the antenna structure is printed as a whole.The cosecant square beam has a coverage of 40°,and obtains peak gains of 12.4dBi,13.3dBi and 14 dBi at 35 GHz,35.3GHz and 35.6GHz,respectively. |
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