Broadband Low Sidelobe Array Antenna

With the increase of wireless electronic devices,the electromagnetic environment becomes more complex and the electromagnetic interference of communication system and radar system are also more serious.The low sidelobe array antenna has the advantages of narrow beam,low sidelobe and high gain,which makes it have strong anti-electromagnetic interference ability and good sensitivity.In this paper,we design the X-band low sidelobe linear array antenna,and the feed network is designed and analyzed in detail.This paper writes matlab analysis program of low sidelobe linear arraya with ideal dipole as element according to the theory of array antenna and Taylor synthesis method,and we verify the correction of the program analysis result by electromagnetic simulation software HFSS.Using this program,the amplitude and phase distribution of the linear array antenna unit with the array number of 64,the array element spacing of 0.67 and the sidelobe level of40dB are obtained.In this paper,a waveguide feed network is designed.Firstly,a number of different ridge waveguide directional couplers are designed based on the theory of porous coupling.The ridge waveguide directional coupler uses a method of opening two rows of rectangular windows In wide public wall,which can achieve different coupling degrees by controlling the size and number of windows.The coupler has wide frequency band and good stability.In this paper,a ridge waveguide T junction is designed.The simulation results show that the return loss of the T junction in the working frequency band is greater than 20dB,and the transmission loss is less than 0.5dB.In this paper,a waveguide surface conversion structure is designed.The return loss is more than 15dB and the transmission loss is less than 0.3dB.Meanwhile,a new topology is designed,which solves the problem of 90~o phase difference between the output ports of the waveguide directional coupler.The simulation shows that the return loss of the feeding network is greater than 20dB,the output power error of the port is within 0.5dB,and the error is less than 10~o.In order to connect the waveguide feed network and microstrip feed network,the design of a ridge waveguide to microstrip line transition structure,this structure in the working band return loss mostly in more than 25dB,and the transmission loss within 0.5dB.In this paper,a microstrip feeding network is designed,which is composed of a series of unequal power division Wilkinson power dividers.The feeding network has the advantages of compact structure and flexible arrangement.The simulation results show that the return loss is above 15dB and the transmission loss is about 1.0dB.Finally,a printed dipole with broadband characteristics is designed.The relative frequency of the antenna is more than 25%and the maximum gain is 5dB,which has good broadband characteristic and directivity.The printed dipole is coaxially arranged to form a linear array and fed to the output power of the feed network,and an array antenna with low sidelobe characteristics is obtained.