| Phased array antennas have been widely used in the field of wireless communication in recent years.Compared with traditional antennas,phased array antennas can change the antenna’s beam direction by changing the phase of the front unit.At the same time,it has the advantages of small size,light weight,and high transmission power,sidelobe suppression and other advantages.In this paper,based on the system requirements of airborne equipment for satellite communications,the phased array antenna is studied,and a microstrip patch antenna with inverted capacitive feeding is selected as the array unit to design a phased array antenna that works in the S-band,can send and receive left-handed circularly polarized signals in the airspace range of 30° to 90° elevation angle.The main work of this paper is as follows:(1)Determine the form of the antenna unit.According to the circular polarization characteristics of the unit and the low elevation angle gain,three S-band antenna forms are designed.The first is a single-feed microstrip patch antenna,which adopts the form of inverted capacitive feeding,which has the characteristics of wide frequency band,simple structure,low elevation angle and high gain;The second is fed by a 3d B directional coupler microstrip antennas have the characteristics of low axial ratio and low profile;The third type of antenna is a cavity-backed slot antenna,which has the characteristics of wide beam,high efficiency,and high isolation.Comprehensively compare the electrical performance and size of each antenna and select the first antenna as the phased array unit for the array design.(2)Determine the plan design of the front.Analyzing the system indicators,it is determined that 5 receiving antennas and 4 transmitting antennas are used to form the front,and the overall layout is 3×3;In order to optimize the low-elevation axis comparison of the antennas,the transmitting and receiving antennas are respectively used in the form of sequential rotating feed.Arrangement under the premise of suppressing the grating lobes,determine the appropriate front unit spacing.(3)The overall design of the phased array antenna.After the phased array antenna adopts a four-transmit and five-receive antenna layout,the overall size of the antenna front is214mm×166mm×23mm.The phased array transceiver antenna is simulated,and 13 receiving beams are divided based on 8.6d Bi and 10 transmitting beams are divided based on 7.4d Bi while maintaining a certain gain margin.The antenna is processed and the gain and axial ratio test is performed in a 3D darkroom.The test proves that the low elevation angle gain value of the transmitting antenna is greater than 6.7d Bi,the gain value of the receiving antenna is greater than 7.6d Bi,and the transmitting and receiving antenna is within the beam coverage.The axial ratios are all less than 6d B,indicating that the designed S-band phased array antenna meets the system index requirements. |
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