Research On L-band Digital Multi-beam Antenna

Digital multi-beam antennas have been widely used in satellite communications in recent years.Compared with traditional phased array antennas,they can solve the contradiction between high gain and wide space coverage by simultaneously forming multiple receiving beams.Based on the background of low-orbit satellite communications,this paper studies digital multi-beam antennas and designs an L-band digital multi-beam(DBF)antenna array.The array can form 16 receiving beams at the same time,completing the coverage of the subsatellite space of ±57°.First,according to the design requirements of low-orbit satellite communication,the overall antenna is designed.The array receiving system and the principle of equal flux gain coverage are described,and the beamforming scheme and array design indicators are determined on this basis.Secondly,according to the beamforming scheme,three L-band left-handed circularly polarized antenna units with different structures are designed.They are the crossed dipole antenna,the four-arm helical antenna,and the microstrip antenna.After that,the three antennas are optimized and compared.Then,according to the design index of the array,the basic layout plan of the array was formulated.Three feed structures for realizing left-hand circular polarization were designed,and the best solution was determined.According to the principle of equal flux coverage,the realization methods of the center beam and the edge beam are respectively determined.Regarding the deterioration of the axial ratio of the edge beam at low elevation angles,the use of rotating feeding reduces the axial ratio.For the problem of insufficient gain of the edge beam,optimization was performed by reducing the coupling angle of the array elements,and the beam width was broadened through the Chebyshev current distribution,and the gain at the overlap with the center beam was improved.Finally,the simulation of the 5×5 array antenna is completed,and the equal flux coverage of the receiving array for the ±57° airspace is verified according to the simulation results.Finally,the physical processing is completed,and the overall size is471mm(L)×471mm(W)×70mm(H).And completed the test of 16 beams in the 3D darkroom,and synthesized the gain coverage pattern.The test data shows that the 16 beams of the designed receiving antenna can fulfill the gain requirement of equal flux coverage.