Research On Anti-jamming Technologies Of Ka Broadband Digital Phased Array For LEO Satellite

With the advent of the 6G era,the terrestrial mobile communication system has developed rapidly.As an effective supplement to the terrestrial communication system,the satellite communication system has received extensive attention from people at home and abroad.Because LEO satellites have the advantages of low orbit height,short transmission delay,and low launch cost,and multiple LEO satellites can realize global access service through networking,many large-scale LEO satellite constellations are rapidly established.LEO satellites generally use phased array antennas for communication.With the change of service bandwidth and service mode,satellite antennas are gradually transformed from analog phased array antennas to digital phased array antennas.This paper studies the anti-jamming technologies of Ka-band broadband digital phased array based on the business requirements of LEO satellite systems.Firstly,this paper reviews the development and evolution of the antenna part in the LEO satellite payload,briefly introduces the basic principle of phased array antenna,compares the traditional analog phased array and the new digital phased array,and analyzes the advantages of digital phased array technology.Aiming at the structure of phased array,starting from the structure of narrowband phased array,by analyzing the difference between narrowband signal and wideband signal,the broadband phased array structure is derived,and two broadband digital phased array structures,TDL and TTD,are introduced.Subsequently,combined with the business requirements of the current LEO satellite system,aiming at the co-frequency interference between high-low-orbit systems and within the low-orbit system in the satellite communication system,this paper considers using the adaptive beamforming algorithm to suppress the interference to LEO satellite in the uplink.Three classical adaptive beamforming algorithms and two constraint-based anti-jamming beamforming algorithms are introduced,and a lowsidelobe anti-jamming beamforming algorithm based on MVDR iteration is proposed,which is applied to one-dimensional linear arrays and counteracts the sidelobes.The anti-jamming performance is simulated and analyzed.In addition,the LCMV algorithm is extended and applied to the two-dimensional array to realize the suppression of sidelobe interference of spatial signals.Finally,aiming at the co-frequency interference between satellite communication systems,this paper further considers solving the problem of collinear interference from the satellite transmitter,and proposes a low sidelobe beamforming algorithm based on MVDR iteration and a one-dimensional sidelobe nulling expansion algorithm based on LCMV The low sidelobe algorithm based on MVDR iteration suppresses beam sidelobes by introducing several power-controllable interference sources.Compared with the traditional array tapering algorithm,it can reduce the redundancy between beam sidelobe level and sidelobe envelope.Thus,the loss of array transmit power and beam main lobe gain is reduced.The one-dimensional sidelobe nulling expansion algorithm based on LCMV divides the weighting coefficients of the rectangular array into row and column elements and solves them in turn.After the nulling is formed in the column elements dimension combined with the elevation angle range of the collinear area,it is expanded in the row element dimension.The complexity of the nulling algorithm is greatly reduced by the operation of dimension reduction.The simulation results show that the MVDR iterative low-sidelobe algorithm is more complex than the array tapering algorithm,but it can reduce the performance loss of the array under the condition of satisfying the sidelobe constraints,which provides a better solution for low-sidelobe beamforming in practical engineering.The one-dimensional nulling expansion algorithm can realize the nulling of the transmit beam in the collinear region with extremely low complexity,and without losing too much transmit power and beam main lobe gain,which provides a feasible scheme of transmitted beamforming for the interference avoidance in practical engineering.