Research On Time-modulated Array Beamforming Technology For Radar-communications Integration

With the development of electronic technology and the increase in the demands of modern battlefield environments,in many cases,multiple electronic devices such as radar and communications are required to work simultaneously,and the advantages of the radar-communications integration are becoming more and more obvious.The integrated design of radar and communication systems is in line with the development trend of multifunctional integration,miniaturization and networking of today's combat platforms.It has many advantages such as high spectrum efficiency,low RF front-end cost,and electromagnetic compatibility in the system.At present,there are many ways to realize the integrated design of radar and communications,which can be divided into the following categories in general: the time division-based technology,the frequency division-based technology,the space division-based technology and the waveform integration-based technology.In which,the integration technology based on the time and frequency division system have the defects of inability to continuously communicate/detect or additional spectrum resources occupation.The waveform integration-based technology has the disadvantages of complicated design and implementation,limited communication efficiency or limited radar detection distance.The research focus of the space division-based technology is the antenna array at the RF front-end.The time-modulated array solves the problems of complex feed network implementation and limited feed accuracy in traditional antenna array,and the TMA requires only one radio frequency channel to achieve multi-beam.Based on the above background,this thesis combines time-modulated array technology,focusing on the research of beamforming technology of space division multiple access based radar-communications integration system and its distributed network joint detection technology.This thesis mainly conducts research from the following three aspects:Firstly,the space division radar-communications integration technology based on multi-beam time-modulated array is proposed.Aiming at the problems of which the beam scanning is not independent and the specific communications and radar waveforms are needed in traditional scheme,this thesis proposed the use of each harmonic component of the time-modulated array to send and receive radar and communication signals for the first time.First,the beam control algorithm of radar-communications integration based on time-modulated array is given.By controlling the static excitation of the time-modulated array and the opening and closing moments of each RF switch,the antenna beam can be controlled freely.Then,the transmit and receive architecture of the radar-communications integration system based on the time-modulated array is proposed.Benefiting from the space-frequency conversion characteristics of the time-modulated array,the different harmonic components are used for radar detection and wireless communications.Radar and communication signals are distinguished from the air domain,occupying the same time and frequency resources without mutual interference.The two use independent waveforms to avoid the shortcomings of the waveform integration-based technology,and the application scenarios are wide.Only one RF channel is used to generate multiple beams,reducing the complexity of hardware implementation.The high integration of the radio frequency front-end of the radar and the communications system is realized.Secondly,aiming at the energy leakage caused by the sideband radiation of the timemodulated array,this thesis proposed optimization algorithms for harmonic suppression in the radar-communications integration scenario,which solves the problems that the traditional time-modulated array-based radar-communications integration scheme does not consider the energy losses,and the traditional harmonic suppression algorithms are not suitable for integration scenarios.This thesis first uses the periodic modulation function which phase reversed in the second half period to suppress the fundamental and even harmonic components of the time-modulated array.On this basis,a closed-form expression of the sideband signal radiation energy is given.Second,the differential evolution algorithm is used to propose an indirect energy losses optimization algorithm that minimizes sideband signal peaks,and a direct energy losses optimization algorithm that minimizes sideband signal radiated energy.The former one has lower complexity and the latter one has higher energy efficiency.The proposed optimization algorithms can greatly improve the energy leakage of the time-modulated array and effectively improve the power efficiency of the TMA-based radar-communications integration system while ensuring the normal operation of the radar and communications subsystems.Thirdly,aiming at the vacancy of radar-communications integration in the research direction of networking and the lack of existing radar networks that require independent communication systems to support,the networking application of integrated system is given,the radar-communications integration networking and joint detection beam control algorithm are proposed.Firstly,a scheme of network for integrated node of radar and communications based on time-modulated planar array and the joint detection beam control algorithm are proposed to increase the effective detection aperture of the radar and improve the detection capability in a distributed joint detection mode.Then for environments with interference,the noise + interference covariance matrix is reconstructed based on Capon spatial spectral estimation and MVDR criterion,and a multi-interference suppression technology for radar-communications integrated network based on timemodulated planar array is proposed.Finally,several joint networking schemes of multibeamforming and time-modulated planar array are proposed,and the balance between beam freedom and system complexity is balanced according to the requirements.The principle of multi-beamforming is extended to distributed networking,and a virtual multibeamforming technique for radar-communications integration network is given.Make full use of the characteristics of radar and communications system to enable multiple radarcommunications integration nodes to work together effectively.In summary,this thesis uses time-modulated array to design an integrated radio frequency front-ends of radar and communication systems,and proposes an energyefficient space division system multi-beam radar-communications integration system,and its multi-node joint detection beam control technology.Under the premise of not affecting radar detection performance and wireless communications performance,a high degree of integration of radar and communications is realized.