Font Size: a A A

Research On Transmiting Beamforming Technology And Its Applications Of Frequency Diverse Array

Posted on:2019-04-10Degree:DoctorType:Dissertation
Country:ChinaCandidate:J XiongFull Text:PDF
GTID:1318330569487531Subject:Communication and Information System
Abstract/Summary:PDF Full Text Request
Compared with conventional phased-array,frequency diverse array(FDA)transmits different carrier frequencies with a frequency increment across the array elements.Due to the frequency increment,FDA beampattern is not only related with the angle,but also related with the range.Therefore,more Degrees of Freedom(DoFs)are applied in the FDA which can provide promising potential applications in interferences suppressing,target resolution,low probability of intercept and so on.This paper introduces several transmit beamforming applications of FDA range-angle dependent beampattern,including range-angle beampattern decoupling,secure communications,low probability of radar interception,radar-communications and so on.The main contributions of this paper are summarized as follows:(1)Since the traditional FDA produces range and angle coupled beampattern,two kinds of methods are proposed to decouple it in this thesis.The first method uses a single carrier for each element to destroy the original linear frequency increments as binary codes,and then use the genetic algorithm(GA)to optimize their values to achieve a dot-shape beampattern.Multiple carriers for each element is used in the second method,and different weights are adopted to different carriers.Due to the additional DoF,a better dot-shape beampattern is achieved for the multiple carriers.(2)Since traditional secure communications can only guarantee the security in angle dimension,three methods for FDA secure communications are proposed in this thesis.The first method uses FDA instead of phased-array for directional modulation.It can enhance the range dimensional security.Time-modulation array(TMA)and FDA is combined in the second method to achieve secure communications,where radio frequency switches are used to control each element for on-off selection.Finally,orthogonal frequency division multiplexing(OFDM)and FDA are compared in the third method.By putting different OFDM subcarriers to different elements for transmitting and then using optimal weight on each subcarrier,range-angle dependent secure communications are achieved.(3)Since high-gain beam is accessible for anti-radar device to monitor,three methods for low probability of intercept(LPI)beamforming are proposed in this thesis.The first method is inspired by LAWRENCE's idea and replaces traditional high-gain beam by a series of low-gain beams with nonlinear frequency increments via FDA antenna.It can reduce the system visibility and achieve the same performance as the original high-gain beam.The second method uses low-gain beams from multiple directions instead of one high-gain beam from a single direction to illuminate the targets.Compared with the first method,it can save valuable time to synthesize the original high-gain beampattern.Finally,in the third method,the range-angle dependent characteristics are utilized for generating the distinct distribution for the beam power to result in the high power for desired receiver,but low power for target.The simulation results show that these methods can effectively reduce the probability of radar interception.(4)An adaptive flexible sidelobe control method using FDA and multiple-input multiple-output(MIMO)is presented for joint radar-communications.This flexible beamforming control method uses mainlobe for radar function and sidelobe for communication function.It enables communication links to use the same pulse radar spectrum.Multiple orthogonal waveforms are used to embed communication information bits during a radar pulse at each scanning.The simulation results show that the system is effective and efficient for joint radar-communcations...
Keywords/Search Tags:Frequency diverse array(FDA) radar, range-angle decoupling, secure communication, low probability of intercept, radar-communications
PDF Full Text Request
Related items