Study On Broadband Digital Phased Array Antenna Beamforming Technology Of Large Aperture

The development of broadband radar and the technology of broadband communication have promoted the development of wideband digital array.Wideband digital array antenna can transmit and receive wideband signal.If the conventional narrowband beam-forming technique is used for the wideband signals,it will cause the beam-pointing offset,scan inaccurately and decrease effective resolution because of the spatial dispersion.And it will cause the traditional phase weighting can't achieve the wideband signal time delay correction because of the temporal dispersion.In order to overcome these problems to actualize the scan in broadband and wide-angle range,It use the real time delay line to replace the phase shifter of each antenna element in the traditional phased array radar at present.However,the analog real-time delay can only be fixed value delay,so we need the digital delay filter.In this paper,we mainly study the technology of broadband phased array antenna technology of the airborne with large aperture,and solve the technical problems of wideband phased array antenna.The main idea is the structure of the subarray and the digital time delay filter.For each subarray,the traditional narrowband method is adopted The research mainly includes the following parts:(1)The basic structure of narrowband and broadband phased array antenna be introduced.Because wideband digital array antennas transmit or receive wideband signals,and the amplitude and phase of the signal can't be ignored when transmitting and receiving,so the mathematical model is different from the narrowband signal.According to the mathematical model of narrowband signal,we can establish the mathematical model of array signal processing for the sub-array configuration of wideband signal.(2)We further introduced the method of subarray configuration.For the broadband system,the purpose of sub-array mode is to overcome the time dispersion and aperture dispersion of large aperture arrays.In the broadband system,the array aperture is large,and the number of array elements is very large.If the time delay is used for each element,the number of the delay is very large.Therefore,we should further study how to divide to meet the requirements of the signal bandwidth,that the size of the subarray.(3)We studied the design method of digital time delay filter which can get arbitrary delay for input signal and used for time delay of subarray.Delay filter design includes the following methods: the time-domain method,the frequency domain method and the filter with Farrow structure.The key to the design of these filters is the filter coefficient which determines the delay.So the expressions for the coefficients of the above filters are calculated.Then the above design methods of several kinds of delay filters are used to simulate MATLAB for transmitting array and receiving array according to the coefficient expression.Finally,we compare the advantages and disadvantages of these kinds of delay filters.