Wideband Direction-Finding Antenna Array And Algorithm Implementation

In order to meet the needs of reconnaissance and anti-reconnaissance,jamming and anti-jamming in the modern battlefield,and the potential safety hazards caused by UAV flying in no-fly zone in the civil field,the technology of radio direction finding becomes more and more important.And the direction-finding method of correlation interferometer is widely used because of its high direction-finding accuracy.In this thesis the realization of broadband direction-finding antenna array and the direction-finding algorithm is studied.The thesis is divided into the following parts:A planar ultra-wideband antenna with loading impedance elements is designed.The bandwidth is from 20 MHz to 6GHz,and the relative bandwidth is 198.67%.The antenna adopts a monopole form of mixed loading of lumped elements and open stubs.The open ended stub introduces the capacitance to the ground,which effectively reduces the operating frequency of the antenna.The inductance element can also reduce the operating frequency without increasing the antenna size.When operating at the frequency of 20 MHz,the antenna length is approximately 0.023 ?.Circular array is adopted in this design.After considering the direction-finding accuracy and array size and other factors,the placement of the antenna unit is determined.And then the core direction-finding algorithm is analyzed.Then use MATLAB to simulate and compare the differences of several correlation algorithms,and the effect of the size of array radius on the result is discussed.Then determine the size of array radius and select the most suitable algorithm for subsequent work.After the array is processed,it is tested and then assembled into a direction-finding system together with the receiver.Then,the measured sample database is established,and the direction-finding operation is carried out based on the measured sample database,and analyzes the result and find out the problems.After improvement,the test results perform well and the direction-finding function is realized.Then,a scheme to improve the accuracy of high frequency direction finding is proposed,which aims at the low accuracy of high frequency direction finding.A small antenna array is introduced on the basis of the original array for high-frequency bands.The small array unit adopts the form of a monopole with a slot.Simulation results show that the introduction of a small array can improve the direction-finding accuracy at the high frequency.And two algorithms for improving the accuracy of calculation of phase difference are proposed,one is based on IQ signal algorithm and the other is based on FFT algorithm.Finally,in order to adapt to the scene of fast direction finding,a fast algorithm which can effectively shorten the time of direction finding is proposed.These algorithms are all simulated by MATLAB and perform well.