Research On Low Elevation Method Of Meter Wave Radar Based On Beam Space

The meter wave radar itself has the advantageous properties of anti-radiation missiles and anti-stealth,but due to its own wide beam width,relatively low angular resolution,and strong ground reflected signal power,it is prone to multipath effects.Resulting in the presence of multipath signals in the signals received by the radar,causing great troubles to the measurement of the target height at low elevation angles.The array super-resolution algorithm can be widely used in low-altitude target angle estimation.In response to different application scenarios,a variety of corresponding algorithms have been developed.Among them,the most widely used and representative algorithms are: Multiple Signal Classification(MUSIC)algorithm and maximum Likelihood(ML)algorithm,etc.But when we are dealing with a large array radar,a lot of calculation and data transmission and storage are required in the process.In view of the above problems,this article mainly studies the measurement of low elevation angle of meter wave radar in beam space.The content of this thesis is mainly composed of the following four parts.In the first part,the angle measurement performance of several common array super-resolution algorithms is analyzed in the array element space,and several important factors affecting the performance of each algorithm are analyzed in combination with simulation.First,the angle estimation principle of the MUSIC algorithm is briefly summarized,and the main factors affecting the performance of the algorithm are analyzed.Secondly,in view of the insufficiency of the application of the MUSIC algorithm in the problem of coherent sources,an improved algorithm based on this algorithm,which can effectively deal with the problem of coherent source angle estimation,is introduced,namely the spatial smoothing method.Finally,three spatio-temporal cascaded maximum likelihood algorithms that are also applicable to coherent source angle estimation are analyzed,combined with simulation to study the effect of signal-to-noise ratio and direct wave angle on the angle measurement performance of the above three algorithms,verifying the same conditions In the case of,the accurate maximum likelihood(RML)algorithm has the smallest angle measurement error and the angle measurement performance has significant advantages compared to the other two algorithms.In the second part,the beam space conversion matrix is established,and the RML algorithm with the best angle measurement performance and the most a priori information is discussed in the beam domain.Combined with the multipath geometric model of the array radar,the low elevation angle estimation method of the meter wave radar based on the beam space is studied.Combining simulation examples to explore the influence of various factors on the angle measurement performance of the beam space RML algorithm.Compared with the angle measurement performance of the array element domain RML algorithm,the beam domain RML algorithm can effectively reduce the amount of calculation when the algorithm executes the program.To ensure the accuracy and robustness of the algorithm.In the third part,on the basis of the existing beam space-based low elevation angle estimation method for meter wave radar,considering the complex reflection surface,a beam space-based array radar low elevation angle estimation method for complex terrain is proposed.The existing methods do not consider the complex situation of the reflecting surface.Sometimes the target echo contains multipath signals and sometimes does not contain multipath signals.The new algorithm improves this,and uses the signal characteristics of the beam domain to determine whether the received signal after conversion to the beam space contains multipath signals.Then select a more appropriate algorithm for the low elevation angle estimation of the target according to the situation.When the converted received signal contains a multipath signal,the beam space RML algorithm is used;when the converted received signal does not contain the multipath signal,Use sum difference single pulse angle measurement method.In addition,the beam space RML algorithm used when the received signal contains multipath signals is an improved algorithm based on the existing beam space-based meter wave radar low-elevation estimation method.It uses three sum beams at the same time.Three difference beams are also used,which is equivalent to using more data information.It can be seen that the new algorithm has the advantages of low computational complexity,high accuracy,and good robustness.The fourth part introduces the multipath geometric model of the meter wave MIMO radar in the low-angle tracking environment.For the meter wave MIMO radar,not only the receiving beam forming is performed in the echo signal processing process,but also the transmitting beam forming is performed,and the MIMO radar It is often necessary to form multiple beams at the same time.When the number of array elements is large,the amount of remote calculation will be greater.The existing RML algorithm based on the array element space is not suitable for this system radar.Therefore,it is of great practical significance to study how to reduce the computational complexity of MIMO system meter wave radar when measuring altitude at low elevation angles.For this reason,a low-elevation estimation method for meter wave MIMO radar based on beam space is proposed.The algorithm can not only guarantee the accuracy of angle measurement,but also save a lot of calculation time,which meets the actual engineering requirements.