The research direction of applying modern signal processing methods to improve the ability to distinguish target angular coordinates for radar systems with small antenna sizes has been of particular interest to scientists. of interest, typically the methods MUSIC (multiple signal classification) and ESPRIT (estimation of signal parameters via rotational invariant techniques).
Factors that affect the ability to distinguish target corner coordinates include: Signal/noise ratio, sample size used for calculation, number of elements of the receiving antenna, correlation level of signal space and Noise in the receiving channels, phase difference between the receiving channels and the magnitude of the direction angle of the reflected signal source, serve as a basis for forming technical solutions in the design and manufacture of pinpoint radar systems. Target corner coordinates are based on spatial correlation assessment of reflected signals and noise.
In recent years, there have been many scientific publications on solutions to improve the ability to distinguish angular coordinates of radar targets. The proposed solutions are mainly based on the application of phased array antenna systems combined with modern signal processing methods. According to radar antenna theory, the ability to distinguish the angular coordinates of a radar target is inversely proportional to the size of the antenna system.
Illustration photo / qdnd.vn
Thus, to increase the ability to distinguish the angular coordinates of the target, it is necessary to increase the size of the antenna, but increasing the size of the antenna will make the radar more cumbersome and complex, causing a lot of time. during deployment and recovery and are vulnerable to enemy reconnaissance and destruction.
The urgent problem is to improve the ability to distinguish the angular coordinates of the target while still ensuring the small size of the antenna. To solve this problem, it is necessary to use MUSIC and ESPRIT methods. However, the use of these methods requires meeting some high requirements for processing equipment, probe signal generation equipment as well as receiver channel parameters because of the sensitivity of coordinate measurements. The angle depends on the signal/noise ratio, the sample size used for calculation, the number of elements of the receiving antenna, the correlation value of the signal space and the noise of the receiving channels, and the phase difference between receiving channels and the magnitude of the target angle θ… Therefore, it is necessary to research, survey and evaluate the influence of these factors on the ability to distinguish target angular coordinates based on the use of signals. Linear frequency modulation probe was proposed by the research team.
The probe signal has a frequency that varies linearly with time. The reflected signal from the target is received by the antenna elements and sent to the frequency mixer. The signal reflected from the target at the output of the mixers has a frequency that depends on the distance and radial speed of the target. Therefore, the structure of the receiving channel radar system must be carefully calculated between the mathematical matrices and the actual “matrix” that can be deployed. At the same time, a survey of factors affecting the ability to distinguish target angular coordinates of small antenna size radar systems must be conducted in steps.
Research, survey, and evaluate the effects of signal/noise ratio, sample size used for calculation, number of elements of the receiving antenna, spatial correlation value of the signal and noise of the receiving channels , phase difference between receiving channels… to the ability to distinguish target angular coordinates of the multi-channel receiving radar system. The ability to distinguish the target angular coordinates is sensitive to the inhomogeneity of the antenna elements, amplitude, phase and noise in the receiving channels, etc. The direction angle of the target compared to the normal of the antenna The larger it is, the lower the ability to distinguish target corner coordinates.
The assessments made based on the survey results are an important basis for designing and optimizing radar systems with high requirements for the ability to distinguish target corner coordinates.
Lieutenant Colonel, MSc LE DUY DUC (Department of Basic Engineering, Air Force Academy)