With the wide application of electromagnetic stealth technology in military equipment (especially aircraft), the importance of the research on electromagnetic scattering characteristics of radar targets has become increasingly prominent. At present, there is an urgent need for a detection method of the electromagnetic scattering characteristics of the target, which can be used for the qualitative analysis of the electromagnetic stealth performance and stealth effect of the target. Radar Cross Section (RCS) measurement is an important method to study the electromagnetic scattering characteristics of targets. As an advanced technology in the field of aerospace measurement and control, radar target characteristics measurement is widely used in the design of new radar. It can determine the shape and size of targets by measuring RCS at important attitude angles. High precision measurement radar generally obtains target information by measuring target motion characteristics, radar reflection characteristics and Doppler characteristics, among which RCS characteristics measurement is to measure target reflection characteristics.
Definition and measurement principle of radar scattering interface
Definition of scattering interface When an object is illuminated by electromagnetic waves, its energy will scatter in all directions. The spatial distribution of energy depends on the shape, size, structure of the object and the frequency and characteristics of the incident wave. This distribution of energy is called scattering. The spatial distribution of the energy or power scattering is generally characterized by the scattering cross section, which is an assumption of the target.
Outdoor measurement
External field RCS measurement is important for obtaining electromagnetic scattering characteristics of large full size targets [7] The outdoor field test is divided into dynamic test and static test. The dynamic RCS measurement is measured during the flight of the solar standard. The dynamic measurement has some advantages over the static measurement, because it includes the effects of wings, engine propulsion components, etc. on the radar cross section. It also meets the far-field conditions well from 11 to 11 However, its cost is high, and affected by the weather, it is difficult to control the attitude of the target. Compared with the dynamic test, the angle glint is serious. The static test does not need to track the solar beacon. The measured target is fixed on the turntable without rotating the antenna. Only by controlling the rotation angle of the turntable, the omni-directional measurement of the measured target 360 can be realized. Therefore, the system cost and test cost are greatly reduced At the same time, because the center of the target is stationary relative to the antenna, the attitude control accuracy is high, and the measurement can be repeated, which not only improves the accuracy of measurement and calibration, but also is convenient, economical, and maneuverable. Static testing is convenient for multiple measurements of the target. When RCS is tested outdoors, the ground plane has a great impact, and the schematic diagram of its outfield test is shown in Figure 2 The method that first came up with was to isolate the large targets installed within a range from the ground plane, but in recent years it is almost impossible to accomplish this It is recognized that the most effective way to deal with ground plane reflection is to use the ground plane as a participant in the irradiation process, that is, to create a ground reflection environment.
Indoor compact range measurement
The ideal RCS test should be carried out in an environment free of reflected clutter. The incident field illuminating the target is not affected by the surrounding environment. The microwave anechoic chamber provides a good platform for indoor RCS test. The background reflection level can be reduced by reasonably arranging the absorbing materials, and the test can be carried out in a controllable environment to reduce the impact of the environment. The most important area of the microwave anechoic chamber is called the quiet area, and the target or antenna to be tested is placed in the quiet area Its main performance is the size of the stray level in the quiet area. Two parameters, reflectivity and inherent radar cross section, are commonly used as the evaluation indicators of the microwave anechoic chamber [.. According to the far field conditions of the antenna and RCS, R ≥ 2IY, so the scale D of the day is very large, and the wavelength is very short. The test distance R must be very large. To solve this problem, high-performance compact range technology has been developed and applied since the 1990s. Figure 3 shows a typical single reflector compact range test chart. The compact range uses a reflector system composed of rotating paraboloids to convert spherical waves into plane waves at a relatively short distance, and the feed is placed at the reflector The focal point of the object surface, hence the name "compact". In order to reduce the taper and waviness of the amplitude of the static zone of the compact range, the edge of the reflecting surface is processed to be serrated. In indoor scattering measurement, due to the limitation of the size of the darkroom, most darkrooms are used as the measurement scale target models. The relationship between the RCS () of the 1: s scale model and the RCS () converted to the 1:1 real target size is one+201gs (dB), and the test frequency of the scale model should be s times the actual solar scale test frequency f.
Post time: Nov-21-2022