With the wide application of electromagnetic stealth technology in military equipment (especially aircraft), the importance of radar target electromagnetic scattering characteristics has become increasingly prominent. At present, a detection method of target electromagnetic scattering characteristics is urgently needed for quantitative and qualitative analysis of target electromagnetic stealth performance and stealth effect. Radar cross-section measurement (RCS) 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 characteristic measurement is widely used in the design process of new radar. It can determine the shape and size of the target by measuring the RCS at important attitude angle positions. High-precision measurement radar generally obtains target information by measuring the motion characteristics, radar reflection characteristics, and Doppler characteristics of the target, among which radar RCS characteristic measurement is to measure the reflection characteristics of the target.

Definition and Measurement Principle of Radar Scattering Interface

Definition of Scattering Interface When an object is illuminated by an electromagnetic wave, its energy will be scattered in all directions. The spatial distribution of energy depends on the shape, size, and structure of the object, as well as the frequency and characteristics of the incident wave. This distribution of energy is called scattering. This spatial distribution of energy or power scattering is generally characterized by a scattering cross section, which is a hypothesis of the target.

outdoor measurement

Outdoor field RCS measurement is an important step to obtain the electromagnetic scattering characteristics of large-scale full-size targets [7]. Outdoor field testing is divided into dynamic testing and static testing. Dynamic RCS measurement is measured during the flight of the Japanese standard, and dynamic measurement has certain advantages over static measurement, because it includes effects such as wings and engine push components on radar scattering cross sections. It also meets the far-field conditions well. However, its cost is higher and affected by the weather, the target attitude control is difficult, and the angular flicker is serious. Compared with dynamic testing, static testing does not require tracking the Japanese standard, the measured target is fixed on the turntable, and the antenna does not need to be rotated. All-round measurement of the measured target 360 can be achieved by controlling the rotation angle of the turntable, thus greatly reducing the cost and testing cost of the system. At the same time, since the target center 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 facilitates convenient, economical, and operable static testing to facilitate multiple measurements of the target. During the outdoor test of the RCS, the influence of the ground plane is very large, and the schematic diagram of the field test is shown in Figure 2. The earliest idea was to isolate a large-sized target installed within a range from the ground plane, but in recent years, it has been considered almost impossible to complete. It has been realized that the most effective way to deal with ground plane reflections is to use the ground plane as a participant in the irradiation process, that is, to create a ground reflection environment.

Indoor compaction field measurement

The ideal RCS test should be carried out in an environment without reflection clutter F disturbance, and the incident field of the irradiated target is not affected by the surrounding environment. The microwave anechoic chamber provides a good platform for indoor RCS testing. The background reflection level can be reduced by reasonable arrangement of absorbing materials, and the test can be carried out in a controlled environment to reduce the impact of the environment. The most important area of the microwave anechoic chamber is called the quiet zone, and the target or antenna to be measured is placed in the quiet zone. Its main performance is the size of the spurious level in the quiet zone. Two parameters, reflectivity and intrinsic radar cross section, are commonly used as evaluation indicators for microwave anechoic chambers [...] According to the antenna and RCS far-field conditions, R ≥ 2IY, so the scale size D is very large, and the test distance R must be very large when the wavelength is very short. To solve this problem, after the 1990s, high-performance compression field technology was developed and applied. Figure 3 shows a typical single-reflector compression field test diagram. The compression field uses rotation. The reflector system composed of an object surface can convert a spherical wave into a plane wave at a relatively short distance, and the feed is placed at the focus of the parabolic surface, hence the name "compression". In order to reduce the cone cutting and corrugation of the amplitude of the dead zone of the compression field, the edge of the reflector is treated as a zigzag. In indoor scattering measurement, due to the limitation of the size of the darkroom, most darkrooms are used as measurement scaled target models. The relationship between the RCS () of the 1: s scaled model and the RCSO converted to 1:1 true target size is one + 201gs (dB), and the test frequency of the scaled model should be s times the actual daily standard test frequency f.