The anechoic chamber is a professional electromagnetic simulation analysis software that can perform full three-dimensional scene calculation. It can analyze the propagation characteristics of electromagnetic waves when they act on complex electrically large objects (such as airplanes, vehicles, electromagnetic anechoic chambers, etc.). This product is an electrically large-scale high-frequency electromagnetic simulation tool based on high-frequency geometric diffraction and ray tracing methods. It overcomes the defects of traditional high-frequency progressive methods that cannot handle multiple reflection, transmission, diffraction and surface creeping waves, and is suitable for solving electrically large-scale problem. It can simulate an open field environment, and can provide a free propagation space of electromagnetic waves without external interference, no leakage, and no reflected echo for electromagnetic simulation tests and electromagnetic compatibility tests. It can realize an indoor field test environment with confidentiality and all-weather work. Unparalleled superiority. At present, many domestic scientific research institutions have invested a lot of financial and material resources to build anechoic chambers of different scales and different purposes. Because the construction cost is quite expensive, it is difficult to make major changes after it is completed, so perform performance before construction. Simulation analysis is very important.
The electromagnetic distribution performance of the test area is the embodiment of the comprehensive performance of the anechoic chamber, and is the key to the design of the anechoic chamber. This paper uses the simulation software to create an anechoic chamber model, and reasonably design the layout of the absorbing materials on each wall of the anechoic chamber to make the test area normalized site attenuation, site voltage standing wave ratio, field uniformity and other electrical performance indicators to meet the design requirements .
Use simulation software to establish a darkroom model, set the material properties of each part of the interior, lay different absorbing materials on the wall and the ground, define the transceiver antenna according to the actual test situation, import the object model under test, and simulate the actual test scene. Evaluate the electric field and magnetic field according to the scattering characteristics and the reflection and transmission coefficients of related materials. By combining the scattering field with the specific antenna mode, and through the secondary calculation, analyze the normalized field attenuation and field voltage standing wave ratio of the anechoic chamber test area , Field uniformity and other parameters.
The site voltage standing wave ratio needs to meet the requirements of CISPR16, and the standing wave ratio is less than 6dB in the range of 1GHz～18GHz. Site voltage standing wave ratio simulation conditions: the test distance is 3m, and the layout is shown in Figure 10. According to relevant standards, when the height of the transmitting antenna and the receiving antenna are both 1m, calculate when the transmitting antenna is located in C1～C6, L1～L6, When the positions of R1 to R6 and F1 to F6 are located, calculate the received power ratio to obtain the voltage standing wave ratio. When the height of the transmitting antenna and the receiving antenna are both 2m, calculate the transmitting antenna to be located at F1 to F6.
The voltage standing wave ratio is obtained from the received power ratio at the position. Due to space limitations, this article only introduces the simulation results of the vertical polarization field voltage standing wave ratio. The transmitting antenna is a dipole antenna, and the receiving antenna is an omnidirectional antenna. The simulation frequencies are 1GHz and 2GHz. , 3GHz, 4GHz, 6GHz, 8GHz, 18GHz, the site voltage standing wave ratio is required to be less than 6dB. In the simulation, five walls are pasted with absorbing materials, and the ground is a metal plate. A 2m wide and 5m long absorbing material is laid between the turntable and the receiving antenna. The layout is shown, and the simulation uses the absorbing material.
The field uniformity needs to meet the technical requirements of standards such as IEC61000-4-3. In the range of 80MHz to 2GHz, the deviation of 75% of the field strength value on the imaginary vertical plane of the quiet zone is within 0 to 6dB. According to the relevant standards, the simulation model shows that the transmitting antenna is 1.55m from the ground, and there are 16 receiving antennas. The 4³4 array is located at the center C of the turntable. The array is evenly distributed within 1.5m³1.5m. The bottom of the array is 0.8m from the ground. It is an omnidirectional antenna.
This paper uses professional simulation software to analyze the electromagnetic characteristics of the three most important parameters (normalized site attenuation, site voltage standing wave ratio, field uniformity) that affect the electrical performance of the anechoic chamber, rationally design the layout of the absorbing material, and optimize the radio wave The performance of the anechoic chamber has been successfully applied to the engineering design of an electric wave anechoic chamber.