Antenna testing method

　　1. Far field method

　　The far-field method, also known as the direct method, obtains far-field data that does not require computation or post-processing and is a directional pattern. However, it often requires a long distance to test the characteristics of the antenna, so most far-field methods are conducted at outdoor testing sites. The outdoor field is divided into elevated field and inclined field, collectively known as the free space testing field. The main disadvantage is that it is easily affected by external interference and site reflection. If the far-field method is performed in a dark room, it is called an indoor field. Due to the large space required, indoor venues often have high costs.

　　The compact field is classified as a far-field testing field, but it does not require a large testing field. Instead, it uses a parabolic antenna and a feed source, with the feed source placed in the focal area of the parabolic antenna. The wave reflected by the parabolic surface is a plane wave. So the tested antenna is in the plane wave region. The machining accuracy requirements for compact field equipment are very high, and changing the operating frequency band requires replacing the feed source, which is costly.

　　2. Near field method

　　Near field measurement technology is a technique that uses a probe with known characteristics on a surface in the near-field region of an antenna to sample the amplitude and phase characteristics of the field, and obtains the far-field radiation characteristics of the antenna through rigorous mathematical transformations. According to the shape of the sampling surface, near-field testing fields are divided into three types: planar testing field, cylindrical testing field, and spherical testing field.

　　The main advantage of near-field measurement technology is that it requires a small field and can perform high-precision measurements in a microwave anechoic chamber, eliminating the difficulty of building large microwave anechoic chambers. The measurement is minimally affected by the surrounding environment, ensuring smooth operation 24/7. The amount of information measured is large, and by sampling a surface in the near-field region, the far-field amplitude, phase, and polarization characteristics of the antenna in any direction can be accurately obtained. near