Classification of Antenna Radiation by Special Characteristi

　　In order to classify antenna electromagnetic wave, we must do measurement first. But how to do measurement is a very troublesome problem. Today, the manufacturer of electronic antenna has made a summary for you. Let's go and have a look.

　　The far-field method can be divided into outdoor field, indoor field and compact field, and the near-field method can be divided into plane, spherical and cylindrical near-field methods.

　　1. Far-field method

　　Far-field method is also called direct method. The obtained far-field data need not be calculated and post-processed, but is the pattern. However, it often takes a long distance to test the antenna
characteristics, so most of the far-field methods are carried out in outdoor test sites. The outdoor field is divided into elevated field and skew field, which are collectively called free space test field. The main drawback is that it is easy to be affected by external interference and site reflection. Far field method is called indoor field if it is carried out in darkroom. Because of the large space required, indoor venues are often expensive.

　　The compact field belongs to the far field test field in classification, but it does not need a large test field. Instead, it uses a parabolic antenna and a feed, which is placed in the focus area of the parabolic antenna. The reflected wave through the parabolic surface is a plane wave. So the antenna under test is in the plane wave area. The processing accuracy of the equipment in the contraction yard is very high. It is necessary to replace the feeder to change the working frequency band, and the cost is high.

　　2. Near-field method

　　Near-field measurement technology is a technology that uses a probe with known characteristics to sample the amplitude and phase characteristics of the field on a surface of the near-field area of the antenna, and obtains the far-field radiation characteristics of the antenna through strict mathematical transformation. According to the shape of the sampling surface, the near-field test field can be divided into three types: plane test field, cylindrical test field and spherical test field.

　　The main advantage of near-field measurement technology is that it needs a small site and can be used in high-precision measurement in microwave anechoic chamber, thus avoiding the difficulty of building large-scale microwave anechoic chamber. The measurement is very little affected by the surrounding environment, so that it can be carried out smoothly all day. The measured information is large, and the far-field amplitude, phase and polarization characteristics of the antenna in any direction can be accurately obtained by sampling a surface in the near-field region.

　　The near-field measurement technology will be discussed in detail in the next phase of the test explanation of the electronic antenna manufacturer. Please pay more attention to it.