Methods of the standard EMF generation
The previous chapter referred to two calibration methods: the standard transmitting antenna method (STA) or standard field method, and standard receiving antenna method (SRA) or substitution method. Let's characterize them briefly. 1. The STA method is based upon EMF generation with the use of a transmitting antenna whose parameters (radiation pattern, efficiency) are known to a required accuracy and established either theoretically or experimentally. The EMF at an observation point is calculated taking into account the parameters of the antenna, its excitation, and the geometry of propagation. 2. The SRA method requires a receiving antenna of well-known parameters and a system that makes it possible to measure current in the antenna or the voltage at its input. The SRA is placed in an EMF generated by an arbitrary source and then replaced by an antenna (meter, probe, device) under test. Two assumptions are made in this procedure: the EMF is stable enough to not change during the replacement, the antenna under test is immersed in the same field as the SRA and makes identical EMF deformations to the SRA. In the previous discussions we took into account EMF standards with dipole or loop antennas. However, an almost identical approach may be adopted when other types of standards are in use. For instance, in guided wave standards, the EMF is established on the ground of excitation measurement of a system of known parameters, which is similar to the standard field method. In the case of different types of chambers the substitution method is more appropriate.
Methods of the standard EMF generation, Page 1 of 2
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