Reciprocity in antenna measurement

　　The working state of the tested antenna in antenna measurement can be either the transmitting state or the receiving state. This can be flexibly selected based on factors such as the measurement content, measurement equipment, site conditions, etc. According to the principle of antenna reciprocity, the results of measuring the parameters of the antenna in two working states should be consistent.

　　However, in practical measurements, the reciprocity principle must be applied under certain conditions.

　　(1) Antennas must be linear and passive, such as satellite TV receiving antennas, whose feed source is integrated with the high-frequency head (LNB) and cannot be used for transmission.

　　(2) The impedance matching of the transceiver system should be good. Although there are multiple reflections between the test antenna and the source antenna, the impact is not severe due to the attenuation of free space propagation. The impedance matching between the source antenna, feeder, signal source, and the tested antenna, feeder, and receiver is an important condition for satisfying the reciprocity principle.

　　(3) When swapping antennas, there are no active components in the transmitting and receiving branches, such as power amplifiers, low-noise amplifiers, mixers, etc.