The working state of the tested antenna in antenna measurement can be either transmitting state or receiving state. This can be flexibly selected according to the measurement content, measurement equipment, site conditions and other factors. 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 measurement, the reciprocity principle must be applied under certain conditions.
(1) Antenna must be linear and passive, such as satellite TV receiving antenna, whose feed is integrated with LNB, and can not be used for transmission.
(2) The impedance matching of transceiver system should be good. Although there are multiple reflections between the antenna to be measured and the source antenna, this effect is not serious due to the attenuation of free space propagation. The impedance matching between source antenna, feeder, signal source, antenna to be measured, feeder and receiver is an important condition to satisfy reciprocity principle.
(3) When switching the antenna, there are no active devices in the transceiver branch, such as power amplifier, low noise amplifier, mixer, etc.