Antenna Measurements basics
This page covers different antenna measurement basics. It mentions test setup used for antenna measurements.
As we know antenna radiates EM waves in various directions to certain proportion. This radiation is referred as radiation pattern of the antenna. There are two regions around the antenna viz. near field region (< 3*λ )and far field region (> 3*λ ). Refer near field vs far field➤. Antenna can be tested and various parameters are measured in indoor chamber or in outdoor range facility.
Antenna measurement test setup
Typical setup for antenna measurement and testing is shown in the figure-1 above. The horn antenna is used as standard transmitting antenna. The antenna under test (i.e. AUT) is used as receiving antenna in the setup. The AUT is placed on rotating table or positioner. As mentioned RF synthezier or sweeper is used at transmitter which feeds the signal of desired frequency and power. AUT is rotated in azimuth and elevation and radiation pattern is recorded at the receiver.
For outdoor range, receiving antenna is placed in far field region. For indoor range, entire setup is placed in anechoic chamber, where in walls are covered with wave absorbing material. This will allow AUT testing free from any building structure and will have testing as if antenna is placed in unbounded free space medium.
Various antenna measurements are taken using this setup.
Typical parameters which are measured include antenna radiation pattern,
gain, side-lobes, directivity, HPBW(Half Power Bandwidth),
cross-polarization, back radiation etc.
Refer Antenna Terminology which describes various terms related to the RF antenna.