Antenna Measurements in a Reverberation Chamber
Radiation Efficiency is the most important performance parameter of an antenna on a mobile terminal in a multipath propagation environment.
The radiation efficiency can be measured in a reverbaration chamber.
The radiation efficiency is reduced by three contributions:
- Reflections due to mismatch at input port of antenna.
- Absorption in antenna itself due to lossy materials.
- Absorption in lossy objects (phantom) near antenna.
The input impedance can also be measured, as it would be seen if the antenna and the phantom were located in an anechoic chamber. This is obtained by complex averaging of S11 over the stirrer positions. Thereby the statistic contribution from the chamber is removed.
The results below are for a validation case consisting of a dipole at distance from a PVC cylinder filled with tissue equivalent liquid.
Bluetest RC800 reverberation chamber and setup for antenna measurements. The field is stirred by 2 mechanical stirrers, a platform stirrer, polarization stirring and 25 MHz frequency stirring.
Validation case when it is located in anechoic chamber.
Comparison between radiation efficiencies of validation case measured in reverberation chamber and computed with FDTD, at different distances from lossy cylinder.
Comparison between reflection coefficients at dipole port, for 10 mm distance to lossy cylinder.
