Low-Noise Components

Rugged Low-Noise Amplifiers

The signals received through a wireless link are commonly very weak. Therefore, low-noise amplifiers (LNA) are used in the first receiver stage in order to amplify the signal to a power level required for further processing without adding significant distortion.

Although LNAs are designed to amplify very low power levels, there are chances that they receive very strong signals, which is not desired. This could happen for example if receive and transmit units are placed close to each other, like in mobile base stations. The traditional approach to prevent damage of the LNA due to input overdrive is to place power-limiting circuits between the antenna and the LNA.

LNAs based on GaN transistors, on the other hand, have the potential to withstand high input overdrive powers without requiring protection circuitry, since the material system intrinsically provides high breakdown voltages and high-power handling capability.

The FBH is currently developing highly rugged LNAs for space applications. A LNA for 3,5 - 7 GHz providing  a noise figure below 1.8 dB has been demonstrated. It survived an input overdrive power of 33 dBm (2 W) for 16 h without any degradation [Publication, Rudolph 2006], [Publication, Rudolph 2007]. Commercially available LNAs based on GaAs technology, for comparison, are commonly specified for maximum input powers below 20 dBm (100 mW).