3.4 Immunity

Immunity describes the robustness of an application. It is the type and level of injected disturbances that can be handled by the application prior to the malfunction occurrence. Examples are:

• In-band disturber (Signal to Noise Ratio (SNR))
• Blocking

For the certification of an application, mainly the radiated emission of the application is verified because all other factors vary, and, therefore, it is difficult to standardize them. The radiation of the application at a certain distance is very easy to standardize.

Even if an application passes the certification, it does not mean that there are no disturbances. It only says that the unwanted radiated signals are below the threshold. For the application, this might result in the situation that it will disturb themselves. A simple example would be an RF-based control of an engine. If the engine is off, the system has an excellent performance, but once the engine is started, the RF performance becomes poor. The reason for such an effect is the worsened SNR caused by the engine. That means the application disturbs its own RF communication. Such use cases must be validated by the application developer team as the performance validation is not part of the certification.