Hi, please can you comment...Theoretically, if an antenna is perfectly matched with the load (for example the rectifier), the amplitude of the voltage on the load will be the antenna amplitude over two! And this result is independent of the current absorbed by the load.

So, in condition of matching the efficiency of the rectifier has no influence on the maximum operative range of the tag. Is it correct? Why do people try to maximize the efficiency of the rectifier and not to minimize its input voltage needed to work?

Actually, the efficiency of the rectifier defines the amount of the DC power delivered to the load. From this point of view, the efficiency of the rectifier does have influence on the operative range of the tag. After all, the electronics of the tag have a minimum power requirement, not a minimum voltage requirement.

For example, assume that we can achieve the desired DC voltage levels at a certain distance (of e.g. 80cm). However, the output power of the rectifier (which is defined by the efficiency of the rectifier) may not be sufficient to provide the load with the desired current levels.