I have a little bit of problem understanding complex attenuation calculations when there is a shield involved between the transmitter and the receiver.
Let's take a simple example:
We have a theoretical isotropic transmitter with 0 dBi gain radiating 30 dBm (1 W) of power in all directions at 1 GHz frequency. Then we have a shield at 5 cm distance. So before the shield we reduce the power to 23.58 dBm, due to free space path loss. Furthermore the shield provides us 50 dB electric shielding, so after the shield we have −26.42 dBm power. And we have another 50 cm distance between the outer shield and the isotropic receiver antenna with 0 dBi gain. That reduces the power to -52.84 dBm. So given that both the receiver and the transmitter works at 100% efficiency, in a theoretical way, that would leave us with -52.84 dBm power at the receiving end. So the total setup would provide us with 82.84 dB attenuation. And therefore our receiver antenna would pickup only 5.2 Nano Watts from the total 1 Watt radiated.
Is my theory/thoughtprocess valid? Can we add up decibel values like this. I am still learning about dealing with decibels in a complex calculation.
Calculations done with:
- Indeed sorry for typo and errors @Mike, also as @Andy aka pointed out yes its 0 dBi. So I recalculated everything now using the calculator links provided above (for some reason the other website doesnt load). And yes the calculator apparently uses the free-space-path-loss equation, whereas tomnexus has pointed out that I may have to use antenna path loss between antennas.
- @Dan Mills pointed out that shielding could be different in the near field, but I specifically referred to the electrical shielding, since the magnetic shielding will be different. So let's just consider 50 dB overall electric attenuation of the shield itself from the incident wave to the transmitted wave, if that is possible.