Re: Antenna gain in CST.
Hmm. I do not have CST, but .. 2)
10 dB indicates radiated power is more than input power (violation of conservation of energy)
"I think 10dB" does not mean that at all!
What it really means is the ratio of maximum value of the radiation intensity (it will be in a particular direction), as compared to a reference radiator such as the
theoretical isotropic source which radiates the same intensity of radiation in
all directions equally. In this case, the ratio is denoted "dBi"
If the reference is taken to be a standard dipole, then the gain is cited as "dBd" This gain has a value 2.15dB less than when using dBi.
There is no violation of any conservation law. The energy that would have been radiated equally everywhere is, by the action of the the antenna, concentrated in a particular direction at the expense of all other directions.
-2.6dB is also possible, if an antenna has such dissipative losses that a plot of the gain lobe has a maximum value that is less than the value a isotropic source would have managed.
Let us not inadvertently mis-apply the term "power" either.
Power (Watts) is the
rate of energy transfer (Joules/Sec).
dB are highly convenient for expressing values of power that span many decades, and we commonly use dBm (relative to 1 milliWatt) or dBW (relative to 1 Watt). Easy to see that this rate, raised by the antenna gain, gives a value much bigger. This does
not mean that many Watts was fed into the antenna! Its the Watts that one would have had to offer a theoretical isotropic radiator to get that value.
This is why the input power, raised by the antenna gain, is known as the
Effective Isotropically Radiated Power (EIRP)