The triple resonant box was checked again. Each resonant frequency was tuned and the box is ready to go.
Before the actual installation I want to hear opinions about RF reflections because the RF reflection at 29 MHz isn't negligible.
It might be a problem since the reflection will go back to the RF generation box and would damage the amplifiers.
(Frequency adjustment and resultant reflection coefficient)
In order to tune the resonant frequencies the RF reflection was continuously monitored while the variable inductors were tweaked.
The plot below shows the reflection coefficient of the box after the frequency adjustment.
In the upper plot, where the amplitude of the reflection coefficient of the box is plotted, there are three notches at 11, 29.5 and 55 MHz.
A notch means an RF power, which is applied to the resonant box, is successfully absorbed and consequently the EOM obtains some voltage at this frequency.
These power absorptions take place at the resonant frequencies as we designed so.
A good thing by monitoring this reflection coefficient is that one can easily tune the resonant frequency by looking at the positions of the notches.
Note that :
If amplitude is 0dB ( =1), it means all of the signal is reflected.
If a circuit under test is impedance matched to 50 Ohm the amplitude will be ideally zero (= -infinity dB).
at 11 MHz = -15 dB (3% of RF power is reflected)
at 29.5 MHz = -2 dB (63% of RF power is reflected)
at 55 MHz = -8 dB (15% of RF power is reflected)