rf feedback in rfmode element
Posted: 07 Dec 2022, 08:24
Dear Michael
In the past days, I spent some time to go back to the papers on the low level rf control and cavity state-space theory. Now I think I get a better understanding on your IPAC15 paper about rf-feedback in rfmode element.
Still, I would like to discuss a little bit to make sure my understanding is correct. I summarize my understanding in short:
1. The cavity voltage error \vec{V_{err}}=\vec{Vc} -\vec{V_{ref}} and generator current \vec{Ig} are sampled at the time n{T_rf}, n is integer number.
2. Amplitude IIR filter take the previous Abs{V_{err}} and Abs{\vec{Ig}} as input and generate the \delta{Abs{\vec{Ig}}} as output
3. Phase IIR filter takes the previous Arg{V_{err}} and Arg{\vec{Ig}} as input and generate the \delta{Arg{\vec{Ig}}} as output
4. \delta{\vec{Ig}} + \vec{Ig} is applied as the updated generated current to get the cavity voltage with feedback by the state-space equation.
Please let me know if my understanding is appropriate or not.
However, there is two things I still did not get clearly, hope you can help me to cover that,
The first one:
In step 2, amplitude filter translates the Abs{V_{err}} signal into Abs{\vec{Ig}}, which indicates that the amplitude filter coefficient b_i/a_0 with unit the same as 1/Z, where Z is impedance. In step 3, the phase filter translates the Arg{V_{err}} to Arg{\vec{Ig}}, which indicates the amplitude filter coefficient b_i/a_0 is dimensionless, is it?
The second one:
How should I set the gain info in the rf feedback? The filter gives an output value which is related to \delta{\vec{Ig}} to be update. Physically, how large the \delta{\vec{Ig}} should be? There should be another parameter as a gain factor to specify to connect the filter output and generator current to be modified \delta{\vec{Ig}, is it?
Looking forward to you reply.
yours Chao
In the past days, I spent some time to go back to the papers on the low level rf control and cavity state-space theory. Now I think I get a better understanding on your IPAC15 paper about rf-feedback in rfmode element.
Still, I would like to discuss a little bit to make sure my understanding is correct. I summarize my understanding in short:
1. The cavity voltage error \vec{V_{err}}=\vec{Vc} -\vec{V_{ref}} and generator current \vec{Ig} are sampled at the time n{T_rf}, n is integer number.
2. Amplitude IIR filter take the previous Abs{V_{err}} and Abs{\vec{Ig}} as input and generate the \delta{Abs{\vec{Ig}}} as output
3. Phase IIR filter takes the previous Arg{V_{err}} and Arg{\vec{Ig}} as input and generate the \delta{Arg{\vec{Ig}}} as output
4. \delta{\vec{Ig}} + \vec{Ig} is applied as the updated generated current to get the cavity voltage with feedback by the state-space equation.
Please let me know if my understanding is appropriate or not.
However, there is two things I still did not get clearly, hope you can help me to cover that,
The first one:
In step 2, amplitude filter translates the Abs{V_{err}} signal into Abs{\vec{Ig}}, which indicates that the amplitude filter coefficient b_i/a_0 with unit the same as 1/Z, where Z is impedance. In step 3, the phase filter translates the Arg{V_{err}} to Arg{\vec{Ig}}, which indicates the amplitude filter coefficient b_i/a_0 is dimensionless, is it?
The second one:
How should I set the gain info in the rf feedback? The filter gives an output value which is related to \delta{\vec{Ig}} to be update. Physically, how large the \delta{\vec{Ig}} should be? There should be another parameter as a gain factor to specify to connect the filter output and generator current to be modified \delta{\vec{Ig}, is it?
Looking forward to you reply.
yours Chao