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Michael Abbott

Michael Abbott

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NamePVDescription
I, Q

:PLL:FILT:I

:PLL:FILT:Q

Detector readbacks in I and Q components.  To regard the response as a complex number, compute

Mathinline
bodyr = I + i\times Q
.

Magnitude

:PLL:FILT:MAG

:PLL:FILT:MAG_DB

Magnitude of the detector response and converted to dB, relative to overflow at magnitude = 1.0.
Phase:PLL:FILT:PHASEPhase of the detector response.
Debug
Links to the Tune PLL Debug for a detailed view of the detector response.

:PLL:DEBUG:ENABLE_SThis PV indicates whether the debug readbacks are enabled.  This readback is normally not required, and the extra processing load can usefully be avoided by leaving this disabled when not required.
Mag rel std:PLL:DEBUG:RSTD_ABS, :PLL:DEBUG:RSTD_ABS_DB

"Magnitude relative standard deviation".  This pair of fields and "IQ rel std" below are an attempt to capture the quality of signal and lock as a single number.  This number should be small if there is a strong detector signal, but is not affected by the quality of the lock.  Given a debug IQ waveform

Unit
body\vec{z}
the relative standard deviation here is calculated as:

Mathblock
\frac{\text{std}(|\vec{z}|)}{\langle| \vec{z}|\rangle}

The :RSTD_ABS_DB  is simply

Mathinline
body20\log_{10}(\text{RSTD_ABS})
.

IQ rel std:PLL:DEBUG:RSTD, :PLL:DEBUG:RSTD_DB

"IQ relative standard deviation".  This is intended to capture the quality of the PLL lock as a single number: this number should be small if there is little deviation in angle.  Give waveform

Unit
body\vec{z}
this is calculated as:

Mathblock
\frac{\text{std}(\vec{z})}{|\langle \vec{z}\rangle|}

Again, :RSTD_DB  is simply

Mathinline
body20\log_{10}(\text{RSTD})
.

Status

The status indicators here show the status of the detector and the feedback controller, and show the reason for stopping if feedback is not running.  When feedback is running all indicators in the left hand column will be green, otherwise one with be red to indicate a reason for stopping.  Similarly the right hand column shows the current active state of each part of the Tune PLL system.

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