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Commits on Dec 11, 2020

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Showing with 54 additions and 3 deletions.
  1. BIN images/filters/ac-couple.png
  2. BIN images/filters/autocorrelation.png
  3. +54 −3 section-decodes.tex
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57 changes: 54 additions & 3 deletions section-decodes.tex
Original file line number Diff line number Diff line change
@@ -253,10 +253,18 @@ \subsection{Output Signal}
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\pagebreak
\section{AC Couple}
\label{filter:accouple}

Automatically removes a DC offset from an analog waveform by subtracting the average of all samples from each sample.
Dynamic range is lost compared to doing true AC coupling in the instrument front end, but there are certain situations
where offset removal is necessary in postprocessing.

This filter should only be used in postprocessing already acquired data, or other situations in which AC coupling in
the hardware (via an AC coupled probe, or coaxial DC block) is not possible.

\begin{figure}[h]
\centering
\includegraphics[width=17cm]{images/filters/ac-couple.png}
\caption{Example AC coupling}
\end{figure}

\subsection{Inputs}

@@ -275,14 +283,17 @@ \subsection{Parameters}
\subsection{Output Signal}

This filter outputs an analog waveform with identical sample rate to the input, vertically shifted to center the signal
about zero volts.
at zero volts.

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\pagebreak
\section{ADL5205}
\label{filter:adl5205}

Decodes SPI data traffic to one half of an ADL5205 variable gain amplifier.

TODO: Screenshot

\subsection{Inputs}

\begin{tabularx}{16cm}{llX}
@@ -304,6 +315,46 @@ \subsection{Output Signal}
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\pagebreak
\section{Autocorrelation}
\label{filter:autocorrelation}

This filter calculates the autocorrelation of an analog waveform. Autocorrelation is a measure of self-similarity
calculated by multiplying the signal with a time-shifted copy of itself. In Fig. \ref{filter_accouple}, strong peaks
can be seen at multiples of the 8b/10b symbol rate.

For best performance, it is crucial to keep the maximum offset as low as possible, since filter run time grows linearly
with offset range.

\begin{figure}[h]
\centering
\includegraphics[width=17cm]{images/filters/autocorrelation.png}
\caption{Example of autocorrelation on a serial data stream}
\label{filter_accouple}
\end{figure}


\subsection{Inputs}

\begin{tabularx}{16cm}{llX}
\thickhline
\textbf{Signal name} & \textbf{Type} & \textbf{Description} \\
\thickhline
din & Analog & Input waveform \\
\thickhline
\end{tabularx}

\subsection{Parameters}

\begin{tabularx}{16cm}{llX}
\thickhline
\textbf{Parameter name} & \textbf{Type} & \textbf{Description} \\
\thickhline
Max offset & Integer & Maximum shift (in samples)\\
\thickhline
\end{tabularx}

\subsection{Output Signal}

This filter outputs an analog waveform with the same timebase as the input, one sample for each correlation offset.

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\pagebreak