deletions | additions       diff --git a/minres.tex b/minres.tex  index 6eea0d9..11d9a52 100644  --- a/minres.tex  +++ b/minres.tex 
...
where $k$ is the slope of the line fit to the spectrum of the pulsar, $S/N$ is the signal-to-noise ratio at the y-intercept (approximately the $S/N$ in the first harmonic) and it is assumed that harmonics past $S/N\sim1$ are not important. By eye, increasing the S/N by two orders of magnitude will add around 100 to 300 harmonics for 0437 and 2241, so 2048 phase bins should suffice for observing these pulsars with SKA1.  Now, it is reasonable to assume that more extreme pulsars with faster spin periods than currently known will be found given the sensitivity of SKA1. Taking the example of a sub-millisecond pulsar with a 500 $\mu$s spin period that requires 2048 phase bins to resolve all the structure in its pulse profile, we find that this implies a maximum time resolution of 200~ns. Na\"ively speaking 200~ns time resolution would imply 5~MHz frequency channels via a reciprocal bandwidth argument. However due to the nature of the temporal response of poly-phase polyphase  filterbanks, we suggest that the required channel width here is actually closer to 10~MHz. The above frequency and time resolutions allow us to suggest rewording for requirements 2691 and 2692 such that they are framed in terms of fractional resolutions of spin period with an absolute limit of 200 ns: 
...
\item \textbf{SKA1-SYS\_REQ-2962:} \textit{\bf SKA1\_Low Pulsar Timing resolution.} The SKA1\_Low when in pulsar timing mode shall resolve a pulsars pulse profile to better than 0.05\% of its spin period with a maximum resolution of 200 ns.  \end{itemize}  These two requirements should constrain both the acceptable channel widths provided to the SKA1 pulsar timing instruments and the polyphase filterbank design used to channelise the digitized baseband voltages.