diff --git a/doc/papers/2010/ExpA/lofar.tex b/doc/papers/2010/ExpA/lofar.tex index f9ef577d11b40aa5a4e59b967b7eaf8bef1f6280..95ff5429343ddd039e033d0e2f1f4123f077c6fa 100644 --- a/doc/papers/2010/ExpA/lofar.tex +++ b/doc/papers/2010/ExpA/lofar.tex @@ -86,7 +86,7 @@ grestore \title{The LOFAR Correlator%\thanks{Grants or other notes %about the article that should go on the front page should be -%placed here. General acknowledgments should be placed at the end of the article.} +%placed here. General acknowledgements should be placed at the end of the article.} } %\subtitle{Do you have a subtitle?\\ If so, write it here} @@ -464,7 +464,7 @@ Since the most common observation mode uses 256 channels, we optimized this case a bit further, and manually wrote a more efficient assembly implementation for the 256-point FFT. -In priciple, any reasonable number of channels per subband is supported. +In principle, any reasonable number of channels per subband is supported. However, powers of two are more efficient, since power-of-two FFT sizes are more efficient. Also, the number of FIR filter taps is fixed to~16, so the quality of the @@ -549,7 +549,7 @@ and transient pipelines. We briefly describe the modes here; more information can be found in the paper on pulsar modes elsewhere in this issue~\cite{Hessels:10}. -The beamforming pipelines fall into two catagories: the coherent modes and +The beamforming pipelines fall into two categories: the coherent modes and incoherent modes. The coherent modes add the complex samples from all stations, resulting in a complex voltage. @@ -584,14 +584,14 @@ direction-dependent) complex weight, and then added to the weighted samples of the other stations. To create multiple pencil beams with different directions, different delays -are appied to a station before addition. +are applied to a station before addition. Note that the center beam needs no correction, as the phase correction for this direction was already performed at high precision (see \circlenumber{7}). The other pencil beams are corrected with respect to the center beam. -The directions of the pencil beam can be choosen freely (of course, observing +The directions of the pencil beam can be chosen freely (of course, observing outside the station beams makes no sense). -However, there is provision for specifing a honeycomb structure around the +However, there is provision for specifying a honeycomb structure around the center beam (see Figure~\ref{fig:pencil-beams}). This simplifies the specification of an observation, since a honeycomb structure requires only two parameters: the diameter of a pencil beam and the number @@ -609,7 +609,7 @@ Since the beam of the incoherent sum covers the station beams, there is no need to create multiple pencil beams. As a consequence, the output data rate of this mode is much smaller. Either Stokes I,Q,U,V~(\circlenumber{15}) or to Stokes~I -only~(\circlenumber{16}) can be choosen. +only~(\circlenumber{16}) can be chosen. \paragraph{Integration of Beam-Formed Products \circlenumber{17}}