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Dispersion Removal


Filter Banks
tex2html_wrap_inline3922   Cheap, reliable
tex2html_wrap_inline3922   Difficult to get very narrow channels
tex2html_wrap_inline3922   Variable gains introduces systematics
tex2html_wrap_inline3922   Poorly matched gains of two polarisation causes systematics
tex2html_wrap_inline3922   Fine for slow pulsars

Figure 37: A logical signal path for observations at 1400 MHz

tex2html_wrap_inline3922   Overcome above systematics
tex2html_wrap_inline3922   Flexible but expensive
tex2html_wrap_inline3922   All or nothing approach

Frequency sweeping
tex2html_wrap_inline3922   Swept local oscillator follows frequency drift of pulse
tex2html_wrap_inline3922   Very precise
tex2html_wrap_inline3922   Inflexible
tex2html_wrap_inline3922   Limited to a few pulsars with suitable DMs

Coherent dedispersion
tex2html_wrap_inline3922   Record base-band voltages
tex2html_wrap_inline3922   Apply inverse transform in software
tex2html_wrap_inline3922   Best way to remove dispersion
tex2html_wrap_inline3922   Recording data is difficult tex2html_wrap_inline3992 MB/sec
tex2html_wrap_inline3922   Now becoming possible with DLT tapes

Jon Bell
Thu Dec 19 15:15:11 GMT 1996