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projects:mkat_sband:pub:decfilters [2021/11/26 18:25]
wucknitz 		projects:mkat_sband:pub:decfilters [2022/06/15 10:49] (current)
wucknitz
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 We want to include the analog-aliasing in the total analog gain and exclude the range that is bad anyway from the optimisation of the digital filters. The limit for the latter is a bit arbitrary, let us try to exclude the > -30 dB range. We want to include the analog-aliasing in the total analog gain and exclude the range that is bad anyway from the optimisation of the digital filters. The limit for the latter is a bit arbitrary, let us try to exclude the > -30 dB range.
 +
 +
 +
 +
 +===== Final design (ver2) =====
 +
 +After consistency checks of a preliminary version (ver0) by Eddy, final filters were produced. Relative leakage was limited to -50dB (per frequency) including the effect of the analog bandpass. Near the edges the analog bandpass was cut with a lower limit to avoid upscaling too much. For the outer bands (LP and HP) the usable band was defined as 92%, for the bandpasses it is only 83%, because losses on both sides have to be accepted. This numbers were chosen to keep the passband ripple at a reasonable level, similar to the one already produced by the analog gain. For alternative filters we could trade passband flatness for usable bandwidth. With the available 35 coefficients, the following filters are optimal in this sense.
 +
 +Here is one example plot from the actual fitting process, showing where the analog gain curve was limited: \\
 +{{:projects:mkat_sband:pub:ver2_fitting.png?direct&550}}
 +
 +
 +=== S0 ===
 +
 +{{:projects:mkat_sband:pub:ver2_S0.pdf|All plots for S0 in one PDF file.}}
 +
 +== With analog gain (full band and passband) ==
 +
 +
 +{{:projects:mkat_sband:pub:ver2_S0_with_analog_fullband.png?direct&400}}{{:projects:mkat_sband:pub:ver2_S0_with_analog_passband.png?direct&400}}
 +
 +
 +== Without analog gain (full band and passband) ==
 +
 +{{:projects:mkat_sband:pub:ver2_S0_without_analog_fullband.png?direct&400}}{{:projects:mkat_sband:pub:ver2_S0_without_analog_passband.png?direct&400}}
 +
 +
 +
 +
 +
 +
 +=== S1 ===
 +
 +{{:projects:mkat_sband:pub:ver2_S1.pdf|All plots for S1 in one PDF file.}}
 +
 +== With analog gain (full band and passband) ==
 +
 +
 +{{:projects:mkat_sband:pub:ver2_S1_with_analog_fullband.png?direct&400}}{{:projects:mkat_sband:pub:ver2_S1_with_analog_passband.png?direct&400}}
 +
 +
 +== Without analog gain (full band and passband) ==
 +
 +{{:projects:mkat_sband:pub:ver2_S1_without_analog_fullband.png?direct&400}}{{:projects:mkat_sband:pub:ver2_S1_without_analog_passband.png?direct&400}}
 +
 +
 +
 +=== S2 ===
 +
 +{{:projects:mkat_sband:pub:ver2_S2.pdf|All plots for S2 in one PDF file.}}
 +
 +== With analog gain (full band and passband) ==
 +
 +
 +{{:projects:mkat_sband:pub:ver2_S2_with_analog_fullband.png?direct&400}}{{:projects:mkat_sband:pub:ver2_S2_with_analog_passband.png?direct&400}}
 +
 +
 +== Without analog gain (full band and passband) ==
 +
 +{{:projects:mkat_sband:pub:ver2_S2_without_analog_fullband.png?direct&400}}{{:projects:mkat_sband:pub:ver2_S2_without_analog_passband.png?direct&400}}
 +
 +
 +
 +=== S3 ===
 +
 +{{:projects:mkat_sband:pub:ver2_S3.pdf|All plots for S3 in one PDF file.}}
 +
 +== With analog gain (full band and passband) ==
 +
 +
 +{{:projects:mkat_sband:pub:ver2_S3_with_analog_fullband.png?direct&400}}{{:projects:mkat_sband:pub:ver2_S3_with_analog_passband.png?direct&400}}
 +
 +
 +== Without analog gain (full band and passband) ==
 +
 +{{:projects:mkat_sband:pub:ver2_S3_without_analog_fullband.png?direct&400}}{{:projects:mkat_sband:pub:ver2_S3_without_analog_passband.png?direct&400}}
 +
 +
 +
 +=== S4 ===
 +
 +{{:projects:mkat_sband:pub:ver2_S4.pdf|All plots for S4 in one PDF file.}}
 +
 +== With analog gain (full band and passband) ==
 +
 +
 +{{:projects:mkat_sband:pub:ver2_S4_with_analog_fullband.png?direct&400}}{{:projects:mkat_sband:pub:ver2_S4_with_analog_passband.png?direct&400}}
 +
 +
 +== Without analog gain (full band and passband) ==
 +
 +{{:projects:mkat_sband:pub:ver2_S4_without_analog_fullband.png?direct&400}}{{:projects:mkat_sband:pub:ver2_S4_without_analog_passband.png?direct&400}}
 +
 +
 + --- //Olaf Wucknitz 2022/01/26 11:36//
 +
 +
 +===== Old filters for comparison =====
 +
 +Here are the corresponding plots for the filters used until end of May 2022.
 +
 +{{:projects:mkat_sband:pub:orig_S0.pdf|All plots for S0 in one PDF file.}} \\
 +{{:projects:mkat_sband:pub:orig_S1.pdf|All plots for S1 in one PDF file.}} \\
 +{{:projects:mkat_sband:pub:orig_S2.pdf|All plots for S2 in one PDF file.}} \\
 +{{:projects:mkat_sband:pub:orig_S3.pdf|All plots for S3 in one PDF file.}} \\
 +{{:projects:mkat_sband:pub:orig_S4.pdf|All plots for S4 in one PDF file.}}
 +
 +
 +
 +===== Test observations =====
 +
 +The new coefficients were tested in five 10-min scans, one per subband, of J1939-6342 on 8th June 2022. Here are combined results for all subbands. For each subband we have one observation with old and one with new filter. The new ones have timestamps in the title that start with 1654..., old ones are smaller. Note that not all antennas participated in all observations.
 +
 +{{:projects:mkat_sband:pub:sefd_filtertest.pdf|PDF with SEFD curves}} \\
 +{{:projects:mkat_sband:pub:bandpass_filtertest.pdf|PDF with bandpass curves}}\\
 +{{:projects:mkat_sband:pub:bandpass_corr_filtertest.pdf|PDF with bandpass curves, amplitude corrected for digital decimation filter for a better comparison}}\\
 +{{:projects:mkat_sband:pub:sefd_bandpass_filtertest.pdf|PDF with SEFD and bandpass curves (dB)}}\\
 +{{:projects:mkat_sband:pub:sefd_bandpass_corr_filtertest.pdf|PDF with SEFD and bandpass curves (dB), amplitude corrected for digital decimation filter for a better comparison}}
  
 
projects/mkat_sband/pub/decfilters.1637947524.txt.gz · Last modified: 2021/11/26 18:25 by wucknitz     Back to top

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