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Message ID: 422     Entry time: Wed Apr 16 21:11:12 2008
Author: rana 
Type: Summary 
Category: DAQ 
Subject: AA/AI Filters for the DAQ & FE systems 
I used Foton to make up some new filters which will be used all over the project in order to downsample/upsample.

There will be 2 flavors:

  • The first one will be a downsampling filter for use in the DAQ system.
    Whenever you specify a sampling rate in the .ini files below the natural rate of the ADC,
    the data will be downsampled using this filter (called ULYAW_0 in the plot). This one was
    designed for flat bandpass and a 'good' bandstop but no care given to the phase shift.

  • The second one will be used in the FE systems to downsample the ADC signal which is often
    sampled at 64 kHz down to something manageable like 2k or 16k. This one was tweaked for
    getting less phase lag in the 'control' band (usually 3x or so below Nyquist).

Here is the associated filter file:
# SAMPLING ULYAW 16384
# DESIGN   ULYAW 0 zpk([0.512+i*1024;0.512-i*1024;2.048+i*2048;2.048-i*2048], \
#                      [515.838+i*403.653;515.838-i*403.653;318.182+i*623.506;318.182-i*623.506;59.2857+i*827.88; \
#                      59.2857-i*827.88],0.988553,"n")
# DESIGN   ULYAW 1 zpk([0.512513+i*1024;0.512513-i*1024;1.53754+i*2048;1.53754-i*2048], \
#                      [200+i*346.41;200-i*346.41;45+i*718.592;45-i*718.592],1,"n")
# DESIGN   ULYAW 2 zpk([0.768769+i*1024;0.768769-i*1024;1.53754+i*2048;1.53754-i*2048], \
#                      [194.913-i*331.349;194.913+i*331.349;53.1611+i*682.119;53.1611-i*682.119],1,"n")
###                                                                          ###
ULYAW    0 21 3      0      0 DAQAA         0.00091455950698073    -1.62010355523604     0.67259370084279    -1.84740554170818     0.99961738977942
                                                                   -1.72089534598832     0.78482029284220    -1.41321371411946     0.99858678588255
                                                                   -1.85800352005967     0.95626992044093     2.00000000000000     1.00000000000000
ULYAW    1 21 2      0      0 FEAA            0.018236566955641    -1.83622978049494     0.85804776530302    -1.84740518752455     0.99961700649533
                                                                   -1.89200532023258     0.96649324616546    -1.41346289594856     0.99893883979950
ULYAW    2 21 2      0      0 ELP             0.015203943102927    -1.84117829296043     0.86136943504058    -1.84722827171918     0.99942556512240
                                                                   -1.89339022414279     0.96048849609619    -1.41346289594856     0.99893883979950
Attachment 1: DAQ_filters_080416.pdf  31 kB  | Hide | Hide all
DAQ_filters_080416.pdf
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