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THEMIS-D Digital Fields Board, Filter Bank

ResourceID
spase://SMWG/Instrument/THEMIS/D/FBK

Description

The Filter Bank is part of the Digital fields board and provides band-pass filtering for EFI and SCM spectra as well as E12HF peak and average values. The Filter Bank provides band-pass filtering for less computationally and power intensive spectra than the FFT would provide. The process is as follows: Signals are fed to the Filter Bank via a low-pass FIR filter with a cut-off frequency half that of the original signal maximum. The output is passed to the band-pass filters, is differenced from the original signal, then absolute value of the data is taken and averaged. The output from the first low-pass filter is also sent to a second FIR filter with 2:1 decimation. This output is then fed back through the system. The cascade runs 12 cycles for input at 8,192 samples/s and 13 for input at 16,384 samples/sec (EAC input only), reducing the signal (and computing power) by a factor 2 at each cascade. At each cascade a set of data is produced at a sampling frequency of 2^n from 2 Hz to the initial sampling frequency (frequency characteristics for each step are shown below in Table 1). The average from the Filter Bank is compressed to 8 bits with a pseudo-logarithmic encoder. Analog signals sent to the FBK are E12DC and SCM1. The average of the coupled E12HF signal and it's peak value are recorded over 62.5 ms windows (i.e. a 16 Hz sampling rate). Accumulation of values from signal 31.25 ms windows is performed externally. Sensor and electronics design provided by UCB (J. W. Bonnell, F. S. Mozer), Digital Fields Board provided by LASP (R. Ergun), Search coil data provided by CETP (A. Roux).

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Details

Version:2.0.0

Instrument

ResourceID
spase://SMWG/Instrument/THEMIS/D/FBK
ResourceHeader
ResourceName
THEMIS-D Digital Fields Board, Filter Bank
AlternateName
THEMIS-D FBK
ReleaseDate
2019-05-05 12:34:56Z
Description

The Filter Bank is part of the Digital fields board and provides band-pass filtering for EFI and SCM spectra as well as E12HF peak and average values. The Filter Bank provides band-pass filtering for less computationally and power intensive spectra than the FFT would provide. The process is as follows: Signals are fed to the Filter Bank via a low-pass FIR filter with a cut-off frequency half that of the original signal maximum. The output is passed to the band-pass filters, is differenced from the original signal, then absolute value of the data is taken and averaged. The output from the first low-pass filter is also sent to a second FIR filter with 2:1 decimation. This output is then fed back through the system. The cascade runs 12 cycles for input at 8,192 samples/s and 13 for input at 16,384 samples/sec (EAC input only), reducing the signal (and computing power) by a factor 2 at each cascade. At each cascade a set of data is produced at a sampling frequency of 2^n from 2 Hz to the initial sampling frequency (frequency characteristics for each step are shown below in Table 1). The average from the Filter Bank is compressed to 8 bits with a pseudo-logarithmic encoder. Analog signals sent to the FBK are E12DC and SCM1. The average of the coupled E12HF signal and it's peak value are recorded over 62.5 ms windows (i.e. a 16 Hz sampling rate). Accumulation of values from signal 31.25 ms windows is performed externally. Sensor and electronics design provided by UCB (J. W. Bonnell, F. S. Mozer), Digital Fields Board provided by LASP (R. Ergun), Search coil data provided by CETP (A. Roux).

Acknowledgement
NASA contract NAS5-02099 and V. Angelopoulos for use of data from the THEMIS Mission. Specifically: J. W. Bonnell and F. S. Mozer Bob Ergun, and Alain Roux.
Contacts
RolePersonStartDateStopDateNote
1.PrincipalInvestigatorspase://SMWG/Person/Vassilis.Angelopoulos
2.CoInvestigatorspase://SMWG/Person/John.W.Bonnell
3.CoInvestigatorspase://SMWG/Person/Robert.E.Ergun
4.CoInvestigatorspase://SMWG/Person/Forrest.S.Mozer
5.CoInvestigatorspase://SMWG/Person/Alain.Roux
InformationURL
Name
THEMIS-D Spacecraft
URL
Description

Spacecraft description from NSSDC database

InformationURL
Name
THEMIS-D Electric Fields Instrument
URL
Description

Instrument (EFI) description from NSSDC database

InformationURL
Name
THEMIS-D Search Coil Magnetometer
URL
Description

Instrument (SCM) description from NSSDC database

PriorIDs
spase://SMWG/Instrument/THEMIS-D/FBK
InstrumentType
Unspecified
InstrumentType
DoubleSphere
InstrumentType
Antenna
InstrumentType
SearchCoil
InvestigationName
THEMIS Digital Fields Board Filter Bank
ObservatoryID