Update to the BLRMS Code: Custom BLRMS, Transposed Direct Form 2, and Reduced DC Order

Document #:

LIGO-T2200025-v2

Document type:

T - Technical notes

Abstract:

We describe an update to the Band-Limited Root-Mean-Square (BLRMS) code to implement 65 Hz to 100 Hz and 130.5 Hz to 200 Hz BLRMS, and resolve some issues with the DC BLRMS. Users may find this technical note helpful if they wish to implement additional custom BLRMS in the future.

Files in Document:

• T2200025_v2-Update_to_BLRMS_Code-20220805.pdf (690.6 kB)

Topics:

• Seismic Isolation

Authors:

• Nathan Holland
• Jim Warner
• Brian Lantz

Keywords:

ECR BLRMS CPS ISI

Notes and Changes:

Address some minor comments about powerline 3rd harmonics, and clearing up details about SOS implementation.

Related Documents:

• LIGO-T1100613: SEI System Real-Time Band-Limited RMS Filter (ISI Performance Matrix, Matrices)
• LIGO-G0900928: Digital Filter Noise (Direct Form 2 or DF2 vs. Biquad)

Referenced by: