Shingo, YamaT

Objective
Determine whether it is necessary to create FIR filters for the IM and MN stages in the offline/low-latency reconstruction pipelines.

Conclusion
We create a FIR filter for the IM stage, but do not create a FIR filter for the MN stage.

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Method
The influence of each stage was evaluated by applying the transfer function to the amplitude spectral density. The graph (Fig. 1) showed that the MN stage's influence is over two orders of magnitude smaller than that of the TM stage (less than 1%). Considering the O4a target uncertainty, which specifies an amplitude of 20% within 30 Hz to 1500 Hz (JGW-G2415719), the influence of the MN stage is significantly smaller than the target uncertainty and can be ignored.
Note: 
There is no change in the conclusion, but it appears that the influence of the MN stage (red line in Fig. 2) is larger than originally anticipated (black line in Fig. 2, assuming a transfer function model with a 6th-order roll-off.).

Details
・Channels used to calculate amplitude spectral density: "K1:VIS-ETMX_{TM, IM, MN}_DRIVEALIGN_IN_DQ"
・Reference time (JST): May 24, 2023, 19:47
・Transfer function: Measured on May 24, 2023, at 17:14 (during O4a period), from "K1:VIS-ETMX_{TM, IM, MN}_CAL_EXC_OUT" to "K1:LSC_DARM1_IN1"