Scale RSLC mixed-mode filter by bandwidth ratio#269
Merged
bhawkins merged 1 commit intoMay 20, 2026
Conversation
gshiroma
approved these changes
May 20, 2026
rad-eng-59
reviewed
May 20, 2026
Contributor
rad-eng-59
left a comment
rad-eng-59
left a comment
There was a problem hiding this comment.
It seems like my comments/reviews are already too late again.
|
|
||
| if channel_in.band != channel_out.band: | ||
| log.info("Re-scaling by mixed-mode filter bandwidth ratio") | ||
| chirp *= np.sqrt(channel_out.band.width / channel_in.band.width) |
Contributor
There was a problem hiding this comment.
This will also scale noise power, NEB, that already being estimated within output bandwidth after range comp filtering. I guess that should be okay given SNR has not changed by this scaling. I wonder what we used to report for NEB in mixed mode case.
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
4 participants
Add this suggestion to a batch that can be applied as a single commit.This suggestion is invalid because no changes were made to the code.Suggestions cannot be applied while the pull request is closed.Suggestions cannot be applied while viewing a subset of changes.Only one suggestion per line can be applied in a batch.Add this suggestion to a batch that can be applied as a single commit.Applying suggestions on deleted lines is not supported.You must change the existing code in this line in order to create a valid suggestion.Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be applied on multi-line comments.Suggestions cannot be applied while the pull request is queued to merge.Suggestion cannot be applied right now. Please check back later.
The range reference function is normalized by its white noise gain, which helps keep the calibration constant when we change the window parameter. However, in the mixed-mode case that normalization also increases the pass-band gain in proportion to the bandwidth reduction. The latter effect is not desirable since it causes a radiometric offset.
To test this change, I found a case near the south pole where we mix 77 MHz (half-swath) with 40+5 MHz (full-swath) data. Looking at the 77 & 5 MHz mix is most obvious, since the change is almost 12 dB in that case. With the change, we get a nice continuous backscatter image.
Note 1: I just used the browse QA images for the above figure, so they have independent color maps. You can see from the histogram and profile that it's actually the 77 MHz getting darker to match the 5 MHz part.
Note 2: This test case also requires #268