fix(presets): three fading-preset rows deviate from their canonical CCIR/standard values - #5
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fix(presets): three fading-preset rows deviate from their canonical CCIR/standard values#5spinkham wants to merge 1 commit into
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ccir-poor: spread 0.5 -> 1.0 Hz (CCIR 520-2 Poor is 2 ms / 1 Hz; the row
carried the Moderate spread with the Poor delay).
midlat-quiet: spread 0.5 -> 0.1 Hz (canonical mid-latitude quiet is
0.5 ms / 0.1 Hz, same as CCIR Good).
midlat-moderate: garbled single-path {0, 1.0, 0.5} -> canonical two-path
1 ms / 0.5 Hz (delay/spread had collapsed into one entry with a spurious
offset).
Values per the PathSim technical guide's own standard-settings table
(pathsimtech100 sec 4.1.11) and CCIR Rec. 520-2. Verified by feeding a
tone through the binary and measuring the realized Doppler spread of the
output (autocorrelation fit): before = 0.497 / 0.983 / 0.493 Hz, after =
0.967 / 0.501 / 0.107 Hz vs canonical 1.0 / 0.5 / 0.1.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
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Three rows in
PathSimParams.cppdon't match the canonical channel definitions (CCIR Rec. 520-2 and the standard-settings table in PathSim's own technical guide, pathsimtech100 §4.1.11):ccir-poormidlat-quietmidlat-moderate{0, 1.0, 0.5}All other rows check out against the same sources.
Verified end-to-end by running a 1 kHz tone through the binary and measuring the realized Doppler spread of the output fading (autocorrelation fit against the Gaussian-PSD model, 900 s dwell):
ccir-poormidlat-moderatemidlat-quiet(The same measurement confirms
GaussFIRitself realizes exactly the spread it's asked for — the filter is fine, only these table values were off. Practical effect of the bug:--ccir-poorhas been simulating fading at half the canonical rate, which makes modem results on that preset optimistic relative to other CCIR-Poor simulators.)Companion to #4 (the doc note on the sqrt(2) in the filter width constant).
🤖 Generated with Claude Code