fix(rf): fix frequency sampling in MicrowaveModeData

[dmarek-flex]

Greptile Overview

Updated On: 2025-10-31 16:22:57 UTC

Greptile Summary

Fixes frequency sampling in MicrowaveModeData when group index calculation is enabled. Group index calculation requires triplet frequencies (backward, center, forward) for numerical differentiation, but the TransmissionLineDataset was incorrectly retaining all triplet frequencies instead of filtering back to the original center frequencies.

Key Changes:

• Extracted _group_index_freq_slices() helper method in ModeData to centralize frequency slice logic
• Overrode _group_index_post_process() in MicrowaveModeData to filter transmission_line_data frequencies
• Added comprehensive test test_mode_solver_with_microwave_group_index() to verify frequency filtering

Issues Found:

• Missing None check for transmission_line_data before accessing attributes (could cause AttributeError)
• Minor grammar issue in CHANGELOG entry ("to when" → "when")

Confidence Score: 3/5

• This PR fixes a valid bug but has a critical logic error that could cause runtime failures
• The fix correctly addresses the frequency sampling issue by filtering transmission line data to match the original frequencies after group index calculation. However, the implementation in _group_index_post_process() accesses transmission_line_data attributes without checking if it's None first (it's declared as Optional[TransmissionLineDataset]), which will cause an AttributeError in cases where transmission line data is not populated
• Pay close attention to tidy3d/components/microwave/data/monitor_data.py - the _group_index_post_process() method needs a None check before accessing transmission_line_data

Important Files Changed

File Analysis

Filename	Score	Overview
CHANGELOG.md	4/5	Added changelog entry with minor grammar issue
tidy3d/components/data/monitor_data.py	5/5	Extracted frequency slice logic into reusable helper method
tidy3d/components/microwave/data/monitor_data.py	3/5	Overrides group index post-processing to filter transmission line frequencies, but lacks None check
tests/test_components/test_microwave.py	5/5	Comprehensive test validates frequency filtering in transmission line data during group index calculation

Sequence Diagram

sequenceDiagram
    participant MS as ModeSolver
    participant MSD as MicrowaveModeSolverData
    participant MMD as MicrowaveModeData
    participant MD as ModeData
    
    MS->>MS: _get_data_with_group_index()
    Note over MS: Expands frequencies to triplets<br/>(back, center, forward) for<br/>numerical differentiation
    MS->>MS: _freqs_for_group_index()
    Note over MS: Creates [f1*(1-δ), f1, f1*(1+δ),<br/>f2*(1-δ), f2, f2*(1+δ), ...]
    MS->>MSD: Solve with expanded frequencies
    Note over MSD: data_raw contains triplet frequencies<br/>in transmission_line_data
    MS->>MMD: _group_index_post_process(frequency_step)
    MMD->>MD: super()._group_index_post_process()
    MD->>MD: _group_index_freq_slices()
    Note over MD: Returns (back, center, fwd) slices<br/>slice(0, n, 3), slice(1, n, 3), slice(2, n, 3)
    MD->>MD: Calculate n_group from triplets
    MD->>MD: Filter frequencies to center values
    MD-->>MMD: Returns filtered ModeData
    MMD->>MMD: _group_index_freq_slices()
    Note over MMD: Reuse same frequency slices
    MMD->>MMD: Filter transmission_line_data
    Note over MMD: Z0.isel(f=center_inds)<br/>voltage_coeffs.isel(f=center_inds)<br/>current_coeffs.isel(f=center_inds)
    MMD->>MMD: updated_copy(**update_dict)
    MMD-->>MS: Returns MicrowaveModeData<br/>with original frequencies only

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Diff Coverage

Diff: origin/develop...HEAD, staged and unstaged changes

• tidy3d/components/data/monitor_data.py (100%)
• tidy3d/components/microwave/data/monitor_data.py (100%)

Summary

• Total: 16 lines
• Missing: 0 lines
• Coverage: 100%

[weiliangjin2021]

Looks good. Thanks for the fix!