UWB / SFF Analysis¶

Ultra-Wideband antenna characterization. Gain alone doesn't capture pulse fidelity over wide bandwidths. You also need to know how well the antenna preserves pulse shape across angles.

System Fidelity Factor (SFF)¶

Normalized cross-correlation between the transmitted pulse and the received pulse after the antenna chain:

$$\text{SFF} = \max_\tau \frac{\left|\int s_t(t)\, s_r(t-\tau)\, dt\right|}{\sqrt{\int |s_t|^2 dt \cdot \int |s_r|^2 dt}}$$

Range: 0 to 1. 0.95+ is typically considered "good" for UWB.

What you need¶

One or more 2-port captures (Touchstone .s2p or S2VNA .csv with S21(s))
For per-angle SFF: filenames containing the angle, e.g. Antenna_45deg.csv

Pulse types supported¶

`pulse_type`	Use case
`gaussian_monocycle` (default)	Generic UWB pulse, baseline
`modulated_gaussian`	Carrier-modulated UWB
`5th_derivative_gaussian`	FCC UWB spectral mask compliance

Programmatic / MCP¶

Full channel analysis (one file)¶

analyze_uwb_channel("/path/to/cap.s2p", distance_m=1.0)

Returns SFF, group delay, transfer function, impulse response, return loss.

SFF vs angle (many files)¶

calculate_sff_from_files(
    file_paths=["ant_0deg.csv", "ant_45deg.csv", "ant_90deg.csv", ...],
    pulse_type="gaussian_monocycle",
    min_freq_ghz=3.1,
    max_freq_ghz=10.6,
)

Returns mean SFF plus per-angle SFF with quality labels.

Batch / orchestrator¶

process_folder("/path/to/uwb_sweep", intent="uwb")

Runs analyze_uwb_channel on every .s2p / matching .csv in the folder. See Recipes.

Frequency-domain transfer function¶

extract_transfer_function returns H(f) magnitude and complex form, plus a flatness_dB metric (peak-to-peak variation in the band).

Impulse response¶

IFFT of the transfer function gives the time-domain impulse response. compute_impulse_response reports:

pulse_width_ps: full-width-half-max of the main lobe
ringing_dB: secondary peaks relative to the main pulse

Common gotchas¶

Frequency band filter: UWB sweeps are wide. Use min_freq_ghz / max_freq_ghz to restrict the analysis to your standard's band (3.1–10.6 GHz for FCC UWB).
Group delay column: without S21(s), RFlect falls back to magnitude-only SFF, which is less informative. Capture group delay if possible.
Angle parsing: calculate_sff_from_files extracts angle from filename via regex (\d+)(deg|DEG). If filenames don't follow that pattern, angles default to 0°, 45°, 90°, … by file order.