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.