Skip to content

S11 & Impedance Bandwidth

Return-loss and bandwidth analysis from VNA .csv or Touchstone .s2p files.

VNA / S-parameter results

What you need

  • A 2-port (or 1-port) VNA capture with S11 in dB
  • Optional: a -10 dB (or custom) threshold to define "in-band"

In the GUI

  1. Scan type: VNA
  2. Ctrl+O and pick the .csv or .s2p file
  3. The S11 plot appears with optional limit lines
  4. Set Limit Lines dialog lets you mark pass/fail thresholds per band

What you get

Metric Definition
min_s11_dB Best (most negative) return loss in the sweep
bandwidth_mhz Frequency span where S11 ≤ threshold (default -10 dB)
band_start_ghz / band_stop_ghz Edges of the matched band
fractional_bandwidth_pct $200 \cdot (f_2 - f_1) / (f_2 + f_1)$
VSWR Voltage Standing Wave Ratio derived from S11

Programmatic / MCP

get_impedance_bandwidth("/path/to/sweep.s2p", threshold_dB=-10.0)

Returns the same metrics as JSON. See tools reference.

Common gotchas

  • Calibration matters. RFlect doesn't apply VNA calibration — bring already-calibrated data.
  • Threshold convention. -10 dB ≈ 90% power match. Some specs use -6 dB or -3 dB; set explicitly.
  • Single-band assumption. The bandwidth metric reports the widest contiguous matched band; multi-band antennas will need per-band analysis.

See also