Spectrum-Analyser Setup
CANBench Duo v1.2 — Schematic-stage refresh of the V1.1 fabricated prototype. V1.2 is electrically identical to V1.1 and carries the InvenTree-canonical component metadata; no V1.2 boards exist yet — testing and bring-up reference the V1.1 hardware.
Other versions: v1.1 — fabricated prototype (current)
The CANBench Duo presents a 50 Ω source at each SMA output across the CISPR 25 measurement band (150 kHz – 108 MHz). Any spectrum analyser that covers this band and accepts a 50 Ω input will work; the differences are in resolution, dynamic range, and ergonomics.
General configuration (any analyser)
These are the parameters to set regardless of which analyser you have:
| Parameter | Value |
|---|---|
| Input impedance | 50 Ω |
| Start frequency | 150 kHz (CISPR 25 low edge) |
| Stop frequency | 30 MHz for routine work; 108 MHz for full CISPR 25 band |
| Detector | Peak (Max-hold for time-varying disturbances) |
| Reference level | Adjust per analyser; typical −60 dBm to −20 dBm |
| Attenuation | 10 dB starting point — see notes below |
| Resolution bandwidth (RBW) | Per CISPR 25 (9 kHz for 150 kHz – 30 MHz; 120 kHz for 30 – 108 MHz) where formal compliance is the goal; otherwise match the analyser's auto-RBW |
| Averaging | Off for peak detection; enable for stable noise-floor comparisons |
Attenuation notes:
- Each CANBench Duo measurement port has built-in attenuation of ≈ 10 dB. Account for this in your reference-level / amplitude calculations.
- Start with 10 dB analyser attenuation to leave headroom for transients.
- Drop to 0 dB only after confirming the input signal will not exceed the analyser's first-mixer compression point (typically +10 dBm at the analyser's input — well above anything the CANBench Duo's protection cascade lets through under normal operation).
LNA / preamplifier: OFF for the CANBench Duo's typical −60 dBm to −90 dBm signal range. Only enable if you need to characterise the analyser's own noise floor with the LISN unpowered.
tinySA ULTRA (recommended)
The tinySA ULTRA is the analyser used by SCADYS for engineering validation. It is inexpensive, portable, and adequate for conducted-emissions characterisation work below the formal compliance level.
Recommended baseline:
| Setting | Value |
|---|---|
| Mode | Spectrum Analyzer |
| Start Frequency | 150 kHz |
| Stop Frequency | 30 MHz (extend to 108 MHz for full CISPR 25 band) |
| Detector | Peak |
| LNA | OFF |
| Attenuation | Manual |
| Initial Attenuation | 10 dB |
| Vertical Scale | Fixed |
| Typical Range | −60 dBm to −100 dBm |
For higher-resolution work near the noise floor, drop the attenuation and add averaging. For routine pre-compliance sweeps, the table above is a good starting point.
Other analysers
The CANBench Duo's signal levels and frequency band are within the working range of practically any modern spectrum analyser — Rigol DSA / RSA series, Siglent SSA, Keysight FieldFox, Tektronix RSA, R&S FSC / FPC, etc. For these:
- Use the General configuration table above as a starting point.
- For formal CISPR 25 compliance work, you also need the prescribed RBW values (9 kHz / 120 kHz), a Quasi-Peak detector option, and a calibrated RF chain — the CANBench Duo is a pre-compliance instrument, not a substitute for a certified compliance setup.
- For EMI receivers with built-in CISPR 25 measurement templates, configure the receiver to drive the SMA input directly and let the receiver handle the band sequencing.
What the CANBench Duo does NOT do
- It does not amplify. Maximum useful sensitivity is the analyser's noise floor minus the CANBench Duo's ≈ 10 dB attenuation.
- It does not provide quasi-peak detection — that lives in the analyser.
- It does not auto-sequence the CISPR 25 sub-bands — you (or the analyser) drive the sweep configuration.
See Measurement Procedure for the step-by-step sweep workflow.