How do I perform an interlaboratory comparison for RF measurement validation?

How do I perform an interlaboratory comparison (ILC) for RF measurement validation? An ILC involves two or more laboratories measuring the same artifact, with the results systematically compared to validate measurement consistency and identify systematic errors: (1) ILC procedure: select measurement parameter: define exactly what will be measured (e.g., S21 of a 20 dB attenuator at 1, 10, 26.5 GHz). Select artifact: choose a stable, transportable artifact with known characteristics. The artifact must survive shipping without damage (use a rugged travel case). Define measurement conditions: frequency points, power level, temperature, connector torque, and calibration method. Each lab must measure under the same specified conditions. Circulate the artifact: send the artifact sequentially to each lab (star pattern or round-robin). Each lab performs the measurement and reports results with uncertainty. The reference lab measures first and last (to verify artifact stability over the ILC period). Analyze results: calculate E_n for each lab relative to the reference. Plot the results with uncertainty bars. Identify outliers (|E_n| > 1.0). (2) Reference value: Option 1: assigned by the reference laboratory (highest-level lab in the comparison). Option 2: consensus value (weighted mean of all laboratories, weighted by 1/U_i²). The reference uncertainty is the uncertainty of the reference method or consensus calculation. (3) Practical considerations: artifact stability: measure the artifact at the reference lab before and after the ILC. If the artifact changes by more than the reference uncertainty: the ILC is invalid. Shipping: transport the artifact in its case, with cushioning. Include a tilt/shock indicator in the package. Turnaround: each lab should complete measurements within 1-2 weeks to minimize the total ILC duration (reducing the risk of artifact drift). Documentation: each lab submits a measurement report including: the measurement result, the expanded uncertainty with budget, the measurement conditions, and the calibration traceability. (4) ISO 17025 requirement: accredited labs must participate in ILCs or proficiency testing schemes at regular intervals. The results are reviewed by the accreditation body during surveillance audits.