A Traceable Low-Frequency Attenuation Standard from 1 kHz to 10 MHz for Next-Generation Wireless and EMC Calibration

TL;DR

This paper introduces a new standard for measuring signal attenuation from 1 kHz to 10 MHz with high accuracy and traceability for wireless and EMC applications.

Contribution

A novel dual-channel null-detection system with inductive voltage divider and heterodyne detection for traceable attenuation calibration.

Findings

Expanded uncertainties of 2.2 × 10−3 dB at 20 dB, 3.0 × 10−3 dB at 40 dB, and 4.0 × 10−3 dB at 60 dB attenuation.

A resistive step attenuator is proposed as a practical transfer standard for wider dissemination of the calibration method.

Abstract

The growing demand for traceable, high-precision attenuation measurements in electromagnetic compatibility (EMC) testing and low-frequency wireless communication systems has driven the development of a primary attenuation standard covering 1 kHz to 10 MHz. The system employs a dual channel null-detection method using an inductive voltage divider (IVD) as a reference, ensuring the highest accuracy and traceability while eliminating sensitivity to detector nonlinearity. Attenuation at 1 kHz, 9 kHz, and 10 kHz is measured directly against the IVD ratio, while higher-frequency measurements (100 kHz–10 MHz) are performed via heterodyne detection, down-converting signals to 1 kHz for comparison. To ensure comparable accuracy at higher attenuation levels, a double-step method is applied at 9 kHz and 10 kHz to mitigate the increased IVD uncertainty above 1 kHz. Linearity is ensured by suppressing common-mode currents with toroidal ferrite chokes and minimizing inter-channel coupling. Type B (non-statistical) measurement uncertainties are evaluated, with major contributions from the IVD reference, system errors, and mismatch. The expanded uncertainties are 2.2 × 10−3 dB at 20 dB, 3.0 × 10−3 dB at 40 dB, and 4.0 × 10−3 dB at 60 dB attenuation. To facilitate wider dissemination and extend the calibration range, a resistive step attenuator with 10 dB pads is evaluated as a practical transfer standard, providing a simple and robust solution for traceable attenuation calibration in this frequency range.

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