Reverberation Chamber Signal-to-Noise (SNR) Measurements of Low-Level Radiated Emissions

For very low-level radiated emissions, the thermal noise present in the reverberation chamber limits the sensitivity of the measurement. This aspect of the measurements is addressed here where we investigate the factors that determine the signal-to-noise ratio achieved in the reverberation chamber and contrast them with comparable signal-to-noise ratio measurements performed on the same EUT in an anechoic chamber. 

The thermal noise originates in the walls and stirrer of the reverberation chamber. Its received power has been shown to be dependent only on the receiving antenna’s input reflection coefficient which is dependent on the stirrer position. In contrast, the signal received is determined by the chamber insertion loss. 

We have shown that this leads to a set of optimum stirrer positions which maximise the signal-to noise ratio. These stirrer positions are not readily deterministic and depend on the position and orientation of the EUT in the chamber. The signal-to-noise ratios achieved in the reverberation chamber are greater than that achieved in the anechoic chamber over a sub-set of the stirrer positions for an EUT radiating the same power. 

This effect offers potential advantages for the detection of low-level radiated emissions in applications such as signal security.

The work was supported by a Leverhulme Emeritus Fellowship (EM-2021-039/4) held by Professor Emeritus Marvin.

Publications

• “Thermal Noise Measurements in a Reverberation Chamber”. Marvin A.C. & Bale S.J. in IEEE Transactions on EMC. 64, 3, pp 893-896, 4p.
• “An Experimental Study of the Signal to Noise Ratio of Radiated Emissions in the Presence of Thermal Noise in a Reverberation Chamber” Marvin, A. & Bale, S. J., 2022 International Symposium on Electromagnetic Compatibility – EMC Europe.5 Sept 2022, p. 183. 188 p.
• “A Comparative Study of the Signal to Noise Ratio of Received Signals in a Reverberation Chamber and an Anechoic Chamber”. Marvin, A., Bale, S. J. & Flintoft, I. D., 2023 International Symposium on Electromagnetic Compatibility – EMC Europe. 6 Sept 2023.

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