Measuring Receiver Benchmark for Conducted and Radiated Emissions Testing in Space Applications

This paper compares the measurement results obtained from three different implementations of measuring receivers regarding spectral level accuracy. The objective is to validate the suitability of direct sampling electromagnetic emissions measurements with respect to those delivered by a high-end EMI receiver in frequency swept and FFT modes. The experimental setups follow the verification methods described in the ECSS-E-ST-20-07C Rev.2 standard to set realistic and reproducible conditions. Between 50 kHz and 100 MHz, common mode and differential mode currents are measured when multisine excitation signals with controlled amplitude profiles are used as references. Subsequently, conducted and radiated emissions tests are run to investigate the correlation between measurements with the different receivers. The instruments used are a low-cost USB digitiser Picoscope PS5444D, a high-performance benchtop oscilloscope R&S RTO6 and the R&S ESW44 full-compliant EMI test receiver. The analysis concludes that the emissions measurements performed with the direct sampling approach are excellent for the intended application, exhibiting an accuracy comparable to the dedicated EMI test receiver and a well adequate dynamic range and noise level.The project (21NRM06 EMC-STD) has received funding from the European Partnership on Metrology, co-financed by the European Union's Horizon Europe Research and Innovation Programme and by the Participating States. EMC Barcelona's project under grant number SNEO-20211223 has received funding from CDTI, which is supported by "Ministerio de Ciencia e Innovación" and financed by the European Union - NextGenerationEU - through the guidelines included in the `Plan de Recuperación, Transformación y Resiliencia". Dr. Azpúrua has received funding from the StandICT.eu 2023 project, financed by the European Union's Horizon Europe - Research and Innovation Programme - under grant agreement No. 951972. Dr. Pous' work was supported in part by the European Union's Horizon 2020 research and innovation programme under Marie Skłodowska-Curie grant agreement No. 801342 (TecniospringINDUSTRY) and the Government of Catalonia's Agency for Business Competitiveness (ACCIÓ) and in part by the Spanish "Ministerio de Ciencia e Innovaci´on" under project PID2019-106120RBC31/AEI/10.13039/501100011033

Evaluation of Spectral Estimation Parameters for Direct Sampling FFT-Based Measuring Receivers

The standard CISPR 16-1-1 defines the measuring receiver using a black-box approach and sets requirements for its accuracy and spectral properties. Traditionally, such test receivers were developed using a superheterodyne architecture. Recently, time-domain electromagnetic emission measurement systems have been built employing direct sampling instruments, mainly oscilloscopes, and relying on specific signal processing to emulate the performance of compliant instruments. In these cases, the short-time Fourier transform is used for spectral estimation, but the corresponding electromagnetic compatibility standards lack details for its correct use with respect to parameters such as windowing function, overlapping factor, and frequency interpolation. Moreover, it is unclear which combination of spectral estimation parameters is best fit for this purpose. Obtaining reliable, consistent and low uncertainty spectral estimates of electromagnetic emissions measured in time-domain needs appropriate configuration and tuning of the signal processing algorithms. This paper investigates the error in the calculated spectrum for various reference signals: multitone, chirp pulses and rectangular pulses. The analysis is carried out for each CISPR band from A to D, that is, between 9 kHz and 1 GHz. After $489.6\times 10^{3}$ iterations, distributed in 1700 different digital implementations of the CISPR 16-1-1 measuring receiver, the simulations outcomes point to certain sets of parameters that showed satisfactory performance overall, being the Nutall, Kaiser, and Parzen windows with more than 75% of overlapping and using interpolation factor higher than 5, generally suitable. Calibration results are used to experimentally verify that a valid set of parameters is adequate to fulfil CISPR 16-1-1 requirements