SDR receiver for power measurement with internal noise compensation

Abstract

This paper presents a solution for implementing a power measurement receiver made with PlutoSDR. The paper proposes the dynamic elimination of the contribution of internal noise to the measured signal level by compensating with the level of internal noise produced by the receiver in the adjacent RF band. Our approach is based on the fact that the internal noise level in the working band is approximately equal to that in the frequency band in the immediate vicinity. As far as we know, our work is the first to use the idea of measuring the noise in an adjacent band to estimate the internal noise of the measuring instrument. Another aspect necessary to ensure a complete measurement solution that does not require pre-measurement calibration concerns the compensation of the nonlinearities of the reception path. The compensation was automatically performed by modifying the amplification of the reception path depending on the working frequency. For high levels of the measured CW signal (-50 dBm ... -10 dBm) the solution allows obtaining measurement errors of less than 0.55 dB. From the perspective of measurement uncertainty, with a value of U=±1 dB (k=2), the instrument with the method used fits very well into the requirements for pre-compliance EMC measurements. For levels lower than -60 dBm, the error starts to increase rapidly, so that at values of -70 dBm the signal can no longer be measured.