Speaker
Description
Applying Software Defined Radios (SDRs) for measuring exposure to Radio Frequency (RF) Electromagnetic Fields (EMF) requires calibrated sensors and antennas. A complicating factor is the influence of the person wearing the measurement device on the recorded exposure, as well as the sensor’s orientation relative to the EMF source. SDRs are not designed as power meters; they are typically used to decode RF EMF in various radio protocols. What matters is that the received signal is distinguishable from noise. However, when an SDR is repurposed as an EMF power measurement device, it is essential to determine the exact received power levels. This requires accurate calibration of the device, not only in a controlled environment but also under the same conditions as used in the field. A human body in close proximity to the sensor influences the measured field strength, even though the actual exposure to body tissue remains unchanged. The aim of this work is to implement a calibration routine for SDRs, enabling them to be used in environmental exposure studies as body sensors. To assess the stability of the SDR, various measurements were conducted, comparing the output from a Vector Network Analyzer to the values recorded by the SDR. Additionally, to account for the influence of the human body, SDRs were tested in an anechoic chamber under a known field while being carried by a person. Using the calibration factors obtained, it becomes possible to convert the SDR’s output into accurate physical EMF power measurements.
