Calibration of Electric and Magnetic Fields Meters Response to Simultaneous Multiband Modulated Signals

With the development of wireless system and the widespread use of radio wave, the frequency range of electromagnetic radiation in the environment will span from thousands of hertz to millimeter-wave bands. The electromagnetic radiation is formed by the superposition of multiple frequency bands and various modulated signals, which is called “concurrent.” This complex electromagnetic radiation is the actual measurement object of the current electric and magnetic fields meters (EMF meters). In order to ensure the accuracy and reliability of the EMF meters, it is necessary to quantitatively simulate this real electromagnetic radiation. In this article, based on the additive property of radiation power density in frequency domain, a calibration method for the power density parameters of multifrequency band concurrent modulated signal’s electromagnetic radiation was proposed. To simulate and reproduce such an electromagnetic environment, we designed and implemented an ultrawideband coaxial cone TEM cell with the ultrawideband test capability from dc to 40 GHz. We carried out experiments to calibrate the EMF meters and measured the response of the EMF meters in three different electromagnetic radiation environments: 5G NR downlink signal + LTE downlink signal concurrent electromagnetic radiation, 5G NR millimeter-wave signal + DVB signal concurrent electromagnetic radiation, and 5G NR signal + WLAN signal concurrent electromagnetic radiation. These experimental results evidently show that various EMF meters exhibit different measurement errors when measuring multifrequency band concurrent modulated electromagnetic radiation. Some calibration factors deviate significantly from the ideal value of 1. Additionally, for the same modulation combination under different radiation power levels, the same instrument shows varying calibration factors. Therefore, it is necessary to add the measurement of multifrequency band concurrent modulated signal electromagnetic radiation in the future instrument calibration specifications.