Dynamic reflection of RF signals from fluorescent lights: Their spectral analysis and effects on backscattered RFID tag signals

Radio frequency (RF) energy reflected from active power line ballast driven fluorescent tubes are known to be modulated at twice the line frequency. When the lamps are driven by electronic ballasts, it is found that the reflected (backscattered) RF wave is amplitude modulated with sidebands located at multiples of electronic ballast frequency components, extending to hundreds of kilohertz with significant power levels spread within this range. Detailed analysis of the measured sidebands spectrum indicated that the sidebands themselves are modulated at multiples of twice the power line frequency. Fluorescent lamps driven by different types of electronic ballasts operating at different unsynchronized frequencies exhibited different power levels. Consequently in an environment with abundance of active fluorescent lamps, the reflected RF signals can significantly affect the reception of modulated backscattered transponder RFID signals at UHF and higher bands.