KEYWORDS: Electromagnetic coupling, Digital signal processing, Electromagnetism, Radio over Fiber, Antennas, Error analysis, Telecommunications, Electromagnetic interference, Photonics, Wavelength division multiplexing
In the field of high-speed railways (HSRs), electromagnetic interference (EMI) to the wireless train-ground communication system (e.g., the GSM-R system for train scheduling and dispatching) severely reduces the operational efficiency and even results in accidents. The direction-of-arrival (DoA) estimation of EMI is crucial for detection and removal. A photonics-assisted system is proposed to estimate the DoA of EMI for the GSM-R system along the HSRs in a remote and real-time mode. The proposed scheme is featured by simultaneous photonics-assisted detection and location (DoA estimation) of the EMI, with the advantages of strong EMI immunity, low loss transmission, and remote distribution. Here, an integrated optical multichannel transceiver operating as the photonic front end is used to acquire multiple delayed replicas of the electromagnetic signals, and then, a multiple signal classification algorithm is used to estimate their DoAs at the center station. In the indoor experiments, the DoAs ranging from −60 deg to +60 deg are successfully estimated with errors less than 1.2 deg in a 10-km radio-over-fiber link. In the field trials, the GSM-R signal accompanied by a suspected EMI is detected with DoA errors less than 1.8 deg.