The Electromagnetic Compatibility between FAST and Public Mobile Communication Stations and its Cognitive Using Frequency Strategy

To master the electromagnetic environment characteristics around the Five-hundred-meter Aperture Spherical radio Telescope(FAST)and ensure a better ecological environment in the radio-quiet zone of FAST,we analyzed the radiation characteristics of the public communication stations around FAST.By comparing the FAST received signal power from the communication stations and the interference protection threshold of the radio astronomy applications,we found that the total proportion of the communication stations exceeding the radio astronomy protection threshold is 69.01%.Furthermore,to fully protect the regular operation of FAST,we proposed four interference avoidance and frequency coordination strategies based on the cognitive theory.Namely:(1)increasing the operating frequency of the communication station;(2)adjusting the direction of the transmitter antennas;(3)reducing the height of the transmitter antennas;(4)decreasing the transmitting power of the communication station.As a result,the impact on FAST can effectively be reduced,and the FAST's received power from the communication stations will be lower than the radio astronomy protection threshold by using the above mentioned four strategies.Through the analysis of the experiment,the prediction is consistent with the overall trend of the measurement,and using frequency strategies can significantly reduce the signal power at the receiving locations.Furthermore,we construct a quality evaluation system for frequency coordination and analyze the satisfaction of the four strategies under the four criteria.The results show that adjusting the direction of the transmitter antennas has better satisfaction,and the maximum satisfaction is 0.85.The above research results can be further expanded to potentially improve the electromagnetic ecological environment around FAST and support the regular operation of FAST.