Airborne Distributed Coherent Aperture Radar(ADCAR)is one of the most promising next-generation radars to significantly improve target detection and discrimination abilities.However,time and phase synchronization amon...Airborne Distributed Coherent Aperture Radar(ADCAR)is one of the most promising next-generation radars to significantly improve target detection and discrimination abilities.However,time and phase synchronization among unit radars should be done before an ADCAR is intended to cohere on a potential target.To address this problem,a time and phase synchronization technique using clutter observations is proposed in this paper.Clutter returns from different azimuths and elevations on the surface of the earth are employed to calibrate system uncertainties.Two stages are mainly considered:a scene registration among range-Doppler units from different transmit/receive pairs is performed to enhance the clutter coherence in the first stage,followed by a joint estimation of those synchronization errors in the second stage.To relieve the computational burden,a novel Separable and Sequential Estimation(SSE)method is provided to separate the unknowns at the sacrifice of a range-Doppler unit.Moreover,performance analyses including the clutter coherence ability,estimation lower bound,and signal coherence loss are also performed.Finally,simulation results indicate that ADCAR time and phase synchronization is realized by using our methods.展开更多
Remarkable achievements have been witnessed in free-space quantum key distribution(QKD),which acts as an available approach to extend the transmission range of quantum communications.The feasibility of transmitting qu...Remarkable achievements have been witnessed in free-space quantum key distribution(QKD),which acts as an available approach to extend the transmission range of quantum communications.The feasibility of transmitting qubits through the free-space channel with the aid of moving platforms like satellites,aircraft,unmanned aerial vehicles(UAVs)has been verified.In view of the limited working time and resource consumption of the satellite-based QKD and the last-mile challenges of connecting satellite nodes with terrestrial networks,the airborne QKD is expected to provide flexible and relay links for the large-scale integrated network.This paper reviews the recent significant progress of QKD based on aircraft or UAVs,highlights their critical techniques,and prospects the future of airborne quantum communications.展开更多
文摘Airborne Distributed Coherent Aperture Radar(ADCAR)is one of the most promising next-generation radars to significantly improve target detection and discrimination abilities.However,time and phase synchronization among unit radars should be done before an ADCAR is intended to cohere on a potential target.To address this problem,a time and phase synchronization technique using clutter observations is proposed in this paper.Clutter returns from different azimuths and elevations on the surface of the earth are employed to calibrate system uncertainties.Two stages are mainly considered:a scene registration among range-Doppler units from different transmit/receive pairs is performed to enhance the clutter coherence in the first stage,followed by a joint estimation of those synchronization errors in the second stage.To relieve the computational burden,a novel Separable and Sequential Estimation(SSE)method is provided to separate the unknowns at the sacrifice of a range-Doppler unit.Moreover,performance analyses including the clutter coherence ability,estimation lower bound,and signal coherence loss are also performed.Finally,simulation results indicate that ADCAR time and phase synchronization is realized by using our methods.
基金supported by the National Key Research and Development Program of China(No.2018YFA0306400)National Natural Science Foundation of China(Nos.61627820,61822115,61971436,and 61675189)Anhui Initiative in Quantum Information Technologies(No.AHY030000)。
文摘Remarkable achievements have been witnessed in free-space quantum key distribution(QKD),which acts as an available approach to extend the transmission range of quantum communications.The feasibility of transmitting qubits through the free-space channel with the aid of moving platforms like satellites,aircraft,unmanned aerial vehicles(UAVs)has been verified.In view of the limited working time and resource consumption of the satellite-based QKD and the last-mile challenges of connecting satellite nodes with terrestrial networks,the airborne QKD is expected to provide flexible and relay links for the large-scale integrated network.This paper reviews the recent significant progress of QKD based on aircraft or UAVs,highlights their critical techniques,and prospects the future of airborne quantum communications.
