An array extension method in a noisy environment was proposed to improve angular resolution and array gain. The proposed method combines the FOC （fourth-order cumulants） technique with the ETAM （extended towed arra...An array extension method in a noisy environment was proposed to improve angular resolution and array gain. The proposed method combines the FOC （fourth-order cumulants） technique with the ETAM （extended towed array measurements） method to extend array aperture and suppress Gaussian noise, First, successive measurements of a virtual uniform linear array were constructed by applying lburth-order cumulants to measurements of uniform linear array; Gaussian noise in these measurements was also eliminated. Then, the array was extended by compensating phase differences using the ETAM method, Finally, the synthetic aperture was extended further by the fourth-order cumulants technique. The proposed FOC-ETAM-FOC method not only improves angular resolution and array gain, but also effectively suppresses Gaussian noise. Furthermore, it inherits the advantages of the ETAM method. Simulation results showed that the FOC-ETAM-FOC method achieved better angular resolution and array gain than the ETAM method. Furthermore this method outperforms the ETAM method in Gaussian noise environment.展开更多
The ground-based EAS array is usually operated with a high duty cycle （〉 90%） and a large field of view （- 2sr）, which can continuously monitor the sky. It is essential and irreplaceable to understand the gamma-r...The ground-based EAS array is usually operated with a high duty cycle （〉 90%） and a large field of view （- 2sr）, which can continuously monitor the sky. It is essential and irreplaceable to understand the gamma-ray emission mechanism and intrinsic physics progress of the variable source AGN. The EAS arrays, AS-y experiment （since 1990） and ARGO-YBJ experiment （since 2007）, have continuously monitored the northern sky at energies above 3 TeV and 0.3 TeV, respectively. They have made substantial contributions for long-term monitoring of Mrk 421 and Mrk 501. In this paper, we will review the results obtained by the EAS arrays. The next generation of EAS array, LHAASO project, will boost the sensitivity of current EAS array at least up to 30 times with a much wider energy range from 40 GeV to 1 PeV. Beside increasing the number of VHE gamma-ray sources, it will guide us look sight into the properties of jet, and throw light on the determining of the EBL, intergalactic magnetic fields, and the validity of the Lorentz Invariance.展开更多
基金Supported by the National Science Foundation of China (No.60872146)
文摘An array extension method in a noisy environment was proposed to improve angular resolution and array gain. The proposed method combines the FOC （fourth-order cumulants） technique with the ETAM （extended towed array measurements） method to extend array aperture and suppress Gaussian noise, First, successive measurements of a virtual uniform linear array were constructed by applying lburth-order cumulants to measurements of uniform linear array; Gaussian noise in these measurements was also eliminated. Then, the array was extended by compensating phase differences using the ETAM method, Finally, the synthetic aperture was extended further by the fourth-order cumulants technique. The proposed FOC-ETAM-FOC method not only improves angular resolution and array gain, but also effectively suppresses Gaussian noise. Furthermore, it inherits the advantages of the ETAM method. Simulation results showed that the FOC-ETAM-FOC method achieved better angular resolution and array gain than the ETAM method. Furthermore this method outperforms the ETAM method in Gaussian noise environment.
基金the National Natural Science Foundation of China (Grant No. 11205165)the Xiejialin Fund of the Institute of High Energy Physics, Chinese Academy of Sciences (Grant No. Y3546140U2)
文摘The ground-based EAS array is usually operated with a high duty cycle （〉 90%） and a large field of view （- 2sr）, which can continuously monitor the sky. It is essential and irreplaceable to understand the gamma-ray emission mechanism and intrinsic physics progress of the variable source AGN. The EAS arrays, AS-y experiment （since 1990） and ARGO-YBJ experiment （since 2007）, have continuously monitored the northern sky at energies above 3 TeV and 0.3 TeV, respectively. They have made substantial contributions for long-term monitoring of Mrk 421 and Mrk 501. In this paper, we will review the results obtained by the EAS arrays. The next generation of EAS array, LHAASO project, will boost the sensitivity of current EAS array at least up to 30 times with a much wider energy range from 40 GeV to 1 PeV. Beside increasing the number of VHE gamma-ray sources, it will guide us look sight into the properties of jet, and throw light on the determining of the EBL, intergalactic magnetic fields, and the validity of the Lorentz Invariance.
