Peng H.,Xidian University |
Pan W.,Chinese Research Institute of Radiowave Propagation |
Guo L.,Xidian University
Dianbo Kexue Xuebao/Chinese Journal of Radio Science | Year: 2013
Extremely low frequency (ELF) propagation formulas for horizontal electric dipole sources radiating in a spherical uniform earth-ionosphere cavity have a range dependence characterized by either the Legendre function of the first kind of complex degree v and order zero or one of its first two derivatives. Using the iterative formulas of Legendre function, A new method is presented in this paper. The resulting waves are expressed as a superposition of T M and T E modes. In the near-filed range, the method of images is expected to be similar to the near fields of a dipole located on a flat finitely conducting, the far field is same as the result of Bannister (dir.+ind.) formulas. This shows that the method is accurate. The result of frequencies under 1 Hz show that the horizontal electric and magnetic components are independent of the azimuth φ, and the direction of horizontal electric components is parallel to the dipole axis in the isolines chart with distance, whereas, the direction of horizontal magnetic components is orthogonal to dipole axis. Copyright © 2013 by Editorial Department of Chinese Journal of Radio Science.
Wang X.,Chinese Research Institute of Radiowave Propagation |
Han X.,Chinese Research Institute of Radiowave Propagation |
Peng H.,Xidian University |
Chen Y.,Chinese Research Institute of Radiowave Propagation
Dianbo Kexue Xuebao/Chinese Journal of Radio Science | Year: 2014
In the region near the submarine, the static electromagnetic field may be generated by the electro-chemic current. The knowledge about the distribution of the field in the region is very important for finding the submarine. In this paper, the excited source of the field is idealized as a horizontal static electro dipole, based on the integral expressions of field excited by a low frequency electro dipole in the conducting half-space, taking the limit of ω→0, the integral expressions, of the field excited by the static electro dipole are obtained. These integral expressions related to Bessel-fanction may the simplified as a set of very simple analytical formula, and based on which the discussion is made and the space distribution of electromagnetic field is calculated. ©, Chinese Research Institute of Radiowave Propagation.
Wang C.,Xidian University |
Xu Z.-W.,Chinese Research Institute of Radiowave Propagation |
Zhang M.,Xidian University |
Chen C.,Chinese Research Institute of Radiowave Propagation
IET Conference Publications | Year: 2013
The interest in the use of space-borne SAR at low-frequency for collecting earth biomass information such as forest structure, soil moisture and soil type has been increased. It is crucial to understand the potential effects of radio wave propagation due to the ionospheric perturbation. In this paper, we present some effects of ionosphere on space-borne SAR imaging, especially the higher-order dispersion of the background and random scattering of irregularities are considered. Both the analysis and numerical simulation have been investigated to get some useful conclusions.
Wang Y.-X.,Shanghai JiaoTong University |
Wang Y.-X.,Chinese Research Institute of Radiowave Propagation |
Jin R.-H.,Shanghai JiaoTong University |
Geng J.-P.,Shanghai JiaoTong University
Wireless Personal Communications | Year: 2012
Electromagnetic wave radiation from a SLF/ELF horizontal electric dipole (HED) related to seismic activity is discussed. In order to estimate the effects on the electromagnetic waves associated with the seismic activity, SLF/ELF waves on the ground radiated from a possible seismic current source modeled as a electric dipole, are precisely computed by using a speeding numerical convergence algorithm. A theoretical calculation of the VLF/SLF electric wave propagating among the Earth-ionosphere cavity generally utilizes the full wave method to solve the model equation. The field in the cavity is comprehended as the sum of each wave mode. However, this method is very complex, and unsuitable to the ELF frequency band. In 1999, Barrick proposed an algorithm, which was only suitable to solve the electromagnetic problems under the ideal electric conductor condition. To solve the problems under the non-ideal electric conductor condition, we have further developed Barrick's method and proposed a speeding numerical convergence algorithm. The spherical harmonic series expressions of electromagnetic fields excited by SLF/ELF HED in non-ideal Earth-ionosphere cavity are derived. The speed of this algorithm is faster thirty times than it of calculating directly the sum of the series. If it calculates directly the sum of the series, it needs 1,000 series items, while it needs only 200 series items by this algorithm. Our algorithm is compared with the second order spherical surface approximate algorithm, and two algorithms agree with each other very well. Therefore, our algorithm is correct. Schumann resonance is also verified. © 2011 Springer Science+Business Media, LLC.
Peng H.-Y.,Xidian University |
Peng H.-Y.,Chinese Research Institute of Radiowave Propagation |
Tao W.,Wuhan Naval University of Engineering |
Tao W.,Naval Academy of Armament |
And 2 more authors.
Dianbo Kexue Xuebao/Chinese Journal of Radio Science | Year: 2012
Extremely low frequency (ELF) propagation formulas for vertical electric dipole sources radiating in a spherical uniform earth-ionosphere cavity have been derived. These formulas have a range dependence characterized by either the Legendre function of the first kind of complex degree v and order zero or one of its first two derivatives. It is difficult to get the value of the Legendre function unless through appropriate approximations. In this paper, a new numerical integral method for the Legendre function is present. It is more efficient and accurate, and can be used in wider frequency band. The field excited vertical dipole at several frequencies are calculated through the numerical integral method. The fields calculated can image the physical phenomena of ELF propagation in earth-ionosphere cavity, and the frequencies of Schumem resonance is the same as previous researches. ©2012 by Editorial Department of Chinese Journal of Radio Science.