Narrow-band discrete distribution parabolic equation method for forecasting ASF with high precision

A technology of discrete distribution and parabolic equations, applied in special data processing applications, complex mathematical operations, instruments, etc., can solve the problems of low prediction accuracy of existing frequency domain methods and inapplicability of long-distance radio waves

Active Publication Date: 2017-06-20
XIAN UNIV OF TECH
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Problems solved by technology

[0003] The purpose of the present invention is to provide a narrow-band discrete distribution parabolic equation method for predicting ASF with high precision, to solve the problem that the existing time domain method is not suitable for long-distance radio wave propagation, and the existing frequency domain method has low prediction accuracy

Method used

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  • Narrow-band discrete distribution parabolic equation method for forecasting ASF with high precision
  • Narrow-band discrete distribution parabolic equation method for forecasting ASF with high precision
  • Narrow-band discrete distribution parabolic equation method for forecasting ASF with high precision

Examples

Experimental program
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Effect test

Embodiment 1

[0106] Surface ASF Prediction in Long-Distance Flat Surface Paths

[0107] The vertical electric dipole consists of a Loran-C form current signal i s (t) excitation, the total size of the calculation area is ρ max : 200km×z max : 102.4km, the geoelectric parameters take two different situations: ε r =8, σ=6×10 -4 S / m (forest) and ε r = 13 , σ=3×10 -3 S / m (land). The FEF calculation area is the first 20km, and the SSPE calculation area is the last 180km. The grid division sizes are respectively 500m for dρ and 100m for dz. Number of grids in time domain N t =23333, step size Δt=1.668×10 -8 s; frequency domain integration range 75kHz ~ 250kHz, namely f min and f max 75kHz and 125kHz respectively, grid number N f =51, step size Δf=1kHz. Sliding window grid number N w =2400. image 3 In two 200km long flat ground paths, the method of the present invention is compared with the ASF distribution obtained by the FDTD method and the SSPE method. Depend on image 3 It c...

Embodiment 2

[0109] Time Domain Characteristics of Radio Waves and Surface ASF Prediction in Long-distance Complicated Terrain Paths

[0110] The vertical electric dipole consists of a Loran-C form current signal i s (t) excitation, the total size of the calculation area is ρ max : 200km×z max : 102.4km, the geoelectric parameter is taken as: ε r =8, σ=6×10 -4 S / m (forest). The terrain function is:

[0111]

[0112] Among them, ρ represents the distance on the propagation path, in km. The FEF calculation area is the first 20km, and the SSPE calculation area is the last 180km. The grid division size of the flat ground is 500m for dρ, 100m for dz, and dρ is reduced to 100m for the undulating terrain. Other parameter settings remain unchanged. Figure 4 The normalized time-domain magnetic field waveform at a distance of 150km is given, and it can be seen from the figure that the Loran-C magnetic field signal curve obtained by the method of the present invention and the FDTD method a...

Embodiment 3

[0114] Surface ASF Prediction in Ultra-Long Distance Complex Terrain Paths

[0115] Expand the total size of the calculation area in Example 2 to ρ max : 1000km×z max : 409.6km, the FEF calculation area is the first 20km, and the SSPE calculation area is the rear 980km. Other parameter settings remain unchanged. The vertical electric dipole consists of a Loran-C form current signal i s (t) excitation, the geoelectric parameter is taken as: ε r =8, σ=6×10 -4 S / m (forest). The terrain function is:

[0116]

[0117] Among them, ρ represents the distance on the propagation path, in km. The FEF calculation area is the first 20km, and the SSPE calculation area is 180km. The grid division size of the flat ground is 500m for dρ, 100m for dz, and dρ is reduced to 100m for the undulating terrain. The time-domain and frequency-domain grid division rules remain unchanged. Figure 6 It is the ASF distribution comparison obtained by the method of the present invention and the SS...

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Abstract

The invention discloses a narrow-band discrete distribution parabolic equation method for forecasting ASF with high precision. The method specifically comprises the following steps: firstly, sampling a loran-C current time-domain signal; performing discrete fourier transform on the sampled signal; decomposing the sampled signal into a plurality of frequency current components; adopting a flat ground formula for calculating a magnetic field irradiated by each frequency current component in a near zone; calculating a far zone magnetic field by regarding a magnetic field result at a boundary of a near-far zone as an initial field for a discrete distribution parabolic equation method for an uneven grid part, thereby acquiring the magnetic field generated by each frequency current component on the earth surface; and lastly, adopting fourier inversion on the basis of sliding window thought, thereby acquiring a time-domain magnetic field signal recovered by the frequency domain magnetic fields irradiated by the frequency current components on the earth surface. The method provided by the invention can overcome the defect that the present theory is difficult to forecast practical long-distance loran-C signal ASF distribution. Compared with the existing frequency domain method, the method has the advantage that the forecast precision is obviously increased and has the characteristic of high practicability.

Description

technical field [0001] The invention belongs to the technical field of radio wave propagation, and in particular relates to a narrow-band discrete distribution parabolic equation method for predicting ASF with high precision. Background technique [0002] At present, the methods for obtaining the additional secondary delay (Additional Secondary Factor, ASF) of Loran-C can be divided into two categories: time domain methods and frequency domain methods. Among them, the time-domain method is based on the FDTD method. This type of method has high prediction accuracy, but consumes a lot of memory and takes too long to calculate, so it is not suitable for long-distance radio wave propagation. Frequency domain methods mainly include: flat surface formula, Fock diffraction method, Wait integral, Millington formula, integral equation (Integral Equation, IE) method, parabolic equation (Parabolic Equation, PE) method, etc. The frequency domain method is only applicable to the predict...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G06F17/50G06F17/14
CPCG06F17/141G06F30/20
Inventor 席晓莉王丹丹张金生蒲玉蓉李征委
Owner XIAN UNIV OF TECH
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