A Method for Predicting the Underwater Propagation Characteristics of Loran‑c Pulses with High Accuracy

Abstract

The method for predicting the underwater propagation characteristics of Roland-C pulses with high precision is to first sample the time-domain signal of the Roland-C current, and then perform discrete Fourier transform on the sampled signal to decompose it into multiple frequency current components; then use the existing The long-wave frequency domain algorithm calculates the ground wave field strength radiated by each frequency current element on the earth's surface directly above the underwater receiving point; the ground wave field strength radiated by each frequency current element on the earth's surface is obtained, considering the boundary constraints Conditions and the amplitude attenuation and phase delay of underwater electric wave propagation, and further obtain the ground wave field strength radiated by each frequency current element at the underwater receiving point; finally, using the discrete Fourier inverse transform, the multiple frequency current elements obtained The ground wave field strength radiated at the underwater receiving point is restored to the Loran-C field strength time domain signal received underwater. This method can reduce the error of the existing ground wave propagation characteristic prediction algorithm, improve the prediction accuracy, and has strong practicability specialty.

Description

technical field [0001] The invention belongs to the technical field of radio wave propagation calculation, in particular to a method for predicting the underwater propagation characteristics of Roland-C pulses with high precision. Background technique [0002] The Roland-C signal uses a 100 kHz pulse phase modulation signal. When making high-precision predictions on its radio wave propagation characteristics, in addition to considering the influence of factors such as the irregularity of the earth's surface, the interference of sky-to-ground waves, and the antenna radiation environment, it is also necessary to consider its radio frequency. Dispersive effects when propagating on the surface of a dissipative medium or in a dissipative medium. When analyzing the dispersion effect, in the existing algorithm, if the receiving point is on the ground surface, only the dispersion effect of the Roland-C signal propagating along the ground surface with different electrical parameters ...

AI Technical Summary

Problems solved by technology

When analyzing the dispersion effect, if the receiving point is on the ground surface in the existing algorithm, only the dispersion effect of the Loran-C signal when it propagates in the air along the ground surface with different electrical parameters is considered. When the Loran-C signal enters the water from the air , the dispersion in the air is ignored, and only the dispersion effect of the Loran-C signal in the underwater propagation is considered, without considering the constraints of the field components on the boundary of the air and sea water

Moreover, in the existing algorithm research, when analyzing and processing the electric field signal in the time domain and frequency domain, the Loran-C emission current signal waveform is used to approximate the electric field signal waveform, and the prediction of the propagation characteristics will further introduce errors

[0003] In fact, the Loran-C signal transmitter station is located on land. When it is used for long-distance underwater positioning and navigation, the existing analysis of the propagation characteristics of the Loran-C signal from the air into the water does not take the Loran-C signal along the ground surface first. The two parts of the dispersion effect are considered comprehensively when propagating and re-entering the water, and the constraints of the field components on the boundary of the air and sea water are not taken into account.

Images