Timing demodulation method of Loran-C signals under condition of low signal to noise ratio

Abstract

The invention discloses a timing demodulation method of Loran-C signals under the condition of low signal to noise ratio. The timing demodulation method comprises the steps of: sampling the Loran-C signal by adopting an acquirer, then searching and tracking a station signal; tracking a point position and a weight value according to a first pulse of a pulse train, and reconstructing a first pulse waveform, wherein in the single pulse train, an interval between every two adjacent pulses is 1ms and only 6 pulses carry time-code information; reconstructing possible existential states of other pulses according to the first pulse reconstructing method; in order to overcome the defect of insufficient time-code information carried by the waveform under the condition of low signal to noise ratio, carrying out decoding operation by using a full-waveform relevant algorithm, obtaining actual demodulation information through comparing relevant values, and then obtaining time information included by the pulse train according to a time-code demodulation mapping table; and finally, circularly implementing the steps according to the quantity of the pulse trains to obtain the time information carried by all tracking signals. The timing demodulation method overcomes the problem of failed receiving signal demodulation caused by the low signal to noise ratio, more accurately obtains the time information of the Loran-C signals, and is superior to the conventional time-code demodulation algorithm.

Description

technical field [0001] The invention relates to radio timing technology, in particular to a Loran C signal timing demodulation method under the condition of low signal-to-noise ratio. Background technique [0002] Roland C is a long-range high-precision radio navigation system, which belongs to the land-based, low-frequency, pulse-phase radio navigation system. Loran C timing receivers are usually installed on ships, aircraft and mobile vehicles. By tracking the signals of more than three stations at the same time, or tracking the signal of one station when the specific position of the carrier is known, the reference standard time can be obtained. . At present, domestic Roland C timing receivers often use whip antennas to receive electric field signals emitted by stations, and when they are closer to the transmitting station, the received signal amplitude is stronger. However, the signal strength is inversely proportional to the square of the distance. In areas far from th...

AI Technical Summary

Problems solved by technology

This algorithm can realize the data demodulation function when the signal condition is good, but as the user's requirements for timing accuracy and area of ​​use continue to increase, its shortcomings are gradually revealed

When the receiving point is far away from the transmitting station or the magnetic antenna is used for underwater reception, the received useful signal is weak, and the timing signal cannot be accumulated to improve the signal-to-noise ratio. At this time, the phase correlation demodulation algorithm The demodulation success rate is low, and the timing information in the signal cannot be successfully obtained

Images