ASM system receiving frequency deviation estimation realization method of ship VDES system

Abstract

The invention discloses an ASM system receiving frequency deviation estimation realization method of a ship VDES system. The method comprises the following steps: performing I and Q orthogonal frequency mixing on an intermediate-frequency signal, respectively outputting an in-phase component I and an orthogonal component Q; respectively performing extraction and low-pass filtering on the in-phase component I and the orthogonal component Q, performing the phase discrimination processing on the in-phase component I and the orthogonal component Q after the low-pass filtering, outputting the phase discrimination error; caching the phase discrimination error in a RAM to perform the variable rate processing so as to adapt to the FFT rapid calculation; performing the maximum peak detection on the output data of the FFF calculation; finding out the subscript n of a maximum value, computing out an estimated frequency deviation fd; compensating the computed frequeny deviation fd to the nominal frequency f0, namely, the nominal frequency at this time is changed as f0+fd. By using the method disclosed by the invention, the accurate estimation can be performed by starting from any moment under a situation of not foreseeing bit synchronization information, and the frequency deviation range is large, and the estimation precision is high; furthermore, the method adopts the maximum peak detection judgment which is more suitable for the low signal-to-noise signal estimation in comparison with the threshold judgement detection method.

Description

technical field [0001] The invention relates to the technical field of signal detection and estimation, in particular to a method for realizing receiving frequency offset estimation of an ASM system of a ship VDES system. Background technique [0002] In a general communication system, due to differences in frequency references and relative motion between the receiving and transmitting ends, relative frequency deviations will occur. If there is no frequency deviation estimation method to compensate for the frequency deviation, the signal will not be able to be demodulated. [0003] In October 2015, the International Telecommunication Union Recommendation ITU-R M.2092-0 proposed the technical characteristics of the VHF data exchange system (VDES) in the VHF maritime mobile frequency band, and made corresponding regulations on the communication technical characteristics of the ASM system in the VDES system , but there is no corresponding regulation on the implementation method...

AI Technical Summary

Problems solved by technology

[0002] In a general communication system, due to the difference in frequency reference and relative movement between the receiving and sending ends, relative frequency deviation will be caused. If there is no frequency deviation estimation method to compensate for the frequency deviation, the signal will not be able to be demodulated.

[0003] In October 2015, the International Telecommunication Union Recommendation ITU-R M.2092-0 proposed the technical characteristics of the VHF data exchange system (VDES) in the VHF maritime mobile frequency band, and made corresponding regulations on the communication technical characteristics of the ASM system in the VDES system , but there is no corresponding provision for the implementation method

Especially for the implementation of the frequency offset estimation of the received signal, there is no clear description of the implementation

[0004] The existing frequency estimation method is to use the phase difference between the symbols of the synchronization sequence to estimate, but for the case of large frequency deviation, the synchronization sequence is difficult to find, so the frequency estimation cannot be performed

Images