Low signal-to-noise ratio code capturing method based on frequency modulation signal

Abstract

The invention discloses a low signal-to-noise ratio code capturing method based on a frequency modulation signal. The method comprises steps of receiving a signal obtained by splicing the frequency modulation signal and the spread spectrum modulation signal, performing down-conversion processing on the received spliced signal, performing matched filtering processing on the spliced signal and a local frequency modulation signal, and solving the quadratic sum of in-phase and orthogonal branches of a matched filtering result to obtain judgment data; sending the judgment data to an adaptive constant false alarm rate judgment device, and judging whether the splicing signal is successfully captured or not by adopting a 3 / 4 judgment strategy; sending the spliced signal subjected to down-conversion processing and judgment data into a spreading code discriminator, judging whether a spreading signal arrives or not, and determining a spliced point of a frequency modulation signal and the spreading modulation signal; and according to the splicing point of the frequency modulation signal and the spread spectrum modulation signal, sending the spread spectrum modulation signal in the spliced signal subjected to down-conversion processing to a dispreading module, and carrying out correlation accumulation with a local spread spectrum code to obtain a dispreading signal. The method has higher detection probability and anti-interference performance.

Description

technical field [0001] The invention belongs to the technical field of communication, in particular to a code acquisition method with a low signal-to-noise ratio based on a frequency modulation signal. Background technique [0002] Spread spectrum communication has the advantages of strong anti-interference ability and convenient code division multiple access, and is widely used in security communication, GPS navigation and other fields. Spread spectrum code acquisition is one of the key technologies of the spread spectrum communication system. The probability of spread spectrum code capture and anti-interference ability directly affect the system performance. In the process of capturing the spread spectrum code, many factors will affect the final result, resulting in performance degradation. The low signal-to-noise ratio of the input signal is the key reason for capture failure, especially in short burst communications. [0003] The traditional spread spectrum signal captu...

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Problems solved by technology

[0004] Increase the length of the spreading code, the longer the correlation operation time in the despreading process, the higher the signal-to-noise ratio gain can be obtained, and the acquisition performance of the system can be improved, but when the spreading code period is longer, a lot of delay and addition are required Computing is too complex to implement and consumes too much resources

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