TDDM spread spectrum navigation signal capturing method based on two-channel combined utilization

Abstract

The invention discloses a TDDM spread spectrum navigation signal capturing method based on two-channel combined utilization. According to the method, a local spread spectrum code sequence without data modulation is used for generating two-way local spread spectrum sequences acquired after being modulated through +1 navigation messages and -1 navigation messages respectively. According to a first scheme, subsection correlation is conducted on the two-way spread spectrum sequences and base-band signals, N groups of relevant data are completely collected to conduct FFT calculation, and after the module of a calculation result is worked out, maximum peaks of the two ways are overlaid to acquire the combined judgment amount; according to a second scheme, I-way integral values and Q-way integral values of the two ways are respectively added, N groups of data are completely collected to conduct FFT calculation, and after the module of a calculation result is worked out, the capturing judgment amount is acquired. Whether the phase of a received signal is searched out or not is judged according to the detection judgment amount and a capturing threshold value; if the judgment amount is smaller than the capturing threshold value, the signal is not searched out yet, a numerically-controlled oscillator is regulated by a capturing control unit according to a set searching step length regulation code, and signal phase searching and detecting are continuously conducted on the next searching unit; if the signal is searched out, a receiver judges that the signal is successfully captured.

Description

technical field [0001] The invention belongs to the technical field of navigation and positioning, and in particular relates to a method for capturing TDDM navigation signals. Background technique [0002] With the improvement of the signal system of the new generation of satellite navigation system, the way of spreading the navigation signal has a new development. TDDM (TimeDivisionDataModulation) technology has become the focus of attention as a new modulation method. It no longer complies with the traditional conventional data modulation process, and allows no data information component (ie pilot component) in the navigation signal. The emergence of this new modulation method poses new challenges for the receiver to correctly recover the navigation message, and the original acquisition method is no longer suitable for the new signal modulation method. Therefore, the research on TDDM signal capture method has certain forward-looking and important practical significance. ...

AI Technical Summary

Problems solved by technology

However, the direct capture method has the risk of cross-symbol integration. In the worst case, the +1 and -1 spreading code sequences last half of the pre-detection integration time, and the capture decision will be reduced to no cross-symbol integration. When capturing half of the judgment amount, the signal-to-noise ratio will be lost by 3dB, which will affect the judgment result

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