Calculation method of decision function for captured spread spectrum signals

Abstract

The invention provides a calculation method of a decision function for captured spread spectrum signals. According to the technical scheme, the calculation method comprises the following steps of: generating continuous M*N sections of local spread spectrum codes of spread spectrum phases to be searched by virtue of a receiver, wherein each period of time is Tc, and the local spread spectrum codes are used for performing correlation operation with I branch data and Q branch data; generating multiple correlation values by virtue of M*N correlation values obtained from a correlation operation structure of an I branch and M*N correlation values obtained from a correlation operation structure of a Q branch, and performing FFT (Fast Fourier Transformation) operation with the multiple correlation values; calculating intermediate quantity for forming equivalent preliminary detection integral time; and finally calculating an operation result from envelope detection and envelopes, thereby forming the decision function for calculating the captured spread spectrum signals. According to the calculation method, the steps are simple, the flexibility is high, a hardware structure for completing the correlation operation in a PMF (Passive Match Filter) method does not need to be modified, and the preliminary detection integral time with different lengths can be formed through the recombination of the correlation values so as to be applicable to capturing direct sequence spread spectrum signals in undefined ranges of different Doppler.

Description

technical field

[0001] The present invention relates to a communication or ranging system of a direct sequence spread spectrum system, and more particularly, to a signal acquisition method suitable for a satellite navigation system using a direct sequence spread spectrum signal as a distance measuring signal. Background technique

[0002] The direct sequence spread spectrum system is a spread spectrum system that uses pseudo-random spread spectrum codes to achieve spectrum expansion. It has the advantages of high confidentiality and strong anti-interference ability. It is obtained in the Global Navigation Satellite System (GNSS for short). widely used. The acquisition of the direct sequence spread spectrum signal is the premise of the receiver's work, and the acquisition process is the process of the receiver completing the two-dimensional search of the spread spectrum code phase and Doppler frequency. Passive Match Filter (PMF) method combined with time-frequency domain is...

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