GNSS signal capturing method based on FPGA step-by-step code phase refinement
A code phase and signal technology, applied in the field of satellite positioning and navigation, can solve the problems affecting the correlation characteristics of data and local codes, carrier frequency and code phase value errors, and the tracking loop cannot be locked, so as to reduce the acquisition time and hardware. Resources, the effect of saving capture time
Active Publication Date: 2019-11-26
SHANDONG UNIV
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Problems solved by technology
Although downsampling will reduce the amount of calculation and resource requirements, it will affect the correlation characteristics of data and local codes, resulting in certain errors in the output carrier frequency and code phase values.
When the error is too large, the follow-up tracking loop cannot lock, making the capture result unusable
[0006]
Most of the existing methods to reduce the code phase error are to reduce the search step size in the time domain and search again after the frequency domain search is completed. This method takes a long time to capture and consumes a lot of resources.
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[0056] A method for capturing GNSS signals based on FPGA step-by-step code phase refinement, such as figure 2 As shown, running on the capture system, such as figure 1 As shown, the acquisition system includes a local oscillator, a down-sampling module, a Fourier transform module, a local pseudo-random code generator, an inverse Fourier transform module, and a controller; the local oscillator is used to generate quadrature positive and cosine local Carrier signal; the down-sampling module is used to down-sample the long signal with a high sampling rate into a short signal on average; the Fourier transform and inverse Fourier transform modules realize the corresponding mathematical operations; the local pseudo-random code generator is used to generate different satellites The local pseudo-random code; the controller is used to control the data acquisition, down-sampling rate, and part of the local pseudo-random code acquisition for the next capture according to the result of t...
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The invention relates to a GNSS signal capturing method based on FPGA step-by-step code phase refinement. The GNSS signal capturing method comprises the steps of: (1) firstly, carrying out coarse capture, wherein the coarse capture is implemented by mixing all received data with locally generated carriers and correlating the data with complete pseudo-random codes to find out a maximum correlationvalue, acquiring carrier and coarse code phases if the maximum correlation value meets a capture threshold value, and carrying out fine capture, otherwise, repeating the step (1); (2) and carrying outfine capture, wherein the fine capture is implemented by feeding back the carrier and coarse code phase values in the step (1) to a controller, controlling to intercept a part of received signals tobe mixed with the local carriers obtained in the step (1) by means of the controller, eliminating the influence of the carriers and correlating the signal with a part of the pseudo-random codes to obtain a code phase with higher precision. The GNSS signal capturing method based on FPGA step-by-step code phase refinement can reduce the calculation amount of capture, shorten the capture time, and improve the code phase precision without additionally arranging other calculation modules, thereby saving hardware resources.
Description
technical field [0001] The invention relates to a method for capturing GNSS signals based on FPGA step-by-step code phase refinement, and belongs to the technical field of satellite positioning and navigation. Background technique [0002] Satellite positioning technology is widely used in daily production and life and military fields, and can provide all-weather real-time positioning, navigation, and timing services. The satellite positioning system consists of three parts, including the space constellation part, the ground monitoring part and the user receiving equipment part. Among them, the user receiving equipment is used to receive satellite signals, perform satellite signal acquisition, tracking, position calculation and other processing, and finally realize satellite positioning. The purpose of the acquisition processing in the receiving device is to identify all the visible stars of the user, obtain the rough carrier frequency and code phase of the satellite signal...
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IPC IPC(8): G01S19/24G01S19/30G01S19/29
CPCG01S19/24G01S19/30G01S19/29
Inventor 孙娟娟陈蒙琪黄学政王永王兴吴子涵
Owner SHANDONG UNIV