【数字信号】基于matlab模拟GPS信号频谱

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智能优化算法       神经网络预测       雷达通信       无线传感器        电力系统

信号处理              图像处理               路径规划       元胞自动机        无人机 

⛄ 内容介绍

全球定位系统（GPS）使用的信号频谱包括L1、L2和L5三个频段。L1频段的中心频率为1575.42 MHz，L2频段的中心频率为1227.60 MHz，L5频段的中心频率为1176.45 MHz。

其中，L1频段是GPS主要信号频段，它是一种带有码伪造的载波信号，可用于计算位置、速度和时间等信息；L2频段是GPS的辅助信号频段，可用于计算大气延迟误差等信息；L5频段是GPS的高精度信号频段，其波长更短，受多径误差以及干扰影响较小，可提供更加准确的定位数据。

此外，GPS还包括P码和C/A码信号，其中P码信号使用在L1和L2频段，提供高精度的定位数据；C/A码信号是低精度信号，主要用于民用卫星导航。

⛄ 部分代码

function CAcode = generateCAcode(PRN)

% generateCAcode.m generates one of the 32 GPS satellite C/A codes.

%

% CAcode = generateCAcode(PRN)

%

%   Inputs:

%       PRN         - PRN number of the sequence.

%

%   Outputs:

%       CAcode      - a vector containing the desired C/A code sequence 

%                   (chips).  

%--------------------------------------------------------------------------

%                           SoftGNSS v3.0

% 

% Copyright (C) Darius Plausinaitis

% Written by Darius Plausinaitis

% Based on Dennis M. Akos, Peter Rinder and Nicolaj Bertelsen

%--------------------------------------------------------------------------

%This program is free software; you can redistribute it and/or

%modify it under the terms of the GNU General Public License

%as published by the Free Software Foundation; either version 2

%of the License, or (at your option) any later version.

%

%This program is distributed in the hope that it will be useful,

%but WITHOUT ANY WARRANTY; without even the implied warranty of

%MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

%GNU General Public License for more details.

%

%You should have received a copy of the GNU General Public License

%along with this program; if not, write to the Free Software

%Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301,

%USA.

%--------------------------------------------------------------------------

%CVS record:

%$Id: generateCAcode.m,v 1.1.2.5 2006/08/14 11:38:22 dpl Exp $

%--- Make the code shift array. The shift depends on the PRN number -------

% The g2s vector holds the appropriate shift of the g2 code to generate

% the C/A code (ex. for SV#19 - use a G2 shift of g2s(19) = 471)

g2s = [  5,   6,   7,   8,  17,  18, 139, 140, 141, 251, ...

       252, 254, 255, 256, 257, 258, 469, 470, 471, 472, ...

       473, 474, 509, 512, 513, 514, 515, 516, 859, 860, ...

       861, 862 ... end of shifts for GPS satellites 

       ... Shifts for the ground GPS transmitter are not included

       ... Shifts for EGNOS and WAAS satellites (true_PRN = PRN + 87)

                 145, 175,  52,  21, 237, 235, 886, 657, ...

       634, 762, 355, 1012, 176, 603, 130, 359, 595, 68, ...

       386];

%--- Pick right shift for the given PRN number ----------------------------

g2shift = g2s(PRN);

%--- Generate G1 code -----------------------------------------------------

%--- Initialize g1 output to speed up the function ---

g1 = zeros(1, 1023);

%--- Load shift register ---

reg = -1*ones(1, 10);

%--- Generate all G1 signal chips based on the G1 feedback polynomial -----

for i=1:1023

    g1(i)       = reg(10);

    saveBit     = reg(3)*reg(10);

    reg(2:10)   = reg(1:9);

    reg(1)      = saveBit;

end

%--- Generate G2 code -----------------------------------------------------

%--- Initialize g2 output to speed up the function ---

g2 = zeros(1, 1023);

%--- Load shift register ---

reg = -1*ones(1, 10);

%--- Generate all G2 signal chips based on the G2 feedback polynomial -----

for i=1:1023

    g2(i)       = reg(10);

    saveBit     = reg(2)*reg(3)*reg(6)*reg(8)*reg(9)*reg(10);

    reg(2:10)   = reg(1:9);

    reg(1)      = saveBit;

end

%--- Shift G2 code --------------------------------------------------------

%The idea: g2 = concatenate[ g2_right_part, g2_left_part ];

g2 = [g2(1023-g2shift+1 : 1023), g2(1 : 1023-g2shift)];

%--- Form single sample C/A code by multiplying G1 and G2 -----------------

CAcode = -(g1 .* g2);

⛄ 运行结果

⛄ 参考文献

[1]周柱,石峰,张尔扬,等.一种GPS接收机级联抗干扰方法[J].信号处理, 2010, 26(9):7.DOI:10.3969/j.issn.1003-0530.2010.09.010.

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