GPS信号捕获跟踪的MATLAB仿真

%This Function approximate Ionospheric Group Delay %CopyRight By Moein Mehrtash %************************************************************************ % Written by Moein Mehrtash, Concordia University, 3/21/2008 * % Email: moeinmehrtash@yahoo.com * %************************************************************************ % *********************************************************************** % Function for computing an Ionospheric range correction for the * % GPS L1 frequency from the parameters broadcasted in the GPS * % Navigation Message. * % ================================================================== % References: * % Klobuchar, J.A., (1996) "Ionosphercic Effects on GPS", in * % Parkinson, Spilker (ed), "Global Positioning System Theory and * % Applications, pp.513-514. * % ICD-GPS-200, Rev. C, (1997), pp. 125-128 * % NATO, (1991), "Technical Characteristics of the NAVSTAR GPS", * % pp. A-6-31 - A-6-33 * % ================================================================== % Input : * % Pos_Rcv : XYZ position of reciever (Meter) * % Pos_SV : XYZ matrix position of GPS satellites (Meter) * % GPS_Time : Time of Week (sec) * % Alfa(4) : The coefficients of a cubic equation * % representing the amplitude of the vertical * % dalay (4 coefficients - 8 bits each) * % Beta(4) : The coefficients of a cubic equation * % representing the period of the model * % (4 coefficients - 8 bits each) * % Output: * % Delta_I : Ionospheric slant range correction for * % the L1 frequency (Sec) * % ================================================================== function [Delta_I]=Error_Ionospheric_Klobuchar(Pos_Rcv,Pos_SV,Alpha,Beta,GPS_Time) GPS_Rcv = ECEF2GPS(Pos_Rcv); Lat=GPS_Rcv(1)/pi;Lon=GPS_Rcv(2)/pi; % semicircles unit Lattitdue and Longitude S=size(Pos_SV); m=S(1);n=S(2); for i=1:m [El,A0]=Calc_Azimuth_Elevation(Pos_Rcv,Pos_SV(i,:)); E(i)=El/pi; %SemiCircle Elevation A(i)=A0; %SemiCircle Azimoth % Calculate the Earth-Centered angle, Psi Psi(i)=0.0137/(E(i)+.11)-0.022; %SemiCircle %Compute the Subionospheric lattitude, Phi_L Phi_L(i)=Lat+Psi(i)*cos(A(i)); %SemiCircle if Phi_L(i)>0.416 Phi_L(i)=0.416; elseif Phi_L(i)<-0.416 Phi_L(i)=-0.416; end %Compute the subionospheric longitude, Lambda_L Lambda_L(i)=Lon+(Psi(i)*sin(A(i))/cos(Phi_L(i)*pi)); %SemiCircle %Find the geomagnetic lattitude ,Phi_m, of the subionospheric location %looking toward each GPS satellite: Phi_m(i)=Phi_L(i)+0.064*cos((Lambda_L(i)-1.617)*pi); %Find the Local Time ,t, at the subionospheric point t(i)=4.23*10^4*Lambda_L(i)+GPS_Time; %GPS_Time(Sec) if t(i)>86400 t(i)=t(i)-86400; elseif t(i)<0 t(i)=t(i)+86400; end %Convert Slant time delay, Compute the Slant Factor,F F(i)=1+16*(.53-E(i)^3); %Compute the ionospheric time delay T_iono by first computing x Per(i)=Beta(1)+Beta(2)*Phi_m(i)+Beta(3)*Phi_m(i)^2+Beta(4)*Phi_m(i)^3; if Per(i) <72000 %Period Per(i)=72000; end x(i)=2*pi*(t(i)-50400)/Per(i); %Rad AMP(i)=Alpha(1)+Alpha(2)*Phi_m(i)+Alpha(3)*Phi_m(i)^2+Alpha(4)*Phi_m(i)^3; if AMP(i)<0 AMP(i)=0 end if abs(x(i))>1.57 T_iono(i)=F(i)*5*10^(-9); else T_iono(i)=F(i)*(5*10^(-9)+AMP(i)*(1-x(i)^2/2+x(i)^4/4)); end end%for Delta_I=T_iono;