CL-Xiong / GNSS_Signals

Navigation and Communication -Signals

GNSS Signals:signal_strength:

Subroutines

NO.	M FILES	FUNCTION
1	CAcode.m	Generate different PRN's C/A code and calculate the correlation function between two C/A codes.
2	AllanVariance.m	Calculate the Alan variance and Modified Alan variance of the clock difference(phase) sequence or frequency sequence.

Several commonly used variances[1].

type	symbol	description
Standard Variance		Calculated based on the relative frequency deviation relative to the square of its mean.
Allan Variance		Calculated based on the relative frequency deviation relative to the square of its mean.
Overlapping Allan Variance		Calculating the Allan variance based on full overlap sampling.
Total Variance		Calculate the Allan variance using the extended data.
Modified Allan Variance		Calculating the Allan variance based on the relative frequency deviation or the mean of the time difference data.
Modified Total Variance		Calculate "Modified the Allen Variance" with the extended data.
Time Variance
Time Total Variance
Hadamard Variance		Calculation based on the second difference of the relative frequency deviation or the cubic difference of the time difference data.
Overlapping Hadamard Variance		The Hadamard variance is calculated based on full overlap sampling.
Hadamard Total Variance		Calculate the Hadamard variance using the extended data.

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• CAcode.m

The purpose of the function is to generate a C/A code and calculate the correlation function between C/A codes.

function C_A = generateC_A(PRN,CodeLength,Delay)
% Generate C/A code
% Given:
%     PRN             i      PRN number
%     CodeLength      i      C/A code length
%     Delay           i      C/A code delay
% Returned:
%     C_A             d      C/A code

function Rkl = Relafunc(Rk,Rl,CodeLength,NUM)
% Generate two C/A code correlation functions
% Given:
%       Rk , Rl       i      First C/A code and Second C/A code
%       CodeLength    i      C/A code length
%       NUM           i      Number of chips  
% Returned:
%       Rkl           d      Correlation functions

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• AllanVariance.m

  The purpose of the function is to calculate the Alan variance and Modified Alan variance of the phase or frequency sequence.

function AllanVariance = AVAR_Phase(PhaseSequence,tau)
% Calculate the Alan variance of the clock difference (phase) sequence.
% Given:
%       PhaseSequence        Phase sequence  
%       tau                  Sampling interval              
% Returned:
%       AllanVariance        Allan variance

function AllanVariance = AVAR_Freq(FrequencySequence)
% Calculate the Alan variance of the frequency sequence.
% Given:
%       FrequencySequence    Frequency sequence                 
% Returned:
%       AllanVariance        Allan variance

function Mod_AllanVariance = MAVAR_Phase(PhaseSequence,tau,m)
% Calculate the Modified Allan variance of the time difference (phase) sequence.
% Given:
%       PhaseSequence        Phase sequence  
%       tau                  Sampling interval  
%       m                    Smoothing factor       
% Returned:
%       Mod_AllanVariance    Modified Allan variance

function Mod_AllanVariance = MAVAR_Freq(FrequencySequence,m)
% Calculate the Modified Allan variance of the frequency sequence.
% Given:
%       FrequencySequence    Frequency sequence         
%       m                    Smoothing factor
% Returned:
%       Mod_AllanVariance    Modified Allan variance

[1]Guo,H.R. . Study on the Analysis Theories and Algorithms of the Time and Frequency Characterization for Atomic Clocks of Navigation Satellites[D].Information Engineering University,2006.