369 lines
18 KiB
Plaintext
369 lines
18 KiB
Plaintext
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function [trackResults, channel]= tracking_V0_IQ(fid, channel, settings)
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% Performs code and carrier tracking for all channels.
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%
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%[trackResults, channel] = tracking(fid, channel, settings)
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%
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% Inputs:
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% fid - file identifier of the signal record.
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% channel - PRN, carrier frequencies and code phases of all
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% satellites to be tracked (prepared by preRum.m from
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% acquisition results).
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% settings - receiver settings.
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% Outputs:
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% trackResults - tracking results (structure array). Contains
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% in-phase prompt outputs and absolute starting
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% positions of spreading codes, together with other
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% observation data from the tracking loops. All are
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% saved every millisecond.
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%--------------------------------------------------------------------------
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% SoftGNSS v3.0
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%
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% Copyright (C) Dennis M. Akos
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% Written by Darius Plausinaitis and Dennis M. Akos
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% Based on code by DMAkos Oct-1999
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%--------------------------------------------------------------------------
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%This program is free software; you can redistribute it and/or
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%modify it under the terms of the GNU General Public License
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%as published by the Free Software Foundation; either version 2
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%of the License, or (at your option) any later version.
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%
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%This program is distributed in the hope that it will be useful,
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%but WITHOUT ANY WARRANTY; without even the implied warranty of
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%MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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%GNU General Public License for more details.
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%
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%You should have received a copy of the GNU General Public License
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%along with this program; if not, write to the Free Software
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%Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
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%USA.
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%--------------------------------------------------------------------------
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%CVS record:
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%$Id: tracking.m,v 1.14.2.32 2007/01/30 09:45:12 dpl Exp $
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%% Initialize result structure ============================================
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% Channel status: trạng thái kênh
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trackResults.status = '-'; % No tracked signal, or lost lock
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% The absolute sample in the record of the C/A code start: khởi tạo mẫu tuyệt đối
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% trong bản ghi C/A
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trackResults.absoluteSample = zeros(1, settings.msToProcess);
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% Freq of the C/A code: tần số mã C/A
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trackResults.codeFreq = inf(1, settings.msToProcess);
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% Frequency of the tracked carrier wave: tần số của sóng mang được theo dõi
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trackResults.carrFreq = inf(1, settings.msToProcess);
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% Outputs from the correlators (In-phase): đầu ra của các bộ tương quan (I)
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trackResults.I_P = zeros(1, settings.msToProcess);
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trackResults.I_E = zeros(1, settings.msToProcess);
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trackResults.I_L = zeros(1, settings.msToProcess);
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% Outputs from the correlators (Quadrature-phase): đầu ra của các bộ tương
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% quan (Q)
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trackResults.Q_E = zeros(1, settings.msToProcess);
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trackResults.Q_P = zeros(1, settings.msToProcess);
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trackResults.Q_L = zeros(1, settings.msToProcess);
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% Loop discriminators
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trackResults.dllDiscr = inf(1, settings.msToProcess);
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trackResults.dllDiscrFilt = inf(1, settings.msToProcess);
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trackResults.pllDiscr = inf(1, settings.msToProcess);
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trackResults.pllDiscrFilt = inf(1, settings.msToProcess);
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%--- Copy initial settings for all channels -------------------------------
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trackResults = repmat(trackResults, 1, settings.numberOfChannels);
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%% Initialize tracking variables ==========================================
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codePeriods = settings.msToProcess; % For GPS one C/A code is one ms (với GPS thì 1 mã C/A là 1 ms)
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%--- DLL variables --------------------------------------------------------
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% Define early-late offset (in chips): Xác định độ lệch sớm-muộn (tính
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% bằng chip)
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earlyLateSpc = settings.dllCorrelatorSpacing;
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% Summation interval: khoảng tính tổng
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PDIcode = 0.001;
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% Calculate filter coefficient values: Tính toán giá trị hệ số bộ lọc
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[tau1code, tau2code] = calcLoopCoef(settings.dllNoiseBandwidth, ...
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settings.dllDampingRatio, ...
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1.0);
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%--- PLL variables --------------------------------------------------------
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% Summation interval
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PDIcarr = 0.001;
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% Calculate filter coefficient values
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[tau1carr, tau2carr] = calcLoopCoef(settings.pllNoiseBandwidth, ...
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settings.pllDampingRatio, ...
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0.25);
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% CARRIER TRACKING LOOP
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Bl_carr =5; % Bandwith in hertz: băng thông tính bằng Hz
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wn_carr = Bl_carr/0.7845; % Natural Frequency: tần số tự nhiên
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% k_carr = 1; % Gain of the overall loop
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% loop filter coefficients: hệ số lọc vòng lặp
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a3=1.1*wn_carr^2;
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b3=2.4*wn_carr;
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wn3=wn_carr^3;
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% filter values initialization: khởi tạo giá trị bộ lọc
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olderrort_carr = 0;
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oldolderrort_carr = 0;
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oldcarrier_nco = 0;
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oldoldcarrier_nco = 0;
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T_int = 1e-3; % integration time
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Acoeff=((T_int^2)*wn3/4)+(a3*T_int/2)+b3;
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Bcoeff=((T_int^2)*wn3/2)-2*b3;
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Ccoeff=((T_int^2)*wn3/4)-(a3*T_int/2)+b3;
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hwb = waitbar(0,'Tracking...');
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try
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%% Start processing channels ==============================================
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for channelNr = 1:settings.numberOfChannels
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% Only process if PRN is non zero (acquisition was successful)
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% Chỉ xử lý nếu PRN khác 0 (acquisition thành công)
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if (channel(channelNr).PRN ~= 0)
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% Save additional information - each channel's tracked PRN:
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% Lưu thông tin bổ sung - PRN được tracked ở mỗi kênh
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trackResults(channelNr).PRN = channel(channelNr).PRN;
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% Move the starting point of processing. Can be used to start the
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% signal processing at any point in the data record (e.g. for long
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% records). In addition skip through that data file to start at the
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% appropriate sample (corresponding to code phase). Assumes sample
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% type is schar (or 1 byte per sample)
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% Di chuyển điểm bắt đầu xử lý. Có thể được sử dụng để bắt đầu xử lý
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% tín hiệu tại bất kỳ điểm nào trong bản ghi dữ liệu (ví dụ: đối với
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% các bản ghi dài). Ngoài ra, hãy bỏ qua tệp dữ liệu đó để bắt đầu
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% với mẫu thích hợp (tương ứng với giai đoạn mã). Giả sử loại mẫu là
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% schar (hoặc 1 byte cho mỗi mẫu)
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fseek(fid, ...
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settings.skipNumberOfBytes + (channel(channelNr).codePhase-1)*settings.dataTypeSize*2, ...
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'bof');
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% Get a vector with the C/A code sampled 1x/chip
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% Nhận 1 vector có mã C/A được lấy mẫu 1x/chip
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caCode = generateCAcode(channel(channelNr).PRN);
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% Then make it possible to do early and late versions: từ đó
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% mới có thể tạo được early và late
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caCode = [caCode(1023) caCode caCode(1)];
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%--- Perform various initializations ------------------------------
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% Thực hiện các khởi tạo khác nhau
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% define initial code frequency basis of NCO
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% Xác định tần số cơ sở mã ban đầu của NCO
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codeFreq = settings.codeFreqBasis;
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% define residual code phase (in chips)
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% Xác định pha mã dư (trong chip)
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remCodePhase = 0.0;
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% define carrier frequency which is used over whole tracking period
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% Xác định tần số sóng mang được sử dụng trong toàn bộ thời
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% gian tracking
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carrFreq = channel(channelNr).acquiredFreq;
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carrFreqBasis = channel(channelNr).acquiredFreq;
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% define residual carrier phase: xác định pha sóng mang dư
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remCarrPhase = 0.0;
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%code tracking loop parameters: tham số vòng lặp tracking
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oldCodeNco = 0.0;
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oldCodeError = 0.0;
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%carrier/Costas loop parametersL: tham số vòng lặp sóng mang/
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%Costas
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oldCarrNco = 0.0;
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oldCarrError = 0.0;
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%=== Process the number of specified code periods =================
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% Xử lý khoảng thời gian mã được chỉ định
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for loopCnt = 1:codePeriods
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%% GUI update -------------------------------------------------------------
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% The GUI is updated every 50ms. This way Matlab GUI is still
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% responsive enough. At the same time Matlab is not occupied
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% all the time with GUI task.
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% GUI được cập nhật cứ sau 50ms. Bằng cách này, GUI Matlab vẫn
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% đủ đáp ứng. Đồng thời Matlab không phải lúc nào cũng bận rộn
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% với nhiệm vụ GUI.
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if (rem(loopCnt, 50) == 0)
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try
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waitbar(loopCnt/codePeriods, ...
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hwb, ...
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['Tracking: Ch ', int2str(channelNr), ...
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' of ', int2str(settings.numberOfChannels), ...
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'; PRN#', int2str(channel(channelNr).PRN), ...
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'; Completed ',int2str(loopCnt), ...
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' of ', int2str(codePeriods), ' msec']);
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catch
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% The progress bar was closed. It is used as a signal
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% to stop, "cancel" processing. Exit.
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disp('Progress bar closed, exiting...');
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return
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end
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end
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%% Read next block of data ------------------------------------------------
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%% Đọc khối dữ liệu tiếp theo
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% Find the size of a "block" or code period in whole samples
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% Tìm kích thước của một "khối" hoặc đoạn mã trong toàn bộ mẫu
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% Update the phasestep based on code freq (variable) and
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% sampling frequency (fixed)
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% Cập nhật bước pha dựa trên tần số mã (biến) và tần số lấy mẫu (cố định)
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codePhaseStep = codeFreq / settings.samplingFreq;
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blksize = ceil((settings.codeLength-remCodePhase) / codePhaseStep);
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% Read in the appropriate number of samples to process this
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% interation: Đọc số lượng mẫu thích hợp để xử lý sự tương tác này
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[tmp, samplesRead] = fread(fid, ...
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2*blksize, settings.dataType);
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rawSignal=tmp(1:2:end)+1i*tmp(2:2:end);
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rawSignal = transpose(rawSignal); %transpose vector: vector chuyển vị
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% If did not read in enough samples, then could be out of
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% data - better exit: Nếu không đọc đủ mẫu thì có thể hết
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% dữ liệu - tốt hơn là thoát
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if (samplesRead < 2*blksize)
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disp('Not able to read the specified number of samples for tracking, exiting!')
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fclose(fid);
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return
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end
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%% Set up all the code phase tracking information -------------------------
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%% Thiết lập thông tin theo dõi pha mã
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% Define index into early code vector
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tcode = (remCodePhase-earlyLateSpc) : ...
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codePhaseStep : ...
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((blksize-1)*codePhaseStep+remCodePhase-earlyLateSpc);
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tcode2 = ceil(tcode) + 1;
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earlyCode = caCode(tcode2);
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% Define index into late code vector
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tcode = (remCodePhase+earlyLateSpc) : ...
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codePhaseStep : ...
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((blksize-1)*codePhaseStep+remCodePhase+earlyLateSpc);
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tcode2 = ceil(tcode) + 1;
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lateCode = caCode(tcode2);
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% Define index into prompt code vector
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tcode = remCodePhase : ...
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codePhaseStep : ...
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((blksize-1)*codePhaseStep+remCodePhase);
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tcode2 = ceil(tcode) + 1;
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promptCode = caCode(tcode2);
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remCodePhase = (tcode(blksize) + codePhaseStep) - 1023.0;
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%% Generate the carrier frequency to mix the signal to baseband -----------
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%% Tạo tần số sóng mang để trộn tín hiệu vào băng cơ sở
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time = (0:blksize) ./ settings.samplingFreq;
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% Get the argument to sin/cos functions
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% Lấy đối số cho hàm sin/cos
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trigarg = ((carrFreq * 2.0 * pi) .* time) + remCarrPhase;
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remCarrPhase = rem(trigarg(blksize+1), (2 * pi));
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% Finally compute the signal to mix the collected data to bandband
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carrCos = cos(trigarg(1:blksize));
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carrSin = sin(trigarg(1:blksize));
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%% Generate the six standard accumulated values ---------------------------
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% First mix to baseband
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iqBasebandSignal=(carrSin+1i*carrCos).* rawSignal;
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qBasebandSignal = imag(iqBasebandSignal);
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iBasebandSignal = real(iqBasebandSignal);
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% Now get early, late, and prompt values for each
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I_E = sum(earlyCode .* iBasebandSignal);
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Q_E = sum(earlyCode .* qBasebandSignal);
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I_P = sum(promptCode .* iBasebandSignal);
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Q_P = sum(promptCode .* qBasebandSignal);
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I_L = sum(lateCode .* iBasebandSignal);
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Q_L = sum(lateCode .* qBasebandSignal);
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%% Find PLL error and update carrier NCO ----------------------------------
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% Implement carrier loop discriminator (phase detector)
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carrError = atan(Q_P / I_P) / (2.0 * pi);
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% Implement carrier loop filter and generate NCO command
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carrNco = oldCarrNco + (tau2carr/tau1carr) * ...
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(carrError - oldCarrError) + carrError * (PDIcarr/tau1carr);
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oldCarrNco = carrNco;
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oldCarrError = carrError;
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% Modify carrier freq based on NCO command
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carrFreq = carrFreqBasis + carrNco;
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trackResults(channelNr).carrFreq(loopCnt) = carrFreq;
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%% Implement phase loop filter and generate NCO command (second order open loop transfer function F(Z))
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% errort_carr=atan(Q_P / I_P) / (2.0 * pi);
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% errort_carr_filt=(Acoeff*errort_carr + Bcoeff*olderrort_carr + Ccoeff*oldolderrort_carr);
|
||
|
|
% carrNco = 2*oldcarrier_nco - oldoldcarrier_nco + errort_carr_filt;
|
||
|
|
% carrFreq = carrFreqBasis + carrNco; %% NCO integrator (with the added pole of the integrator we complete the second order loop transfer function)
|
||
|
|
%
|
||
|
|
% oldolderrort_carr = olderrort_carr;
|
||
|
|
% olderrort_carr = errort_carr;
|
||
|
|
% oldoldcarrier_nco = oldcarrier_nco ;
|
||
|
|
% oldcarrier_nco = carrNco;
|
||
|
|
|
||
|
|
%% Find DLL error and update code NCO -------------------------------------
|
||
|
|
codeError = (sqrt(I_E * I_E + Q_E * Q_E) - sqrt(I_L * I_L + Q_L * Q_L)) / ...
|
||
|
|
(sqrt(I_E * I_E + Q_E * Q_E) + sqrt(I_L * I_L + Q_L * Q_L));
|
||
|
|
|
||
|
|
% Implement code loop filter and generate NCO command
|
||
|
|
codeNco = oldCodeNco + (tau2code/tau1code) * ...
|
||
|
|
(codeError - oldCodeError) + codeError * (PDIcode/tau1code);
|
||
|
|
oldCodeNco = codeNco;
|
||
|
|
oldCodeError = codeError;
|
||
|
|
|
||
|
|
% Modify code freq based on NCO command
|
||
|
|
codeFreq = settings.codeFreqBasis - codeNco+carrFreq*codeFreq/(-carrFreq+1575.42e6);
|
||
|
|
|
||
|
|
trackResults(channelNr).codeFreq(loopCnt) = codeFreq;
|
||
|
|
|
||
|
|
%% Record various measures to show in postprocessing ----------------------
|
||
|
|
% Record sample number (based on 8bit samples)
|
||
|
|
trackResults(channelNr).absoluteSample(loopCnt) = (1/settings.dataTypeSize/2)*ftell(fid);
|
||
|
|
trackResults(channelNr).remCodePhase(loopCnt) = remCodePhase;
|
||
|
|
|
||
|
|
|
||
|
|
trackResults(channelNr).dllDiscr(loopCnt) = codeError;
|
||
|
|
trackResults(channelNr).dllDiscrFilt(loopCnt) = codeNco;
|
||
|
|
trackResults(channelNr).pllDiscr(loopCnt) = carrError;
|
||
|
|
trackResults(channelNr).pllDiscrFilt(loopCnt) = carrNco;
|
||
|
|
|
||
|
|
trackResults(channelNr).I_E(loopCnt) = I_E;
|
||
|
|
trackResults(channelNr).I_P(loopCnt) = I_P;
|
||
|
|
trackResults(channelNr).I_L(loopCnt) = I_L;
|
||
|
|
trackResults(channelNr).Q_E(loopCnt) = Q_E;
|
||
|
|
trackResults(channelNr).Q_P(loopCnt) = Q_P;
|
||
|
|
trackResults(channelNr).Q_L(loopCnt) = Q_L;
|
||
|
|
end % for loopCnt
|
||
|
|
|
||
|
|
% If we got so far, this means that the tracking was successful
|
||
|
|
% Now we only copy status, but it can be update by a lock detector
|
||
|
|
% if implemented
|
||
|
|
trackResults(channelNr).status = channel(channelNr).status;
|
||
|
|
|
||
|
|
end % if a PRN is assigned
|
||
|
|
end % for channelNr
|
||
|
|
catch exception
|
||
|
|
disp(exception.message);
|
||
|
|
end;
|
||
|
|
% Close the waitbar
|
||
|
|
close(hwb)
|