simu.rar_GPS generate_GPS中频_GPS信号生成_卫星信号生成_卫星采样信号

******************************* ReadMe ****************************** OpenGPSSim - A simple GPS simulator Version: 0.1.0 OpenGPSSim is a _simple_ GPS receiver simulation tool. It has been developed and tested with Borland's bccBuilder (Win9X/WinNT) and gcc (Linux). OpenGPSSim is based on Clifford Kelley's ([email protected]) OpenSourceGPS distribution (see www.home.earthlink.net/~cwkelley). Several routines are taken from Antonio Tabernero Galan's gar2rnx tool (see artico.lma.fi.upm.es/numerico/miembros/antonio/async/) * 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., 675 Mass Ave, Cambridge, MA 02139, USA. * ***************************************************************** The files 'gpsfuncs.cpp', 'gpsrcvr.cpp' and 'gp2021.cpp' are modified versions of the files with the same name from Clifford Kelley's OpenSourceGPS distribution. The unmodified files can be obtained from http://www.home.earthlink.net/~cwkelley ***************************************************************** ---------------------------------------------------------------------- OpenGPSSim is composed of three programs: 'ogsxmit' calculates a downconverted, 2-bit quantized GPS signal and writes the data to './data/ogsraw.dat'. Navigation data is read from input files, one file for each satellite. Sampling frequency is 5.7 MHZ, 4 samples are stored in one byte (8 bit). Therefore, 'ogsxmit' produces about 1.4 MByte per second simulation time. Simulation time and other parameters are set in parameter file './bin/xmit_par.dat'. 'ogsrcvr' reads the downconverted GPS signal from './data/ogsraw.dat', tracks it and - if successful - writes the navigation message (1 frame, 1500 bits) to files './data/nav-out-PRN' (PRN=1,...,32)., in-phase and quad-phase values are written to './data/iq-out-PRN', carrier frequency doppler is stored in './data/carfrq-out-PRN'. Parameters are set in parameter file './bin/rcvr_par.dat'. 'ogsencdec' translates navigation messages between binary and ASCII formats. ---------------------------------------------------------------------- Installation: 1) unzip the zip-archive 2) cd to subdirectories './encdec', './xmit' and './rcvr' and compile with 'make -f makefile.bcc' or 'make -f makefile.unix'. makefile.bcc : Borland's bcc & Win9X/WinNT makefile.unix : gcc & Linux/Unix executables 'ogsencdec', 'ogsxmit' & 'ogsxmit' are placed in subdirectory './bin'. ---------------------------------------------------------------------- Example simulation procedure: 1) generate navigation messages: First the 1500 bit navigation message has to be generated. (1500 bit at 50 Hz corresponds to 30 seconds simulation time. For longer time periods the same message is re-used. Subcommutation of subframe 4 & 5 is not yet implemented). Two template files are found in './data/': nav-01-template-01-06.txt nav-11-template-01-06.txt Files names can be chosen freely. However, the satellite PRN must be present and the extensions has to be '.txt' (indicating ASCII format). ./bin/ogsencdec nav-01-template-01-06.txt ./bin/ogsencdec nav-11-template-01-06.txt translates both files into 1500 byte binary format; the result is written to: nav-01-template-01-06 nav-11-template-01-06 [Remark: If you own a GPS receiver you might be able to use Antonio Tabernero Galan's async/gar2rnx tool to extract the navigation data from real observations (see artico.lma.fi.upm.es/numerico/miembros/antonio/async/). An example file is './data/393540x36.g12', the navigation data can be extracted using 'ogsencdec' as well. The command ./bin/ogsencdec -l -a 393540x36.g12 lists all PRN present in this data file. Then, e.g. ./bin/ogsencdec -s 1 -a 393540x36.g12 extracts all navigation frames transmitted by satellite PRN=1. A pair of files (binary and ASCII) is created for each complete navigation frame found: nav-PP-WWWW-SSSSSS-AA-BB nav-PP-WWWW-SSSSSS-AA-BB.txt where PP : PRN WWWW : GPS week number SSSSSS : time of week [sec] AA : page number in subframe 4 BB : page number in subframe 5 Files with extension 'txt' are in ASCII format, file without extension are binary files.] 2) once the navigation messages are generated, calculation of simulated GPS signal can be started with: ./bin/ogsxmit -n nav-PRN-template-01-06 Control parameters are read from './bin/xmit_par.dat'. 'ogsxmit' writes output to './data/ogsraw.dat'. Currently, a simulation time period is set to 45 seconds in './bin/xmit_par.dat'. Therefore, './data/ogsraw.dat' grows to more than 60 MByte. 3) the signal tracking process is started by ./bin/ogsrcvr -i -r produces for each PRN found in the signal output files (in our example PRN 1 and 11 are present): nav-out-01 and nav-out-11 iq-out-01 and iq-out-11 carfrq-out-01 and carfrq-out-11 4) analyse navigation data files ./bin/ogsencdec -r nav-out-01 ./bin/ogsencdec -r nav-out-11 translates the contents of nav-out-01 and nav-out-11 to ASCII format and writes it to nav-out-01.txt nav-out-11.txt The values found in these files should correspond to those of the input files nav-01-template-01-06.txt nav-11-template-01-06.txt It is instructive to plot the in-phase and quad-phase values stored in data files: iq-out-01 and iq-out-11 (These are binary files - data formats are described in './doc/dataformats.txt') ---------------------------------------------------------------------- Notes: 'ogsxmit' writes about 1.4 MByte of data per second simulation time. Thus, a 30 seconds simulation (1 data frame) produces about 42 MByte of data. Currently, 'ogsxmit' does _not_ take into account GPS satellites positions and receiver location. Thus, calculation of receiver position is not performed. That might be added in the future. The simulation is _much_ slower than real time: it takes about 20 sec to construct and about 10 sec to track 1 sec of data on a 450 MHZ PC. Tracking speed can be increased by reducing the number of active channels (parameter 'number active channels' in parameter file 'bin/rcvr_par.dat', maximum value is 12). The software receiver is a 12 channel, single wavelength receiver, C/A code only, carrier and code 2nd order Costas PLL (code aiding not yet implemented). PLL parameters set by parameter file './bin/rcvr_par.dat' File formats are described in './doc/dataformats.txt' ---------------------------------------------------------------------- Send comments and suggestions to [email protected] ****************************************************************