APS011: Sources of error in TWR schemes
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TABLE OF CONTENTS
1 INTRODUCTION ........................................................................................................................................ 4
1.1 OVERVIEW ................................................................................................................................................. 4
1.2 ABOUT THIS DOCUMENT................................................................................................................................ 4
2 RANGING ACCURACY IN THE PRESENCE OF CLOCK DRIFT ......................................................................... 5
2.1 INTRODUCTION ........................................................................................................................................... 5
2.2 DW1000 OSCILLATOR AND QUARTZ CRYSTAL.................................................................................................... 5
2.3 TWO-WAY RANGING (TWR) WITH CLOCK DRIFT ................................................................................................. 6
2.4 SYMMETRIC DOUBLE-SIDED TWO-WAY RANGING (SDS-TWR) WITH CLOCK DRIFT..................................................... 8
2.5 SYMMETRIC DOUBLE-SIDED TWO-WAY RANGING (SDS-TWR) WITH FREQUENCY DRIFT ............................................. 9
3 RANGING ACCURACY VS RECEIVED SIGNAL LEVEL .................................................................................. 10
3.1 INTRODUCTION ......................................................................................................................................... 10
3.2 DECARANGING IMPLEMENTATION................................................................................................................. 10
3.3 DESIGN SPECIFIC DETAILS ............................................................................................................................ 11
3.4 FRIIS' PATH LOSS FORMULA AND RANGE BIAS CORRECTION VALUE ........................................................................ 11
3.4.1 Example Calculation ...................................................................................................................... 14
4 CONCLUSION .......................................................................................................................................... 15
4.1 RANGING ACCURACY IN THE PRESENCE OF CLOCK DRIFT ..................................................................................... 15
4.2 RANGING ACCURACY VS. RECEIVED SIGNAL POWER ........................................................................................... 15
5 REFERENCES ........................................................................................................................................... 16
5.1 LISTING .................................................................................................................................................... 16
6 ABOUT DECAWAVE ................................................................................................................................ 17
7 APPENDIX A: DERIVING THE ERROR IN RANGING ACCURACY DUE TO DRIFT .......................................... 18
7.1 TWR WITH CLOCK DRIFT ............................................................................................................................. 18
7.2 SDS-TWR WITH CLOCK DRIFT ...................................................................................................................... 18
7.3 SDS-TWR WITH FREQUENCY DRIFT ............................................................................................................... 19
8 APPENDIX B: RANGE BIAS FIGURES FOR 900 MHZ CHANNELS ................................................................ 20
LIST OF TABLES
TABLE 1: SAMPLE RANGE BIAS CORRECTION TABLE FROM DECARANGING TWR SOFTWARE FOR CHANNEL 2 ................................ 11
TABLE 2: RELATIONSHIP BETWEEN RSL AND RANGE BIAS CORRECTION FACTOR ...................................................................... 13
TABLE 3: CALIBRATION DISTANCE FOR CHANNELS AND PRF ................................................................................................ 13
TABLE 4: TABLE OF REFERENCES .................................................................................................................................. 16
TABLE 5: RANGE BIAS CORRECTION FACTORS VS. RECEIVED SIGNAL LEVEL FOR 900MHZ CHANNELS ........................................... 20
