APU007: An Introduction to Automotive Keyless Entry
Systems
© DecaWave 2013 This document is confidential and contains information which is proprietary to
DecaWave Limited. No reproduction is permitted without prior express written permission of the
author
TABLE OF CONTENTS
1 INTRODUCTION ..................................................................................................................... 3
2 IMPLEMENTATION OF KEYLESS ENTRY SCHEMES .................................................................... 4
2.1 REQUIREMENTS FOR A KEYLESS ENTRY SYSTEM .................................................................................. 4
2.2 HOW TO MEET THESE REQUIREMENTS WITH THE DW1000 .................................................................. 4
2.2.1 Distance from the vehicle .................................................................................................. 4
2.2.2 Operation only within a given distance from the vehicle .................................................. 5
2.2.3 Detecting on which side of the vehicle the fob is located ................................................. 6
2.2.4 Physical Implementation of the in-vehicle unit ................................................................. 9
2.2.5 Other Considerations ....................................................................................................... 12
WHYDW1000IS IDEAL FOR KEYLESS ENTRY SYSTEMS ................................................................... 14
3 REFERENCES ........................................................................................................................ 15
3.1 LISTING ..................................................................................................................................... 15
4 ABOUT DECAWAVE ............................................................................................................. 16
LIST OF TABLES
TABLE 1: REQUIREMENTS FOR A KEYLESS ENTRY SYSTEM ................................................................................... 4
TABLE 2: ANALYSIS OF MEASURED DISTANCES .................................................................................................. 7
TABLE 3: MEETING KEYLESS ENTRY SYSTEM REQUIREMENTS WITH THE DW1000 ............................................... 14
TABLE 4: TABLE OF REFERENCES .................................................................................................................. 15
LIST OF FIGURES
FIGURE 1: MEASURING THE DISTANCE FROM THE FOB TO THE VEHICLE ................................................................. 5
FIGURE 2: OPERATION ONLY WITHIN 2M OF THE VEHICLE BY ALLOWING COMMUNICATIONS .................................... 5
FIGURE 3: DETECTING ON WHICH SIDE OF THE VEHICLE THE FOB IS LOCATED .......................................................... 6
FIGURE 4: TWO IN-VEHICLE UNITS ON VEHICLE CENTRE LINE................................................................................ 6
FIGURE 5: TWO IN-VEHICLE UNITS MOUNTED ACROSS THE VEHICLE ...................................................................... 7
FIGURE 6: MAXIMUM MEASUREMENT ERROR DETERMINES PHYSICAL SEPARATION OF IN-VEHICLE UNITS .................... 8
FIGURE 7: IN-VEHICLE UNITS SEPARATED BY LESS THAN THE MAX MEASUREMENT ERROR......................................... 8
FIGURE 8: BASIC SINGLE UNIT IMPLEMENTATION ............................................................................................. 9
FIGURE 9: POSSIBLE TWO-UNIT IMPLEMENTATION BY SWITCHING ANTENNAS ....................................................... 9
FIGURE 10: TWO TRANSCEIVERS / SINGLE MICRO IMPLEMENTATION ................................................................. 11
FIGURE 11: IN-VEHICLE UNIT BASED ON TWO ENTIRELY SEPARATE SUB-UNITS ...................................................... 11
FIGURE 12: LOCATION OF IN-VEHICLE UNITS .................................................................................................. 13
