An Ultra Wideband Local Positioning System for Highly Complex Indoor Environments

Transcription

1 An Ultra Wideband Local Positioning System for Highly Complex Indoor Environments Benjamin Waldmann, Robert Weigel Institute for Electronics Engineering University of Erlangen Nuremberg Randolf Ebelt, Martin Vossiek Chair of High Frequency Technology University of Erlangen Nuremberg

2 Outline Motivation and Goals of this Work Local Positioning Radar Principles Multipath Issues Channel Measurement System Expansion to UWB Demonstrator System System Evaluation and Measurement Results

3 Motivation High demand for indoor wireless local positioning Tool tracking Indoor guidance Security applications Surgery assistance Key features: accuracy and multipath robustness Resolution and multipath robustness is proportional to applied bandwidth UWB

4 transponder base station d 1 d 2 (x,y,z) d 4 d 3 y z x Tool Tracking in Industrial Environment

5 Goals Development of an accurate and precise local positioning system with enhanced robustness towards multipath interference

6 Identical hardware setup for base station and mobile client Simple RTOF concept: 1. Synchronize mobile client to base station 2. Send synchronized reply back to base station 3. Base station calculates distance from Round Trip Time of Flight ( ) Basic System Setup

7 f t T B f 2 f 1 2 f 2 f 1 2 Synchronization Multiply both signals and evaluate spectrum Const. mixing products during upsweep & downsweep Correct t, f offsets in time and frequency

8 d c 0 T 2B f d Distance Measurement Standard FMCW approach Distance measurement during downsweep Multiply LO and RX signal and evaluate spectrum

9 Multipath Issues

10 Multipath Issues

11 Multipath Issues

12 Multipath Issues

13 Multipath Issues

14 Multipath Issues

15 Multipath Resolution The ability to resolve closely spaced paths depends on: Type of window function FFT bin size (frequency resolution) Sweep bandwidth B Multipath resolution ~1/B Multipath Issues

16 d NLOS1 LOS 90cm d NLOS2 LOS 210cm d NLOS3 LOS 300cm f 1 450Hz f kHz f 3 1.5kHz Multipath Resolution B=150 MHz

17 d NLOS1 LOS 90cm d NLOS2 LOS 210cm d NLOS3 LOS 300cm f 1 900Hz f 2 2.1kHz f 3 3kHz Multipath Resolution B=300 MHz

18 d NLOS1 LOS 90cm d NLOS2 LOS 210cm d NLOS3 LOS 300cm f 1 1.5kHz f 2 3.5kHz f 3 5kHz Multipath Resolution B=500 MHz

19 d NLOS1 LOS 90cm d NLOS2 LOS 210cm d NLOS3 LOS 300cm f 1 3kHz f 2 7kHz f 3 10kHz Multipath Resolution B=1 GHz

20 Measurement Setup

21 Measurement Constellation

22 Measured Impulse Responses

23 Expansion of sweep bandwidth to 1GHz UWB Measurement settings: RBW = 1 MHz VBW = 3 MHz RMS detector Sweep time = =(no. of bins x 1 ms) Average PSD each bin Violating EIRP limit Pure FMCW system UWB system EIRP / dbm/mhz Expansion to UWB FMCW frequency / GHz

24 Pulsed Frequency Modulated UWB PFM UWB Spectrum broadening 1 t P drop 20 log 10 ( t pw ) T pp t on Chopping of TX signal

25 FCC conform system design: Peak power = 0 dbm t pw = 3ns T pp = 36ns f pr = 27,8MHz t pw /T pp = 1/12 Instantaneously occupied spectrum B UWB > 500 MHz EIRP / dbm/mhz Expansion to UWB FMCW frequency / GHz

26 Reconstruction of chopped RX signal Mixing with continuous LO signal Low-pass filtering with f lp << f pr IF signal easy to digitize Reconstruction of Received Signal

27 Hardware Implementation

28 Prototype System

29 RF Board

30 Prototype System

31 Connection of 2 units via a 100m coax cable Measurement of electrical length of delay line No distortions caused by multipath components Delay Line Measurements

32 2500 measurement samples Gaussian distribution d = 6.57 mm Sync. Results f < 45 Hz t < 45 ps Delay Line Measurements

33 1D distance measurement in outdoor environment Base station at fixed position, mobile client on trolley Reference measurement by laser distance system Max. distance d max = 72m Outdoor Measurements

34 Outdoor Measurements

35 Outdoor Measurements

36 1D distance measurement in office environment Base station at fixed position, mobile client on automatic sledge Highly accurate reference system Indoor Measurements

37 Indoor Measurements

38 1D distance measurement in narrow hallway Distinctive multipath characteristic Base station at fixed position, mobile client on trolley Use of omnidirectional antennas Reference measurement by laser distance system Max. distance d max = 33m Indoor Measurements

39 Indoor Measurements

40 Exemplary IF d=20m

41 Indoor Measurements

42 base stations cordless screwdriver with PFM UWB LPR mobile client Final Demonstration at BMW Fabrication Hall

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44 Ongoing Research LokProd3D Project in the DFG SPP 1202:

45 ASIC XTAL FMCW Synthesizer FPGA ΔΣ DSP ADC LokProd3D: Chip Integration of Multi Channel System

46 VCO with K VCO Linearization PFD + CP MMD LokProd3D: FMCW Synthesizer

47 Distribution NW & RF Switches Mixers Variable Gain Amplifier LokProd3D: RF Frontend

48 PFM USR: Switched Injection Locked Oscillator Approach

49 PFM USR: SILO Based Harmonic Sampling

50 PFM USR: 7 GHz SILO Chip Photograph

51 Conclusions Channel measurement campaign to gain knowledge of industrial UWB channels Expansion of common FMCW to Ultra Wideband First time demonstrated positioning system using PFM- UWB signals for synchronization and distance measurement High accuracy and precision maintained in distinctive multipath environments - 1D accuracy 5 cm in office environment 15 cm in narrow hallway - Standard deviation 1.2 cm in all measurement scenarios

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