Determining speeds of radio frequency tags

ANTENNA 104 i M HHGHT,h 106 D$TANCE,d I?I(}. 1 SPEED,v ANTENNA 108 104 / K 204A 21/OA X IN-PHASE LOWPASS _> HLTER PHASE 204B ARCTANGENT = PRg€@§§NG QUAD-PHASE LOWPASS FNTER '_’ COSWE \ \ \ 210B 212 214 90° / 208 206

vco FIG. 2

FIG. 3 150 DOPPLER SHIFT FOR 40 TO 80 MPH / 300 100 — 50 — 1- 302 FREQUENCY 0 — -50 — -100 — -150 I I I -1.0 -0.5 0.0 0.5 1.0 TIME FIG. 4 160 SPEED VERSUS DOPPLER SLOPE 140 — 120 — 100 — SPEED 80 (KM-PER-HOUR) 60 — 40 _ — h = 5m 20 _ ---- h = 6m 0 I I I 0 500 1000 1500 2000

DOPPLER SLOPE

FIG. 5 PHASE ESTIMATE STANDARD DEVIATION / 500 15 — DEGREES 10 — 5 _ 0 I I I I I 10 15 20 25 30 35 40 SNR(dB) I?I(3; (5 PHASE ESTIMATE DISTRIBUTION (2055 SNR) 007 005PROBAHLWY 004DENSHY 003_ 0020010-00 I I I -40 -20 0 20 40

PHASE (DEGREES)

FIG. 7 ESTIMATED PHASE AND CURVE FIT 1 0 (25dB SNR) 700 -1 1 1’

HISTOGRAM OF VELOCITY ESTIMATES

8000 7000 — ;:_ / 800 6000 — 1 5000 BINS 4000 — 3000 — 2000 — 1000 — __ 0 -|_._.;._;_;.;. ;._ I 110 115 120 125 130 SPEED (KM-PER-HOUR)

902 \( INITIATE SPEED ESTIMATION ) go
904 \ READ TAG AT TIME 1,, , COMPUTE PHASE 0,,
906 \ READ TAG AT TIME rm , COMPUTE PHASE 0,7,1

908 / CARRIER FREQUENCY FOR WAVELENGTH ( DONE SPEED ESTIMATION ) FIG_ 9 1002 \C BEGIN SPEED+ ESTIMATION ) J/000 1004 \ READ TAG AT TIME 10 , COMPUTE PHASE (90 1006 \ READ TAG AT TIME f1I.C0|\/IPUTE PHASE 01

1008 I
HAS

READ TAG AT TIME tn, J

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