Transcript
UHF RFID Antenna Array for Intelligent Shelf Applications
Dr. Stoyan Iliev CST European User Conference 2014, Berlin, Germany
Outline
Motivation Single element of the antenna array Feeding network Measurement results Kathrein Reader Antenna Interface ©KRAI Read range of the antenna Conclusions
Motivation Typical use with Wide Range antennas RFID reader
Wide Range Antenna
The read range is more than 18 m in the focus of the main beam of the reader antenna with 2W e.r.p.
By reducing the power the read range will be accordingly smaller The smallest reader output power is 50mW In combination with Wide Range antenna, this results in read range of over 4m For smaller read range, antennas with negative gain are needed
Single element of the antenna array
(a) Micro - strip line with characteristic impedance of 50 Ω (b) The termination resistor is equal to the characteristic impedance of the line (c) the feed point of the line is denoted
The length of the line is one wave length at 866 MHz and this way circularly polarized wave is exited
Feeding Network The feeding network is implemented with coplanar lines and standard “corporate” tree
Feed lines as coplanar lines for small parasitic radiation
Simulations Matching
Very broadband matching due to the micro strip character of the radiating structures
Simulations Directivity of the antenna
Negative gain -6 dBic No side lobes Very high front to back ration >20dB HPBW 60°
Excellent directivity for obtaining very well defined read range
Comparison with Measurement Directivity of the antenna Phi = 0 340
350-5
0
10
Phi = 90 340
20
330
-15
310 300
80
CST Simulation
-55
270
90
Messung
260
100
250
110
240
120
230
130
220
140 210
150 200
190
180
170
160
50 60
-35
290
70
40
-25
300
60
-45
280
20 30
310
50
-35
290
10
-15
320
40
-25
0
330
30
320
350-5
70
280
-45
80
270
-55
90
CST Simulation Messung
260
100
250
110
240
120
230
130
220
140 210
150 200
190
180
170
160
Good agreement between simulation und measurement
Kathrein Reader Antenna Interface ©KRAI Operating mode with Wide Range Antennas
UHF Signals
©KRAI Signals
Both signals are distributed via the standard coax antenna cable
Kathrein Reader Antenna Interface ©KRAI © KRAI Interface •
Cascade function
•
Polarization switch LHCP/RHCP/Ver/Hor and read rate improvement
•
Beam Forming +/- 35° for direction detection and use as EAS system
Improves the efficiency and performance of the UHF RFID systems by increasing the reading rate and their flexibility
Read range based on E field distribution One reader can support up to 32 SMSH shelf antennas
The signaling is done via coax cable and ©KRAI
Read range based on E field distribution 31dBm
Read range without dynamic adjustment 29dBm
0.50m
23dBm
1.50m
21dBm
25dBm
27dBm
Read range with dynamic adjustment
21dBm
21dBm
21dBm
21dBm
21dBm
0.50m
21dBm
Precise adjustment of the SMSH shelf antenna read range due to ©KRAI
Conclusions
UHF antenna array based on novel radiating elements Broadband feeding network
Very well defined read range, without unwanted reading zones Unprecedented functionality in the UHF RFID systems
