1. ZoomedIn
Structural mode depends on:
tag's size, shape and material.
Tag mode depends on:
transmission delay-line length and
the value of the terminating load.
Remote Identification and Wireless Temperature Sensing Based on UWB Passive Chipless Time-Coded RFID
tags with LOS and NLOS Scenarios
𝑀𝑖𝑛𝑎 𝑊𝑎ℎ𝑖𝑏1
, 𝑀𝑎𝑟𝑡𝑖𝑛 Schüßler 2
, 𝐵𝑒𝑟𝑛𝑑 𝐾𝑢𝑏𝑖𝑛𝑎2
, 𝑅𝑜𝑙𝑓 𝐽𝑎𝑘𝑜𝑏𝑦2
1 German University in Cairo, Microwave Department, New Cairo City, Main Entrance El Tagamoa El-Khames, Cairo, Egypt (minawahib@hotmail.com)
2 Technische Universität Darmstadt, Fachgebiet Mikrowellentechnik, Merckstrasse 25, 64283 Darmstadt, Germany
Proposed identification technique
Introduction: Chipless RFID technology Conclusion
Load extraction (Method 1) Results (Remote Identification and Wireless Temperature Sensing)
Simulated time-domain responses for different resistive loads at
different distances
Wireless Temperature Sensing
Time-coded chipless tag
Extracted resistive loads (Method 1)
Thermalimagerused
Load extraction (Method 2)
The extracted load values for the first 3 distances can
be seen above. The average extracted load values as a
function of the 5 distances is also presented. It’s
obvious that the deviation of the average extracted
load values from the reference ones is basically due to
the parasitic effects encountered.
Method 1 Method 2
It’s obvious that those extracted resistive values using Method 1 are more accurate
than those extracted using Method 2. However, in both cases the extracted resistive
load values are decreasing with increasing temperature since it’s an NTC thermistor.
A novel remote identification technique for UWB time-coded passive chipless tags based on the remote
extraction of the terminating load impedance and the length of the transmission delay-line was presented.
The passive chipless tag was identified based on LOS and NLOS scenarios at large distances up to 180 cm.
The tag was
simulated at
distances starting
from 20 cm up to
180 cm in a step of
40 cm. The
simulated time-
domain responses
for the first 3
distances can be
seen in front of
you.
LOS / NLOS Remote Identification
An NTC thermistor was soldered to the fabricated
tag. The tag was heated up by a heat gun and the
temperature was measured at the tag’s back.
Temperatures starting from 20℃ up to 100 ℃ were
measured. The corresponding resistive values for the
thermistor were extracted by the help of the
proposed technique (Method 1 and 2)
The passive chipless tag was successfully utilized as a temperature sensor , sensing temperatures starting
from 20℃ up to 100℃ using both proposed load extraction methods.Passive chipless time-coded tag
Chipless tags : tags having no on-board IC silicon chip (No memory chip).
Encoding can be done in the backscattered frequency-domain spectrum or time-domain signal.
Available time-coding techniques modulates the tag mode pulse position and polarity.
Only small number of unique tags can be identified using this time-domain method.
Cheap
Simple design
Suitable for harsh environments
Can be used for sensing applications
Time-coded tag structure
UWB operation for time-coded tag detection
Identification technique concept
Data can be encoded in the time-delay separation between the
structural mode peak and the tag mode peak and in the value of the
terminating resistive load. By applying this identification technique
the number of unique identifiable tags can be greatly increased. Two
different load extraction techniques will be proposed for this aim.
Proof of concept fabricated tag [1]
S-parameters and gain
The 10-dB impedance bandwidth extends over an UWB range from
3.63 GHz to 14 GHz
[1] Study of a Uniplanar Monopole Antenna for Passive Chipless UWB-RFID
Localization System Sanming Hu, Student Member, IEEE, Yuan Zhou, Student
Member, IEEE, Choi Look Law, Senior Member, IEEE, and Wenbin Dou, Member,
IEEE.
The time-delay separation between the two green peaks corresponds
to the time-delay encountered by the UWB pulse while travelling
through the transmission delay-line of length 𝐿2
Any time-coded chipless system can be represented by this black-box
representation. Our main aim is to extract the value of the load impedance
𝒁 𝑳𝑶𝑨𝑫 through the value of the input impedance 𝒁𝒊𝒏 𝑿
𝐴 𝑂𝑝𝑒𝑛
𝐴 𝑈𝑛𝑘𝑛𝑜𝑤𝑛𝐿𝑜𝑎𝑑
Time-coded chipless system two-port network circuit model
[2] D. M. Pozar, Microwave Engineering, 3rd edition. John Wiley & Sons Ltd., 2005.
[2]
The effect of obstacles placed in the vicinity of the tag was studied. The tag was fixed as shown
in the figure and the plastic obstacle was placed at different locations behind and in front of
the tag. The backscattered time-domain signal was measured for each case as shown below.
1.5 2 2.5 3
0
0.5
1
1.5
2
2.5
3
3.5
4
x 10
-3
Structural Mode Peak
Tag Mode Peak
Without an
obstacle at
location 5
With an obstacle
at location 5
LOC.1
LOC.2
LOC.3
LOC.4
LOC.5
Plastic obstacle
Reader
At location 5, even though the obstacle is in front of the tag we are still able to get the reflection from
the tag – however somehow shifted because of the obstacle - with the same exact time-delay between
both peaks. Thus the tag can be readily identified based upon an NLOS scenario.
Chipless tag
Reference
Extracted
860 Ω
550 Ω
400 Ω
It’s preferable to use lower resistive loads to minimize the parasitic effects encountered during the load
extraction process and thus leading to a more precise tag identification process (Less errors)
Parasitic effects
↑ Resistive load → ↑ Parasitic effects
Simulated Structure
NLOS
LOS
LOS: Line-Of-Sight
NLOS: Non Line-Of-Sight
Can be Inkjet Printed in the near future
Can substitute Barcodes in the future
𝑳 𝟏 + 𝑹 𝟏 → 𝟎𝟎𝟎
𝑳 𝟏 + 𝑹 𝟐 → 𝟎𝟎𝟏
𝑳 𝟐 + 𝑹 𝟏 → 𝟎𝟏𝟎
𝑬𝒙:
.
.
.
.