Day 4 - 25 July
- Sara Faour
Advanced antenna design for RFID devices
Prof. Andrea Michel
RFID is not used only for identification, it can be also used for sensing, localization, communication…
RFID tags contain a small chip to which is attached a unique identifier and other info, everything is registered on registers on the chip. For chip-less RFID no chip is used.
Depending on the application, different frequency bands can be employed.
Inductive LF tags:
Inductive HF tags
RFID for Sensing
Prof. Filippo Costa
UHF RFID Technology
The chip has a minimum threshold of power to be activated.
The RFID capability to direct beam is not very high, so it is a dipole antenna.
The aim of using chip-less RFID is the ability to print the tag directly without needing any additional steps and cost.
Acoustic Chipless RFID sensors use some piezoelectric material to transform EM signals to acoustic signals, and this possible on it because the frequency of acoustic signals is lower.
NFC wireless sensor example:
NFC RFID wireless sensor example
RFID usually works with one frequency only, so usually it measures the change in amplitude.
RFID localization for Industry 4.0: trends and challenges
Prof. Alice Buffi
Proximity methods:
The tag position is associated to that of the detecting antenna.
If several antennas detect the tag, its position is estimated as the position of the antenna receiving the strongest signal.
the tag localization can be improved by intersecting the antenna detection areas
inconvenient:
Accuracy dependent on the number of reader antennas
Mandatory calibration procedure to determine the antenna detection area
Amplitude-based methods:
transmit power control
Measurements with variable power levels to determine the minimum power Pmin required to tag
identification
antenna beam control
Measurements with variable beam to determine the tag direction with respect to the reader antenna
RSSI measurements
Channel propagation model formulation to predict the tag distance from the RSSI
Phase-based methods:
Time Domain PDOA (TD-PDOA)
Frequency Domain FDOA (FD-PDOA)
Spatial Domain FDOA (SD-PDOA)
Synthetic Aperture Radar (SAR) based localization: Phase measurements during antenna/tag relative motion are employed to estimate the tag position
RFID circuit & system components
Prof. Giuseppe Lannaccone
→ Very technical but an excellent presentation!
ISM bands: Industrial Scientific Medical bands
Coupling between reader and transponder:
Classification of RFID systems on the basis of communication type:
Full Duplex or Half Duplex
Transponder and reader can transmit simultaneously. The reader must detect the weak signal coming from the transponder in the presence of signal leaking from the reader transmitterSequential
Reader and transponder transmit alternatively.
Half duplex (HDX):
Reader transmits (downlink) and transponder transmits (uplink) in alternative time intervals.
The reader continuously transfers energy to the transponder. Example of HDX communication: Transponder transmits via load modulation or backscatter modulation
Sequential transmission (SEQ):
Reader and transponder transmit alternatively. Reader transfers energy to the transponder only when the
reader transmits information. During this time, the transponder must
receive information
store energy (typically in a capacitor) for the next transmission.
Passive RFID systems with electromagnetic coupling:
The antenna is the coupling element
Th voltage is multiplied at each of the red points (but the peak to peak remains the same)
Refer to the presentation for more technical details
The gain of the transponder does not need to be as high as the reader gain (it can be close to 1).
m: modulation factor → should be high but in reality it is bad to have a high m because the reflected power will be small
Electromagnetic Information Security for IoT devices (to be continued)
Prof. Agostino Monorchio
EMC: electromagnetic compatibility
Actually scientists don’t really know if EM signals are dangerous?!
This accident took place because of replacing a coaxial cable by a simple wire → again an EMC problem
This problem is the same as the interference problem!
Especially for IoT this is a very important problem.
This HIGH EM emission can be used to destroy some devices and shut-down them.
Iot are very susceptible to these leakage since they don’t have an directed antenna, they send signals in all directions.
when we have low power consumption, it doesn’t matter the transmitted signal but the the receiver, when we shut-down and reduce nearby EM emissions we can listen to them.
All of these 3 factors together can cause an EMC problem.
The scenario on left happens if some wires work as an antenna