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Long Range and Low Powered RFID Tagswith Tunnel Diode
Francesco Amato, Christopher W. Peterson, Muhammad B. Akbar, Gregory D. Durgin
School of Electrical and Computer Engineering, Georgia Institute of Technology. Atlanta, GA 30332
Overview
Abstract Reflection Amplifier Characterization
Modulation and Backscattering
Future Applications
References[1] F. Amato, C. W. Peterson, B. P. Degnan, and G. D. Durgin, “A 45 µW bias power, 34 dB gain reflection amplifier exploiting the tunneling effect for RFID applications,” in RFID (RFID), 2015 IEEE International Conference on, Apr. 2015.
Observations
Fig. 4. Realized prototype of a tunnel diode based reflection amplifier.
We present a 5.8 GHz RFID tag equipped with a high gain, low power reflection amplifier based on a tunnel diode. Experimental results show that the realized prototype achieves gains above 40 dB and requires only 29 µW of biasing power. The tag detects very low RF signals (< -90 dBm). Long communication ranges and Manchester encoding are achieved by biasing on and off the tunnel diode.
Fig. 1: conceptual block diagram of a tunnel diode-based reflective system
C1
Tunnel Diode
RFin
VBias
Bias Tee
Tuning stub
Fig. 5. Measurement setup and return gains as function of the RF power, Pin, at the reflection amplifier input.
-100 -90 -80 -70 -60 -50 -40 -30
0
5
10
15
20
25
30
35
40
45
Pin
[dBm]
Re
turn
Ga
in [d
B]
Vector
Analyzer
AVbias
Reflection
Amplifier
AVbias
Reflection
Amplifier
1 2
3
Signal
Generator
Signal
Analyzer
A1 A2
Pin
#1 #2
a)1 b)
A3
• A reflection amplifier displays a negative resistance (-R) that increases the modulation factor to values above 1 and amplifies reflected RF signals.
• Bias requirements, reported in the literature, ranges from 0.32 mW to 1 W (Fig. 2).
• A low-powered (29 µW) reflection amplifier (Fig. 4) with tunnel diode displays a 42 dB gain at 5.8 GHz (Fig. 5).
Fig. 3: Realized prototype of a long range RFID tag
• Modulation takes place by turning on and off the reflection amplifier.
• A square wave of amplitude ranging between 0 and 69 mV at 250 kHz and 1.25 MHz has been used.
• For communication purposes, the word 0xA4 has been generated using Manchester encoding. (Fig. 7)
• The complete backscatter link has been tested (Fig. 9) at 23.3 m range.
Fig. 9. A 250 kHz modulated signal of -78 dBm appears on the receiver at 23.3 m away from the tag.
Fig. 7. Comparing the ideal Manchester encoded word 0xA4 with the one reflected by the reflection amplifier.
PT = -20 dBmGT = 6 dBGR = 42 dB
Pt = -83 dBmM = 38 dBGt= 6 dB
Fig. 8. Experimental setup to test the backscatter link
Fig. 6. Demodulated signal in the time domain for a modulation frequency of 250 kHz.
0.4002 0.4002 0.4003
-6.2
-2.2
1.8
5.8
t [s]
Am
plit
ud
e -
[m
V]
I - channel
Q - channel
The prototyped RFID tag has high gains and very low bias power requirements (Fig. 2).
The prototype (Fig. 1 and 3) can be a competitor of WiFi and BLE nodes (Tab. 1).
10-2
10-1
100
101
102
103
5
8
11
14
17
20
23
26
29
32
35
38
41
44
Bias Power [mW]
Gain
[dB
]
State of the art for reflection amplifiers
This work: tunnel diode-based reflection amplifiers
Fig. 2. State-of-the-art reflection amplifiers
Tab. 1. Comparing performances with other wireless technologies
• 23.3 m of backscattering communication with EIRP of -14 dBm have been achieved.
• For -90 dBm of RF input power impinging on the tag, a modulation gain of 43 dB was measured using only 29 µW of biasing power (Fig. 5).
• With higher EIRPs and higher sensitivities, longer ranges are possible. (Fig. 10).
Fig. 10. Comparing link budgets of the RFID tag prototype with a ideal semi-passive tag. EIRP = 36 dBm.
101
102
103
104
-140
-130
-120
-110
-100
-90
-80
-70
-60
Range [m]
PR
min
[d
Bm
]
Range of tag prototype
Range of ideal semi-passive tag
Reader sensitivity [2]
430 m80 m
RFID transceiver will communicate with flying objects.Readers mounted on cars, will interact with the surrounding environment and support driverless cars.
[2] Motorala FX9500 (2012)
Dalman72
Kimionis2014
Chan2013
Chan2011Lazaro2013
cantu2008
Cantu2006
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