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

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