Design and Evaluation of a Multi-Modulation Retrodirective RFID Tag - - PowerPoint PPT Presentation

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Design and Evaluation of a Multi-Modulation Retrodirective RFID Tag - - PowerPoint PPT Presentation

Apr 30, 2023 338 likes •556 views

Introduction Design Measurements Discussions Summary Design and Evaluation of a Multi-Modulation Retrodirective RFID Tag Mohammad Alhassoun Michael Varner Prof. Gregory Durgin The Propagation Group Georgia Institute of Technology IEEE

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SLIDE 1

The Propagation Group

Introduction Design Measurements Discussions Summary

Design and Evaluation of a Multi-Modulation Retrodirective RFID Tag

Mohammad Alhassoun Michael Varner

  • Prof. Gregory Durgin

The Propagation Group Georgia Institute of Technology

IEEE International Conference on RFID, 2018

c Mohammad Alhassoun; malhassoun@gatech.edu The Propagation Group @ Georgia Tech Design and Evaluation of a Multi-Modulation Retrodirective RFID Tags

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SLIDE 2

The Propagation Group

Introduction Design Measurements Discussions Summary Motivation

Problem Overview

Next-generation IoT sensors should Operate at high frequencies (mm-waves) Have high gain (reasonable communication distance) Be orientational independent Consume minimal power

c Mohammad Alhassoun; malhassoun@gatech.edu The Propagation Group @ Georgia Tech Design and Evaluation of a Multi-Modulation Retrodirective RFID Tags

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SLIDE 3

The Propagation Group

Introduction Design Measurements Discussions Summary Motivation

Possible Solutions

Problems

1 High gain tags 2 Orientation-independent tags

Solutions

1 Use antenna arrays 2 Use isotropic (or semi-isotropic) antennas

From antenna theory, you cannot do both!

c Mohammad Alhassoun; malhassoun@gatech.edu The Propagation Group @ Georgia Tech Design and Evaluation of a Multi-Modulation Retrodirective RFID Tags

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SLIDE 4

The Propagation Group

Introduction Design Measurements Discussions Summary Motivation

The Best Solution

We cannot use active beamformers because power consumption Alternatively, we can use retrodirective arrays Retrodirective arrays are the best RF-based solution to compensate for

1 Narrow beamwidth of passive arrays 2 Short range of high-frequency tags

c Mohammad Alhassoun; malhassoun@gatech.edu The Propagation Group @ Georgia Tech Design and Evaluation of a Multi-Modulation Retrodirective RFID Tags

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SLIDE 5

The Propagation Group

Introduction Design Measurements Discussions Summary Retrodirective Arrays

Retrodirective Arrays: Definition

Retrodirective arrays send waves back to the direction of incidence. Ideally, no power loss and maximum gain (in optics, similar to corner reflectors)

Retrodirective Feed Network

Retrodirective arrays act as passive, adaptive beamformers

c Mohammad Alhassoun; malhassoun@gatech.edu The Propagation Group @ Georgia Tech Design and Evaluation of a Multi-Modulation Retrodirective RFID Tags

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SLIDE 6

The Propagation Group

Introduction Design Measurements Discussions Summary Retrodirective Arrays

Retrodirective Arrays: Example

Van Atta arrays Connects each antenna pair by a transmission lines L2 = L1 + nλm L2 L1 d d d Problems with Van Atta array are:

1 Limited to OOK or at best BPSK 2 You cannot incorporate two-terminal devices (e.g., tunnel

diodes)

c Mohammad Alhassoun; malhassoun@gatech.edu The Propagation Group @ Georgia Tech Design and Evaluation of a Multi-Modulation Retrodirective RFID Tags

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SLIDE 7

The Propagation Group

Introduction Design Measurements Discussions Summary Theory

Proposal

A rat-race coupler can be a retrodirective feed network. The two port scattering matrix is

  • S
  • = 1

2

  • (Γ1 + Γ2)e−jπ

(Γ1 − Γ2) (Γ1 − Γ2) (Γ1 + Γ2)e−jπ

  • Conditions

1 |Γ1| = |Γ2| 2 ∠Γ2 = ∠Γ1 + π

Γ1 Γ2

Ant.#1 Ant.#2

c Mohammad Alhassoun; malhassoun@gatech.edu The Propagation Group @ Georgia Tech Design and Evaluation of a Multi-Modulation Retrodirective RFID Tags

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SLIDE 8

The Propagation Group

Introduction Design Measurements Discussions Summary Theory

Examples of Terminations

1 Port 1 is open ⇒ Γ1 = 1

Port 2 is short ⇒ Γ2 = −1

2 Port 1 is short ⇒ Γ1 = −1

Port 2 is open ⇒ Γ2 = 1 Observation In both cases, the coupler is retrodirective; however, two (opposite) locations on Smith Chart.

0.2 0.5 1.0 2.0 5.0 +j0.5 −j0.5 +j2.0 −j2.0

  • @5.8 GHz
  • @5.8 GHz

Case 1 Case 2

c Mohammad Alhassoun; malhassoun@gatech.edu The Propagation Group @ Georgia Tech Design and Evaluation of a Multi-Modulation Retrodirective RFID Tags

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SLIDE 9

The Propagation Group

Introduction Design Measurements Discussions Summary Theory

More to say

Switching between retrodirective terminations changes

  • nly the phase

Switching between a retrodirective and non-retrodirective state implements OOK No restrictions on the type of terminations Now, it is time to test the RCS of the device

c Mohammad Alhassoun; malhassoun@gatech.edu The Propagation Group @ Georgia Tech Design and Evaluation of a Multi-Modulation Retrodirective RFID Tags

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SLIDE 10

The Propagation Group

Introduction Design Measurements Discussions Summary Campaign

Set Up

VNA Tag d = 1.22 m Tx Rx Metal Plate

c Mohammad Alhassoun; malhassoun@gatech.edu The Propagation Group @ Georgia Tech Design and Evaluation of a Multi-Modulation Retrodirective RFID Tags

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SLIDE 11

The Propagation Group

Introduction Design Measurements Discussions Summary Campaign

Specifications

Location: Rooftop of the building (open range) Power: 25 dBm (+6 dBi antenna gain) Frequency Span: (3.8 − 7.8) GHz (4 GHz BW) Angular Span: −90◦ to 90◦ Target Height: 1.73 cm Post-Processing Technique: Time Gating Tag designs:

1 Retrodirective (BPSK and OOK) 2 Single-element (BPSK and OOK)

c Mohammad Alhassoun; malhassoun@gatech.edu The Propagation Group @ Georgia Tech Design and Evaluation of a Multi-Modulation Retrodirective RFID Tags

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SLIDE 12

The Propagation Group

Introduction Design Measurements Discussions Summary BPSK

BPSK Configuration and Results

Recall A rat-race coupler is retrodirective if |Γ1| = |Γ2| and ∠Γ2 = ∠Γ1 + π

For retrodirective tag: State#1: Γ1 = 1, Γ2 = −1 State#2: Γ1 = −1, Γ2 = 1 For single antenna tag: State#1: Open circuit State#2: Short circuit The measured differential RCS

−90 −70 −50 −30 −10 10 30 50 70 90 −60 −45 −30 −15 angles (degrees) ∆σ (dBsm) Retrodirective Non-retrodirective

c Mohammad Alhassoun; malhassoun@gatech.edu The Propagation Group @ Georgia Tech Design and Evaluation of a Multi-Modulation Retrodirective RFID Tags

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SLIDE 13

The Propagation Group

Introduction Design Measurements Discussions Summary BPSK

BPSK: Global Performance

We expect 6 dB increase in the differential RCS What if we look at the global performance? Within the beamwidth of the (patch) antenna, how much increase on average?

−50 −30 −10 10 30 50 −4 −8 −12

6.1 dB

angles (degrees) ∆σ (dBsm)

Retrodirective Mean retrodirective Non-retrodirective Mean non-retrodirective

c Mohammad Alhassoun; malhassoun@gatech.edu The Propagation Group @ Georgia Tech Design and Evaluation of a Multi-Modulation Retrodirective RFID Tags

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SLIDE 14

The Propagation Group

Introduction Design Measurements Discussions Summary BPSK

BPSK: Constellations

For retrodirective tag: State#1: Γ1 = 1, Γ2 = −1 State#2: Γ1 = −1, Γ2 = 1 For single-antenna tag: State#1: Open circuit State#2: Short circuit

−1 −0.5 0.5 1 −0.8 −0.6 −0.4 −0.2 0.2 0.4 0.6 0.8 distance = 0.97 distance = 0.53

  • In-phase (Volts)

Quadrature (Volts)

OS Retrodirective SO Retrodirective Open single Short single c Mohammad Alhassoun; malhassoun@gatech.edu The Propagation Group @ Georgia Tech Design and Evaluation of a Multi-Modulation Retrodirective RFID Tags

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SLIDE 15

The Propagation Group

Introduction Design Measurements Discussions Summary OOK

OOK: Constellations

For retrodirective tag: State#1: Γ1 = 1, Γ2 = −1 State#2: Γ1 = −1, Γ2 = −1 For single-antenna tag: State#1: Open circuit State#2: 50 Ω Load

0.2 0.4 0.6 0.8 1 0.2 0.4 0.6 0.8 d i s t a n c e = 1 distance = 0.56 In-phase (Volts) Quadrature (Volts)

OS Retrodirective SS Retrodirective Open single Load single c Mohammad Alhassoun; malhassoun@gatech.edu The Propagation Group @ Georgia Tech Design and Evaluation of a Multi-Modulation Retrodirective RFID Tags

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SLIDE 16

The Propagation Group

Introduction Design Measurements Discussions Summary Retrodirectivity Ideality Facor (RIF)

Retrodirectivity Ideality Facor (RIF): Why?

We want to measure the performance of the a retrodirective feed network Phase is the most important quantity Phase of the feed network must be compared with an ideal retrodirective network The ideal feed network is that of Van Atta arrays, a simple TEM Transmission line Therefore, we introduced a new metric: The Retrodirectivity Ideality Facor (RIF)

c Mohammad Alhassoun; malhassoun@gatech.edu The Propagation Group @ Georgia Tech Design and Evaluation of a Multi-Modulation Retrodirective RFID Tags

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SLIDE 17

The Propagation Group

Introduction Design Measurements Discussions Summary Retrodirectivity Ideality Facor (RIF)

Retrodirectivity Ideality Facor (RIF): Definition

Definition Maximum deviations between the samples of the measured phase and the samples of the interpolated equivalent linear phase.

max{RIFj}, ∀j = 1, . . . , #of states RIF = 1 +

N

  • i=1

(Φi,21 − ˆ Φi,21)2

N

  • i=1

ˆ Φ2

i,21 c Mohammad Alhassoun; malhassoun@gatech.edu The Propagation Group @ Georgia Tech Design and Evaluation of a Multi-Modulation Retrodirective RFID Tags

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SLIDE 18

The Propagation Group

Introduction Design Measurements Discussions Summary Retrodirectivity Ideality Facor (RIF)

Retrodirectivity Ideality Facor (RIF): Measured

Definition Maximum deviations between the samples of the measured phase and the samples of the interpolated equivalent linear phase. The definition is valid only within the bandwidth. For BPSK,

BW ∈ (5.7 − 5.85) GHz max{1.0003, 1.0001} = 1.0003

c Mohammad Alhassoun; malhassoun@gatech.edu The Propagation Group @ Georgia Tech Design and Evaluation of a Multi-Modulation Retrodirective RFID Tags

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SLIDE 19

The Propagation Group

Introduction Design Measurements Discussions Summary Retrodirectivity Loss Factor (RLF)

Retrodirectivity Loss Factor (RLF): Motive

Recall A rat-race coupler is retrodirective if |Γ1| = |Γ2| and ∠Γ2 = ∠Γ1 + π

Two constraints: Magnitude and Phase; but, to which the design is more sensitive? Mathematically, RLF =

  • 1 + αejπ(1+δφ)

1 − αejπ(1+δφ)

  • 2

c Mohammad Alhassoun; malhassoun@gatech.edu The Propagation Group @ Georgia Tech Design and Evaluation of a Multi-Modulation Retrodirective RFID Tags

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SLIDE 20

The Propagation Group

Introduction Design Measurements Discussions Summary Retrodirectivity Loss Factor (RLF)

Retrodirectivity Loss Factor (RLF): Result

0.5 0.6 0.7 0.8 0.9 1 1.1 1.2 1.3 1.4 1.5 0.5 0.4 0.3 0.2 0.1 −0.1 −0.2 −0.3 −0.4 −0.5 Change in magnitude (α) Change in phase (δφ) −14 −12 −10 −8 −6 −4 −2 RLF (dB)

RLF =

  • 1 + αejπ(1+δφ)

1 − αejπ(1+δφ)

  • 2

Phase sensitive

c Mohammad Alhassoun; malhassoun@gatech.edu The Propagation Group @ Georgia Tech Design and Evaluation of a Multi-Modulation Retrodirective RFID Tags

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SLIDE 21

The Propagation Group

Introduction Design Measurements Discussions Summary

Summary

In this paper, we Designed a retrodirective feed network using a rat-race coupler Derived the retrodirectivity conditions for the coupler Showed the proposed feed network is capable implemented various modulation schemes. Developed two metrics to evaluate retrodirectivity

1 Retrodirectivity Ideality Factor (RIF) {Recast} 2 Retrodirectivity Loss Factor (RLF)

c Mohammad Alhassoun; malhassoun@gatech.edu The Propagation Group @ Georgia Tech Design and Evaluation of a Multi-Modulation Retrodirective RFID Tags