Designing a Small Planar Antenna Designing a Small Planar Antenna - - PowerPoint PPT Presentation

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Designing a Small Planar Antenna Designing a Small Planar Antenna for Agricultural Sensor Network for Agricultural Sensor Network

Wonbin Hong Wonbin Hong Purdue University Purdue University

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Overview Overview

• Agricultural Sensor Network

Agricultural Sensor Network

• Usage of Smart Sensor Network

Usage of Smart Sensor Network

• Antenna/ Packaging

Antenna/ Packaging

• System Design Requirements

System Design Requirements

• Antenna Design

Antenna Design

• Design Approach

Design Approach

• Methods

Methods

• Results

Results

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Smart Sensor Network? Smart Sensor Network?

Where do we use

Where do we use it? it?

How does it work?

How does it work?

How big is it?

How big is it?

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Microstrip vs. Dipole Antenna Microstrip vs. Dipole Antenna

Why use a microstrip

Why use a microstrip antenna? antenna?

Size and operating

Size and operating frequency frequency

c = wavelength/ frequency c = wavelength/ frequency

Packaging

Packaging

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Planar Antenna Planar Antenna

Design Approach

Design Approach

• Inverted L antenna

Inverted L antenna

• Inverted F antenna

Inverted F antenna (PIFA) (PIFA)

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Designing the PIFA Designing the PIFA

Coupling

Coupling – – Magnetic vs. Electric Magnetic vs. Electric

Matching with the 50

Matching with the 50 Ω

Ω port

port

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Designing the PIFA Designing the PIFA

Results with capacitive

Results with capacitive coupling coupling

• Bandwidth

Bandwidth

• Radiation Efficiency

Radiation Efficiency

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Efficiency and Bandwidth Efficiency and Bandwidth

Efficiency and Radiation

Efficiency and Radiation resistance resistance

Bandwidth and Q

Bandwidth and Q

• Bandwidth ~ 1/ Q

Bandwidth ~ 1/ Q C L Lower-Q High-Q

R R Loss

Efficiency

R R R

= +

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PIFA with Capacitive Load PIFA with Capacitive Load

Smaller l

Smaller l greater greater impedance (Z = cot(Bl)) impedance (Z = cot(Bl))

• smaller capacitance

smaller capacitance

• Counter the reduction

Counter the reduction

Length can be reduced

Length can be reduced dramatically dramatically

β β

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Coupling Two Resonators Coupling Two Resonators

Electrically couple two

Electrically couple two resonators to increase the resonators to increase the bandwidth bandwidth

• Creates two resonant

Creates two resonant frequencies frequencies

Parameters determining

Parameters determining the coupling the coupling

• Gap between the two

Gap between the two plates plates

• Distance between the

Distance between the shorted walls shorted walls

• Capacitive feed

Capacitive feed

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Results Results

Not enough coupling

Not enough coupling

Radiation Efficiency is

Radiation Efficiency is sufficient sufficient – – 84 percent 84 percent

Possible Solutions?

Possible Solutions?

• Usage of patch antennas

Usage of patch antennas with slots with slots

• Lumped element

Lumped element – – chip chip resistor? resistor?

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Acknowledgment Acknowledgment

• Prof. William J. Chappell
• Prof. William J. Chappell

Bosui Lui

Bosui Lui

Xun Gong

Xun Gong

James Brad Dodson

James Brad Dodson

Mike R. Arens

Mike R. Arens

Chin

Chin-

• Lung Yang

Lung Yang

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“ D D” ” Sivaprakasapillai Sivaprakasapillai