Design Review: November 17,2011
Team Members: Allan Davis
Carlos Gonzalez
Cooper McBride
Objective
 Design, fabricate and test a 900-Mhz
directional panel antenna for Schweitzer
Engineering Laboratories
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Applications
 Radios provide comm channels for electric utility
protection, monitoring, and control
 Economical alternative to fiber-optic cable
 Backup primary protection channels
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Other Uses
 Oil and gas pipelines and refineries
 Water and wastewater treatment facilities
 Fire and security alarm remote monitoring
 Many more possible applications of wireless
communications for critical infrastructure
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What SEL Needs
 An antenna that will have performance similar to a 5-
element Yagi antenna
 The antenna will be used with the SEL-3031 transceiver
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Why a Panel Antenna?
 SEL is currently selling directional Yagi antennas
 An example of a 5-element Yagi is shown here
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 This is a panel antenna made by the same company
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 Panel Antenna Pros:
 Lower cost than Yagi
 Compact package
 Ease of installation
 SEL can manufacture a panel antenna using existing
facilities and equipment
 Panel Antenna Cons:
 Can’t increase directivity by adding elements as with Yagi
 More ways for material inconsistencies to affect
performance
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Specifications
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Directional
Vertical or Horizontal Polarization
Gain: ≥8 dBi
HP Horizontal Beamwidth: 45°
HP Vertical Beamwidth: 65°
Operating Frequency Range: 900-930 MHz
 ~ 3% Bandwidth
 VSWR: ≤1.5:1
 Characteristic Impedance: 50 Ω
 Designed Using Printed Circuit Board Technology
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Example Radiation Patterns
Dipole
Yagi
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Current Design - Bowtie
 This is a type of planar dipole antenna
 θ0 is called the opening angle
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Bowtie Formulas
 Characteristic impedance*
 ZC = ln[cot(θ0 /4)]
 Length*
 L = 0.5 λ0 /(εeff)1/2
 Effective dielectric constant*
 εeff = 0.5(εr + 1) + 0.5(εr – 1)(1 + 10 d/W)-0.555
 We plan to use FR-4 substrate
 εr ~ 4.0-4.8 (decreases as frequency increases)
 d is typically 1.6 mm, but other thicknesses available
*Source: C. Guo and R. Liu. (2009, June). A 900MHz shielded bow-tie antenna system for ground
penetrating radar. [Online]. Available:
http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=5550125&tag=1
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Possible Design Options
 Edge cutting can be used to increase bandwidth of
bowtie and decrease physical size
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 Another type of radiating element
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 Metal Patch antenna
 Gain not very high
 Not very robust
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Design Challenges
 How much gain can we get?
 Feeding the antenna
 Impedance matching
 Determining spacing between PCB and backplate
 Correctly interpreting simulation results
 Simulation will require a lot of trial and error
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Impedance Matching
 Want to match impedances to minimize transmission
line reflections from antenna toward radio
 Max Power Transfer
 Low reflection coeff.  Low VSWR
 This can be done both by changing antenna feed point
and by designing microstrip feedline impedance to be
Zmicrostrip = (ZcoaxZant)1/2
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Validation
 Conduct impedance analysis using network analyzers
in Applied EM Waves Lab.
 Time reserved for use of anechoic chamber at SEL
 Use to make antenna pattern measurements
 900-MHz feed & measurement system available
(antenna, signal generator, network analyzer, etc.)
 Most of our measurements will be focused on figures
of merit, since SEL will have to have the antenna
characterized before production
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Software
 Agilent Advanced Design System (ADS) with
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Electromagnetic Professional (EMPro)
SEL is planning to incorporateADS Design Suite for
future projects
FEM Simulator
FDTD Simulator
Method of Moments
Impedance Analysis
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Progress
 Currently a little behind according to our timeline
 Issue with EMPro software
 The software is unable to work correctly with standard
Intel Graphic Chipsets
 Needed to order an Nvidia graphics card and install into
a laboratory computer
 Works great now
 In the future we will want to upgrade the RAM from
2GB to 4GB
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 Working on getting tutorials to learn the software
 Need to wait for the University license instead of our
trial version to obtain access to the tutorials
 Have put in our order for the University license
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Budget
 EMPro Software - $2000
 Nvidia GT 430 Graphics Card - $85
 Kingston 2GB RAM - $25
 N-Connectors - $4 Each
 PC Board and metal back plate
 Provided by SEL
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Schedule
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Questions?
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