design review: november 17,2011 team members: allan davis carlos gonzalez cooper mcbride
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Panel AntennaDesign Review: November 17,2011Team Members: Allan Davis
Carlos Gonzalez Cooper McBride
ObjectiveDesign, fabricate and test a 900-Mhz
directional panel antenna for Schweitzer Engineering Laboratories
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ApplicationsRadios provide comm channels for electric
utility protection, monitoring, and controlEconomical alternative to fiber-optic cableBackup primary protection channels
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Other UsesOil and gas pipelines and refineriesWater and wastewater treatment facilitiesFire and security alarm remote monitoringMany more possible applications of wireless
communications for critical infrastructure
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What SEL NeedsAn antenna that will have performance
similar to a 5-element Yagi antennaThe antenna will be used with the SEL-3031
transceiver
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Why a Panel Antenna?SEL is currently selling directional Yagi
antennasAn example of a 5-element Yagi is shown here
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Panel Antenna Pros:Lower cost than YagiCompact packageEase of installationSEL can manufacture a panel antenna using
existing facilities and equipment
Panel Antenna Cons:Can’t increase directivity by adding elements as
with YagiMore ways for material inconsistencies to affect
performance
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SpecificationsDirectionalVertical or Horizontal PolarizationGain: ≥8 dBiHP Horizontal Beamwidth: 45°HP Vertical Beamwidth: 65°Operating Frequency Range: 900-930 MHz
~ 3% BandwidthVSWR: ≤1.5:1Characteristic Impedance: 50 ΩDesigned Using Printed Circuit Board Technology
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Bowtie FormulasCharacteristic 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 substrateεr ~ 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 OptionsEdge cutting can be used to increase
bandwidth of bowtie and decrease physical size
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Design ChallengesHow much gain can we get?Feeding the antenna
Impedance matchingDetermining spacing between PCB and
backplateCorrectly interpreting simulation results
Simulation will require a lot of trial and error
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Impedance MatchingWant to match impedances to minimize
transmission line reflections from antenna toward radioMax Power TransferLow 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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ValidationConduct impedance analysis using network
analyzers in Applied EM Waves Lab.Time reserved for use of anechoic chamber at
SELUse to make antenna pattern measurements900-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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SoftwareAgilent Advanced Design System (ADS) with
Electromagnetic Professional (EMPro)SEL is planning to incorporate ADS Design
Suite for future projectsFEM SimulatorFDTD SimulatorMethod of MomentsImpedance Analysis
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ProgressCurrently a little behind according to our
timelineIssue 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 nowIn 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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BudgetEMPro Software - $2000Nvidia GT 430 Graphics Card - $85Kingston 2GB RAM - $25N-Connectors - $4 EachPC Board and metal back plate
Provided by SEL
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