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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This is a panel antenna made by the same company

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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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Example Radiation Patterns

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Dipole Yagi

Current Design - BowtieThis is a type of planar dipole antenna

θ0 is called the opening angle

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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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Another type of radiating element

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Metal Patch antennaGain not very highNot very robust

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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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Schedule

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Questions?

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