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Motorola Confidential Proprietary 3 November 2000Florida EME Research Lab
Modeling of a Half wave Modeling of a Half wave MonopoleMonopole Antenna on a Antenna on a
portable radioportable radioS. L. S. L. OoiOoi
Motorola Florida Corporate Research LabsMotorola Florida Corporate Research Labs8000 West Sunrise Blvd 8000 West Sunrise Blvd
Plantation Plantation FL 33324FL 33324
sooliamsooliam..ooiooi@@motorolamotorola.com.com
Ansoft HF Workshop 25th Feb 2002 2SL Ooi
Why Antenna Modeling?Why Antenna Modeling?Why Antenna Modeling?
Predict the antenna characteristics• radiation pattern• impedance
Opportunity for improvement
• find the best matching• re-tuning the antenna• effect of placement of surrounding mechanical parts,
e.g. shields, speaker, chassis length,etc.
Ansoft HF Workshop 25th Feb 2002 3SL Ooi
SummarySummarySummary
Modeled the whip antenna on both ground plane and chassis.
Accurate S11 prediction was obtained.
Challenges• Geometry information on drawing incomplete.• Material property information not readily available.• minimum information obtained from vendor.• Information obtained by breaking down samples.
Ansoft HF Workshop 25th Feb 2002 4SL Ooi
New Radio, new AntennaNew Radio, new AntennaNew Radio, new Antenna
Ansoft HF Workshop 25th Feb 2002 5SL Ooi
New Antenna for New BandNew Antenna for New BandNew Antenna for New Band
• Old Frequency 806 - 870 MHz• New Frequencies 765 - 870 MHz• Center frequency 815 MHz.
Ansoft HF Workshop 25th Feb 2002 6SL Ooi
Proposed sample longer than originalProposed sample longer than originalProposed sample longer than original
Original length=170 mmReducing the center frequency
Adding length = new tooling = $$$$$ + Cycle TimeProposed length= 180 mm
Ansoft HF Workshop 25th Feb 2002 7SL Ooi
Antenna DesignAntenna DesignAntenna Design
Circular holderConductive tape around
the feeding coil.
Feeding coil
Half-wave whip, enclosed in polyurethane jacket.
Polycarbonate cylinder
Ansoft HF Workshop 25th Feb 2002 8SL Ooi
antenna modelantenna modelantenna model
Polyurethane coating
εr=3.6
Polycarbonatehousing with
tuning conductive
tape
Steel cable
Base-loading coil
Ansoft HF Workshop 25th Feb 2002 9SL Ooi
First StageFirst StageFirst Stage
Model the existing antenna sample on ground plane to establish correlation.
Ansoft HF Workshop 25th Feb 2002 10SL Ooi
Model on ground planeModel on ground planeModel on ground plane
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Dummy Cylinders to enhance meshingDummy Cylinders to enhance meshingDummy Cylinders to enhance meshing
Ansoft HF Workshop 25th Feb 2002 12SL Ooi
Feeding Structure - port and capFeeding Structure Feeding Structure -- port and capport and cap
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Matching conductive tapeMatching conductive tapeMatching conductive tape
Modeled by PEC boundary condition
on the polycarbonate cylinder.
Ansoft HF Workshop 25th Feb 2002 14SL Ooi
Impedance on ground plane(S11)Impedance on ground plane(S11)Impedance on ground plane(S11)
Ground plane MeasuredSimulatedCenter frequency 805.2 806.1Lower S11@-10dB 770.7 772.1Higher S11@-10dB 841.8 838.4
Ansoft HF Workshop 25th Feb 2002 15SL Ooi
Stage 2Stage 2Stage 2
Model the antenna on the radio chassis.
Ansoft HF Workshop 25th Feb 2002 16SL Ooi
Radio modelRadio modelRadio model
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Full modelFull modelFull model
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Radio chassis S11Radio chassis S11Radio chassis S11
Chassis Measured SimulatedCenter frequency 813.6 816.3Lower S11@-10dB 760 775.5Higher S11@-10dB 852.2 845
Ansoft HF Workshop 25th Feb 2002 19SL Ooi
Measured S11 on ChassisMeasured S11 on ChassisMeasured S11 on Chassis
Ansoft HF Workshop 25th Feb 2002 20SL Ooi
Feeding, knobs and switches Feeding, knobs and switches Feeding, knobs and switches
Ansoft HF Workshop 25th Feb 2002 21SL Ooi
Radiation patternsRadiation patternsRadiation patterns
Ansoft HF Workshop 25th Feb 2002 22SL Ooi
Stage 3Stage 3Stage 3
Use the original length of 170 mm, conduct parametric sweep varying the width of the conductive tape.
Ansoft HF Workshop 25th Feb 2002 23SL Ooi
Varying the width of the conductive tape.Varying the width of the conductive tape.Varying the width of the conductive tape.
Antenna at original length of 170 mm.
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Final, production versionFinal, production versionFinal, production version
Ansoft HF Workshop 25th Feb 2002 25SL Ooi
Final products - XTS2500 RadiosFinal products Final products -- XTS2500 RadiosXTS2500 Radios
Ansoft HF Workshop 25th Feb 2002 26SL Ooi
BenefitBenefitBenefit
• Complete understanding of the antenna.
• Track changes, and possible drift in performance.
• Check for impact of future changes of radio mechanics and metal part placement.