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

Ansoft HF Workshop 25th Feb 2002 11SL Ooi

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

Ansoft HF Workshop 25th Feb 2002 13SL Ooi

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

Ansoft HF Workshop 25th Feb 2002 17SL Ooi

Full modelFull modelFull model

Ansoft HF Workshop 25th Feb 2002 18SL Ooi

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.

Ansoft HF Workshop 25th Feb 2002 24SL Ooi

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.