the use of suimulation (feko) to investigate antenna performance on mobile platforms

Applied EMAG Laboratory

The Use of Simulation (FEKO) to Investigate

Antenna Performance on Mobile Platforms

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Daniel N. Aloi, Ph.D. Director, Applied EMAG & Wireless Lab

2015 Altair Technology Conference Ford Motor Company Conference and Event Center

Dearborn, Michigan

May 6, 2015


Overview

• Applied EMAG and Wireless Lab

• FEKO Case Studies

– Antenna Placement

– Antenna Coupling

– Antenna Design

• Conclusions

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Applied EMAG & Wireless Lab

The Applied Electromagnetics and Wireless Laboratory at Oakland University was formed to address the needs created by the increasing evolution of wireless systems into our everyday world.

The global proliferation of wireless technologies onto dynamic platforms has generated challenging engineering issues in such areas as antenna design, antenna placement, signal propagation modeling, interference, radar and overall wireless system performance.

The AEWL combines its expertise in electromagnetics & wireless communications, along with its measurement and modeling capabilities to address these issues.

Mission Statement


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Measurement & Simulation Capabilities

Automotive Antenna Range

• Frequency (10 MHz-6 GHz) • Satellite Gantry (0°-90° elev.) • Terrestrial Tower (0° elev.) • Sirius/XM Certified • 6-m turntable diameter • Antenna measurement service

to industry.

Anechoic Chamber

• Frequency (1000 MHz-6 GHz) • 15’x12’x10’ dimensions • Line with RF absorbing material • Component-level antenna

measurements on free space or ground plane

Modeling

• FEKO SW License • Wireless InSite SW License • Matlab/Simulink

Fabrication

• Circuit board plotter • Metal shop.


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ANTENNA PLACEMENT EXAMPLE

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Daniel N. Aloi, Elias GhafariPh.D., Mohammad S. Sharawi and Ashley SteffesM.S., “A Detailed Experimental Study on the Benefits of Electrically Grounding Interior Glass Mounted GPS Antennas to the Vehicle Roof,” Microwaves, Antennas & Propagation, IET 8.10 (2014): 782-793.


Objective

• To study the radiation pattern performance impact of grounding an interior front-windshield mounted GPS antenna to the vehicle roofline via simulation as a function of:

– Ground Strip Width

– Ground Strip Length

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Problem

• Y. Dai, T. Talty and L. Lanctot, GPS Antenna Selection and Place-ment for Optimum Automotive Performance, IEEE International Symposium on Antennas and Propagation (APS), pp. 132-135, 2001.

• M. K. Alsliety and D. N. Aloi, ”A Study of Ground Plane Level and Vehicle Level Radiation Patterns of GPS Antenna in Telematics Applications,” IEEE Antennas and Wireless Propagation LEtters, Vol. 6, pp. 130-133, 2007.

• M. K. Sliety and D. N. Aloi, ”Correlation Between Antenna Radiation Pattern and Field Performance for Global Positioning Systems in Telematics as a Function of Antenna Placement,” IET Microwaves, Antennas and Propagation Journal, Vol. 2, No. 2, pp. 130-140, 2008.

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• Front-Windshield Mounted GPS Antenna Challenges: – Lack of ground-plane.

– Tilted radiation pattern.


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GPS Patch on 1m Diameter Ground Plane

GPS Patch on 1m Diameter GP 3D Polar Plot – RHCP Gain


Comparison of ROOF vs. CAR Models

• Simulation Settings:

– f = 1575.42 MHz.

– PEC ground plane to simulate ground.

– AZ=0:2:358

– EL=0:5:90

– A standard off the shelf ceramic GPS patch antenna with dimensions of 25 × 25 × 0.4 mm3 was used in this study.

• 12 Simulation Scenarios

– ROOF and CAR models

– Tilt Angle= 75°, 60°, 45°

– Width = 30 mm

– Length = 71mm, 119 mm, 167 mm

– Grounded, Not Grounded

• Patch was tuned for all scenarios to a return loss of better than 10 dB.

• FEKO COTS package was utilized to conduct all simulations.


Measurement/Simulation Parameters

10 5/18/2015


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Illustration of Surface Currents

Not Grounded Grounded

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3D Polar Plots / RHCP Gain / L = 71 mm


ECDF Plot / RHCP Gain / L = 71 mm


SIM-ROOF Percentage of RHCP Gain Values ≤ -5.0 dBic

28.9

14.8

21.4 23.1

14.4

21.8 22.8

16.4

24.8

29.8

25.8

22.5

26.9 26.1

20.9

34.9

24.4

38.4

0

5

10

15

20

25

30

35

40

45

T1-L1 T1-L2 T1-L3 T2-L1 T2-L2 T2-L3 T3-L1 T3-L2 T3-L3

Grounded

Not Grounded


SIM-CAR Percentage of RHCP Gain Values ≤ -5.0 dBic

20 20.2 21.9

24.5

31.9

20.2

26.4 28.7

30.2

35.2 33.6

38.5

46.2

40 43

44.8

50.8 50.5

0

10

20

30

40

50

60


Grounded

Not Grounded


Measurements

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MEAS-ROOF Percentage of RHCP Gain Values ≤ -5.0 dBic

8.5

20.8

17.2

7.3

19.7 17.6

10.6

17.4

25.4

7.6

18.2

22.7

7.4

25.4 27.5

6.8

23

48.9

0

10

20

30

40

50

60


Grounded

Not Grounded


Conclusions

• Show why ROOF model is representative of a CAR model. – Simulations conducted on grounding strip at constant tilt angle and

ground strip width while varying the ground strip length. – Repeated for CAR and ROOF models. – Compared Grounded vs. Non-Grounded Results – Trends were the same for both models (albeit roof more pronounced),

hence a ROOF model was used in measurements.

• Measurements were conducted at an automotive antenna measurement facility. – Results were similar to simulation results. – Grounding antenna to vehicle roof does clearly improve GPS antenna

radiation pattern. – Grounding strip is significant cost in high-volume production

environments adding cost. – Cost vs. performance?


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ANTENNA COUPLING EXAMPLE

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Objective

To use a full-wave, three-dimensional electromagnetic simulation tool to determine the ideal placement of three antennas that are in the same frequency band on a locomotive rooftop configuration without modifying or removing its existing antennae. Figures of merit for this analysis include VSWR, Gain Pattern and Isolation.

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Roof Configuration – Isometric View

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Applied EMAG, Inc. 25

Placement

Volume


New Antennas To Be Installed

• Antenna #1 – Frequency: 380-430 MHz – Dim.: (HxWxL): 24.2 cm x 10.2 cm x 9.8 cm – Maximum Gain: 2.0 dBi

• Antenna #2 – Frequency: 450-470 MHz – Dim.: 8.1 cm OD x 10.7 cm – Maximum Gain: UHF: 2.0 dBi

• Antenna #3 – Frequency: 410-430 MHz – Dim. (HxWxL): 16 cm x 12 cm x 11 cm – Maximum Gain: 2.0 dBi

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Optimal Antenna Placement Criteria

• Goal is to not modify existing roof antenna configuration. • Establish a volume to place new antennas:

– Height of volume is top of AC unit. – Placement area extends between AC unit and rear roof profile.

• New antenna locations should be insulated from the roof. • Account for shading of objects on the roof such as the rear

roof and AC unit. • Minimize isolation and de-sensitization between new and

existing antennas. • VSWR of new antennas should not be degraded due to

objects near it on the roof.

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Antenna Simulation Strategy

• Design component-level antennas on a finite GP.

• Add component-level antennas to roof configuration.

• Monitor following performance metrics:

– VSWR

– Isolation/Desensitization between antennas.

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Antenna #1 (380-430 MHz)

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• Inverted-F Antenna - VLP

• PEC Materials

• Antenna Dimensions

– Length: 24.2 cm

– Width: 10.2 cm

– Height: 9.8 cm

• Ground Plane Dimensions

– 76.2 cm x 76.2 cm


Antenna #2 (450-470 MHz)

• Scaled version of Antenna #1.

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Antenna #3 (410-430 MHz) – Existing Antenna

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• λ/4 Monopole - VLP • PEC Materials • Antenna Dimensions

– Length: 16.8cm – Diameter: 1 cm

• Ground Plane Dimensions – 76.2 cm x 76.2 cm


Roof Layout – Isometric View

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ANT#3 410-430

ANT#1 380-430

ANT#2 450-470


Figures of Merit – Isolation Testing

• Desensitization: – Forward transmission gain between TX and RX

antennas @ TX resonant frequencies.

• Spurious Emissions – Forward transmission gain between TX and RX

antennas @ RX antenna resonant frequencies.

PRX fTX( ) = PTX fTX( )+S12( fTX )

PRX fRX( ) = PTX fRX( )+S12( fRX )


Simulated Roof – Return Loss

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ANT#1

ANT#2

ANT#3


Simulated Roof – Port-to-Port Isolation

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ANT#1-ANT#3

ANT#1-ANT#2

ANT#2-ANT#3


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Roof Configuration Measured

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Isolation Summary

ANT#1 (380-430) To

ANT#3 (410-430)

ANT#1 (380-430) To

ANT#2 (450-470)

ANT#3 (410-430) To

ANT#2 (450-470)

410-420 MHz

450-470 MHz

410-420 MHz

450-470 MHz

410-420 MHz

450-470 MHz

Simulated -34 N/A -30 -20 -30 -32

Measured -33 N/A -26 -24 -40 -36

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• Bandpass filter centered around HOT frequencies should be used. • Difficult to achieve 47 dB of isolation or better between the two TETRA antennas in the 410-420 MHz band. • Measurements were lower than what is simulated. - Worst case scenario is the C21 roof. - Will measure isolation in C21 roof this week.


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ANTENNA DESIGN EXAMPLE

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Elias Ghafari, Andreas Fuches, Huzefa Bharmal and Daniel N. Aloi, “On-Vehicle DSRC Antenna Elements Comparison Study,” ICEAA – IEEE APWC 2014, Palm Beach, Aruba, August 3-9, 2014.


Research Objective

• NSF Research Experience for Undergraduate Students were given a 10 week project to design a directive antenna for DSRC applications.

• Required to simulate, fabricate and measure the antenna.

• Results are presented here.


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DSRC Overview • The Dedicated Short Range Communications (DSRC) system is a new standard intended for

inter-vehicular communications to improve traffic safety for Intelligent Transportation Systems (ITS).

• The system is intended for inter-vehicular communications (V2V) and for vehicles-to-infrastructure (V2I) communications [1].

• The DSRC system’s applications include vehicular safety such as intersection collision avoidance, emergency vehicles warning, rollover warning and highway-rail intersection warning, as well as public services such as electronic toll collection and parking payment.

• The DSRC standards established in Europe specify the operational frequency bands and system’s bandwidths.

• In the USA, the frequency band 5850MHz – 5925MHz has been allocated for the DSRC system to be used by the ITS

http://www.google.com/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&cad=rja&uact=8&docid=Y-pOAWCexcaJsM&tbnid=N1VqluUs6HtRlM:&ved=0CAUQjRw&url=http://www.traffictechnologytoday.com/news.php?NewsID=8350&ei=eKytU8SdG6j-4QSdi4HYBA&bvm=bv.69837884,d.ZGU&psig=AFQjCNFLmzLlR1QLDJkE5laTIp9zU9wPDQ&ust=1403977109237983


DSRC Antenna Design Challenges

• Multi-band automotive antennas such as Cellular/LTE/GPS/SDARS are in a single radome in the center of the rear roof-line.

• Typical roof profiles have a 10 degree slope for the rear of the roof to the apex of the roof.

• A quarter-wave monopole at 5.9 GHz has a height of approximately 1.25 cm which is below the apex of the roof-line.

• 3-5 dB of gain is lost toward the front of the vehicle.


Antenna Design Objective

• The goal of this research was to take an omni-directional antenna and make it more directive toward the front/rear of the vehicle.

• Result is extended range of the DSRC signal for safety of life applications.


Antenna Designs

• A raised monopole was tuned to resonate between 5862.5 MHz and 5937.5 MHz

• Simulations in FEKO were conducted initially to come up with dimensions for optimized raised monopole by itself and with 1, 2 and 3 directors.

• Antennas were then fabricated on Rogers RO3003 laminate.

9.7 10.9 12.1

1.9 10.8 13.4 12.0

14.7

11.8 9.5

7.8

1.9

• All units in mm. • Width of all directors

and air gaps are 0.5 mm

• Printed of Rogers RO3003 laminate

• 0.13mm thickness • εr = 3.0


DSRC Antenna Measurements

• All antenna samples were measured on a 1-meter diameter rolled edge ground plane.

• All antennas tuned to VSWR better than 2.5:1.

• Antenna was mounted perpendicular to ground plane.

• Performance metrics were maximum gain and linear average gain at antenna horizon.

Start Stop Increment

Frequencies 5862.5 MHz 5937.5 MHz 13.5 MHz

Theta Points 0 degrees 90 degrees 5 degrees

Phi Points 0 degrees 360 degrees 2 degrees


Raised Monopole


Raised Monopole with 1 Director


Raised Monopole with 2 Directors


Comparison of All Antenna Types

Avg.

Gain

(dBi)

Max.

Gain

(dBi)

Min. Gain

(dBi)

Monopole 0.8 2.9* -2.0

Monopole Plus 1 Director

Per Side 1.5 3.7 -1.3

Monopole Plus 2 Directors

Per Side 1.6 4.3 -1.7

Monopole Plus 3 Directors

Per Side 2.2 5.2 -1.5

* occurred at direction at phi angle that represented side of a

vehicle.


Conclusions

• Results for a DSRC antenna were presented for an NSF REU program at Oakland University.

• Directors were added to an omni-directional and increased the maximum gain from 2.9 dBi to 5.2 dBi for a raised monopole and a raised monopole with 3 directors, respectively.

• Resulting antenna yields increase DSRC signal range toward the front/rear of vehicle for safety of life applications.


Questions

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the use of suimulation (feko) to investigate antenna performance on mobile platforms

Documents

antenna performance

wireless laboratory

applied emag wireless

gps antenna selection

antenna radiation pattern

applied electromagnetics

function of antenna

antenna placement example