Over the last few decades, the defogger of vehicles was increasingly used as an antenna for mobile reception of broadcast services. Ever since, the development of vehicular window antennas was a tedious and time consuming task, because the development procedure was subjected to an iterative series of measurements. Due to enhanced computing power of workstations and server-systems, it is now possible, to calculate antenna structures including whole vehicle bodies in electromagnetic simulations. Especially for calculating the performance of antenna structures integrated into vehicular windows, the FEKO wind screen function became an indispensable tool for accurate simulations of real world scenarios. With comparable results in simulation and measurements, errors can be identified and fixed faster as ever before. The possibility to consider current flow, 3D directivity, antenna efficiency and further analyses additionally contributes to a significant improvement in the development process of vehicular window antennas. Recent comparisons of simulation and measurement results in a rear window antenna development project were confirming that simulative calculated predictions are in good correspondence to measurements of produced vehicular window antennas. Speakers Dr.-Ing. Johannes Kammerer, Senior RF Engineer Kathrein Automotive

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28.09.2015 1
Windscreen Antenna Analysis for
Broadcasting Services in Vehicles –
Comparison of Simulation and
Measurement of Integrated Rear
Window Antennas
September 30th 2015
Dr.-Ing. Johannes Kammerer
Kathrein Automotive

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28.09.2015
2
Outline
• Kathrein Automotive – Global Operation Overview
• Using FEKO @ Kathrein Automotive
• Requirements on Automotive Antennas
• FM-Antenna-System for Scan-Phase-Diversity
• Comparison of Simulation and Measurements
• Conclusion

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28.09.2015
3
Kathrein Automotive Global Sites

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28.09.2015
4
Global Sites – Engineering
Kathrein Automotive GmbH
Skill Set: Automotive Antennas
- Screen Antennas
- Roof Top Antennas
Engineering Headcount: 22
Kathrein Werke KG
Skill Set: Automotive Antennas
- Screen Antennas
- Roof Top Antennas
- Phone Compensor
Engineering Headcount: 48
Kathrein Automotive Products Co., Ltd
Skill Set: Automotive Antennas
- Screen Antennas
Engineering Headcount: 26
.
Kathrein Automotive North America, Inc.
Skill Set: Automotive Antennas
- Screen Antenna
- Roof Top Antennas
Engineering Headcount: 4
Suzhou
Kathrein Automotive do Brazil
Skill Set: Antennas & Electronics
- Roof Top Antennas
- Relais & Alarms
- ECUs (e.g. Window-Lifter)
Engineering Headcount: 11
Detroit
Sao Paulo
Detroit
Sao Paulo Rosenheim Hildesheim
Suzhou

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28.09.2015
5
Windscreen Antennas:
- AM
- FM
- DAB
- TV
- RKE
- …
Rooftop and hidden Antennas:
- Mobile
- GNSS
- SDARS
- AM/FM rood ant.
- Wifi
- Car2Car
Automotive Antenna Simulations in
0°
45°
90°
135°
180°
225°
270°
315°
-10
0
10
-20
20
Phi_deg (0.000 to 358.000)
[dB]

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28.09.2015
6
Other Automotive Simulations in
Verification:
- Reference antennas
- Anechoic chambers
- Outdoor measurement areas
- Nearfield – farfield investigations

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28.09.2015
7
System requirements:
• Optimised pattern for all services
and all polarisations
• High efficiency
• High system signal level
• Decorrelation between ports for
same services
OEM requirements:
• Low cost fabrication
• High reproducibility
Requirements on Automotive Antennas

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28.09.2015
8
• Characteristic Angle
FM-
Band
Mode A
Mode B
Eigenmode-Analysis of Windscreen Antennas

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28.09.2015
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• Radiation Pattern in FM-band (usability for antenna structures)
Mode A and mode B: radiation Mode of higher order: no radiation
Eigenmode-Analysis of Windscreen Antennas

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28.09.2015
10
Simulation in
Settings:
• Consideration of all metal
surfaces of a vehicle (MOM
solver)
• Using windscreen function for
rear windshield, defogger and
antenna structures on the rear
windshield
• Simulation in half space on a
lossy, infinite ground

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28.09.2015
11
Measurements
𝜑
REF. rod antenna
Rosenheim broadcast test range:
• Moorland => constant el.
properties
• Distance: 120 m
• Transmitting antenna: Log.-Per.
• Frequency: 47 MHz – 1 GHz
• Elevation: theta = 88°
Test Setup:
• Fully automated measurement
software
• Up to 6 antennas parallel
• Parallel multiband
measurement
• Time domain signal gating
Pol.

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12
Windscreen Antenna for AM/FM/DAB/TV
DEFOGGER
Antenna field
Port 1 Port 2 Port 3

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28.09.2015
13
70 90 110 13050 150
-25
-20
-15
-10
-5
-30
0
freq, MHz
dB(S(3,2))
dB(S(6,5))
70 90 110 13050 150
-25
-20
-15
-10
-5
-30
0
freq, MHz
dB(S(2,1))
dB(S(5,4))
Passiv Windscreen Antenna without Matching Circuit
• S-Parameter of 3-Port Antenna System: Simulation
Measurement
freq (50.00MHz to 150.0MHz)
S(1,1)
S(4,4)
freq (50.00MHz to 150.0MHz)
S(2,2)
S(5,5)
freq (50.00MHz to 150.0MHz)
S(3,3)
S(6,6)
70 90 110 13050 150
-25
-20
-15
-10
-5
-30
0
freq, MHz
dB(S(3,1))
dB(S(6,4))
ZP1
ZP2 ZP3
50 MHz – 150 MHz 50 MHz – 150 MHz 50 MHz – 150 MHz
|S21| |S32| |S31|
Frequency in MHz Frequency in MHz Frequency in MHz
=> high correlation between simulation and measurements

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28.09.2015
14
Scan-Phase-Diversity for FM
50 Ω Phase-Shifter
𝐸 𝐴𝑛𝑡1 𝑟, 𝜃, 𝜑
𝐸 𝐴𝑛𝑡2 𝑟, 𝜃, 𝜑
1
2
3
1
2
3
3
𝐸 𝑃ℎ𝑎𝑠𝑒 𝑟, 𝜃, 𝜑, 𝜙1, 𝜙2, 𝑑21
=
𝑒 𝑗𝜙1
2
𝐸 𝐴𝑛𝑡1 𝑟, 𝜃, 𝜑 +
𝑒 𝑗𝜙2 ∙ 𝑒 𝑗𝛽𝑑21
2
𝐸 𝐴𝑛𝑡2 𝑟, 𝜃, 𝜑
RF-Combiner

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28.09.2015
15
Scan-Phase-Diversity for FM
𝐺𝐼𝐸𝐸𝐸 in dB, Pol: theta, 𝜃 = 88°, f = 110 MHz

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28.09.2015
16
80 85 90 95 100 10575 110
-25
-20
-15
-10
-5
0
5
-30
10
freq, MHz
[dB]
gemittelter Antennengewinn [dB] (IEEE) für FM1 und FM2 H-Pol
80 85 90 95 100 10575 110
-25
-20
-15
-10
-5
0
5
-30
10
freq, MHz
dB
r Antennengewinn [dB] (IEEE) Pol: phi bei index_theta für FM1-FM2
80 85 90 95 100 10575 110
-25
-20
-15
-10
-5
0
5
-30
10
freq, MHz
[dB]
mittelter Antennengewinn [dB] (IEEE) für FM1 und FM2 H-Pol
80 85 90 95 100 10575 110
-25
-20
-15
-10
-5
0
5
-30
10
freq, MHz
[dB]
emittelter Antennengewinn [dB] (IEEE) für FM1 und FM2 V-Pol
80 85 90 95 100 10575 110
-25
-20
-15
-10
-5
0
5
-30
10
freq, MHz
dB
gemittelter Antennengewinn [dB] (IEEE) Pol: theta bei index_theta für FM1-FM2
80 85 90 95 100 10575 110
-25
-20
-15
-10
-5
0
5
-30
10
freq, MHz
[dB]
gemittelter Antennengewinn [dB] (IEEE) für FM1 und FM2
80 85 90 95 100 10575 110
-25
-20
-15
-10
-5
0
5
-30
10
freq, MHz
dB
gemittelter Antennengewinn [dB] (IEEE) Pol: theta bei index_theta fü
80 85 90 95 100 10575 110
-25
-20
-15
-10
-5
0
5
-30
10
freq, MHz
dB
gemittelter Antennengewinn [dB] (IEEE) Pol: phi bei index_theta fü
80 85 90 95 100 10575 110
-25
-20
-15
-10
-5
0
5
-30
10
freq, MHz
[dB]
gemittelter Antennengewinn [dB] (IEEE) für FM1 und FM2 V
Linear Average GainIEEE referred to Ref. Ant. GIEEE
• 50Ω resistor at port 3 Simulation
Measurement
80 85 90 95 100 10575 110
-25
-20
-15
-10
-5
0
5
-30
10
freq, MHz
dB
r Antennengewinn [dB] (IEEE) Pol: theta bei index_theta für FM1-FM2
80 85 90 95 100 10575 110
-25
-20
-15
-10
-5
0
5
-30
10
freq, MHz
[dB]
gemittelter Antennengewinn [dB] (IEEE) für FM1 und FM2 V-Pol
80 85 90 95 100 10575 110
-25
-20
-15
-10
-5
0
5
-30
10
freq, MHz
dB
gemittelter Antennengewinn [dB] (IEEE) Pol: phi bei index_theta für FM1-FM2
Port 1 Port 2 Scan-Phase-Diversity
Frequency in MHz Frequency in MHz Frequency in MHz
Frequency in MHz Frequency in MHz
[dB] [dB] [dB]
[dB] [dB] [dB]

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17
0°
45°
90°
135°
180°
225°
270°
315°
-20
-10
0
-30
10
Phi_deg (0.000 to 358.000)
[dB]
0°
45°
90°
135°
180°
225°
270°
315°
-20
-10
0
-30
10
Phi_deg (0.000 to 358.000)
[dB]
0°
45°
90°
135°
180°
225°
270°
315°
-20
-10
0
-30
10
Phi_deg (0.000 to 356.000)
2+freqoffset/4,::,index_theta])-10*log10(mean(Gain_IEEE_theta_Ref[(Start+Stop)/2+fr
0°
45°
90°
135°
180°
225°
270°
315°
-20
-10
0
-30
10
Phi_deg (0.000 to 356.000)
2+freqoffset/4,::,index_theta])-10*log10(mean(Gain_IEEE_phi_Ref[(Start+Stop)/2+fre
• 50Ω resistor at port 2 and port 3
Simulation
Measurement
Port 1: GainIEEE referred to Ref. Ant. linear average GIEEE
94 MHz
theta= 88°
𝜑𝜑

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0°
45°
90°
135°
180°
225°
270°
315°
-20
-10
0
-30
10
Phi_deg (0.000 to 358.000)
[dB]
0°
45°
90°
135°
180°
225°
270°
315°
-20
-10
0
-30
10
Phi_deg (0.000 to 356.000)
2+freqoffset/4,::,index_theta])-10*log10(mean(Gain_IEEE_theta_Ref[(Start+Stop)/2+fr
0°
45°
90°
135°
180°
225°
270°
315°
-20
-10
0
-30
10
Phi_deg (0.000 to 358.000)
[dB]
0°
45°
90°
135°
180°
225°
270°
315°
-20
-10
0
-30
10
Phi_deg (0.000 to 356.000)
2+freqoffset/4,::,index_theta])-10*log10(mean(Gain_IEEE_phi_Ref[(Start+Stop)/2+fre
Simulation
Measurement
• 50Ω resistor at port 1 and port 3
Port 2: GainIEEE referred to Ref. Ant. linear average GIEEE
94 MHz
theta= 88°
𝜑𝜑

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0°
45°
90°
135°
180°
225°
270°
315°
-20
-10
0
-30
10
Phi_deg (0.000 to 356.000)
t+Stop)/2+freqoffset/4,::,index_theta])-10*log10(mean(Gain_IEEE_phi_Ref[(Start+Sto
0°
45°
90°
135°
180°
225°
270°
315°
-20
-10
0
-30
10
Phi_deg (0.000 to 356.000)
t+Stop)/2+freqoffset/4,::,index_theta])-10*log10(mean(Gain_IEEE_theta_Ref[(Start+St
0°
45°
90°
135°
180°
225°
270°
315°
-20
-10
0
-30
10
Phi_deg (0.000 to 358.000)
[dB]
0°
45°
90°
135°
180°
225°
270°
315°
-20
-10
0
-30
10
Phi_deg (0.000 to 358.000)
[dB]
Simulation
Measurement
• 50Ω resistor at port 3
Scan-Phase-DIV: GainIEEE referred to Ref. Ant. Lin. Avg. GIEEE
94 MHz
theta= 88°
𝜑𝜑

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20
Conclusion
• High correlation between simulations and
measurements of windscreen antennas
• Optimization of windscreen antennas is more efficient
if mode analysis and current flow are taken into
consideration
• The most efficient development process of
windscreen antennas can be accomplished by an
optimized combination of several software tools