Cell Phone Signal Testing with Infra-Red Reflective Windshield

A test was conducted at an independent antenna range using Infra-Red (IR) Reflecting windshield on a 

family sedan (Toyota Camry) and the results compared to the same testing with a standard windshield. 

The testing included signal strength measurements at different locations of the cell phone: Driver Right, 

Rear Passenger Outer, Rear Passenger Inner. The testing was then repeated with several deletion 

patterns, all of which comply with the CARB regulations as written in the 15-day notice published on 

December 15, 2009.

The results of the signal testing showed very little variation between standard windshield and IR 

Reflective windshield. The data shows that the signal strength is almost the same for the cell phone user 

in the front of the vehicle, but is actually stronger in the rear of the vehicle when an IR Reflective 

windshield is present. Therefore, a passenger in the back seat would actually have a higher probability of 

completing a call when an IR Reflective windshield is installed, whereas the driver would see no 

difference.

Test Results:

The testing for a cell phone located at the driver’s right side, towards the middle of the vehicle, shows 

that for this worst case scenario, the signal strength is almost identical regardless of what kind of

windshield is present. Various deletion patterns were tested to determine how specific deletion 

patterns would influence signal strength. The results show that the deletion may not even be necessary 

for cell phone signals. The variations due to coated glass are well within the normal cell signal variation.

The results show that a cell phone in the rear seat location would actually have a better chance at 

getting a call completed when an IR Reflective windshield is installed. There is some variation, based on 

deletion patterns, in the signal strength when the cell phone is in the middle of the rear seat location. 

However, when the cell phone is towards the outside of the vehicle in the rear seat, almost all 

combinations of IR Reflective windshield result in a stronger cell phone signal than with a conventional 

windshield. The results are presented here in detail.

Pittsburgh Glass Works, LLC

30 Isabella Street

Pittsburgh, PA 15212

Telephone (412) 995-6482

mrustagi@pgwglass.com

www.pgwglass.com

Mukesh Rustagi

Director, Strategic Product Management
Driver Cell Phone Signal:

The first figure shows standard glass compared to IR Reflective glass with no deletions, and two different 

deletion patterns. 

The second figure shows additional deletion patterns compared to standard glass. In all cases, the signal 

is actually only marginally different from one frequency to next and well within the normal variations of 

the various signal frequencies.

With various deletion patterns, the average signal loss can be as small as 0.2 dB, which is considered 

insignificant and well within the margin of error. Therefore, a cell phone held at the driver’s right would 

have the same signal in a vehicle equipped with IR Reflecting windshield as one with standard 

windshield.

-20.0

-15.0

-10.0

-5.0

0.0

5.0

824829834839844849

868.5

874

879.3883.6889.4

894

18501860187018801890190019101920

1929.61938.4

19501960

1970.4

19801990

Average Gain (dBi)

Frequency (MHz)

Driver Right Cellular Average Gain - Deletion Patterns

Regular W/S l(Avg Gain -1.7 dBi)

No Deletion (Avg Gain -2.5dBi)

Deletion A (Avg Gain -2.2)

Deletion B (Avg Gain -2.2dBi)

-20.0

-15.0

-10.0

-5.0

0.0

5.0

824829834839844849

868.5

874

879.3883.6889.4

894

18501860187018801890190019101920

1929.61938.4

19501960

1970.4

19801990

Average Gain (dBi)

Frequency (MHz)

Driver Right Cellular Average Gain - Additional Deletion Patterns

Regular W/S l(Avg Gain -1.7 dBi)

Deletion C (Avg Gain -2.0dBi)

 Deletion D (Avg Gain -1.9)

Deletion E (Avg Gain -2.2)

Deletion F (Avg Gain -2.0dBi)
Rear Passenger Inner Cell Phone Signal:

The test results of cell phone signal in the rear center of the vehicle shows an actual improvement of 

signal strength, with some deletion patterns, when an IR Reflective windshield is present.

The next figure demonstrates that other deletion patters are available that can improve the average 

signal by as much as 0.3 dB for a cell phone located in the rear seat middle.

The variation in signal strength in the rear seat demonstrates once again that the signal variation is 

minimal between a vehicle equipped with an IR Reflective windshield and one with a standard 

windshield. The variation in average signal strength is within the margin of error.

-20.0

-15.0

-10.0

-5.0

0.0

5.0

824829834839844849

868.5

874

879.3883.6889.4

894

18501860187018801890190019101920

1929.61938.4

19501960

1970.4

19801990

Average Gain (dBi)

Frequency (MHz)

Rear Passenger Inside Cellular Average Gain - Deletion Patterns

Regular W/S l(Avg Gain -4.2 dBi)

No Deletion (Avg Gain -4.7dBi)

Deletion X (Avg Gain -4.5)

Deletion A (Avg Gain -4.4)

Deletion B (Avg Gain -4.0dBi)

-20.0

-15.0

-10.0

-5.0

0.0

5.0

824829834839844849

868.5

874

879.3883.6889.4

894

18501860187018801890190019101920

1929.61938.4

19501960

1970.4

19801990

Average Gain (dBi)

Frequency (MHz)

Rear Passenger Inside Cellular Average Gain - Additonal Deletion Patterns

Regular W/S l(Avg Gain -4.2 dBi)

Deletion C (Avg Gain -4.2dBi)

Deletion D (Avg Gain -4.6)

Deletion E (Avg Gain -3.9dBi)
Rear Passenger Outer Cell Phone Signal:

The test results of cell phone signal in the rear seat nearer to the windows of the vehicle shows an 

actual improvement of signal strength, without any deletions, when an IR Reflective windshield is 

present.

Additonal deletion patterns reconfirm that the signal is actually stronger, by as much as 0.5 dB with one 

particular pattern.

Therefore, a passenger in the rear seat is more likely to be able to complete a cell phone call if there is 

an IR Reflective windshield than otherwise. Even though this variation is relatively small, the data shows 

that the IR Reflective windshield is consistently better for cell phone signals in the 850 MHz band used 

by AMPS cell phones. For the PCS cell phones, there is no difference in the cell phone reception whether 

an IR windshield is used or not.

-20.0

-15.0

-10.0

-5.0

0.0

5.0

824829834839844849

868.5

874

879.3883.6889.4

894

18501860187018801890190019101920

1929.61938.4

19501960

1970.4

19801990

Average Gain (dBi)

Frequency (MHz)

Rear Passenger Outer Cellular Average Gain - Deletion Patterns

Regular W/S l(Avg Gain -1.9 dBi)

No Deletion (Avg Gain -1.7dBi)

Deletion X (Avg Gain -2.1)

Deletion A (Avg Gain -1.8)

Deletion B (Avg Gain -2.0dBi)

-20.0

-15.0

-10.0

-5.0

0.0

5.0

824829834839844849

868.5

874

879.3883.6889.4

894

18501860187018801890190019101920

1929.61938.4

19501960

1970.4

19801990

Average Gain (dBi)

Frequency (MHz)

Rear Passenger Outer Cellular Average Gain - Additional Deletion Patterns

Regular W/S l(Avg Gain -1.9 dBi)

Deletion C (Avg Gain -1.7dBi)

Deletion D (Avg Gain -1.4)

Deletion E (Avg Gain -1.8 dBi)
Conclusion

When considering the actual cell phone reception in a vehicle, it is important to look at the actual signal 

strength when drawing conclusions. The vehicle is a very dynamic environment and its location and 

orientation changes with respect to a cell tower. If the signal is really weak, a vehicle equipped with an 

IR Reflective windshield may actually be better for a cell phone call in certain situations, whereas a 

vehicle equipped with standard windshields may be better at other times. On average, the data shows 

that there is no significant difference in cell phone reception between a vehicle equipped with IR 

Reflective windshield and one with standard windshield.