TR41.3.5CTRMP / 02-02-003
AST TECHNOLOGY LABS, INC.
P.O. Box 372580
Satellite Beach, FL 32937
PH: 321-773-4876
FAX: 321-773-9326
www.asttechlabs.com
Title
RF Simulator, 3m site, and outdoor range
measurements for a 900 MHz telephone
with a retractable antenna
Source
AST Technology Labs Inc.
PO Box 372580
Satellite Beach, FL 32937
Contact
James Bress
jrbress@asttechlabs.com
321-773-4876
Date
2002-02-16
Distribution
TR41.3.5CTRMP
Keywords
Notice: The contributor grants a free, irrevocable license to the Telecommunications Industry
Association (TIA) to incorporate text contained in this contribution and any modifications thereof
in the creation of a TIA standards publication; to copyright in TIA’s name any standards
publication even though it may include portions of the contribution; and at TIA’s sole discretion
to permit others to reproduce in whole or in part the resulting TIA standards publication.
1
TR41.3.5CTRMP / 02-02-003
TIA Contribution
AST Technology Labs
TIA-TR-41.3.5-CTRMP
1 Introduction
The VTech Ballot Response (2001-10-26) to PN-3-4350-RV3 (Cordless Telephone Range
Measurement Procedures) described technical issues related to range measurements when
testing a 900 MHz cordless telephone with a retractable antenna including:
1. RF measurement issues related to discrepancies between 3m site antenna polar plots
and similar measurements performed in a VTech RF simulator box with the antenna up,
and the tests repeated with the antenna down. The primary issue raised was the polar
plots obtained in the RF simulator box did not correlate well with the polar plots obtained
on the 3m site. The contribution stated:
” The close range radiation pattern of the CPE antenna measured inside the range
simulator may differ substantially from the standard 3 meter radiation pattern. Simulated
range measurements can be influenced by this and therefore must be correlated with
outdoor range data.”
2. In support of the position that the RF simulator may be inaccurate for measurements
with different antennas, a comparison of range data taken from an AST Technology
Labs RF simulator (ART™ system), and outdoor range tests were given. The values
stated were:
 Outdoor Range: 20% reduction in range outdoors for the antenna down vs.
antenna up
 RF Simulator: 1400 ft antenna up, and 800 ft antenna down
This contribution includes data obtained from similar measurements made by AST Technology
Labs using the same model telephone as used for the previous VTech measurements. This
telephone (DUT) was used to measure:
1. Polar plots in the ART™ system and on a 3m site. In both cases polar plots were
measured with the antenna up and measured again with the antenna down.
2. Range measurements on an outdoor range and in the AST ART™ system. Range
measurements were made with the antenna up and the antenna down.
NOTE:
the 3m site measurement is a modification of the classic 3m site measurement
performed for emissions or maximum radiated power measurements. The 3m sitetype tests were performed by placing the receiving antenna in a fixed location
(parallel to the DUT antenna) and making the polar plot measurements by rotating
the DUT 360 degrees. The receiving antenna was not moved for these
measurements.
2 Polar Plots
2.1
Polar Plot Measurements and Data
The following Measurements were made using the DUT handset:
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TR41.3.5CTRMP / 02-02-003
TIA Contribution
AST Technology Labs
TIA-TR-41.3.5-CTRMP
1.
2.
3.
4.
Polar Plot in AST ART™ system (antenna up)
Polar Plot in AST ART™ system (antenna down)
Polar Plot on 3m site (fixed receive antenna) (antenna up)
Polar Plot on 3m site (fixed receive antenna) (antenna down)
Note the data obtained was in dBm measured directly from a spectrum analyzer. No attempt
was made to convert the measured data to Volts/meter (or any other scale) since all data is to
be used for relative comparison and not absolute power levels.
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TR41.3.5CTRMP / 02-02-003
TIA Contribution
AST Technology Labs
TIA-TR-41.3.5-CTRMP
RAW DATA VALUES SUMMARY
AST ART™
System
(Antenna–Up)
-27.3
-28.4
-27.3
-27.8
1.1
Parameter
Measured
Max
Min
0 deg. ref (*)
Average
Max - Min
(*)NOTE:
AST ART™
System
(Antenna–Down)
-34.0
-38.7
-37.6
-36.8
4.7
3m Site (Fixed
Receive Antenna)
(Antenna–Up)
-43.7
-47.8
-47.5
-45.9
4.1
3m Site (Fixed
Receive Antenna)
(Antenna–Down)
-49.9
-56.0
-54.9
-53.6
6.1
The 0 deg. ref orientation is with the handset back (the part not pressed
against a users head) facing the receiving antenna.
The following polar plots were obtained for the ART™ system and the 3m site (with the antenna
up and the antenna down.
Antenna Polar Plots (Raw Data)
0
330
340
320
310
350-20.0
10
20
30
40
-30.0
Antenna
Up: ART Box
(dBm)
50
300
60
-40.0
290
70
-50.0
280
80
270
90
-60.0
260
100
250
110
240
120
230
220
130
140
210
200
190
170
160
150
180
4
Antenna
Down: ART Box
(dBm)
Antenna
Up: 3m
(dBm)
Antenna
Down: 3m
(dBm)
TR41.3.5CTRMP / 02-02-003
TIA Contribution
AST Technology Labs
TIA-TR-41.3.5-CTRMP
If the 0 deg. reference points are used to normalize the 3m site data to the RF simulator data, a
meaningful comparison between the two measurement methods (RF Simulator and 3m site) can
be made for Antenna-Up and Antenna-Down. Normalization simply means to make the 0 deg.
ref. measurements for the 3m site equal to the ART™ system 0 deg. ref value. The value used
for normalization (ART™ system @ 0 deg. ref. – 3m site 0 deg. ref. = 20.2 (Antenna-Up) and
17.3 Antenna-Down)) is then applied to the data points for each polar plot degree measured.
Normalization allows direct comparison of the polar plot shape (contour) while removing the
absolute difference in power level expected since the 3m site and ART™ system have the
receiving antenna at different distances from the DUT. The following summary of parameters is
obtained:
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TR41.3.5CTRMP / 02-02-003
TIA Contribution
AST Technology Labs
TIA-TR-41.3.5-CTRMP
NORMALIZED DATA VALUES SUMMARY
Parameter
Measured
AST RF Simulator
(Antenna–Up)
AST RF Simulator
(Antenna–Down)
-27.3
-28.4
-27.3
-27.8
1.1
-34.0
-38.7
-37.6
-36.8
4.7
Minimum
Maximum
0 deg. ref (*)
Average
Max - Min
3m Site (Fixed
Receive Antenna)
(Antenna–Up)
-23.5
-27.6
-27.3
-25.7
4.1
3m Site (Fixed
Receive Antenna)
(Antenna–Down)
-32.6
-38.7
-37.6
-36.3
6.1
The following plots are obtained for the RF simulator and 3m site (with the antenna up and the
antenna down (using the normalized data):
Antenna Polar Plots (Normalized)
0
340
350-20.0
10
20
330
30
320
40
-30.0
310
Antenna
Up: ART Box
(dBm)
50
300
60
-40.0
290
70
-50.0
280
80
270
90
-60.0
260
100
250
Antenna
Down: ART Box
(dBm)
Normalized 3M
Data Antenna Up
110
240
120
230
130
220
140
210
150
200
190
170
160
180
6
Normalized 3M
Data Antenna
Down
TR41.3.5CTRMP / 02-02-003
TIA Contribution
AST Technology Labs
TIA-TR-41.3.5-CTRMP
2.2
Polar Plot Measurements Conclusion
The normalized polar plot data are comparable for the antenna up when tested using the 3m
site and the AST RF simulator. The data is also comparable for the antenna down
measurements for the 3m site and the RF simulator.
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TR41.3.5CTRMP / 02-02-003
TIA Contribution
AST Technology Labs
TIA-TR-41.3.5-CTRMP
3 Range Measurements
3.1
Range Measurements Outdoors and In RF Simulator
Range measurements of the DUT were performed using the AST RF simulator and on an
outdoor range, both with the antenna up and the antenna down.
AST ART™ System
Antenna Down Range = 57% of Antenna Up Range
(Same as range VTech stated range from a RF simulator at 11-2001 meeting)
Outdoor Range Test
Antenna Down Range = 64% of Antenna Up Range
(VTech stated range was Antenna Down = 80% of Antenna Up at 11-2001 meeting)
3.2
Range Measurements Conclusion
Outdoor range tests and range tests using the AST ART™ simulator were well correlated. The
discrepancies seen from the outdoor range tests performed by AST and those performed by
VTech support the purpose for developing the CTRMP standard. Some of the primary purposes
for developing this standard relate to the fact that outdoor range tests do not yield repeatable
results when performed by different individuals on different range sites due to the subjective
nature of the tests and the different range site characteristics.
4 Near Field (Close Range) Vs. Far Field Measurements
The VTech contribution stated issues with “Close Range” radiation pattern differing from the
radiation pattern on a 3m site measurement. It is assumed that rather than attempting to
establish the 3m site as a reference for antenna measurements to establish then to be in the
“Far Field”, the issue relates more to the fact that the RF simulator may not be measuring in the
Far Field and therefore may yield measurements that are dependent on the transmitting
antenna.
4.1
Supporting Data and Theory
The document published by Industry Canada: Guidelines for the Measurement of
Radiofrequency Fields at Frequencies from 3 kHz to 300 GHz (August 2000) provides an
abundance of information regarding the measurement of electromagnetic fields. This document
states the following regarding the Far Field for antennas:
The criterion commonly used to define the distance from the source where the far field begins is
that the phase of the fields from all points on the radiating antenna does not differ more than
l/16. The distance from the antenna corresponding to this criterion is:
R = 2a2 / 
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TR41.3.5CTRMP / 02-02-003
TIA Contribution
AST Technology Labs
TIA-TR-41.3.5-CTRMP
a = the greatest dimension of the antenna
R = distance from radiating antenna where the far-field begins
For example for a ¼ wavelength antenna:
R = (2)( ¼ )2 / 
R = 1/8 
In order to reduce measurement errors relating to far field and near filed issues it is generally
accepted practice that to be safely in the far field region that:
R >> 2a2 / 
Using 10 times as a minimum criteria for (>>, i.e.: Much Greater Than) this yields the criteria for
R using a ¼  probe antenna as:
R > 10/8  = 1.25 
For a 900 MHz signal  = .33m, therefore:
R > (1.25)(.33m) = .42m
4.2
Recommendation for CTRMP Standard
Given the above described correlation of antenna dimension, and distance from radiator to
measuring probe antenna, is recommended that the following statement be included in the
criteria for cordless telephone range measurement equipment.
Change section 7.1 to read:
7.1 Physical Attributes Of Test System
 is the wavelength at the center of the band of operation.
Minimum distance from Antenna reference point:
 1.25  to probe
 ¼  to walls
4.3
Conclusion For Far Field Measurement Issues
The VTech contribution claim regarding inaccuracies for measurements from different antennas
relating to issues with making measurements in the “Near Field” should not hold true if the
antenna length and probe distance as stated above are maintained in the RF simulator box.
In addition, the other requirements established in the current standard for the RF simulator
system relating to flat transmission frequency response and external noise rejection must be
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TR41.3.5CTRMP / 02-02-003
TIA Contribution
AST Technology Labs
TIA-TR-41.3.5-CTRMP
maintained for accurate measurements. Any system used for range measurements must be
verified to meet the established criteria.
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