Kwok Chan commented on 2009-11-05 16:59:22.526:
For the comments at the end:
The conditions for 1)c) and 1)d) are chosen according to the calibration data of various dipoles in the 300 - 5800 MHz range, which represent the normally expected range of variations for these parameters. While SAR measuement standards are recommending annual calibration, the proposed procedures may enable test labs to extend the calibration interval up to 3 years when specific conditions are met. IEEE 1528-2003 requires a 1% mechanical tolerance to ensure a tight electrical tolerance. When the electrical parameters are deviating beyond the normally expected range, the proposed procedures require the annual calibration recommended by SAR measurement standards to be followed.
For the 8% comment, please see related response to Steve Liu (Steve Liu commented on Nov 3 2009 5:48PM). We will review and decide if we should keep the 8% or deleting the entire paragraph as suggested by this other comment.
John Welch commented on Nov 5 2009 1:29PM:
These comments submitted on behalf of Motorola, Inc.
The provision at point 1) c) should be amended by removing the 3 dB check. The rationale for this recommendation is that relative return loss changes at the test frequency well in excess of 3 dB may be possible if the antenna is matched at > 30 dB return loss without having any significant effect (less than 0.1%) on the measured SAR. The 20 dB threshold is enough to ensure that SAR changes are well within 1%, which was deemed acceptable within the overall SAR measurement uncertainty by IEC and IEEE standards committees. The provision at point 1) d) should also be amended for the same reason.
Comments on the section "Head and Body Tissue Media Considerations for SAR System Verification:" Motorola recommends deleting the sentence that states "dipole measurements must be within 8% of the calibrated SAR value. The rationale for this recommendation is that dipole manufacturers' tolerances exceed 8% and dipole measurement tolerances (for validation and system check) are defined in standards.
John Welch commented on 2009-11-05 13:29:01.073:
These comments submitted on behalf of Motorola, Inc.
The provision at point 1) c) should be amended by removing the 3 dB check. The rationale for this recommendation is that relative return loss changes at the test frequency well in excess of 3 dB may be possible if the antenna is matched at > 30 dB return loss without having any significant effect (less than 0.1%) on the measured SAR. The 20 dB threshold is enough to ensure that SAR changes are well within 1%, which was deemed acceptable within the overall SAR measurement uncertainty by IEC and IEEE standards committees. The provision at point 1) d) should also be amended for the same reason.
Comments on the section "Head and Body Tissue Media Considerations for SAR System Verification:" Motorola recommends deleting the sentence that states "dipole measurements must be within 8% of the calibrated SAR value. The rationale for this recommendation is that dipole manufacturers' tolerances exceed 8% and dipole measurement tolerances (for validation and system check) are defined in standards.
Kwok Chan commented on 2009-11-04 14:50:33.75:
For the comments identified at the end:
The 10% value established by IEEE 1528-2003 has been used as the acceptable dipole SAR measurement tolerance for SAR system verification since 2001 when Supplement C 01-01 was released. This 10% threshold is based on comparing the measured SAR value against the required target SAR value without applying additional measurement uncertainty considerations; i.e., k=1. The expanded measurement uncertainty of 17% described in the comment below correspond to 8.5% for k=1. When both head and body SAR measurements are required for testing a device, the proposed draft procedures allow SAR system accuracy verification to be performed using either head or body tissue-equivalent liquid when the following conditions are satisfied:
1. The same SAR probe with both head and body calibrations at the required device test frequency range must be used for both SAR system accuracy verification and head and body SAR testing of the devive. Therefore, when SAR system accuracy is verified using one type of liquid, it can be inferred that the SAR probe calibration at the same frequency range for the other liquid medium (head or body) should have equivalently acceptable accuracy.
2. When the measured dipole SAR differs from its calibrated SAR target by close to the 10% threshold, it would be justified to question the probe calibration accuracy and require SAR system accuracy verification for both head and body. The 8% has been chosen because most carefully performed dipole SAR measurements using the required tissue dielectric parameters are expected to be well within 10% (typically below 6-7 %).
3. Since tissue dielectric parameters must be measured to demonstrate their values are within the reqruired range and tolerance, their influence on the measured SAR is expected to be small. Therefore, no further conditions are imposed on tissue dielectric parameter tolerances other than requiring the measured dipole SAR to be less than 8% from the required dipole SAR target.
Unless there are other additional or related comments concerning this, we plan to keep this 8% as proposed.
Steve Liu commented on Nov 3 2009 5:48PM:
About the last sentence about 8%-10% system verifications requiring both brain and muscle verifications, it does not seem justified to verify both mediums because of the limit of 8%-10%. A suggestion is to either verify both no matter what (since they are completely different measurements); or 10% should be accepted for a single medium without any exception (due to device usage). The k=2 percentages from typical manufacturers state 17%. So it seems difficult to justify ranges more stringent than a 95% confidence interval provided by a system manufacturer. Thoughts?
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