802.11 RF Exposure Simulation

FCC ID: NM82Q6U100

RF Exposure Info

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Qualcomm Technologies, Inc.




HTC Smart Hub 2Q6U100 802.11ad FCC RF
Exposure Simulation
80-YD078-1 Rev. B
March 14, 2019




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                                                                  U.S.A.

                          © 2019 Qualcomm Technologies, Inc. and/or its subsidiaries. All rights reserved.


       Revision history

                    Revision        Date                                 Description
                       A        March 8, 2019    Initial release
                       B        March 14, 2019   ▪ Modified Section 3.4, Simulation power density results
                                                 ▪ Modified Chapter 5, Conclusion
                                                 ▪ Added Table 5-1, Sector mapping from simulation to device
                                                   software.




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       Contents


       1 Scope ..................................................................................................................................... 5

       2 Product Description .............................................................................................................. 6
                  2.1 802.11ad antenna modules ....................................................................................................................... 6
                  2.2 802.11ad antenna configurations ............................................................................................................... 7

       3 Worst-Case Determination Using the Simulation ............................................................... 8
                  3.1 Modeling .................................................................................................................................................... 8
                  3.2 Setup ......................................................................................................................................................... 9
                          3.2.1 Platform .................................................................................................................................... 9
                          3.2.2 Channels .................................................................................................................................. 9
                          3.2.3 Error computation and convergence ....................................................................................... 10
                          3.2.4 Absorbing boundary condition ................................................................................................ 11
                  3.3 EIRP comparison measured vs. simulation ............................................................................................. 12
                  3.4 Simulation power density results ............................................................................................................. 12

       4 Power Density Measurement ..............................................................................................15

       5 Conclusion ...........................................................................................................................16

       A Uncertainty Budget .............................................................................................................17
                  A.1 Simulation uncertainty budget ................................................................................................................. 17

       B Simulated Power Density Distributions .............................................................................18
                  B.1 Left module Cut1 “Front of Device”.......................................................................................................... 18
                  B.2 Right module Cut1 “Front of Device” ....................................................................................................... 61

       C 802.11ad Antenna Modules Images and Drawings .........................................................104
                  C.1 802.11ad antenna module images inside the EUT ................................................................................ 104
                  C.2 Simulation modeling drawings ............................................................................................................... 105




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HTC Smart Hub 2Q6U100 802.11ad FCC RF Exposure Simulation                                                                                                                             Contents



       Figures

       Figure 3-1     Simulation mesh setup antenna module – Right module ........................................................................... 10
       Figure 3-2     Simulation mesh setup used in antenna module – Left module ................................................................. 11
       Figure 3-3     Simulated peak power density in 4 cm2-averaged area – Left antenna ..................................................... 13
       Figure 3-4     Simulated peak power density in 4 cm2-averaged area – Right antenna ................................................... 14
       Figure C-1     802.11ad antenna modules inside HTC 2Q6U100 .................................................................................. 104
       Figure C-2     Relative position and orientation of right side and left side antenna modules ......................................... 104
       Figure C-3     Orientation of the simulated power distribution relative to the HTC_2Q6U100 device ............................ 105
       Figure C-4     Left module ............................................................................................................................................. 106
       Figure C-5     Right module ........................................................................................................................................... 107



       Tables

       Table 3-1 Measured and Simulated EIRP .................................................................................................................... 12
       Table 5-1 Sector mapping from simulation to device software ..................................................................................... 16
       Table 5-2 Highest simulated power density summary used to define power density measurements ........................... 16
       Table A-1 Standard uncertainty budget for simulated values of power density ............................................................ 17




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       1 Scope


               The purpose of this report is to identify test configurations for measurement of the 60 GHz
               802.11ad radios embedded in the HTC Smart Hub model 2Q6U100 for the FCC RF exposure
               simulation. This simulation report provides the simulated power density in a 4 cm2 area at a
               distance of 10 mm from the device surface.
               Two 802.11ad modules were integrated into the 2Q6U100 Smart Hub platform.
                ■   Each 11ad radio consists of two separate modules (see Section 2.1).
                ■   Appendix C shows the two 802.11ad antenna module placements.
                ■   The closest distance between the 802.11ad antenna module and the body or hands of an end
                    user will be in the near field for the 60 GHz frequency.
               Final compliance is evaluated through measurements in a third-party test report.
               The RF exposure assessment and simultaneous transmission with other radios supported in the
               Smart Hub are evaluated in a separate HTC test report.




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       2 Product Description


               HTC 2Q6U100 is a Smart Hub integrating the following technologies:
                ■   FCC LTE bands: B2, B3, B4, B5 , B7, B8, B12, B13, B25, B26, B66, B71
                ■   TDD LTE bands: B41
                ■   5G band: n41
                ■   802.11a/b/g/n/ac
                ■   Bluetooth
                ■   802.11ad 60 GHz


       2.1 802.11ad antenna modules
               The HTC 2Q6U100 Smart Hub integrates two 802.11ad antenna modules operating in the
               60 GHz band.
               The 11ad antenna modules are connected to a baseboard which receives signals from the
               baseband unit.
                ■   Each 11ad radio consists of two separate modules:
                    □ 802.11ad antenna module
                        ●   60 GHz RF and antenna array elements on a printed circuit board
                        ●   Module interfaces to a baseband unit
                    □ Baseband unit
                        ●   Provides power, control signals, and IF required for the 802.11ad antenna module
                ■   One 11ad module is located at the right side and the second module is at the left side of the
                    Smart Hub.
                    □ The 802.11ad antenna module inside HTC 2Q6U100, and the relative position and
                        orientation of right and left antenna modules.
                        ●   For a closer view of the position and orientation of the 11ad antenna module relative
                            to HTC 2Q6U100 and the right and left drawings of the 802.11ad antenna module, see
                            Appendix C.
                ■   Device firmware selects which 11ad antenna is used for transmission when only one antenna
                    module can transmit at any one time.
                ■   These 802.11ad modules (including the antenna modules and baseband unit) support all
                    mandatory channels in IEEE 802.11ad (i.e., Channels 1, 2, 3 and 4) and comply with the
                    IEEE 802.11ad standard.




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HTC Smart Hub 2Q6U100 802.11ad FCC RF Exposure Simulation                                                Product Description



       2.2 802.11ad antenna configurations
               An antenna configuration or sector is a given combination of amplitude and phase of array
               elements.
                ■   There are 32 antenna configurations available for each channel to steer the antenna beam and
                    establish a good communication link with the best signal to noise ratio.
                ■   This results in a total 32 antenna configurations available per 11ad array module to handle
                    surrounding transmission environments.
                ■   Only one antenna configuration is active at any time.




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       3 Worst-Case Determination Using the
       Simulation


                 Depending on the transmission environment, the 802.11ad antenna modules installed inside HTC
                 2Q6U100 can activate an optimal antenna configuration to establish a good communication link.

         NOTE:   Simulation modeling drawings are based on the array model provided by Qualcomm
                 Technologies, Inc. and the 3D platform provided by the EUT manufacturer (see Appendix C.2).

                 Ansys Electromagnetics suite 18.0.0 simulation software evaluated all possible antenna
                 configurations to save time.
                 ■   The simulation module includes the 802.11ad antenna module and all components
                     surrounded within 5λ.
                 ■   The simulation goal is to perform a relative comparison and determine the worst-case antenna
                     configurations having the highest peak 1 cm2-averaged power density for each channel, and
                     then perform a power density measurement to demonstrate compliance on the worst cases
                     identified.
                     □ It is difficult to accurately simulate power density levels to an absolute-level due to the
                         lack of accurate material properties for non-metal components at 60 GHz.
                     □ Final measurement assessment using a larger averaging area will result in lower reported
                         power density.
                     □ Based on the placement of the 802.11ad antenna modules, the power density was
                         simulated on four evaluation planes to determine the worst case antenna configurations:
                         front, back, bottom, and side (see Figure C-3).
                 ■   The separation distance between the evaluation plane and the corresponding surface of
                     HTC_2Q6U100 is 10 mm per a KDB discussion with the device manufacture.


       3.1 Modeling
                 Complete models of the top and bottom of the 802.11ad antenna modules are from the antenna
                 manufacturer, Murata, respectively (see Appendix C.2).
                 The entire mechanical structure within 4λ surrounding the antenna module are also included in
                 the simulation.
                 ■   The 3D platform of the device was provided by HTC.
                 ■   With the exception of adhesive materials used in the Smart Hub, all components within a
                     2 mm radius of 11ad antennas modules are part of the simulation model.
                 ■   All other antennas in the device were also included in the simulation.



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HTC Smart Hub 2Q6U100 802.11ad FCC RF Exposure Simulation                      Worst-Case Determination Using the Simulation



       3.2 Setup
               Finite element analysis (FEM) simulations were performed to assess the power density of the
               802.11ad antenna module (see Appendix C).
               A layered breakdown of the mechanical structure included in the top and bottom modules of the
               simulation model:
                ■   Full model: Entire assembly.
                ■   Without screen: LCD screen removed (shields, battery, FPCs, screws, LCD mirror and metal
                    frames) and were modeled as aluminum
                ■   Only plastic components: All metal parts removed, all non-conductive components were
                    modeled as lossless ABS material with a relative permittivity of 3.3 and loss tange
               The worst-case exposure is expected from the front of HTC 2Q6U100 because exposure from
               other directions will be significantly reduced by the surrounding metal components (see top
               (Side A) Figure C-1).


       3.2.1 Platform
               The simulation includes the edge of the platform.
               The simulation of the left module was performed with a chuck of the platform that is 34 mm from
               the top edge and 43 mm from the left edge.
                ■   The platform was cut at 20 mm away from the left module’s bottom and right edges to reduce
                    simulation time.
                    □ The simulation of the right module was performed with a chuck of the platform that is
                        32 mm from the top edge and 43 mm from the left edge.
                ■   The platform was cut at 20 mm away from the left module’s bottom and right edges to reduce
                    simulation time.
                ■   The modules are mostly shielded by metallic structures in the –y direction.
                    □ All components in the vicinity of the module were simulated by assuming they were
                        mostly made of metal.


       3.2.2 Channels
               HTC 2Q6U100 supports 801.11ad Channels 1 to 4. Simulations were performed at the center
               frequencies of each channel:
                ■   Channel 1: 58.32 GHz
                ■   Channel 2: 60.48 GHz
                ■   Channel 3: 62.64 GHz
                ■   Channel 4: 64.8 GHz




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HTC Smart Hub 2Q6U100 802.11ad FCC RF Exposure Simulation                      Worst-Case Determination Using the Simulation



       3.2.3 Error computation and convergence
                 In the simulation setup, auto initial mesh was:
                 ■   Selected.
                 ■   Defined “lambda refinement” (Ansys Electromagnetics Suite 18.0.0 refines the initial mesh
                     based on the material-dependent wavelength).
                 ■   Used 30% maximum refinement per pass as our adaptive option.
                 Ansys Electromagnetics Suite 18.0.0 computes the error, and the iterative process (solve → error
                 analysis → adaptive refinement) repeats until convergence criteria are satisfied.

         NOTE:   As long as convergence is reached, the converged results are accurate.

                 Convergence was verified by changing the convergence criteria, maximum magnitude delta S,
                 from 5% to 3%.
                 ■   The influence in power density was less than 0.5%.
                      □ This influence was included in our uncertainty budget (Appendix A).
                 ■   The simulation mesh setup was used over the top (Side A) surface and bottom (Side B)
                     surface of the 802.11ad antenna module (see Figure 3-1 and Figure 3-2).
                 ■   The convergence error (maximum magnitude delta S) setting used in all simulations was less
                     than 3%.




                 Figure 3-1 Simulation mesh setup antenna module – Right module




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HTC Smart Hub 2Q6U100 802.11ad FCC RF Exposure Simulation                       Worst-Case Determination Using the Simulation




               Figure 3-2 Simulation mesh setup used in antenna module – Left module


       3.2.4 Absorbing boundary condition
               The second-order absorbing boundary condition (ABC) served as a radiation boundary for all
               simulations in this report.
                ■   ABC simulates an electrically open surface that allows waves to radiate infinitely far into
                    space.
                ■   The system absorbs the wave by the second-order ABC, essentially ballooning the boundary
                    infinitely far away from the structure and into space.
                ■   The radiation boundaries may also be placed relatively close to a structure and can be of
                    arbitrary shape.
               Per the Ansys Electromagnetics recommendation for their simulation tool, the radiation boundary
                                                                                                                  1
               plane must be located at least a quarter wavelength from a strong radiating structure, or at least 10
               of a wavelength from a weak radiating structure.
                ■   In this simulation, a spacing of at least two wavelengths was used in all directions
                    surrounding the 802.11ad antenna module to ensure minimal influence of reflections from the
                    boundaries.
                ■   This spacing was determined to be sufficient by moving the boundaries closer towards the
                    module by 30% to see the influence on simulated power density.
                ■   Influence was less than 0.05 dB, which confirms that the space between module and
                    computational boundary is sufficient.
                ■   This influence on power density was also included in the simulation uncertainty budget.




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HTC Smart Hub 2Q6U100 802.11ad FCC RF Exposure Simulation                      Worst-Case Determination Using the Simulation



               For the complete estimated total simulation uncertainty, see Appendix A.


       3.3 EIRP comparison measured vs. simulation
               Measured EIRP was compared to simulated EIRP to verify accuracy of the simulation model for
               selected test configurations in Table 3-1.
                ■   As expected, due to unknowns in the device materials, the measured EIRP was less than the
                    simulated EIRP.
                ■   The variance was not fully investigated with the expectation that measured power density
                    results will have greater than 3 dB of margin.

               Table 3-1 Measured and Simulated EIRP
                     Antenna                                      Simulated EIRP         Measured EIRP      Delta
                                     Channel         Sector
                     Module                                           (dBm)                 (dBm)           (dB)
                       Left              1             39              19.68                 18.21          1.47
                       Left              2             40              20.66                 20.12          0.54
                       Left              3             38              16.03                 17.79          -1.76
                       Right             1             5                18.9                 16.84          2.06
                       Right             2             5               18.23                 19.49          -1.26
                       Right             3             6               18.24                 20.74            -2.5



       3.4 Simulation power density results
               A total of 1024 antenna configurations (32 configurations per channel) were evaluated at each
               evaluation plane for each antenna module.
                ■   This represents a total of 1024 configurations evaluated to determine the worst-case power
                    density configurations (32 array configurations x 4 channels x 4 device surfaces x 2 arrays).
                ■   The surface furthest from the 11ad array on the bottom of the device was not included as it
                    was >5 cm from the array.
                ■   The objective of the simulation was to compare the power density levels among antenna
                    configurations for all evaluation planes to determine the worst-case antenna configuration for
                    each channel.
                ■   Then, power density is measured for the identified worst-case antenna configurations to
                    demonstrate compliance. For measurement setup and test results, see Chapter 4.
                ■   The term Cut is used to represent a device surface. The mapping of device surface to Cut is
                    shown in figure Figure C-3.
                    □ Cut 1= Front surface of the device (closed surface to the array)
                    □ Cut 2= Rear surface of device
                    □ Cut 3 = Side surface of the device
                    □ Cut 4 = Top surface of the device




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HTC Smart Hub 2Q6U100 802.11ad FCC RF Exposure Simulation                    Worst-Case Determination Using the Simulation



               For each channel, the simulated peak 4 cm2 averaged power density for all antenna configurations
               at each evaluation plane with a separation distance of 10 mm from the device surface (see Figure
               3-3 and Figure 3-4).
               The highest 4 cm2-averaged power density antenna configurations identified for measurement are
               noted with red circles. These power densities are total power densities (PDtotal) where
                                          PDtotal =√𝑃𝐷𝑥 + 𝑃𝐷𝑦 + 𝑃𝐷𝑧
               The simulation uses sectors 0-31 for both arrays. The software implements as sectors 0-31 for the
               right module and 32-64 for the left module as shown in Table 5-1.




               Figure 3-3 Simulated peak power density in 4 cm2-averaged area – Left antenna




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HTC Smart Hub 2Q6U100 802.11ad FCC RF Exposure Simulation         Worst-Case Determination Using the Simulation




               Figure 3-4 Simulated peak power density in 4 cm2-averaged area – Right antenna




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       4 Power Density Measurement


                 Power density measurements are not assessed in this test report.

         NOTE:   See the SPORTON test report for measured test results.




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       5 Conclusion


               The worst-case antenna configurations having the highest 4 cm2-averaged power density for each
               channel and 11ad module, and the 4 cm2 results for comparison in the measurement report are
               identified in Table 5-2.
               Simulation results are provided for both the top and bottom 11ad antenna arrays on the front, rear,
               top, and bottom device surfaces near the antenna array.

               Table 5-1 Sector mapping from simulation to device software
                    Simulation Sector (Used in    Right Module Software Sector ID      Left Module Software Sector ID
                     Figure 3-3 and Figure 3-4)         (Shown in Table 5-2)                 (Shown in Table 5-2)
                               0-31                             0-31                                32-64

               Table 5-2 Highest simulated power density summary used to define power density
               measurements
                                                                             Simulated Pd 4 cm^2       Simulated Pd
                                                              Exposure
                    Module         Channel        Sector                        at 10 mm with        4 cm^2 at 10 mm
                                                                Plane
                                                                               100% duty cycle           with 85%
                      Left            1            34              1                 8.79                   7.47
                      Left            1            36              1                 8.41                   7.15
                      Left            3            34              1                 8.71                   7.40
                      Left            3            40              1                 8.70                   7.40
                      Left            4            37              1                 8.50                   7.23
                      Left            4            36              1                 8.33                   7.08
                      Left            1            33              2                 0.49                   0.41
                      Left            1            58              3                 5.19                   4.41
                      Left            4            50              4                 4.86                   4.13
                     Right            1            10              1                 8.60                   7.31
                     Right            1            20              1                 8.20                   6.97
                     Right            2             3              1                 8.10                   6.89
                     Right            2            12              1                 7.59                   6.45
                     Right            4            12              1                 8.10                   6.89
                     Right            4             3              1                 7.84                   6.67
                     Right            2            13              2                 0.76                   0.65
                     Right            2            18              3                 3.52                   2.99
                     Right            4             8              4                 2.64                   2.24

               For complete simulation results of point power density distributions on the back plane (bottom
               module) and front plane (upper module) for all antenna configurations, see Appendix B.



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       A Uncertainty Budget


       A.1 Simulation uncertainty budget
               Table A-1 lists the measurement uncertainty analysis for the simulation.

               Table A-1 Standard uncertainty budget for simulated values of power density
                                                    Uncertainty                            Std. unc      Std. unc
                       #         Description                       Prob. dist.    Div.
                                                      (± %)                                 (± %)         (± dB)
                       1      FEM mesh density         0.10%          Norm          1        0.10%         0.00
                       2      Boundary condition       0.80%          Norm          1        0.80%         0.03
                       3         Convergence           0.50%          Norm          1        0.50%         0.02
                    Combined standard uncertainty                                            0.9%          0.04

                    Expanded standard uncertainty                                            1.9%          0.08
                    1 Mesh density on the exposure plane was changed by limiting the "max length" of mesh size
                    from auto setting (9.6 mm) to 2 mm.
                    2 Simulation domain (volume) was decreased by 30% to check the influence of reflections from

                    boundary conditions on power density.
                    3
                      5% versus 3% convergence criteria were compared in Ansys Electromagnetics Suite 18.0.0.




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Document Created: 2019-03-14 22:55:17
Document Modified: 2019-03-14 22:55:17

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