Attachment MBTT System

This document pretains to SES-LIC-20180425-00410 for License on a Satellite Earth Station filing.

IBFS_SESLIC2018042500410_1368388

RF Radiation hazard Assessment Report for a Exhibit B to FCC 312 6.3 m Cassegrain Antenna Page 1 of 10 Intorduction This analysis predicts the RF radiation levels around a multi-band satellite communication system comprised of a 6.3 meter diameter cassegrain type antenna having a sub reflector dimension of approximately 30 cm in diameter. Swappable feeds permit various operational bands and the principal frequencies of interest here are; for Ku band with center frequency at 14.25 GHz and for Ka Band with center frequency at 29.5 GHz. The analysis described in this report follows, in part, the methodology established in FCC Office of Engineering and Technology Bulletin, No. 65 as revised and is used to determine the free space equivalent power density in the far-field, near-field, transition region, between the subreflector or feed and main reflector surface, at the main reflector surface, and between the antenna edge and the ground and to compare these levels to the specified Maximum Permissible Exposure as promulgated for the controlled an uncontrolled environment. The system itself is mounted on a raised platform and the antenna is housed within a radome atop of a building. Access to the building and radome is controlled as depicted in Figure 1. Figure 1: Antenna and relative elevations. RF Exposure Limits When evaluating for Health and Safety compliance, it is the practice that the most conservative standard be applied. Under most conditions, this would be the Massachusetts Radiation Control Program (Ma RCP 105 CMR 122.000) regulations based on the FCC standard 1977; however, in some circumstances the most recent IEEE (IEEE C95.1-2005) standard is more conservative particularly for the General Public at certain frequencies, which IEEE has re-termed the Action Level. The Department of Defense through the DoD instruction process has issued DoD Instruction 6055.11, “Protection of DoD Personnel from Electromagnetic Fields,” August 19, 2009 which is identical to the current IEEE standard. The Basic restriction as set forth by the FCC/IEEE is based on the specific Absorption Rate (SAR), which is difficult to quantify practically, hence the derived quantities listed for the FCC/IEEE MPEs are rms

RF Radiation hazard Assessment Report for a Exhibit B to FCC 312 6.3 m Cassegrain Antenna Page 1 of 10 electric (E) and magnetic (H) field strengths or plane-wave equivalent power density values . The derived quantities listed for the IEEE/FCC MPEs are rms electric (E) and magnetic (H) field strengths for frequencies below 400 and 300 MHZ respectively. Above these frequencies, the derived standard is based on the RMS power density both for the electric and magnetic fields. The FCC/ IEEE state that compliance with these MPEs ensures compliance with the basic restrictions on whole-body averaged SAR. For non-uniform exposure over the length of the body, the FCC/IEEE recommends that the electric or magnetic field strength be spatially averaged over this length. More commonly, the free space power density is used across all frequency ranges for convenience since this can be related to the electric or magnetic field strength by the free space impedance The basic restrictions also permit for time averaging for the uncontrolled/general public (30 mins) and the controlled (6 mins) environs. Controlling the exposure time for individuals whether it be for an informed worker or for the member of the public is generally not considered to be an acceptable means for demonstrating compliance since documentation of the time individuals are in the field or when a given emitter is radiating is generally not taken into account except for specific cases and generally for a retrospective evaluation. However, time averaging with respect to pulsed operation (duty factors) and moving antennas may be considered appropriate especially for the former. The free space power density MPE for each band is provided in Table 1. The highlighted values represent the more conservative of the two standards evaluated and will be used. Tablel 1. MPE values for FCC/MDPH and IEEE/DoDI IEEE 95.1-2005/DoDI-6055.11- Center FCC/MDPH – RCP 2009 Band Frequency MPE (mW cm-2) MPE (mW cm-2) (GHz) Controlled General Public Controlled Action Level Ku 14.25 5 1 10 1 ka 29.5 5 1 10 1 In considering calculations other than numerical, most are based on far field conditions where a plane wave is presumed to exist and extrapolating to distances close in to the aperture can significantly overestimate the free space power density at these distances. This is particularly true for large apertures and small wavelengths. On Axis Far Field Region For far field conditions the following relationship may be applied (OET 65 Equation 3): π‘ƒπ‘ƒπ‘Žπ‘Žπ‘Žπ‘Žπ‘Žπ‘Ž 𝐺𝐺 𝑆𝑆𝑓𝑓𝑓𝑓 = 4πœ‹πœ‹π‘Ÿπ‘Ÿ 2 Where: Sff is the power density in the far field at distance r, Pave is the average power being transmitted, and G is the antenna gain. The Far field is said to exist at a distance described by the relationship

RF Radiation hazard Assessment Report for a Exhibit B to FCC 312 6.3 m Cassegrain Antenna Page 1 of 10 𝐷𝐷 2 𝑅𝑅𝑓𝑓𝑓𝑓 = 0.6 πœ†πœ† Where: Rff is the distance at which the far field is said to begin, D is the antenna diameter, and λ is the corresponding wavelength for a given frequency. Power Density Estimate at the Face of the Aperture The maximum Power density directly in front of the aperture may be estimated as follows (OET 65 equation 11): 4𝑃𝑃 𝑆𝑆𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠 = 𝐴𝐴 Where: Ssurface = maximum power density at the antenna surface, P = power fed to the antenna, and A = physical area of the aperture antenna. Power Density Estimate within the Near Field At distances away from the surface of the aperture but less than the extent of the near field, the maximum value of the near-field, on-axis power density can be expressed as follows (OET 65 Equation 13): 16πœ‚πœ‚πœ‚πœ‚ 𝑆𝑆𝑛𝑛𝑛𝑛 = πœ‹πœ‹π·π· 2 Where: Snf = maximum near-field power density, η = aperture efficiency, typically 0.5-0.75, P = power fed to the antenna, and D = antenna diameter. The aperture efficiency can be approximated by the following relationship. πΊπΊπ‘Žπ‘Žπ‘Žπ‘Žπ‘Žπ‘Ž πœ†πœ†2 πœ‚πœ‚ = πœ‹πœ‹ 2 𝐷𝐷2 Where: λ = is the wavelength, Gabs = the numerical (absolute) gain which may be obtained from Gabs= 10(Gdbi/10), and All other parameters as previously defined. The extent of the near field may be determined from the following. 𝐷𝐷 2 𝑅𝑅𝑛𝑛𝑛𝑛 = 4πœ†πœ† Where: Rnf = the extent of the near field and all other parameters are as previously defined.

RF Radiation hazard Assessment Report for a Exhibit B to FCC 312 6.3 m Cassegrain Antenna Page 1 of 10 In the region between the extent of the near field to the beginning of the far field is described as the transition field and on a first order approximation the free space power density falls off linearly with distance from the extent of the near field to the beginning of the far field. Power Density in the transition region The free space power density in this region follows the following relationship. 𝑅𝑅𝑛𝑛𝑛𝑛 𝑆𝑆𝑑𝑑 = 𝑆𝑆𝑛𝑛𝑛𝑛 𝑅𝑅𝑑𝑑 Where: St is the power density in the transition region at a distance of interest Rt, Snf is the power density in the near field, and Rnf is the extent of the near field. Power density Estimates in the region between the Sub Reflector and the Main Reflector Transmissions from the feed horn are directed toward the subreflector surface, and are confined within a conical shape defined by the feed horn. The relationship for the power density between the main reflector and the subreflector is cast in the same relationship as that for the power density at the plane of the reflector and can be expressed as follows: 4𝑃𝑃 𝑆𝑆𝑠𝑠𝑠𝑠 = 𝐴𝐴𝑠𝑠𝑠𝑠 Where: Ssr is the power density between the subreflector and the main reflector, Asr is the area of the sub reflector, and P is the power at the feed. Power Density Estimates from the edge of the reflector surface to ground Assuming uniform illumination of the reflector surface, the power density between the antenna and the ground can be estimated from the following equation 𝑃𝑃 𝑆𝑆𝑔𝑔 = 𝐴𝐴 Where: Sg is the power density between the reflector and the ground, and all other terms are as previously defined. It should be recognized that this is a conservative value as this system provides for a tapered edge and thus this representation is conservative. Off Axis Power Density in the Far Field Within the far field the radiation field is characterized by a series of maxima and minmum referfered to as side lobes as a function of the off-axis angle from the boresite. Theoretical antntenna patterns that

RF Radiation hazard Assessment Report for a Exhibit B to FCC 312 6.3 m Cassegrain Antenna Page 1 of 10 describe the antenna gain as a function of this angle results in gains that are significantly less than the main beam gain. If the main beam in the far fieldis less than the applicable MPE, then likewise any sidelobes (including back lobes, would result in power densities being below that MPE for any off axis condition. Alternatively, an antenna gain pattern envelope could be used in needed and is expressed in the following form suitable for these type of systems: πΊπΊπ‘œπ‘œπ‘œπ‘œ = 32 − 25 𝐿𝐿𝐿𝐿𝐿𝐿(πœƒπœƒ) Where: Goa is the off axis gain envelope, and θ is the off axis angle relative the main beam Thus, the power density off axis from the main beam in the far field may be determined by the ratio of the relative gains times the on-axis power density in the far field as expressed here: πΊπΊπ‘œπ‘œπ‘œπ‘œ π‘†π‘†π‘œπ‘œπ‘œπ‘œ = 𝑆𝑆𝑓𝑓𝑓𝑓 𝐺𝐺 Near Field Off Axis Power Density For off-axis calculations in the near-field and in the transition region, it can be assumed that, if the point of interest is at least one antenna diameter removed from the center of the main beam, the power density at that point would be at least a factor of 100 (20 dB) less than the value calculated for the equivalent distance in the main beam. Should the near field free space equivalent Power density be less than the MPE, then all areas off axis will be likewise, otherwise it may be worth considering this reduction in a hazard evaluation. Summary and Conclusions: Using the methods described above, hazard assessments were evaluated and are summarized in Tables 2 and 3 for the analysis shown in Tables 4 and 5. Graphical depictions of the RF free space equivalent power levels as a function of down range distance along the boresite of the antenna are presented in Figures 2 and 3. All areas are below the respective MPEs (Controlled and Uncontrolled) with the exception of the region describe as being between the sub reflector and the main reflector at the plane of the main reflector for the uncontrolled environment only. These areas are not accessible to members of the general public. The antenna is maintained within a radome that is access controlled and thus access to the area between the subreflector and the main reflector is prohibited during operation. It should be stated that the underlying assumptions used in the application of OET 65 tends to be conservative in that the presumption of uniform illumination of the main reflector prevails, whereas for this configuration an edge taper exists providing for tighter and greatly reduce sidelobes.

RF Radiation hazard Assessment Report for a Exhibit B to FCC 312 6.3 m Cassegrain Antenna Page 1 of 10 Table 2: Hazard Summary for Uncontrolled environment Region Ku Band Ka Band Radiation Level Hazard Assessment Radiation Level Hazard Assessment mW/cm2 mW/cm2 Far Field 0.35 Satisfies FCC/MDPH and 0.36 Satisfies FCC/MDPH and IEEE C95.1-2005 MPE IEEE C95.1-2005 MPE Near Field 0.82 Satisfies FCC/MDPH and 0.85 Satisfies FCC/MDPH and IEEE C95.1-2005 MPE IEEE C95.1-2005 MPE Transition Region Equal to or less Satisfies FCC/MDPH and Equal to or less Satisfies FCC/MDPH and than Near field IEEE C95.1-2005 MPE than Near field IEEE C95.1-2005 MPE Main Reflector 1.28 Potential Hazard 1.28 Potential Hazard Region (Plane) Between Main 565.9 Potential Hazard 565.9 Potential Hazard Reflector and Subreflector Power Density 0.32 Satisfies FCC/MDPH and 0.32 Satisfies FCC/MDPH and Between Reflector IEEE C95.1-2005 MPE IEEE C95.1-2005 MPE and Ground Far Field Off Axis Satisfies FCC/MDPH and Satisfies FCC/MDPH and IEEE C95.1-2005 MPE IEEE C95.1-2005 MPE Near Field Off Axis 0.0082 Satisfies FCC/MDPH and 0.0085 Satisfies FCC/MDPH and IEEE C95.1-2005 MPE IEEE C95.1-2005 MPE Table 3: Hazard Summary for Controlled Environment Region Ku Band Ka Band Radiation Level Hazard Assessment Radiation Level Hazard Assessment mW/cm2 mW/cm2 Far Field 0.35 Satisfies FCC/MDPH and 0.36 Satisfies FCC/MDPH and IEEE C95.1-2005 MPE IEEE C95.1-2005 MPE Near Field 0.82 Satisfies FCC/MDPH and 0.85 Satisfies FCC/MDPH and IEEE C95.1-2005 MPE IEEE C95.1-2005 MPE Transition Region Equal to or less Satisfies FCC/MDPH and Equal to or less Satisfies FCC/MDPH and than Near field IEEE C95.1-2005 MPE than Near field IEEE C95.1-2005 MPE Main Reflector 1.28 Satisfies FCC/MDPH and 1.28 Satisfies FCC/MDPH and Region (Plane) IEEE C95.1-2005 MPE IEEE C95.1-2005 MPE Between Main 565.9 Potential Hazard 565.9 Potential Hazard Reflector and Subreflector Power Density 0.32 Satisfies FCC/MDPH and 0.32 Satisfies FCC/MDPH and Between Reflector IEEE C95.1-2005 MPE IEEE C95.1-2005 MPE and Ground Far Field Off Axis Satisfies FCC/MDPH and Satisfies FCC/MDPH and IEEE C95.1-2005 MPE IEEE C95.1-2005 MPE Near Field Off Axis 0.0082 Satisfies FCC/MDPH and 0.0085 Satisfies FCC/MDPH and IEEE C95.1-2005 MPE IEEE C95.1-2005 MPE

RF Radiation hazard Assessment Report for a Exhibit B to FCC 312 6.3 m Cassegrain Antenna Page 1 of 10 Figure 2: Graphical Depictions of the RF Free Space Equivalent Power Levels as a Function of Down Range Distance along the Boresite of the Antenna for Ka Band Figure 3: Graphical Depictions of the RF Free Space Equivalent Power Levels as a Function of Down Range Distance along the Boresite of the Antenna for Ku Band

RF Radiation hazard Assessment Report for a Exhibit B to FCC 312 6.3 m Cassegrain Antenna Page 1 of 10 Table 4: RF Analysis for Ka Band Comm Ka @ 29.5 GHz Information Provided Converted Values Center Frequency 29.5 GHz 29500 MHz Dish Diamenter 248.0314961 inches 6.3 m Transmit Power 1.00E+02 W 100 W Antenna Gain 64 dBi 64 dBi Duty Factor 1 1 Diameter of Subreflector 30 cm 0.3 m MDPH IEEE C95.1-2005/DoDI 6055.11 - 2009 Limits (SL) General Public Occupational Action Controlled (mW/cm2) 1 5 1 10 Parameter Symbol Formula Value Units Antenna Diameter D Input 6.3 m Antenna Surface Area A πD2/4 31.172454 m2 Sub Reflector Diameter Dsr Input 0.3 m Sub rflector Surface Area Asr πD2/4 0.0706858 m 2 Frequency f Input 29500 MHz Wavelength λ 300/f 0.0101695 m Transmit Power P Input 100 W Antenna Gain (dBi) G Input 64 dBi Duty Factor DF Input 1 Average Power Pave P*DF 100 Antenna Gain(factor) Gabs 10G/10 2511886.4 N/A Pi π Constant 3.1415927 N/A Antenna Efficiency η Gabsλ2/(π 2D2) 0.6631589 N/A Distance to Far Field Rff 0.6D2/λ 2341.71 m Power Denisty at 2 Reflector Surface Sr 4P/A 12.831842 W/m 1.2831842 mW/cm2 On-Axis Power Density at 2 Far Field Sff GabsP/4πRff2 3.6452214 W/m 0.3645221 mW/cm2 2 Extent of Near Field Rnf D /4λ 975.7125 m Near Field Power Density Snf 16.0ηP/(πD2) 8.5095506 W/m 2 0.8509551 mW/cm2 Transition Region Power Density St SnfRnf/Rt Power density between the sub reflector and 2 main reflector Ssr 4P/Asr 5658.8424 W/m 565.88424 mW/cm2 Power density between 2 antenna and ground Sg P/A 3.2079605 W/m 0.3207961 mW/cm2

RF Radiation hazard Assessment Report for a Exhibit B to FCC 312 6.3 m Cassegrain Antenna Page 1 of 10 Table 5: RF Analysis for Ku Band Ku @ 14.25 GHz Information Provided Converted Values Frequency 14.25 GHz 14250 MHz Dish Diamenter 248.0314961 inches 6.3 m Transmit Power 1.00E+02 W 100 W Antenna Gain 57.5 dBi 57.5 dBi Duty Factor 1 1 Diameter of Subreflector 30 cm 0.3 m MDPH IEEE C95.1-2005/DoDI 6055.11 - 2009 Limits (SL) General Public Occupational Action Controlled (mW/cm2) 1 5 1 10 Parameter Symbol Formula Value Units Antenna Diameter D Input 6.3 m Antenna Surface Area A πD2/4 31.172454 m2 Sub Reflector Diameter Dsr Input 0.3 m Sub rflector Surface Area Asr πD2/4 0.0706858 m 2 Frequency f Input 14250 MHz Wavelength λ 300/f 0.0210526 m Transmit Power P Input 100 W Antenna Gain (dBi) G Input 57.5 dBi Duty Factor DF Input 1 Average Power Pave P*DF 100 Antenna Gain(factor) Gabs 10G/10 562341.33 N/A Pi π Constant 3.1415927 N/A Antenna Efficiency η Gabsλ2/(π 2D2) 0.636256 N/A Distance to Far Field Rff 0.6D2/λ 1131.165 m Power Denisty at 2 Reflector Surface Sr 4P/A 12.831842 W/m 1.2831842 mW/cm2 On-Axis Power Density at 2 Far Field Sff GabsP/4πRff2 3.4973429 W/m 0.3497343 mW/cm2 2 Extent of Near Field Rnf D /4λ 471.31875 m Near Field Power Density Snf 16.0ηP/(πD2) 8.1643371 W/m 2 0.8164337 mW/cm2 Transition Region Power Density St SnfRnf/Rt Power density between the sub reflector and 2 main reflector Ssr 4P/Asr 5658.8424 W/m 565.88424 mW/cm2 Power density between 2 antenna and ground Sg P/A 3.2079605 W/m 0.3207961 mW/cm2


Document Created: 2018-04-06 11:43:27
Document Modified: 2018-04-06 11:43:27
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