Attachment Exhibit C

This document pretains to SES-MOD-20150817-00526 for Modification on a Satellite Earth Station filing.

IBFS_SESMOD2015081700526_1099590

Exhibit'C')'Radiation'Hazard'Analysis! ' ' Fixed'Customer'Premises'Earth'Station'Terminal! 74'cm'Ka'band'Antenna! ! Introduction! ! This!analysis!calculates!the!non/ionizing!radiation!levels!for!a!ViaSat,!Inc.!(“ViaSat”)!fixed! customer!premises!earth!station!terminal!(“CP!terminal”).!The!calculations!performed!in!this! analysis!comply!with!the!methods!described!in!FCC!Office!of!Engineering!and!Technology! Bulletin,!Number!65!(Edition!97/01)!(“Bulletin!65”).!This!analysis!demonstrates!that!ViaSat! CP!terminals!are!compliant!and!will!not!result!in!exposure!levels!exceeding!the!applicable! radiation!hazard!limits.! ! Bulletin!65!and!section!1.1310!of!the!Commission's!rules!specify!two!separate!tiers!of! exposure!limits:!one!for!Occupational/Controlled!Exposures!and!one!for!General! Population/Uncontrolled!Exposures.!Limits!for!Occupational/Controlled!Exposures!apply!in! situations!when!persons!are!exposed!as!a!consequence!of!their!employment!and!are!fully! aware!of!and!can!control!their!exposure.!These!limits!also!apply!in!situations!when!a! person!is!transient!through!a!location!where!such!limits!would!otherwise!apply!provided!the! person!is!made!aware!of!the!potential!for!exposure.!The!limits!for!General! Population/Uncontrolled!Exposure!apply!in!situations!in!which!the!general!public!may!be! exposed,!or!in!which!persons!that!are!exposed!as!a!consequence!of!their!employment!may! not!be!fully!aware!of!the!potential!for!exposure!or!cannot!exercise!control!over!their! exposure.!ViaSat!will!typically!deploy!its!CP!terminals!in!General!Population/Uncontrolled! Environments.!Accordingly,!this!analysis!discusses!only!the!Maximum!Permissible! Exposure!(“MPE”)!limit!for!those!types!of!exposures,!which!is!a!power!density!equal!to!1! milliwatt!per!centimeter!squared!averaged!over!a!thirty!minute!period.! ! As!described!in!the!definitional!section!of!Appendix!A,!this!report!analyzes!the!maximum! power!density!levels!in!the!vicinity!of!a!CP!terminal!antenna!in!five!regions:!(1)!the!far!field,! (2)!the!near!field,!(3)!the!transition!region!between!near!field!and!far!field,!(4)!near!the!main! reflector!surface,!and!(5)!between!the!main!reflector!and!the!feed.!These!radiation!regions! were!analyzed!using!the!definitions!and!formulas!in!Bulletin!65!for!aperture!antennas.!The! results!of!this!analysis!are!summarized!in!Tables!1!and!2!in!Appendix!A,!which!identify!the! potential!exposure!under!nominal!operating!conditions!and!worst/case!conditions,! respectively.! ! CP'Terminal'Description! ! The!CP!terminal!transmits!bursts!of!information!at!designated!times!that!are!assigned!to! the!terminal!by!the!network.!The!length!and!carrier!frequency!of!each!transmission!burst! depend!on!the!CP!terminal's!mode!of!operation.!There!are!three!modes!of!operation!(a)! Idle!Mode,!during!which!the!CP!terminal!is!not!in!active!use^!(b)!Normal!Mode,!when!there! terminal!is!actively!used!under!typical!network!loading!conditions^!and!(c)!High!Capacity! Mode,!When!the!terminal!is!actively!used!under!maximum!uplink!data!transfer!conditions.! !

In!Idle!Mode,!the!CP!terminal!transmits!only!timing!and!system!information!to!the!network! for!0.4!milliseconds!every!640!ms!seconds.!The!average!duty!cycle!(ratio!of!transmitter!on! to!transmitter!off!time)!in!Idle!Mode!is!0.06%.!In!Normal!Mode,!the!CP!terminal!transmits! burst!traffic!to!the!network!with!a!nominal!duty!cycle!of!10%.!To!support!heavy!data!upload! requirements!such!as!file!transfer,!current!network!configuration!allows!CP!terminals!to! increase!their!transmit!duty!cycle!to!30%!in!High!Capacity!Mode.!! ! Table!1!provides!a!summary!of!the!radiation!exposure!analysis!for!each!of!the!three!ViaSat! operating!modes.! ! The!CP!terminal!uses!transmitter!power!control!system!to!reduce!uplink!interference!and! mitigate!the!effects!of!changing!atmospheric!conditions.!Under!clear!sky!and!cloudy! conditions,!all!74!cm!Ka!band!CP!terminals!will!transmit!at!a!nominal!power!level!of!2.8! watts!or!less.!This!includes!terminals!at!the!edge!of!beam!locations.!In!rainy!conditions,!a! CP!terminal!typically!adjusts!its!transmitted!symbol!rate,!modulation,!and!forward!error! correction!coding!to!maintain!a!robust!link,!but!transmit!power!is!not!increased!beyond!the! maximum!power!level!of!2.8!watts.!! ! The!CP!terminal!incorporates!two!“fail!safe”!features!that!limit!the!potential!for!human! exposure.!First,!the!transmitter!is!not!enabled!until!the!received!down!link!connection!to!the! satellite!has!been!established!and!an!acceptable!down!link!bit!error!rate!has!been! achieved.!The!transmitter!is!disabled!very!quickly,!in!less!than!40!milliseconds,!if!a!loss!of! down!connectivity!occurs.!Transmissions!will!not!resume!until!approximately!10!seconds! after!downlink!communications!have!been!reestablished.!!Secondly,!the!terminal's! transmitter!is!not!capable!of!operating!in!a!continuous!transmit!mode!of!operation.!The!CP! terminal's!outdoor!unit!incorporates!a!watchdog!timer!that!will!shut!down!the!transmitter!if!it! remains!in!a!continuous!transmit!state!for!more!than!10!seconds.!Under!these!conditions,! the!transmitter!will!be!turned!off!for!3!ms!then!resume!normal!operation!after!an!internal! reset!has!occurred.! ! Explanation'of'the'Analysis! ! The!“Calculated!Values”!!in!Table!1!are!the!exposure!rates!calculated!using!the!formula! from!the!Office!of!Engineering!and!Technology!Bulletin!Number!65!(Edition!97/01)!for!a! system!with!continuous!(100%!transmit!duty!cycle)!transmission.!The!ViaSat!network,! however,!is!based!on!so/called!“shared!pipes”.!ViaSat!terminals!transmit!short!bursts!of! data!periodically!as!instructed!by!the!network!and!are!neither!designed!for!nor!capable!of! continuous!transmission.!Therefore,!in!order!to!compute!the!effective!radiated!energy!of!a! ViaSat!CP!terminal,!the!terminals!transmitter!duty!cycle!has!been!used!to!adjust!the!values! calculated!from!Bulletin!Number!65.! ! The!columns!in!the!tables!labeled!“Idle!Mode,”!!“Normal!Mode,”!and!“High!Capacity!Mode”! reflect!the!total!potential!for!human!exposure!based!on!the!length!of!time!that!the!CP! terminal!transmits!energy!during!a!rolling!30!minute!period.!In!Idle!Mode,!the!maximum! transmitter!duty!cycle!is!0.06%!and!therefore!the!values!in!the!column!labeled!“Idle!Mode”! are!equal!to!the!calculated!values!multiplied!by!0.0006.!Similarly,!in!Normal!Mode!the! maximum!transmitter!duty!cycle!is!10%!and!the!values!in!the!column!labeled!“Normal! Mode”!are!equal!to!the!Calculated!Values!multiplied!by!0.1.!!And!finally,!in!High!Capacity!

Mode!the!transmitter!duty!cycle!is!30%!and!the!values!in!the!column!labeled!“High! Capacity!Mode”!are!equal!to!the!Calculated!Values!multiplied!by!0.3.! ! The!MPE!level!calculations!for!each!of!the!three!operating!modes!for!conditions!labeled! “Between!feed!and!reflector”!are!calculated!based!on!the!“fail!safe”!features!of!the!ViaSat! CP!Terminal.!When!the!receive!signal!is!lost!due!to!signal!blockage,!the!transmitter!is!shut! down!until!the!received!down!link!is!restored.!The!transmitter!is!shutdown!in!less!than!40! milliseconds!of!the!loss!of!the!downlink.!Since!the!areas!of!high!field!strength!near!the! reflector!and!the!feed!are!very!sensitive!to!blockage!of!the!down!link,!this!“fail!safe”!feature! minimizes!the!potential!for!human!exposure.!If!the!blockage!due!to!human!exposure!occurs! in!these!areas,!the!down!link!will!be!interrupted!causing!the!transmitter!to!turn!off!almost! immediately!and!it!will!remain!off!until!the!blockage!is!removed.!After!the!blockage!is! removed,!the!CP!terminal!will!have!to!reacquire!the!receive!downlink!and!wait!to!be!invited! back!into!the!network!before!the!transmitter!will!be!enabled.!The!complete!downlink! recovery!time!is!10!seconds.!The!values!in!the!column!labeled!“Idle”,!“Normal”,!and!“Worst! Case”!are!multiplied!by!0.004!because!the!transmitter!can!not!transmit!more!than!0.4%!of! any!rolling!30!minute!period!with!significant!blockage!near!the!sub!reflector!and!between! the!sub/reflector!and!the!feed.! ! Results'of'Analysis! ! This!analysis!demonstrates!that!this!terminal!is!not!a!radiation!hazard!because!the!terminal! does!not!exceed!the!MPE!limit!of!1!milliwatt!per!centimeter!squared!averaged!over!a!thirty! minute!period.!As!demonstrated!in!Tables!1!and!2,!the!areas!with!the!greatest!field! concentrations!is!between!the!feed!and!the!reflector!surface.!The!areas!in!which!these!high! field!concentrations!exist!are!very!small!in!size,!which!limits!the!risk!of!human!exposure!to! a!person's!hands!or!arms.!If!the!down!link!(receive!signal)!is!interrupted!by!an!object!in!an! area!of!high!field!concentration,!the!uplink!(transmit!signal)!is!shut!down!in!less!than!40! milliseconds!and!the!receiver!down!link!recovery!time!is!10!seconds.!The!uplink!will!remain! off!until!the!blockage!is!removed!and!the!downlink!recovery!is!complete.!This!feature,! coupled!with!the!terminal's!use!of!uplink!power!control!and!non/continuous!operation,! ensures!that!the!general!population!will!not!be!exposed!to!harmful!levels!of!radiation.! ! Conclusion! ! This!radiation!hazard!analysis!demonstrates!that!these!CP!terminals!will!not!result!in! exposure!levels!exceeding!the!applicable!radiation!hazard!limits.

Definitions! ! 1) Far Field Region ! The far field region extends outward from the mail reflector, beginning at a distance of 2 0.6 ⋅ Dmaj meters where the larger diameter of the elliptical antenna is Dmaj. The maximum power λ density is calculated using the equation recommended in Bulletin 65.! ! 2) Near Field Region! ! The near field region is an elliptical volume co-incident with the boresight of the main beam 2 D maj extending outward from the main reflector the length of the near field meters. The larger 4⋅ λ dimension (Dmaj) of the elliptical antenna is used in place of the diameter of a circular antenna to calculate the worst case length of the near field.! ! 3) Transition Region! ! The transition region is located between the near field region and the far field region. This region has a power density that decreases inversely with increasing distance. Therefore the power density in the transition region will be less than the power density in the near field for the purpose of evaluating potential exposure.! ! 4) Region Near the Main Reflector Surface! ! The power density near the main reflector surface can be estimated as equal to four times the the power divided by the area of the main reflector surface, assuming that the illumination is uniform and that it would be possible to intercept equal amounts of energy radiating towards and reflected from the antenna surface.! ! 5) Region between the Main Reflector and the Feed! ! The power radiated from the feed toward the reflector is conical in shape with the vertex at the feed. The maximum power is at the feed mouth and can be estimated as four times the transmit power divided by the area of the feed mouth. ! ! ! !

Table 1: Radiation from 74 cm Ka Band Fixed Terminal Parameters Antenns Apertre MajeAxis: Bay» $3en Antenns Apertre MinorAxis Dus— 839cn Diamate o Feed Mouth Py = $46t.em Frequency of Operation Feees Max Pover intoAnterna ho ae w Aperture Eficincy 4 —os3s Calculated Wamtergth A=03tm Aea of Refector Any ~0453n° Are of Feed Mouth: Aug — 8080 m Antemns Gain c=asncrnt 10—log(@) = 455. d6i Length of Near Fld Ry — 20389m Beginning of Far Fild Ap — 8 950m

Ide Mode Normal Mode High Capacty Mode mw 5 oom» 002 20— m 5y tss ooae 22 sox » o mw 1012 :09 2 Ir 3 Ite Mode Normal Mode High Capacty Mode soom » 0000250: syons 0sn 28.: s aon e oare 2: en en en Transtion Region: Powerdensit is less than the maximum near fld region power densty and areaterthan the mnimurm for fld region power densiy: Main Refector Ite Mode Normal Mode Figh Capacty Mode se=£2 a» mw nane 0M 5 amee on99 m 5on onMJ mw Feed Mou ie Mode Normat High Capecty Mode Mode Ske= Zn 42 mw m mw s,.. o ooaiss = 0 0174 5,,,0 0t = 01925 5,,,.0 1205 = 057. 28


Document Created: 1170-05-04 00:00:00
Document Modified: 1170-05-04 00:00:00
© 2024 FCC.report
This site is not affiliated with or endorsed by the FCC