Attachment radhazstudy2.doc

This document pretains to SES-LIC-20070403-00433 for License on a Satellite Earth Station filing.

IBFS_SESLIC2007040300433_558931

                                 RADIATION HAZARD STUDY

               Prepared by Paul T. Garrett, CBTE, Frontline Communications

This report is to analyze the non-ionizing radiation levels for a Transportable KU Uplink
utilizing an AvL Technologies Model 1200 1.2 meter Earth Station Antenna. The Office of
Science and Technology Bulletin, No. 65, August 1997, specified that the maximum level of
non-ionizing radiation that a person may be exposed to over a .1 hour (6 minute) period is an
average power density equal to 5mW/cm^2 (five milliwatt per centimeter squared). It is the
purpose of this report to ascertain the power flux densities of the earth station in the far field,
near field, transition region, the main reflector surface, and between the antenna edge and the
ground.

The following parameters were used to calculate the various power flux densities for the earth
station:

       Antenna Diameter, (D)                            = 1.2 meters

       Antenna Surface Area, (Sa)              = pi(D^2)/4      = 1.13097 m^2

       Wavelength at 14.25 Ghz, (lambda) = 0.021 meters

       Transmit Power at Flange, (P)                    = 100 watts

       Antenna Gain, (Ges)                     = 2.24 E+04

               Antenna gain at 14.25GHz = 43.5dBi, converted to a
               power ratio given by: Ges=10 ^ dBi/10

       pi                                      = 3.1415927

       Antenna Aperture Efficiency, (n)        = 0.65

       ANSI Safe Power Density, (Ws)           = 5.0mW/cm^2

1.     Far Field Calculations

       The distance to the beginning of the far field region can be found by the following
       equation:

       Distance to the Far Field Region, (Rf)           = (0.6(D^2))/lambda

                                               = 41.04 meters

       The maximum main beam power density in the far field can be calculated as follows:

       Far Field On-axis power density, (Wf)            = ((Ges)(P))/(4 pi (Rf^2))

                                            Παγε 1 οφ 4


                                          = 105.7731 W/m^2

                                          = 10.57731 mW/cm^2

2.   Near Field Calculations

     Power flux density is considered to be at a maximum value throughout the entire length
     of the defined region. The region is contained within a cylindrical volume having the
     same diameter as the antenna. Past the extent of the near field region, the power density
     decreased with distance from the transmitting antenna.

     The distance to the end of the near field can be determined by the following equation:

     Extent of Near Field, (Rn)           = D^2/4(lambda)

                                          = 17.1 meters

     The maximum power density in the near field is determined by:

     Near Field On-axis power density, (Wn)
                                         = (16(n)P)/(pi(D^2))

                                          = 229.8904 W/m^2

                                          = 22.98904 mW/cm^2

3.   Transition Region Calculations

     The transition region is located between the near and far field regions. As stated above,
     the power density begins to decrease with distance in the transition region. While the
     power density decreases inversely with distance in the transition region, the power
     density decreases inversely with the square of the distance in the far field region. The
     maximum power density in the transition region will not exceed that calculated for the
     near field region. The power density in the near field region, as shown above, will not
     exceed 22.98904 mW/cm^2.

4.   Far Field On-axis Distance to ANSI 5 mW/cm^2 Calculations - (Dsafe)

     Since the power density decreases inversely with the square of the distance in the far
     field region, the distance to the On-axis Power Density of 5 mW/cm^2 can be calculated
     from the following:

     (Dsafe)                              = Rf((Wf / Ws)^.5)

                                          = 59.69116 meters


                                        Παγε 2 οφ 4


5.   Main Reflector Region Calculations

     Transmissions from the feed horn are directed toward the main reflector surface. The
     power density in the main reflector region can be calculated by the following:

     Main Reflector Surface Power Density          = 2(P)/Sa

                                           = 353.6776 W/m^2

                                           = 35.36776 mW/cm^2

6.   Off-axis Evaluation

     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 (20dB)
     less than the value calculated for the equivalent distance in the main beam.

     Near Field On-axis power density,

                                    Wn     = 22.98904 mW/cm^2

     Near Field On-axis power density, 2.4 meters from main beam center

     Wn(off)                               = 0.01 Wn

                                           = 0.22989 mW/cm^2

     Therefore, the area around and behind the dish at a distance of one dish diameter (2.4
     meters) from the center of the main beam will be equal to or less than 0.22989
     mW/cm^2.

     For off-axis calculations in the far-field, the calculated main-beam power density of (Wf)
     can be multiplied by the appropriate relative power density factor obtained from the
     antenna gain pattern to obtain a more realistic estimate.

     The proposed antenna meets or exceeds the performance specifications under part 25.209
     of the FCC rules. The off-axis gain of this antenna, therefore, is equal to or greater than
     10dBi less than the on-axis gain in any direction of 48 degrees or more removed form the
     centerline of the main beam.

     Far Field On-axis power density

                                    Wf     = 10.57731 mW/cm^2

     Far Field Off-axis power density


                                         Παγε 3 οφ 4


       Wf(off)                               = .1 Wf

                                             = 1.057731 mW/cm^2

7.     Summary of Expected Radiation Levels

                                             Calculated Maximum
                                               Radiation Level
       Region                                   (mW/cm^2)                   Hazard Assessment

Far Field Region:     = 41.04 meters         10.5773148447227               Potential Hazard

Near Field Region:    = 17.1 meters          22.989047335496                Potential Hazard

Transition Region:                           22.989047335496                Potential Hazard

Reflector Surface Region:                    35.3677651315323               Potential Hazard

Far Field off-axis Region:                   1.05773148447227               Satisfies ANSI

Near Field off-axis Region:                  0.22989047335496               Satisfies ANSI

Area around dish equal to dish diameter:     0.22989047335496               Satisfies ANSI

8.     Conclusions

       Based on the above analysis it is concluded that the ANSI standards of 5 mW/cm^2 or
       greater would not exist in regions normally occupied by the public or the earth station’s
       operating personnel.

       In the area of the Main Reflector, personnel would only enter that area to perform
       maintenance functions and the transmitter would not be operational at that time, so the
       ANSI standard of 5 mW/cm^2 would be met.

       In the area of the Near Field and Transition Region, since the antenna is mounted at a
       height of 3 meters above the ground, and will not be pointed in the direction of populated
       areas, the ANSI standards would again be met. Warning signs are attached to the vehicle
       to warn individuals of the potential for hazardous radiation.

       Because this is a mobile unit and conditions vary from operating site to operating site,
       procedures have been established for the operational personnel to verify that the antenna
       is not pointing in the direction of populated areas.

       In addition, the transmit power used in these calculations is greater than that which will
       typically be utilized by the earth station. During normal operation, the typical power
       level would generally not be more than 50 watts. A transmit power of 100 watts would
       only occur in conditions of extreme rain fade.

                                           Παγε 4 οφ 4



Document Created: 2007-04-03 10:17:32
Document Modified: 2007-04-03 10:17:32

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