Attachment RadHaz

This document pretains to SES-LIC-20131114-00983 for License on a Satellite Earth Station filing.

IBFS_SESLIC2013111400983_1020479

                                   Radiation Hazard Analysis
                                         KVH Industries
                                         Middletown, RI


This analysis predicts the radiation levels around a proposed earth station complex, comprised of
one (reflector) type antennas. This report is developed in accordance with the prediction methods
contained in OET Bulletin No. 65, Evaluating Compliance with FCC Guidelines for Human
Exposure to Radio Frequency Electromagnetic Fields, Edition 97-01, pp 26-30. The maximum
level of non-ionizing radiation to which employees may be exposed is limited to a power density
level of 5 milliwatts per square centimeter (5 mW/cm2) averaged over any 6 minute period in a
controlled environment and the maximum level of non-ionizing radiation to which the general
public is exposed is limited to a power density level of 1 milliwatt per square centimeter (1
mW/cm2) averaged over any 30 minute period in a uncontrolled environment. Note that the
worst-case radiation hazards exist along the beam axis. Under normal circumstances, it is highly
unlikely that the antenna axis will be aligned with any occupied area since that would represent a
blockage to the desired signals, thus rendering the link unusable.

Earth Station Technical Parameter Table
Antenna Actual Diameter               1 meters
Antenna Surface Area                  0.8 sq. meters
Antenna Isotropic Gain                34.5 dBi
Number of Identical Adjacent Antennas 1
Nominal Antenna Efficiency (ε)        67.50%
Nominal Frequency                     6.138 GHz
Nominal Wavelength (λ)                0.0489 meters
Maximum Transmit Power / Carrier      22.0 Watts
Number of Carriers                    1
Total Transmit Power                  22.0 Watts
W/G Loss from Transmitter to Feed     1.0 dB
Total Feed Input Power                17.48 Watts
Near Field Limit                      Rnf = D²/4λ =5.12 meters
Far Field Limit                       Rff = 0.6 D²/λ = 12.28 meters
Transition Region                     Rnf to Rff

In the following sections, the power density in the above regions, as well as other critically
important areas will be calculated and evaluated. The calculations are done in the order discussed
in OET Bulletin 65.

1.0 At the Antenna Surface

The power density at the reflector surface can be calculated from the expression:

 PDrefl = 4P/A = 8.902 mW/cm² (1)
 Where: P = total power at feed, milliwatts
          A = Total area of reflector, sq. cm

In the normal range of transmit powers for satellite antennas, the power densities at or around the
reflector surface is expected to exceed safe levels. This area will not be accessible to the general
public. Operators and technicians should receive training specifying this area as a high exposure


                                                                                                   1


area. Procedures must be established that will assure that all transmitters are rerouted or turned
off before access by maintenance personnel to this area is possible.

2.0 On-Axis Near Field Region

The geometrical limits of the radiated power in the near field approximate a cylindrical volume
with a diameter equal to that of the antenna. In the near field, the power density is neither uniform
nor does its value vary uniformly with distance from the antenna. For the purpose of considering
radiation hazard it is assumed that the on-axis flux density is at its maximum value throughout the
length of this region. The length of this region, i.e., the distance from the antenna to the end of the
near field, is computed as Rnf above.

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

 PDnf = (16ε P)/(π D²) =     6.009 mW/cm² (2)
                             from 0 to 5.12 meters
Evaluation
 Uncontrolled Environment:        Does Not Meet Uncontrolled Limits
 Controlled Environment:          Does not Meet Controlled Limits

3.0 On-Axis Transition Region

The transition region is located between the near and far field regions. As stated in Bulletin 65,
the power density begins to vary inversely with distance in the transition region. The maximum
power density in the transition region will not exceed that calculated for the near field region, and
the transition region begins at that value. The maximum value for a given distance within the
transition region may be computed for the point of interest according to:

 PDt =       (PDnf)(Rnf)/R = dependent on R (3)
 where:      PDnf = near field power density
             Rnf = near field distance
             R = distance to point of interest
 For:        5.12 < R < 12.3 meters

We use Eq (3) to determine the safe on-axis distances required for the two occupancy conditions:

Evaluation

 Uncontrolled Environment Safe Operating Distance,(meters), Rsafeu:          30.7
 Controlled Environment Safe Operating Distance,(meters), Rsafec:            6.1

4.0 On-Axis Far-Field Region

The on- axis power density in the far field region (PDff) varies inversely with the square of the
distance as follows:

 PDff = PG/(4πR²) = dependent on R (4)
 where: P = total power at feed
        G = Numeric Antenna gain in the direction of interest relative to isotropic radiator



                                                                                                     2


         R = distance to the point of interest
 For:    R > Rff = 12.3 meters
         PDff = 2.574 mW/cm² at Rff

We use Eq (4) to determine the safe on-axis distances required for the two occupancy conditions:

Evaluation

 Uncontrolled Environment Safe Operating Distance,(meters), Rsafeu :        See Section 3
 Controlled Environment Safe Operating Distance,(meters), Rsafec :          See Section 3

5.0 Off-Axis Levels at the FarField Limit and Beyond

In the far field region, the power is distributed in a pattern of maxima and minima (sidelobes) as a
function of the off-axis angle between the antenna center line and the point of interest. Off-axis
power density in the far field can be estimated using the antenna radiation patterns prescribed for
the antenna in use. Usually this will correspond to the antenna gain pattern envelope defined by
the FCC or the ITU, which takes the form of:

 Goff = 32 - 25log(Θ)
 for Θ from 1 to 48 degrees; -10 dBi from 48 to 180 degrees
 (Applicable for commonly used satellite transmit antennas)

Considering that satellite antenna beams are aimed skyward, power density in the far field will
usually not be a problem except at low look angles. In these cases, the off axis gain reduction may
be used to further reduce the power density levels.

For example: At one (1) degree off axis At the far-field limit, we can calculate the power density
as:

Goff = 32 - 25log(1) = 32 - 0 dBi = 1585 numeric

 PD1 deg off-axis = PDffx 1585/G = 1.4629 mW/cm² (5)

6.0 Off-Axis power density in the Near Field and Transitional Regions

According to Bulletin 65, off-axis calculations in the near field may be performed as follows:
assuming that the point of interest is at least one antenna diameter removed from the center of the
main beam, the power density at that point is at least a factor of 100 (20 dB) less than the value
calculated for the equivalent on-axis power density in the main beam. Therefore, for regions at
least D meters away from the center line of the dish, whether behind, below, or in front under of
the antenna's main beam, the power density exposure is at least 20 dB below the main beam level
as follows:

 PDnf(off-axis) = PDnf /100 = 0.06009 mW/cm² at D off axis (6)

See Section 8 for the calculation of the distance vs. elevation angle required to achieve this rule
for a given object height.




                                                                                                      3


7.0 Region Between the Feed Horn and Sub-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 energy between the feed horn and
subreflector is conceded to be in excess of any limits for maximum permissible exposure. This
area will not be accessible to the general public. Operators and technicians should receive training
specifying this area as a high exposure area. Procedures must be established that will assure that
all transmitters are rerouted or turned off before access by maintenance personnel to this area is
possible.

8.0 Evaluation of Safe Occupancy Area in Front of Antenna

The distance (S) from a vertical axis passing through the dish center to a safe off axis location in
front of the antenna can be determined based on the dish diameter rule (Item 6.0). Assuming a flat
terrain in front of the antenna, the relationship is:

 S = (D/ sin α) + (2h - D - 2)/(2 tan α) (7)
 Where: α = minimum elevation angle of antenna
         D = dish diameter in meters
         h = maximum height of object to be cleared, meters

For distances equal or greater than determined by equation (7), the radiation hazard will be below
safe levels for all but the most powerful stations (> 4 kilowatts RF at the feed).

   For         D=            1 meters
               h=            2.0 meters
   Then:
               α             S
               23            3.7 meters
               25            3.4meters
               30            2.9 meters
               35            2.5 meters
               40            2.2 meters


Suitable fencing or other barrier should be provided to prevent casual occupancy of the area in
front of the antenna within the limits prescribed above at the lowest elevation angle required.

Summary

The earth station site will be protected from uncontrolled access with suitable fencing and other
barrier walls. There will also be proper emission warning signs placed and all operating
personnel will be aware of the human exposure levels at and around the earth station. The
applicant agrees to abide by the conditions specified in Condition 5208 provided below:


         Condition 5208 - The licensee shall take all necessary measures to ensure that the
         antenna does not create potential exposure of humans to radiofrequency radiation
         in excess of the FCC exposure limits defined in 47 CFR 1.1307(b) and 1.1310
         wherever such exposures might occur. Measures must be taken to ensure


                                                                                                    4


        compliance with limits for both occupational/controlled exposure and for general
        population/uncontrolled exposure, as defined in these rule sections. Compliance
        can be accomplished in most cases by appropriate restrictions such as fencing.
        Requirements for restrictions can be determined by predictions based on
        calculations, modeling or by field measurements. The FCC's OET Bulletin 65
        (available on-line at www.fcc.gov/oet/rfsafety) provides information on predicting
        exposure levels and on methods for ensuring compliance, including the use of
        warning and alerting signs and protective equipment for worker.

The following table summarizes all of the above calculations:




                                                                                        5


Table 3 Summary of All RadHaz Parameters                                                  Middletown, RI
Parameter                              Abbr.                               Units          Formula
Dish #                                                              Hub
Antenna Diameter                       Df                              1   meters
Antenna Centerline                     h                             2.0   meters
                                                                                   2              2
Antenna Surface Area                          Sa                     0.8   meters         (π * Df )/ 4
Antenna Ground Elevation                      GE                    38.0   meters
Frequency of Operation                        f                   6.138     GHz
Wavelength                                    λ                  0.0489    meters         c/f
HPA Output Power                              PHPA                  22.0    watts
HPA to Antenna Loss                           Ltx                    1.0    dB
Transmit Power at Flange                      P                    12.4    dBW            10 * Log(PHPA) - Ltx
                                                                  17.48    watts
Antenna Gain                                  Ges                  34.5     dBi
                                                                 2788.8     n/a
PI                                            π              3.1415927      n/a
Antenna Aperture Efficiency                   η                 67.50%      n/a           Ges / (PI * Df /λ)2
1. Reflector Surface Region Calculations
Reflector Surface Power Density               PDas                89.02    W/m2           (16 * P)/(π * D2 )
                                                                                      2
                                                                  8.902 mW/cm             Does Not Meet Uncontrolled Limits
                                                                                          Does not Meet Controlled Limits
2. On-Axis Near Field Calculations
Extent of Near Field                          Rn                   5.12    meters         D2 / (4 *λ)
                                                                  16.78     feet
Near Field Power Density                      PDnf                60.09    W/m2           (16 * η * P )/ (π *D2 )
                                                                                      2
                                                                  6.009 mW/cm             Does Not Meet Uncontrolled Limits
                                                                                          Does not Meet Controlled Limits
3. On-Axis Transition Region Calculations
Extent of Transition Region (min)             Rtr                  5.12    meters         D2 / (4 *λ)
Extent of Transition Region (min)                                 16.78     feet
Extent of Transition Region (max)             Rtr                 12.28    meters         (0.6 * D2 ) /λ
Extent of Transition Region (max)                                 40.27     feet
Worst Case Transition Region Power Density PDtr                   60.09    W/m2           (16 *η * P)/ (π * D2 )
                                                                                      2
                                                                  6.009 mW/cm             Does Not Meet Uncontrolled Limits
                                                                                          Does not Meet Controlled Limits
                                               Rsu
Uncontrolled Environment Safe Operating Distance                    30.7     m            =(PDnf)*(Rnf)/Rsu
Controlled Environment Safe Operating Distance Rsc                   6.1     m            =(PDnf)*(Rnf)/Rsc
4. On-Axis Far Field Calculations
                                                                                                   2
Distance to the Far Field Region              Rf                   12.3    meters         (0.6 * D ) /λ
                                                                  40.27     feet
On-Axis Power Density in the Far Field        PDff                25.74    W/m2(Ges * P) / (4 * π * Rf2 )
                                                                             2
                                                                  2.574 mW/cm Does Not Meet Uncontrolled Limits
                                                                               Meets Controlled Limits
5. Off-Axis Levels at the Far Field Limit and Beyond
                                                                                  2                              2
Reflector Surface Power Density               PDs                14.629    W/m            (Ges * P) / (4 * π * Rf )*(Goa/Ges)
Goa/Ges at example angle θ 1 degree                               0.568                   Goa = 32 - 25*log(θ)
                                                                                      2
                                                                1.4629 mW/cm Meets Controlled Limits
6. Off-axis Power Density in the Near Field and Transitional Regions Calculations
                                                                             2                          2
Power density 1/100 of Wn for one diameter PDs                 0.6009 W/m        ((16 * η * P )/ (π *D ))/100
removed                                                                        2
                                                              0.06009 mW/cm Meets Uncontrolled Limits
8. Off-Axis Safe Distances from Earth Station                                    S = (D/ sin α) + (2h - D - 2)/(2 tan α)
α = minimum elevation angle of antenna                              23   deg
h = maximum height of object to be cleared, meters                 2.0    m
GD = Ground Elevation Delta antenna-obstacle                       0.0    m
elevation angle                                    23              3.7    m
                                                   25              3.4    m
                                                   30              2.9    m
                                                   35              2.5    m
                                                   40              2.2    m

Note: Maximum FCC power density limits for 6 GHz is 1 mW/cm2 for general population/uncontrolled exposure as per
FCC OE&T Bulletin No. 65, Edition 97-01 August 1997, Appendix A page 67.



                                                                                                                                6



Document Created: 2013-11-08 16:25:47
Document Modified: 2013-11-08 16:25:47

© 2024 FCC.report
This site is not affiliated with or endorsed by the FCC