Radiation Hazard Analysis

0451-EX-PL-2010 Text Documents

ViaSat, Inc.

2010-09-23ELS_110413

EXHIBIT B RADIATION HAZARD ANALYSIS AND REPORT

This exhibit contains a report of the analysis of the radio frequency (RF) hazard present during the operation of the SurfBeam® 2 terminal. The SurfBeam 2 antenna is a 77 x 72 cm reflector utilizing a watt power amplifier producing a nominal 3 W output at the 1 dB gain compression point. Note that while for the purposes of this radiation hazard analysis the full 3 watt power output of the transmitter has been considered, in practice when transmitting, the antenna will operate in a burst mode with a duty cycle typically less than 10% and several dB less than the maximum P1dB point.

Summary of expected radiation levels for an Uncontrolled environment Region Maximum Power Density Hazard Assessment Far field (Rff) = 42.652 m 0.464 mW/cm2 Satisfies FCC MPE Near field (Rnf) = 17.652 m 1.083 mW/cm2 Potential Hazard Transition region (Rt) (Rt) = Rnf < Rt < Rff 1.083 mW/cm2 Potential Hazard Main Reflector Surface (Ssurface) 2.165 mW/cm2 Potential Hazard Summary of expected radiation levels for a Controlled environment Region Maximum Power Density Hazard Assessment Far field (Rff) = 42.652 m 0.464 mW/cm2 Satisfies FCC MPE Near field (Rnf) = 17.652 m 1.083 mW/cm2 Satisfies FCC MPE Transition region (Rt) (Rt) = Rnf < Rt < Rff 1.083 mW/cm2 Satisfies FCC MPE Main Reflector Surface (Ssurface) 2.165 mW/cm2 Satisfies FCC MPE Conclusions During the test period, the terminals will be located in a controlled environment not accessible to the general public and will only be operated/serviced by trained personnel. Power to the antennas will be removed prior to servicing. Based on the above analysis it is concluded that harmful radiation levels will not be present during servicing, nor will harmful levels exist in regions normally occupied by the public.

Analysis of Non-Ionizing Radiation for a 77 cm x 72 cm Earth Station System This report analyzes the non-ionizing radiation levels for a 77 cm x 72 cm earth station system. The analysis and calculations performed in this report are in compliance with the methods described in the FCC Office of Engineering and Technology Bulletin No. 65. Bulletin No. 65 specifies that there are two separate tiers of exposure limits that are dependant upon the situation in which the exposure takes place and/or the status of the individuals who are subject to the exposure. The two tiers are General Population / Uncontrolled environment, and an Occupational / Controlled environment. The applicable exposure limit for the General Population / Uncontrolled environment at this frequency of operation is 1 mW/cm^2. The applicable exposure limit for the Occupational / Controlled environment at this frequency of operation is 5 mW/cm^2. Definition of terms The terms are used in the formulas here are defined as follows: Ssurface = maximum power density at the antenna surface Snf = maximum near-field power density St = power density in the transition region Sff = power density (on axis) Rnf = extent of near-field Rff = distance to the beginning of the far-field R = distance to point of interest P=3W power fed to the antenna in Watts A = 0.554 m2 physical area of the aperture antenna 4 G = 3.487 x 10 power gain relative to an isotropic radiator D = 0.84 m effective diameter of antenna in meters F = 30 GHz frequency in GHz  = 0.01 m wavelength in meters (300/FMHz)  = 0.55 aperture efficiency

Antenna Surface. The maximum power density directly in front of an antenna (e.g., at the antenna surface) can be approximated by the following equation: Ssurface = (4 * P) / A = (4 * 3) / 0.554 m2 = 2.165 mW/cm2 Near Field Region. In the near-field or Fresnel region, of the main beam, the power density can reach a maximum before it begins to decrease with distance. The extent of the near field can be described by the following equation (D and  in same units): Rnf = D2 / (4 * ) = 0.842 / (4 * 0.01) = 17.652 m The magnitude of the on-axis (main beam) power density varies according to location in the near field. However, the maximum value of the near-field, on-axis, power density can be expressed by the following equation: Snf = (16 *  * P) / ( * D2) = (16 * 0.55 * 3) / ( * 0.842) = 1.083 mW/cm2 Far-Field Region. The power density in the far-field or Fraunhofer region of the antenna pattern decreases inversely as the square of the distance. The distance to the start of the far field can be calculated by the following equation: Rff = (0.6 * D2) /  = (0.6 * 0.842) / 0.01 = 42.365 m The power density at the start of the far-field region of the radiation pattern can be estimated by the equation: Sff = (P * G) / (4 *  * Rff2)

= (3 * 3.487 x 104) / (4 *  * 42.3652) = 0.464 mW/cm2 Transition Region. Power density in the transition region decreases inversely with distance from the antenna, while power density in the far field (Fraunhofer region) of the antenna decreases inversely with the square of the distance. The transition region will then be the region extending from Rnf to Rff. If the location of interest falls within this transition region, the on-axis power density can be determined from the following equation: St = (Snf * Rnf) / R = (1.083 * 17.652) / R = (19.112 m * mW/cm2) / R where R is the location of interest in meters


Document Created: 2010-09-23 16:47:47
Document Modified: 2010-09-23 16:47:47
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