Environmental Assessment

0003-EX-PL-2007 Text Documents

CATERPILLAR, INC.

2007-01-12ELS_79265

                                                              Caterpillar, Inc.
                                                              File No. 0003-EX-PL-2007
                                                              FCC Form 442
                                                              Environmental Assessment
                                                              January 2007

Environmental Assessment
Electromagnetic Compatibility (EMC) immunity testing involves illuminating a device
under test (DUT) with an electromagnetic field of specified electric field strength.
Industry and internal standards for Caterpillar earthmoving equipment require testing of
electronic systems on machines at a field strength level of 100 V/m. Testing at this field
strength often requires transmitter power in excess of 100 watts. Since the testing done
under the terms of this experimental license is performed outdoors and not in a shielded
room, this environmental assessment is required for this experimental license according
to Table 2 of Appendix A of OET Bulletin 65.

Applicable Limits

The testing done under the terms of this license will be performed on Caterpillar property
where access is tightly controlled. Only company employees and authorized contractors
are allowed on the property. All personnel involved in EMC testing will receive training
in RF exposure safety. Access to the immediate testing area will be limited to those
personnel involved in testing. Therefore, the occupational/controlled maximum
permitted exposure (MPE) limits will apply.

Caterpillar’s experimental license authorizes transmissions in the frequency range of 20
MHz to 2 GHz. Therefore, the following MPE limits apply:

   •   From 20 MHz to 30 MHz, 824/f V/m (27.5 V/m at 30 MHz is lowest level)
   •   From 30 MHz to 300 MHz, 27.5 V/m
   •   From 300 MHz to 1500 MHz, f/1500 mW/cm2
   •   From 1500 MHz to 2000 MHz, 1 mw/cm2

While the dwell time on any given frequency is short, a full testing sweep may take more
than six minutes, so power averaging over time will not be used in these calculations.
Continuous exposure will be assumed, though it is recognized that this is a conservative
assumption and actual exposure will often be less than what is calculated.

Calculations by Frequency Range

20 MHz to 300 MHz

In this frequency range, the worst-case antenna that could be used for testing (from an RF
safety standpoint) is a biconical antenna, which, when vertically polarized, has an
omnidirectional azimuth radiation pattern. Since electric field strength decreases with the


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square of distance from the antenna, it is necessary for the antenna to be placed near the
device under test to generate the necessary field without excessive amounts of transmitter
power. A DUT to antenna distance of 1 meters is commonly used to generate a 100 V/m
field strength. Since the biconical antenna is omnidirectional, a 100 V/m field strength
exists at a 1 meter distance from the antenna in all directions. The equation for electric
field strength in terms of EIRP and distance is:

                                                   30 * Pt
                                     E (V / m) =
                                                     r2
Where:
               E = Electric Field Strength in volts per meter
               Pt = Transmitted EIRP in watts
               r = distance from the antenna in meters

We can calculate that in order to generate 100 V/m at a distance of 1 meter, 330 W of
EIRP is needed. We can then calculate that if 330 W of EIRP is radiating from the
antenna, the distance from the antenna to test personnel must be at least 3.6 meters in
order to for the electric field strength to be under the limit of 27.5 V/m.

300 MHz to 1500 MHz

In this frequency range a broadband log periodic antenna is normally used. These types
of antennas generally exhibit 3 dBi to 9 dBi of gain in the main lobe, depending on
frequency. The rear lobe generally exhibits –3 dBi to –15 dBi of gain, again dependant
on frequency. In some cases a broadband horn antenna may be used, in which case the
main lobe exhibits even more gain and the rear lobe even less. Calculations will show
that in all cases, the required distance from the transmitting antenna to personnel in order
to comply with the MPE limits is less than the 3.6 meters calculated in the previous
section.

1500 MHz to 2000 MHz

In this frequency range a broadband horn antenna is normally used. These types of
antennas generally exhibit significant gain in the main lobe, and significant negative gain
in the rear lobe (relative to an isotropic radiator). Calculations will show that in all cases,
the required distance from the transmitting antenna to personnel in order to comply with
the MPE limits is less than the 3.6 meters calculated in the previous sections.

Conclusions

This environmental assessment shows that if personnel are located at least 4 meters from
the transmitting antenna while the transmitter is operational, the FCC limits for maximum
permissible exposure will never be exceeded. With this in mind, the following RF safety
guidelines have been developed and will be enforced during all EMC immunity testing
performed under this license authorization.



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   1) At no time should personnel come between the transmitting antenna and the
      device under test while the transmitter is operational.
   2) If the transmitting antenna is directional, all personnel involved in testing should
      be located outside of the main lobe of the antenna when the transmitter is
      operational.
   3) All personnel should be located at least four meters away from the transmitting
      antenna when the transmitter is operational.

In addition, a portable electric field strength meter will be used to periodically check the
areas where personnel are located during testing to ensure that the maximum permissible
exposure limits are not exceeded.




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Appendix A – Maximum Calculated and Permissible Exposure

The following chart illustrates the maximum calculated exposure based on a distance of
four meters from the transmitting antenna and antennas that are commonly used for EMC
immunity testing. The chart also shows the FCC’s maximum permissible exposure limits
for reference. This chart assumes that a field strength level of 100 V/m is being
generated in the main lobe of the antenna at a distance of 1 meter, where the device under
test is located.


                                           Maximum Calculated and Permissible Exposure
                                         (for 100V/m field generated in main antenna lobe at 1 meter distance)


                                                                                                                          FCC Controlled
                                         100
         Electric Field Strength (V/m)




                                                                                                                          Exposure Limit
                                          90
                                          80                                                                              Maximum Field
                                          70                                                                              Strength at 4
                                                                                                                          Meters (Omni
                                          60               Assuming 0dB gain relative                                     Antenna)
                                                           to main lobe (omni)
                                          50                                                                              Maximum Field
                                                                                                                          Strength at 4
                                          40                                                Assuming -8dB gain in rear    Meters In Rear
                                                                                            lobe relative to main lobe    Lobe (Log
                                          30                                                                              Periodic)
                                                                                                                          Maximum Field
                                          20                                                                              Strength at 4
                                          10        Assuming -10 dB gain in rear                                          Meters in Rear
                                                    lobe relative to main lobe                                            Lobe(Horn)
                                           0
                                               10                    100                    1000                  10000
                                                                    Frequency (MHz)




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Document Created: 2007-01-12 17:11:21
Document Modified: 2007-01-12 17:11:21

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