signal strength calcualtion

0254-EX-PL-2006 Text Documents

Orbital Sciences Corporation

2006-10-20ELS_78454

GPS Booster Station Signal Strength Calculation

Reference file # 0254-EX-PL-2006

This GPS booster station re-radiates the GPS L1 (1575.42 MHz) signal. Calculations are performed per
Section 8.3.28 of the NTIA regulations, where item 7 states “the maximum equivalent isotropically
radiated power must be such that the calculated emissions are no greater than -140 dBm/24 MHz at a
distance of 100 feet (30 meters) from the building where the test is being conducted.” Additionally,
building attenuation has been ignored. This calculation shows that the re-radiated signal strength is in
compliance with the regulation.

(1) Psig = PRec + Grant + Gamp - L1 + GLa + Grrant + LS

Where: Psig = Re-radiated signal strength 30 meters (m) outside the building
PRec = Received power from GPS satellites (L1) = -130 dBm
Grant = Roof active antenna, Antcom PN: 3G15A-XN-1, antenna gain = 5.4 dBi
Gamp = Roof active antenna amplifier gain = 33 dB
L1 = Coaxial cable attenuation, roof antenna to line amplifier
= 32.4 dB/100 m x 0.155 (15.5 m cable length, PN: LMR-240)
= 5.0 dB
GLa = Line amplifier, GPS Source PN: A11, gain = 15 dB
Grrant = Re-radiating antenna, Antcom PN: 2G15P-XS-1, gain = 5.0 dBi
LS = Free space loss

(2) LS = 20Log(λ/4π(D))

Where: λ = c/f = 3E8/1575.42E6 = 19.04E-2 m
D = Distance (d) from antenna to outer wall in meters + 30
= 15.2 m + 30
= 45.2 m

Inserting the values for λ and D into equation (2) yields

LS = 20Log(19.04E-2/4π(45.2))
= -69.5 dB

Inserting these values into equation (1) yields

Psig = -130 + 5.4 + 33 - 5.0 + 15 + 5.0 - 69.5
= -146.1 dBm

Roof Active Antenna

Roof Active Antenna
Low Noise Amplifier

Coaxial Cable

Line Amplifier Re-radiating
Antenna

d

Document Created: 2006-10-20 19:45:30
Document Modified: 2006-10-20 19:45:30

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