MIL-STD-188-164 Interoperability Of Shf Satellite Communications TerminalsThis standard establishes mandatory Radio Frequency/Intermediate Frequency RF/IF and associated interface requirements applicable to Satellite Communications SATCOM Earth Terminals ET operating over military X-band and Ka-band Super High Frequency SHF channels. Military unique requirements for ET that may operate over commercial C-band, Ku-band, and Ka-band are included. Equipment developers may exceed the requirements herein to satisfy specific program requirements, provided that interoperability is maintained. Thus, incorporating additional standard and nonstandard capabilities and interfaces is not precluded. Existing SHF SATCOM terminals need not conform to this MIL-STD unless they undergo a modernization program.

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MIL-STD-188-164B

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is attenuation (dB).

   is uplink pointing error (degrees).

is 3 dB beamwidth (degrees).

For example:  If the uplink beam is offset 0.01 degrees from alignment, then for a 38-foot (11.5824 meter) antenna at 8.4 GHz

with    at 0.219089023 degrees, the attenuation is 0.025 dB.  If because of pointing errors, the uplink beam is now offset by

0.03 degrees, the attenuation is 0.225 dB.  Thus, if the control

system changes the pointing error from 0.01 degrees to 0.03 degrees, the EIRP will change by 0.2 dB.  It is this change that

must be accounted for in the RSS equation.

It is important to note that satellite motion can also impact this loss.  Terminal design must account for EIRP errors due to satellite motion regardless of whether the terminal has a pointing control system or not.

6.9 Accounting for pointing loss differences between uplink and downlink beams.  Since the beamwidth is a function of the frequency used, and because pointing loss is determined by measuring variations in the downlink satellite beacon, the

actual uplink loss will differ from the downlink loss.  At X-

band frequencies, the frequency separation is relatively small and the difference between uplink and downlink pointing losses is negligible.  However, at Ka-band frequencies, the 10 GHz separation between uplink and downlink can cause significant differences.  For the purposes of EIRP stability, the uplink pointing loss will be greater than the downlink pointing loss

and will therefore be used in the RSS equation in 4.2.4.  Unless

otherwise specified, the equation for calculating the uplink pointing loss based on the measured downlink loss is as follows:

   = pointing loss on the uplink at the given frequency in dB

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