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be closely predetermined because spot beam size that affects
satellite Gm is a future operator design choice.
2.5.3 Our-of band ElRP spectral demity. The out-of-band
EIRP inchding discrete spurious, harmonics, intermodulation
products and noise radiated by the AES should not cause
harmful interference to other radio services. In parlicular, they
should not interfere with other aeronautical communicationd
navigation radio services such as global positioning system
(GPS) opewng in the band 1 559 to 1 585 MHz, global
orbiting navigation satellite system (GLONASS) operating in
the band 1 598 to 1 610 MHz (1 597 to 1 605 MHz after the
year 2005), the AMSS receive band 1 525 to 1 559 MHz, and
the VHF band 108 to 137 MHz. Intermodulation product levels
in the 1 598 to 1 610 MHz band should be checked when
satellite navigation receiver operation in this band is planned
on the same aircraft. Frequency management, additional
filtering or increased anterma separation (for greater than
40 dB isolation) may be required aboard the same aircraft if
interference potential to navigation equipment exists.
2.5.3.1 nble 4-3 contained in Annex 10, Volume III,
P~III, Chapter 4, provides for a maximum EIRP density of
-155 dBc/l MHz in the 1 559 to 1585 MHz band, which
protects GPS receiver operation on the same aircraft as
AMSS, and also GPS operation on nearby aircraft.
2.5.3.2 Tgble 4-3 contained in Annex 10, Volume IU, Patt I,
Chapter 4, also indicates that the maximum ElRP spectral
density shall be -143 W1 MHz in the 1585 to 1605 h5I-h
band and -117 &c/l MHz in the 1 605 to 1 610 MHz band.
These limits will prwide protection for GLONASS receiver
operation on the same aircraft as AMSS assuming a minimum
40 dB antenna isolation and on nearby aircraft. The 40 dB
isolation is measured from Ihe AMSS antenna poR to the
GLONASS antenna port at the GLONASS frequencies, with the
AMSS antenna steered for maximum coupling with the
GLONASS antenna This also holds for the GPS antenna
2.5.4 Intermodulation (IM)p roducts. Control of unwanted
emissions from the AES is important to system operations in
order to avoid blocking channels and reducing needed
spectrum. Intermodulation occurs during multicarrier (Level 4)
operation on predictable frequencies related to wanted signals
due to component non-linearities. Potential sources are many,
but can be controlled. Minimizing IM effects is accomplished
both in AES design for linearity meeting the standards and in
operation.
* All figures are locz$ed at the end of this attachment.
At&chnent A Lo Part I Annex 10 - AemnuulZcd Telecommufiications
2.5.4.1 Intermodulation products (IM) that may be
emitted by a Level 4 AES in multicarrier operation arise both
from the high-power amplifier (HPA) and from other passive
components that are subject to high AES RF power levels.
Passive components causing IM may include connectors,
particularly if they are subject to corrosion or looseness; and
the diodes used in phased-array antennas. Depending on the
choice of frequencies and levels in the GES, such IM can
appear at frequencies and levels in the AES receiver that will
degrade BER, disable reception, or affect reception of signals
by other aircraft equipment.
2.5.4.2 AES-transmitted IM can block GES receivers. The
HPA is a primary IM source because its linearity is limifd by
technology and heat dissipation.
2.5.4.3 Intersystem effects may arise from kvel 4 AESs
that may radiate IM. An AES operating with a global beam
satellite must transmit higher EIRP than an AES operating
with a more sensitive spot beam satellite. Therefore, this
higher level of IM would be more readily received by the spot
beam satellite for relay to its GES, where it cauld impair
reception of that channel. Even if the two satellites are using
separated portions of the frequency band and therefore cannot
reuse the same assigned channel frequencies, the global beam
AES transmitter's W1 that is out of assigned channels could
fall into the spot beam satellite's band. All GES frequency and
EIRP level assignments should account for this possibility.
2.5.4.4 Frequency management techniques are used to
eliminate 3rd and 5th order products below 1 610 MHz as
described in 4.2.3.5.7. If GLONASS is to be installed on the
same aircraft as AMSS, it may be necessary to employ
frequency management techniques or other methods to ensure
that AMSS 7th and higher order intermodulation products will
not cause harmful interference to GLONASS operations.
25.5 Frequency mrtagement. Careful frequency
management is needed because:
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