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system);
d) the noise contribution of the receiver low noise
amplifier at the operating temperature;
e) the transmitter power amplifier output level;
f) the attenuation and noise temperature contributions of
a radome, where a radome is fitted; and
g) the RF environmental conditions in which the aircraft
earth station is intended to operate.
2.4.2 Dpical link carrier to noise densities. Tables A-6,
A-7 and A-8 of this guidance material show typical carrier-tonoise
spectral density ratios (UN,'s) for the P, R, T and C
channel services. In these tables modem implementation losses
refer to losses in the practical implementation of a modem
relative to ideal. This includes the effects due to non-ideal
filtering, non-ideal synchronization in either time or frequency,
non-ideal modulation, and non-linearities in the up- and downAnnex
I0 - Aeronautical Telecommunications Volume ZIZ
converter chains. The analysis of the RF link is provided in
the appendix to this guidance material.
2.4.3 Receiver linearity. There are multiple satellite
systems being planned which have maximum L-band EIRP of
58 dBW at the centre of the antenna beam. Considering the
worst case where the antenna beams of two such satellite
systems overlap, the receiver must tolerate a total in-band
power flux density of -100 d ~ ~ / mT*hi.s is derived from the
combined two-satellite EIRP (62 dBW), minus a spreading
loss of 162 dB.
2.4.4 Receiver out-of-band pe@ormance. Potential threats
to receiver performance include terrestrial mobile communications
systems and high-power sources, including television
transmitters with EIRP in the megawatt range and surveillance
radars which are naturally located at airports and may occur
along the flight route.
2.4.4.1 Under radio environmental conditions where
high-power, out-of-band signals may be near the flight path,
the receiver's RF filter should protect against receiver
saturation, which could reduce gain and degrade performance.
Additionally, performance may be affected by such sources
due to receiver image and spurious responses. As an example,
a power flux density at the AES antenna of +3 d3W/m2 could
occur at a distance of a kilometre from a multi-megawatt
transmitter such as permitted for television at frequencies from
470 to near 800 MHz. To protect from saturation, the RF filter
would need a minimum of 75 dB rejection. Protection from
degradation due to image and spurious responses is specific to
the receiver design.
2.4.4.2 For a 5 000 kW peak power radar with a boresight
gain of 34 dB, power levels can reach I00 dBW in the
main beam. It has been calculated that, for an AES located
500 metres from an airport-located weather radar, the flux
density could be as high as 30 dI3w/m2 below 1 459 MHz,
and 38 dI3w/m2 from 1 675 to 18 000 MHz. It is not necessary
to operate under these levels, but the equipment should
survive without damage.
2.4.5 Received phase noise. The phase noise that the
AES receiver must tolerate while operating within the AMSS
SARPs is illustrated.in Figure A-1 * of this guidance material.
This mask includes phase noise contributions of the transmitter
and of the satellite. In practice, the receiver must be able to
tolerate larger amounts of phase noise that are due to fading
of the received signal.
T channels when the satellite elevation angle exceeds
5 degrees. An AES that is capable of an ElRP of 25.5 dBW,
and has the supporting avionics, will be capable of Level 2, 3
and 4 service grade portions of L.eve1s 3 and 4. In practice, the
transmitted power will usual.ly be backed off from these
settings, by an amount that depends on the system
configuration.
2.5.1.1 The "maximum allowable operating EIRP" is
based on a limit established from combined effects of HPA IM
(active) and passive-component IM.
2.5.2 EIRP control. The requirement for control for the
AES EIRP by the GES is for two reasons. The first reason is
for dynamic power control of the C channel to optimize the
system capacity. The secand is to make optima1 use of future
spot beam satellite systems.
2.5.2.1 In initial AMSS operations using satellites with
global beam coverage, an AES EIRP control range of 16 dB
is required for both Class C (Levels 1-3) and Class A (Level
4 multi-channel) high-power amplifiers to cover selectable
channel rates and variables in AES antenna gain. In C channel
operation the AES EIRP is also frequently adjusted according
to the GES-measured bit error rate. Therefore, for Level 4
AESs an additional 16 dB of control is presently required.
　
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