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A-7 and A-8 of this guidance material show typical carrier-tonoise
spectral density ratios (C/No's) for the P, R, T and C
channel sewices. 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 downconverter
chains. The analysis of the RF link is provided in the
appendix to thls 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 ~ ~ /Tmhis ~is d.er ived from the
combid two-satellite EIRP (62 dBW), minus a spreading
loss of 162 dB.
2.4.4 Receiver our-of-band p e ~ o m n c eP.o tential 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 mute.
tllyoo
No. 75
An #:ex 10 - Aero~autical.Telecommunic&ns Volume ZII
2.4.4.1 Under radio environmental conditions where highpower,
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 dIlw/rn2 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 teach 100 dBW in the main
beam. It has been calculated that, for an AES located
500 metres from an airport-located weather radat, the flux
density could be as high as 30 d ~ ~be/lowm 1 4~59 M Hz, and
38 d ~ ~ / r fnro*m 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 he AES
receiver must tolerate while operating within the AMSS
SARPs is illustrated in Figure A- I* of this guidance materid.
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.
2.5 bnsmit&r requirements
2.5.1 EIRP limits. An AES that is capable of an EIRP of
13.5 dBW should always be able to use the 0.6 kbit/s R and T
channels when the satellite elevation angle exceeds 5 degrees.
An AES that is capable of an EIRP of 25.5 dBW, and has the
supporting avionics, will be capable of Level 2,3 and 4 service
grade portions of Levels 3 and 4. In practice, the transmitted
power will usually be backed off from these settings, by anamount
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 ElRP contml. The requirement for control for the
AES ElRP 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 second is to make optimal use of fumre
spot beam satellite systems.
2.5.2.1 In initial AMSS operations using satellites with
global beam coverage, an AES ELRP 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 ETRP 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.
2.5.2.2 In future systems, AES transmission within an
ElRP range satisfactory to satellite service operatow may
require a different control range. For example, the higher G/T
of future spot beam satellites could require less AES EIRP,
leading to a need for a larger cmtml range. The range cannot
　
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