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interference to satellite navigation receiver operation where
such receiver is operated on the same aircraft as the AES.
4.2.3.6 INTERMEDIATE GAIN ANTENNA
SUB-SYSTEMS
4.2.3.6.1 Gain-to-noise temperature ratio. Receiving
sub-systems employing intermediate gain antennas shall
achieve a gain-to-noise temperature ratio (Gm) of not less
than -19 dB/K over not less than 85 per cent of the reference
coverage volume defined in 4.2.3.1.1. The only exception
to this is the region greater than 70 degrees in elevation
from the horizontal plane where the GR shall be not less
than -21 dB/K.
4.2.3.6.2 Axial ratio. The axial ratio shall be less than
6 dB over 85 per cent of the reference coverage volume
referred to in 4.2.3.1.1 where the GIT must exceed -19 dB/K
or the AES antenna shall have sufficient gain to compensate
for the additional polarization loss in excess of that caused by
this axial ratio. The condition for including the compensation
shall assume the satellite axial ratio to be 2.5 dB, with the
major axes of the polarization ellipses orthogonal.
4.2.3.6.3 Recommendation.- The GJT should be not
less than -19 dB/K and the aria1 ratio shoiild be less than
6 dB over 100 per cent of the reference coverage volume.
4.2.3.6.4 Discrimination. The antenna gain pattern for
both transmit and receive functions shall discriminate by not
less than 7 dB between the directions of wanted and unwanted
satellites spaced 80 degrees or greater in longitude over not
less than 85 per cent of the reference coverage volume defined
in 4.2.3.1.1.
4.2.3.6.5 Recornmendation.- The antenna gain pattern
for bath transmit and ~ c e i vfeu nctions should discriminate by
not less than 7 dB between the directions of wanted and
unwanted satellites spaced 80 degrees or greater in longitude
over I00 per cetzt of the reference coverage volume defined
in 4.2.3.1.1.
4.2.3.6.6 Phase discontinuity. Beam steering transitions
between adjacent beam positions of a switched beam antenna
shall not cause RF phase transitions greater than 30 degrees in
the phase of the receive and transmit signal for 99 per cent of
all possible adjacent beam combinations.
4.2.3.6.7 Recommendation.- Beam steering transitions
between adjacent beam positions of a switched beam antenna
should not cause RF phase transitions ggreater than 30 degrees
in the received and transmitted signal for 100 per cent of all
possible adjacent beam combinations.
43 RF CHANNEL
CHARACTERISTICS
4.3.1 Modulation
4.3.1.1 Modulation for channel rates 2.4 kbits/s and
below. For channel rates of 2.4, 1.2 and 0.6 kbitsls, the
modulation shall be aviation binary phase shift keying
(A-BPSK).
4.3.1.2 Modulation for channel rates above 2.4 kbitds.
For channel rates above 2.4 kbitds the modulation shall be
aviation quadrature phase shift keying (A-QPSK).
4.3.2 Radiated power spectral density The following
bounds on radiated power spectral density shall apply in my
direction normalized to the peak spectral density in that
direction. The bounds shall apply to a single camer and shall
be centred at the camer frequency. The lower bound shall not
apply when the AES is transmitting the unmodulated preamble
at the beginning of a burst.
4.3.2.1 From-aircraft. The power spectrum radiated by the
AES shall fall within the mask defined by Table 4-5.
4.3.2.2 To-aircraft. The power spectrum received by the
AES shall be within the mask defined by Table 4-6 for
A-BPSK and, Table 4-7 and Table 4-7A for A-QPSK.
Annex 10 - Aeronautical Telecommunicatians Volume III
4.3.3 Dentodul~topr erfomnce. Where the channel rates
are implemented as defined in 4.1, the bit error rate. (BER)
performance of the channel demodulators after descrambling
shall be equal to or better than that shown in Table 4-8. This
performance shall be attained under the following conditions:
a) in the presence of two adjacent interfering carriers on
either side of the wanted carrier at a level of 5 dB higher
than the wanted carrier with a frequency uncertainty
from the nominal carrier spacing as specified and for the
AES demodulator, with the AES operating up to its
maximum allowable operating EIRP;
b) while receiving a signal tr<msmitted with the maximum
phase noise characteristics described in 4.2.3.5.9;
c) during 12" RF phase discontinuities occurring at the rate
of one per second; and
d) under Rician channel conditions for fading bandwidths
of 20, 60 and 100 Hz wilh a carrier to multipath ratio of
7 dB for systems using a low gain antenna or low and
high gain antennas: or 10 dB for systems using only a
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