3.0 COMMUNICATION PERFORMANCE SPECIFICATION
3.
Coverage
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Exhibit B
Figure B-1 shows four polygons that represent the areas to be covered; namely, mainland China, Thailand/Burma and Pakistan. Specifications of this coverage are listed in tables B-1, B-2, B-3, B-4, B-5, B-6, B-7, B-8, B-9, B-10, B-11 and B-12. Figures B-4, B-5, B-6, B-7, B-8, B-9, B-10, and B-11 show typical antenna patterns (inner-most of frequencies and modes) which represent design goals. These specifications are based, as indicated, on the spacecraft being located at 105.5° E Or 116° E. Performance variations due to yaw errors are based on atttitude corrections being made every three days and do not exceed ± 0.05 dB worst case from either orbit
location.
3.2 Communications Subsystem
The communications subsystem shall be designed to carry video, message and digital traffic using both single and multiple carriers per transponder. The following categories of multiplexing, modulation and multiple access shall be supported:
Digital
Video
Message
FM QPSK
FDM/FM/FDMA
FM
PCM/PSK/TDHA FM/TDKA
BPSK/QPSK/FSK
TDMA
3.2.1 Frequency Polarization and Zone Coverage Plan
The spacecraft shall include a communications subsystem (CSS) with the following characteristics. The CSS shall provide 24 channels in the 6/4 Gliz common carrier band according to the frequency and polarization plan shown in Figure B-2. Frequency interleaving and polarization discrimination utilized to maxmize isolation between channels.
are
Vertically polarized uplink signals for 12 of the 24 channels, originating from within the China coverage region, are retransmitted to the same region using the horizontal polarization as shown in Figure B-2.
for the
12 remaining
of
Horizontally polarized uplink signals 24 channels, originating from within the Thailand, Burma, Pakistan and long the same regions. the Kong coverage are (excepting Hong Kong) retransmitted to using the vertical polarization as shown in Figure B-2.
3.2.2 On-Board Protection
On-board protection of the receivers and THTAS shall be provided. Associated with each group of 12 vertically and 12 horizontally polarized transponder channels there shall be a fully redundant wideband receiver and a means of switching receivers between vertically and horizontally polarized groups so that any two receivers may fall without loss of operation of either group, as shown in Figure B-3.
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Associated with each group of 4 TWTAS; there shall be a fully redundant TWTA and the means of switching so that any one TWTA of a group of four may fail without loss of operation in any group. Each of the 30 TWTs shall be designed for long life and shall employ multiple collectors. The gun design of the TWIs shall be identical or superior to that of the Hughes 235 H TWI and the rest of the TWT design shall be like other recent Hughes C-band TWTs.
B-5