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NEXT GENERATION BROADBAND SATELLITE COMMUNICATION SYSTEMS .pdf

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					                 NEXT GENERATION BROADBAND SATELLITE COMMUNICATION SYSTEMS
                    Satchandi Verma, SMIEEE, Senior Staff, Eric Wiswell, MIEEE, Technical Fellow
                                                    TRW Inc.
                                                 One Space Park
                                           Redondo Beach, CA 90278
                                                  310-812-1742
                                            satchandi.verma@trw.com

                         ABSTRACT                                      •    Larger satellite capacity (higher link frequencies with
                                                                            frequency reuse)
     For next generation satellite systems to provide cost
                                                                       • Onboard Processing Payloads (Analog and Digital)
effective network service it is essential to use efficient and
                                                                            To meet the requirements of future systems TRW has
advanced technologies for adding new satellites or
                                                                       applied these design enhancements in developing the
upgrading legacy systems. This paper discusses the various
                                                                       Gen*Star [2, 3] payloads for next generation satellites. The
technologies that are being developed and utilized for
                                                                       satellite payload was designed for operation at Ka band and
increasing the network capacity, improving service
                                                                       included the companion network and terminal infrastructure.
performance and reducing the cost of satellite systems. An
                                                                       The first payload using this antenna design was completed
overview of enabling technologies is presented describing
                                                                       in December 2001 for the Astrolink satellite. Presently this
the key architecture, capability and performance of the
                                                                       payload design is expanded to provide the efficient cost
broadband satellite payload processor, digital transponder
                                                                       effective system solution for the replacement and or
and satellite antenna developed by TRW. The various
                                                                       enhancement of Ku and C-Band satellite networks.
benefits of using these advanced features in satellites over
the conventional “Bent Pipe” satellite systems are                          NEXT GENERATION SATELLITE ANTENNA
summarized.                                                                 Most of the present satellites use relatively small size
                      INTRODUCTION                                     solid antenna reflectors to provide the desired coverage. The
                                                                       antenna size (2-3m) is limited by the launch vehicle fairings
     Over the last two decades the communication satellites
                                                                       and packaging constraints. Regional coverage is provided
have extensively used “Bent Pipe” transponders at C and
                                                                       by using the antenna shaped beam (wide) while the spot
Ku-Band frequencies to provide the audio, data, video and
                                                                       area coverage is obtained by the high gain multiple narrow
VSAT services using narrow and wideband transmission
                                                                       spot beams. The radiated power coverage efficiency of these
channels. These satellite systems are characterized by broad
                                                                       shaped beam antenna is considerable reduced from the loss
regional coverage, rigid network configurations, relatively
                                                                       of energy (power emission) in the undesired coverage
low satellite antenna gain, EIRP and G/T with modest
                                                                       regions (desert, ocean) with no source of revenue. The small
channel data capacity rates. The network throughput
                                                                       gain reduction (slow antenna side-lobe roll offs) at the
capacity is mostly limited by the availability of small
                                                                       coverage area edges also further degrades the system
numbers of transponders in the satellite.
                                                                       performance.
     In recent years cost effective solutions for Multimedia
Broadband Global Communication systems are being                       Deployable Mesh Satellite Antenna
developed using next generation of communication satellite                  The next generation satellite antenna design will use the
designs. These systems require high quality of service,                lightweight large deployable reflector antenna to provide
affordable prices and good matching of customer demand                 high performance shaped and multi spot beam coverage’s.
with the satellite system capacity for successful and                  For improving the system performance TRW Astro
profitable business operation. The growth of satellite data            Aerospace has developed the technology for manufacturing
services in the next decade is estimated to be substantial             lightweight, shaped beam, deployable mesh reflectors
during this decade [1].                                                antenna systems. These antenna (Figures 1) designs use
     To meet the needs of these cost effective next                    deployable mesh reflectors ranging from 6m to 30m in
generation systems requirements the satellite may employ               diameters to provide 60-100% improvement in the shaped
following advanced techniques in antenna designs, onboard              directivity over the solid reflector antennas [4]. The antenna
payload processing and frequency reuse:                                is designed to provide regional or global service coverage at
• Deployable large mesh reflector (Shaped and spot                     both C and Ku Band frequencies. The antenna performance
     beams) satellite antenna                                          is improved by flattening the coverage area radiation pattern
•     High gain Solid Reflector Multiple Beam Antenna                  and creating the rapid gain reduction at the edge of
     (MBA) for Satellites                                              coverage. The sharper antenna side-lobe roll offs and higher
• Satellite Coverage Flexibility (Local, Regional, Global)             cross polarization which further enhances the system
                                                                       capacity and reduction in satellite DC power consumption.



AIAA_1111                                                          1                                                     02S00729.154
                                           American Institute of Aeronautics and Astronautics
Recently launched Thuraya (L-Band) satellite uses a 12.25m            Global areas for transmission of specific contents.
mesh parabolic reflector while a 9m (L-Band) reflector is in          Local Coverage
production for the INMARSAT4 satellite.
                                                                           The local coverage contains transmissions in the
                                                                      selected areas (City or country) to provide the local content
                                                                      delivery services to meet the demand of customers located
                                                                      in the city. The antenna spot beams in the satellite provide
                                                                      high gain directivity in specific coverage areas. The beams
                                                                      are optimized for the maximum system capacity and
                                                                      performance for local service contents.
                                                                      Regional Coverage
                                                                           The regional coverage contains transmissions in
                                                                      specific regions based on the language (eg: Spanish,
                                                                      German) or country (eg: Spain, Germany). This coverage is
                                                                      provided by a single shaped antenna beam or multiple
                                                                      narrow spot beams covering the required regions. The
                                                                      regional coverage is tailored to radiate the power for
                                                                      customer in conformance with language needs and geo-
                                                                      political concerns (Frequency coordination, content
                                                                      restrictions). The regional beams provide higher directivity,
                                                                      which could be used for increasing the satellite power
                                                                      efficiency or reducing the user system costs on the ground.
Figure 1 – Mesh Reflector Deployable Antenna                          Global Coverage
     The mesh shaped antenna reflector consists of a pair of               The satellite global coverage provides the transmissions
doubly curved geodesic trusses, which are placed back-to-             in the area covered by multiple regions (language, Geo
back in tension across the rims of a deployable graphite-             political) or countries. For example the Pan European
epoxy ring truss. This light and inherently stiff drum-like           coverage beam provides the same service contents to all
structure provides high efficiency, thermal dimensional               customers located in different Europe countries
stability, and stiffness-to-weight ratios. These L-Band                    The wide shaped antenna beam covering the European
antenna designs and manufacturing processes are being                 countries provides the Pan European coverage. A typical
further optimized for the production of C and Ku Band                 example of Local, Regional and Global (Pan European)
satellite systems.                                                    coverage beams for satellites are shown in Figure 2. Using
High Gain Multiple Beam Antenna                                       multi spot beams for global coverages could also develop
     TRW has developed Multi Beam Antenna (MBA) to                    cost effective systems
provide the high capacity flexible coverage beams for Ka-                   LARGER SATELLITE SYSTEM CAPACITY
Band satellite systems. These MBA antenna designs provide                  The satellite system capacity is enhanced by using
high-gain, multiple-hopping spot beams for national,                  larger useable bandwidth at higher frequency bands (Ka,V)
regional and global service coverage’s. The desired                   and by applying the frequency reuse including optimal
coverage area is tiled with narrow beams using frequency              multicolor channel transmissions schemes. The number and
reuse and multi color operation schemes for enhancing the             complexity of transponder implementation in satellite limits
system capacity. These antennas also provide low side-                the improvement in system channel capacity. The maximum
lobes, higher cross-polarization isolation and high degree of         number of transponder in a satellite is controlled by the
network coverage flexibility to meet the dynamic market               capabilities (mass, power, ferrying size) of the spacecraft
demands from the customers [3]. Satellite systems using               bus used.
Multi Beam Antenna have additional advantages of larger
channel capacity and on orbit coverage adaptability for the
changing usage patterns.
            SATELLITE SYSTEM COVERAGE
     The, types of network services, customer population
and required system performance, governs the design of
satellite system coverage. The satellite payloads are
developed to provide the services in Local, Regional and
AIAA_1111                                                         2                                                    02S00729.154
                                          American Institute of Aeronautics and Astronautics
                SAT- 1
                SAT-                      SAT-
                                          SAT-              SAT- 3
                                                            SAT-                       MHz) which is ten times of the transponders available in the
                                          2                                            satellite using a single wide area beam:
                                                                                            ESB = (Number of Cells) x (Allocated Bandwidth)/
                                                                                                      (Frequency Reuse Factor)
                                                                     SAT-
                                                                     SAT- 3 Pan                       = (50x2)x (500 MHz)/4 =12.5 GHz
                                                                      European
                                                                       Beam                 The Equivalent Number of 36 MHz Transponders
     SAT-
     SAT- 1                                                                            (ENT): ENT = 12.5 GHz/40 MHz = 310
    Regional                                              SAT-
                                                          SAT- 2
     Beams                                               Regional
                                                          Beams
                                                                                                                                                           HRB
                                                                                                                                                          SHE
                                                                                                                                                           -3
   9.00                                                                                                                                               NAY
                                                                                                                                                             SEL
                                                                                                                     -3             -3           -3    -3        ITM
                                                                                                                                                                  -3
                                           Scandinavia                                                                                    CTU             SHA
                                                                    43.30
                                                                    43.30
                                                             Stockholm
                                                                  -1.70
                                                                   -1.70
                                                                                            5.00                          -3             -3 -3        -3
                                                                                                                                                                 TPE
                                                                                                                                                                           -3
                                                                                                                                                                                                 20°
                                                                                                                                                      CAN
                                                                                                     20°             -3                     HAN
                                                                                                                                              -3           -3
   8.00                                UK                                                                       -3             -3                                    MNL
                                  London             Germany
                                                        -2
                                                        -2
                                                                                                                                    BKK-3
                                                                                                                                       SGN
                                                                                                                                    -3 -3                       -3
                                      43.64
                             -2              -2
                         43.64         Berlin                                                                                            KUL                     -3
   7.00                                                                                     0.00
            -

                     Paris                     Munich                                                                                    -3 -3
                                                                                                                                                                                      -3        -3
                                                                                                                                            HLP
                                      France
                                  43.30                                                                                                                                                         POM
                              -2
                              -2 -1.70                                                                                                                                                -3
          Spain
   6.00 -1.70                                      Rome                                                                                                                                    -3
               Madrid                                 Italy                                                                                            -3                   -3        -3        BNE
                                                                                            -5.00                                                     PER                        -3    CBR

   5.00
    -4.00        -3.00            -2.00          -1.00      0.00            1.00
                                                                                                                                         20°


Figure 2 – Satellite Coverage Area
Frequency Reuse                                                                        Figure 3 (b) – Multi Spot Beam Coverage
     The system capacity is increased by reusing the
                                                                                       Multi Color Frequency Plans
available frequency spectrum through optimum allocation of
frequencies and polarizations in the communication links.                                   The multi color schemes assign same frequency to
Multi Beam coverage and Multi color frequency schemes                                  different sections of the coverage area having locations with
further expands the systems capacity. The frequency reuse                              spatial diversity. The application of these techniques further
in the system for the Asia/Pacific regions is shown in Figure                          enhances the system capacity. For example the six regional
3.                                                                                     beams in Europe (Figure 2) could use three-color schemes
                                                                                       in association with twice the frequency reuse to obtain the
                                                                                       larger system capacity (Table 1).
                                                                                       Table 1 – European Regional beam Color and
                                                                                       Frequency reuse scheme
                                                                                                  Region Beams Spatial Frequency
                                                                                                 UK                Green            X
                                                                                                 Italy             Green            X
                                                                                                 Spain             Blue             X
                                                                                                 Germany           Blue             X
                                                                                                 France            Red              X
                                                                                                 Scandinavia Red                    X
                                                                                            By incorporating this scheme to a typical satellite (with
                                                                                       no frequency reuse and color scheme) the system capacity
                                                                                       could be increased over 58% (56 to 96) using the same
Figure 3 (a) – Singe Wide Area Coverage                                                assigned frequency slots without changing any ground
     The region coverage is compared for both a single wide                            equipment. The actual system capacity improvement
area beam and the set of multi spot beams. For example for                             depends on the capability of the spacecraft bus to implement
a system using dual polarization links and 50 spot beams the                           the required hardware and operating power changes. The
Effective System Bandwith is substantially increased. This                             system provides higher capacity in six regions speaking six
frequency reuse produces 310 equivalent transponders (36                               different languages.


AIAA_1111                                                                          3                                                                                                                 02S00729.154
                                                           American Institute of Aeronautics and Astronautics
     SATELLITE COMMUNICATION PAYLOADS                                         in Gallium Arsenide (GaAs) high electron mobility
     Most of the satellite communication payloads operate in                  transistor (HEMT) devices TRW has produce compact low
C and Ku frequency bands. Recently few Ka-Band                                noise amplifiers (LNA), downconverters and upconverters
transponders are added in some satellites to support the                      for next generation satellites. The use of advances extremely
development of future Ka-Band systems. The payloads use                       small MMIC (millimeter/microwave integrated circuit)
36 to 72 MHz bandwidth with both linear and circular                          packaging provides small size LNA/Downconverter
polarizations for providing “Bent Pipe” transponders.                         modules, which are easily mounted directly on the antenna,
     Traveling Wave Tube Amplifiers (TWTA) are                                feed horns. This ability to collocate the first stage of
extensively utilized in transponders for obtaining the                        processing with the antenna feed eliminates the waveguides,
downlink EIRPs in the range of 30-40 dBW (C-Band) and                         (prevents the loss of received signal power in the
40-50 dBW (Ku-Band). The next generation satellites                           waveguides) and reduces the payload mass and complexity.
employ communications payloads with advanced antenna,                         For transmitting the downlink signals the upconverters are
on board switching and digital processing. The Onboard                        mounted directly on the TWTAs reducing the signal losses
Processors enables the use of Solid State Power Amplifiers                    and payload complexity.
(SSPA’s) to enhance the system performance and capacity.                      On Board Processor Subsystem
On board switching provides the needed network flexibility                         The next generation satellites extensively need to use
both in analog and digital transponders.                                      On Board Processors (OBP) to design cost effective system
Payload System Configuration                                                  solution for the customer needs. The OBP in satellites
     Generally the communication payloads system consists                     eliminates the inherent disadvantages of the “Bent Pipe”
of antenna, onboard processor and RF systems as described                     transponders. The payloads either employ partial or full on
in Figure 4. The antenna subsystem includes the antenna                       board processing depending upon the system design
(transmit, receive) and the associated feeds, control                         requirements and cost. Full on board processing enables an
electronics and the distribution networks (OMT, BFN).                         ATM like switching process in payloads. The partial
Depending on the reflector size and operating frequencies                     processing on board is used in “Digital Transponders”.
these TRW advanced shaped antenna could provide up to                         Generally the processor in satellite provides the following
15dB larger EIRP per beam than the current payloads of                        on board features and capabilities for system enhancements
equivalent power.                                                             [5]:
                                                                              • Full network connectivity (Mesh, Star)
RF Subsystem
                                                                              • On board switching of signals, beams & coverage areas
     The RF subsystem includes the required RF                                • Simplified payloads with efficient use of TWTA /SSPA
components for receiving and transmitting the signals in the                  • Efficient bandwidth and power level control
payloads. The receive RF subsystem uses low noise                                  (Automatic, Selectable)
amplifiers and down converts for changing the power levels                    • On orbit management of network traffic, capacity and
and frequencies of the signals received from antenna. The                          QOS
signals are formatted to the required input interface of the                  • Flexible system integration, operation and tests
processor. The transmit RF subsystem up converts and
                                                                              Full On Board Processor
amplifiers the power of signals to produce the desired EIRP
at the payload antenna output. Using advanced technologies                         In full OBP satellite system the payloads transforms the
                                                                              incoming signals into fixed length packets using range of
                                    Recieve RF Subsystems            Processor Subsystem              Transmit RF Subsystems
                 Antenna
                Subsystem            LNA Downconverter                Saw Filter Channelizer
                                                                                                              IF to RF Upconverter
                                     Analog IF Conditioning           Transponder Switch
                                                                                                              EPC/LCAMP/TWTA
                                     Frequency Source Unit            Channel Amps & Summers

                                                                         ca                       I
                                                                         mp
                                                                         ca                            BPF
                              LNA                 Freuency               mp   Σ
                                                                         ca
                                                   Source
               Dual                                                      mp                            EPC
                                      VG            Unit
               band           BP
                               F       A                                      bpf
               feed                                                                                   LCAMP       HPA
                                                                         Σ    bpf
                                                                              bpf




                            Figure 4 – Communication Payload System Configuration

AIAA_1111                                                                4                                                           02S00729.154
                                                 American Institute of Aeronautics and Astronautics
protocols. The payload interprets and processes the data to         packet switch processor using a distributed system
provide efficient downlink bandwidth, connectivity and              architecture [6]. The processor design provides both the
QOS. The block diagram of the on board processor using              point-to-point and multicast services up to 10 Gbps network
ATM (asynchronous transfer mode) cells. is shown in                 data rates with 128 ports.
Figure 5. The router consists of an ATM switch and an on-                The data information is routed through a self-routing,
board computer for performing the on board control and              non-blocking cross bar switch to provide the throughput
processing functions. The packets (Cells) are dispatched            capacity up to 6.5 Gbps.
through the switch to the desired destinations. The signal          Digital Transponder
Figure 5 – Gen*Star On Board Processor Block                             Digital transponders in communication satellite
Diagram [4]                                                         payloads use circuit switching and data processing for
                                                                    designing cost effective network services between different
                     1773                        Resource
                                                                    satellite coverage beams (Area, Spot). The various system
                             PCI Bus RH32        Controller 1553
                                    Computer Non-           Bus
                                                                    advantages provided by digital transponder are [7]:
                      Controller
         Controller                Module     Volatile              • Transponder bandwidth flexibility and control.
          Module        Module                                               Transponder provides circuit switching between
                                                Memory                       different spot beams in fractions of transponder
                                                                             bandwidth (0.5 MHz increments). Capacity
            PBI




                                                                             allocation at the transponder level provides the
                                                   Switch
                                                                             flexibility of selling fractional bandwidth to
                        Inbound                                              customers on demand.
        Demodulator                              Outbound           • Reconfigurable Network Connectivity with Backward
                          Module     Switch       Module
                                     Fabric                              Compatibility.
                                                            Digital
  IF                                                        Outputs
                                                                             The transponders can easily be reconfigured at the
Inputs                                                                       sub-transponder level to respond the system
                                                                             connectivity requirements for changing markets and
        Demodulator Router         Multicast Module                          traffic patterns. The backward compatibility to
                                                                             analog transponders in legacy systems is obtained
                                                                             by the programmable bandwidth feature of (27, 36,
                                                                             54, 72 MHz) in the design.
processing requires efficient channel routing, power control        • On Board Channel Aggregation.
and dynamic bandwidth reallocation. The ATM cell                               This feature provides the on board capability of
switching provides flexibility and compatibility with                          combining the Signals from multiple uplinks
existing protocols and interfaces. The scaleable feature of                    located in different coverage regions into a single
switch meets the needs of both the users requiring very little                 downlink channel. The system efficiency is
bandwidth as well as those with high bandwidth demands                         improved by simpler frequency translation and
(large business users over a single network infrastructure).                   time slot (TDM) switching.
     For Gen*star payload TRW has built the broadband
                           Antenna
                          Subsystem
                                               Recieve RF Subsystems          Processor Subsystem              Transmit RF Subsystems

                                                LNA Downconverter                 Digital Channelizer                  IF to RF Upconverter
                          Dual                                                    Circuit Channel Switch               EPC/LCAMP/TWTA
                                                Analog IF Conditioning
                          band                                                    Analog Reconstructor                 Analog IF Conditioning
                                                Frequency Source Unit
                          feed
                                                                                                           I      BPF
              Offst Fed                                                            ADC    DFT
                                         LNA                 Freuency
               Mesh                                           Source
              Reflector                          VG            Unit                                                              VGA   BPF
                                          BP                                       iDFT                        EPC
             Spot Beam                                                                    DAC
                                           F      A
              Antenna
                                                                                                               LCAMP       HPA


                           Dual
                           band
                           feed




                                      Figure 6 – Digital Transponder Payload Configuration

AIAA_1111                                                                     5                                                                 02S00729.154
                                                      American Institute of Aeronautics and Astronautics
•       System Capacity and performance Enhancements.                                        (ALC) normalizes the average power of the signal received
            The system capacity is increased by using more                                   from each user to a constant level. Input power levels being
            efficient modulation (8-PSK, 16 -QAM) and                                        time-varying: rain attenuation, atmospheric scintillation,
            reducing the channel guard bands (filtering,                                     etc., the control is needed to increase TWTA efficiency on
            channel to channel amplitude power leveling). The                                the downlink. The recombiner performs the inverse function
            system performance is improved by using the                                      of the channelizer. It combines the 250 sub-channels into
            digital pre-distortion to HPA for increasing the                                 125 MHz bandwidth channels. Reconstruction filter design
            TWTA amplitude and phase linearity.                                              constraints ensure minimal signal distortion during this
                                                                                             process. The switch, commanded by a control processor,
     The block diagram of the Digital Transponder is                                         routes sub-channel data from the channelizer to the
described in Figure 6. The antenna subsystem includes the                                    appropriate ports in the recombiner.
offset feed spot beam antenna (transmit, receive) including
the associated control electronics and distribution networks
(OMT, BFN). The RF subsystem includes the required RF                                                                      F r e q u e n c y R e sp o n se
components for receiving and transmitting the signals in the
payloads for each beam. Using low noise amplifiers and                                                       0

                                                                                                            -5

down converts the received signal power levels and                                                         - 10


frequencies are changed. The transmit RF subsystem up                                                      - 15

                                                                                                           -2 0

converts and amplifiers the power of signals to produce the                                                -2 5




                                                                                                  IL(dB)
desired EIRP.                                                                                              -3 0

                                                                                                           -3 5


Digital Transponder Processor                                                                              -4 0

                                                                                                           -4 5

     The processor in Digital transponders performs five                                                   -5 0



major functions as shown in the concept diagram [7] of
                                                                                                           -5 5

                                                                                                           -6 0

Figure 6. The incoming analog signal is converted into 125                                                        0   20     40         60          80

                                                                                                                                    F r e q u e n c y (M H z )
                                                                                                                                                                 10 0   12 0     14 0




MHz digital signals at 640 MHz intermediate frequencies.
The digital channelizer divides the complex baseband input
signal into 250 overlapping 0.5 MHz sub channels. The user                                   Figure 8 – 36 MHz & 72 MHz Channel Sharing
signal power level is normalized to a constant level by the
Automatic Level control function in the digitizer. Using                                     The switch is reconfigurable approximately every
subchannel mapping the digital switch routes subchannel to                                   microsecond and supports both point-to-point, multicast and
the appropriate ports for broadcasting or multicasting. The                                  broadcast operations. Switch reconfiguration is performed
subchannels are reconstructed and recombined in the                                          by the ground command. High-speed, indium phosphide,
recombiner to form one signal with a 125 MHz bandwidth.                                      integrated circuit devices convert the digital output of the
Finally the digital samples are converted into analog signal                                 recombiner to 125 MHz analog beams
centered on 512 MHz
                                                                                                   The channel bandwidth of 125 MHz can further be used
                                          Digital Channelizer
                                                                                             for carrying multiple transponder channels (36 MHz, 72
           Digitizer
* Analog to digital conversion      * Divides inputsignal into
                                                                          Anolog             MHz). Figure 8 shows the frequency response of locating 36
* 125 MHz signal @ 512 Msps         sub-channels
                                    * ALC function levels the power
                                                                       Reconstruction        and 72 MHz channels in 125 MHz using digital filters. The
                                                                      Converts digital       use of digital filters provides improved performance of
                                                                        samples into
                                                                       analog signals        insertion loss and frequency response over analog SAW
                                               Recombiner
          Circuit Switch
            Circuit Switch
    * Remaping of Subchannels
                                     * Subchannels reconstructed                             filters. The performance a 36 MHz bandpass SAW filter
    * Remaps subchhanels             * Recombines user channels
    * Subchannel routing to port
    * Routes subchannels to ports    into a one signal
                                                                                             (Best effort analog filter) is compared with an achievable
                                                                                             digital filter (using 4096) taps in Figure 9. The digital filter
Figure 7 Digital Processor Concept Diagram                                                   provides substantial improvement in performance as
     The Uplinked signals are downconverted at the antenna                                   compared to analog SAW filters.
and input to the digitizer in 64 channels using a transmission
bandwidth of 125 MHz. The digitizer samples each channel                                                           CONCLUSIONS
at the rate of 512 Msps (mega samples per second) and                                             For next generation satellite systems to provide cost
sends signals to the Channelizer. The Channelizer divides                                    effective and profitable network service it is necessary to
the baseband input signal, containing the user channels, into                                apply new technologies in satellite antenna and
250 sub-channels. An automatic level control function                                        communication payload designs. The satellite network

AIAA_1111                                                                                6                                                                                     02S00729.154
                                                               American Institute of Aeronautics and Astronautics
         implementation requires upgrading the legacy systems and                                                                                                    onboard processors developed for Ka-Band satellites in
         adding new payloads with advanced features for system                                                                                                       along with multibeam antenna designs can easily provide
         enhancements. This paper discusses the different                                                                                                            increased capacity and cost savings at these lower frequency
         technologies and designs employed in providing the                                                                                                          systems. The use of spot beams provides much higher
         improved network flexibility, capacity and performance.                                                                                                     antenna gain with larger effective isotropic radiated power
         The key drivers for the designs and implementation of next                                                                                                  (EIRP) and G/T than the conventional C and Ku-Band
         generation satellite systems employ: (a) Shaped and spot                                                                                                    systems supporting high performance communication links.
         beams large deployable mesh reflectors antenna (b) High
         gain Solid Reflector Multiple Beam satellite antenna (c)
         Satellite Coverage Flexibility for Local, Regional and                                                                                                                            REFERENCES
         Global services (d) Satellite capacity enhancements through
         frequency reuse (e) Onboard Analog and Digital Processing                                                                                                   [1] Roger J. Rush “Success factors for Broadband Satellite
         Payloads.                                                                                                                                                   Systems”, Seventh Ka-Band Utilization Conference,
                                                                                                                                                                     Taromina, Italy, October, 2001.
             Frequency Response, SAW Filter                                                  Frequency R pons D
                                                                                                        es e, igital Filter
                                                                                                                                                                     [2] H. J. Morgan, Eric R. Wiswell, Joseph Freitag, “The
    -20
                                                 0.750
                                                                                       5                                            16.050                           Gen*Star Program,” 18th AIAA International
                                                 0.730
    -25
                                                 0.710
                                                                                       0
                                                                                                                                                                     Communication Satellite Systems Conference & Exhibit,
                                                                                       -5                                           16.030
    -30
                                                         Group Delay(usec)




                                                 0.690
                                                                                                                                             Group Delay(usec)


    -35                                          0.670
                                                                                      -10
                                                                                                                                                                     April 10-14, 2000.
                                                                                      -15                                           16.010
IL(dB)




                                                                             IL(dB)




    -40                                          0.650
                                                                                      -20
                                                 0.630
                                                                                      -25                                           15.990
                                                                                                                                                                     [3] E. Wiswell, Z. Stroll, A. Baluch, J. Freitag, H.J. Morgan,
    -45

    -50
                                                 0.610
                                                                                      -30                                                                            ”Gen*Star Results Applicable to Ka-Band”, Proc. of the
                         IL(dB)                  0.590
    -55                  G (usec)
                          D                      0.570
                                                                                      -35
                                                                                                           IL(dB)
                                                                                                                                    15.970                           Fifth Ka-Band Utilization Conference, Taromina, Italy,
                                                                                      -40
    -60                                          0.550
                                                                                      -45                   D
                                                                                                           G (usec)                 15.950
                                                                                                                                                                     October 18-20, 1999.
       505 509513 517521 525529 533537 541545 549
                                                                                        90      100       110          120    130
                                                                                                      Frequency(M z)
                                                                                                                 H                                                   [4] Massih Hamidi, Eric Wiswell, Alan Cherrette, Oliver
                     Frequency(MHz)
                                                                                                                                                                     Saunders, Hau Ho “TRW’s Broadband Communication
                                                                                                                                                                     Payloads at C and Ku Frequency Bands”, 2002 IEEE
                                                                                                                                                                     Aerospace Conference, Bigsky, Montana, USA March 9-16,
         Figure 9 – Analog & Digital Filter Comparison                                                                                                               2002.
                                                                                                                                                                     [5] Mark Bever, Scott Willoghby, Eric Wiswell, Kenton Ho,
              This paper reviews architecture and technologies
                                                                                                                                                                     and Stuart Linsky, “Broadband Payloads for The Emerging
         developed by TRW for the Broadband satellite systems. The
                                                                                                                                                                     Ka_Band Market,” Seventh Ka-Band Utilization
         critical features, concepts, performance and benefits of
                                                                                                                                                                     Conference, Santa Margherita, Italy, September 26-28,
         advanced satellite antenna, payload processor, and digital
                                                                                                                                                                     2001
         transponder are summarized. It is shown that the design and
         fabrication of multibeam systems designs using large,                                                                                                       [6] S. Mishima, L. Moy-Yee, G. Yee-Madera, E. Yousefi ,
         deployable mesh antenna reflectors could provide higher                                                                                                     “Broadband Packet Switch Processor,” Seventh Ka-Band
         EIRP with increased system capacity and operation                                                                                                           Utilization Conference, Santa Margherita, Italy, September
         flexibility.                                                                                                                                                26-28, 2001.
              The digital payload processors and switches on board
                                                                                                                                                                     [7] Mark Bever, Eric Wiswell, Kenton Ho, and Stuart
         satellites also effectively increase the system network
                                                                                                                                                                     Linsky, “TRW Broadband Payloads for Emerging Markets”
         capacity, billable bits and Quality of Service (QoS). The
                                                                                                                                                                     PTC Conference Hawaii, USA, February, 2002.
         network flexibility is further achieved through on board
         programmable configurable processor for obtaining the
         various point-to-point, star and full mesh connectivity in the
         network. The multiplexing of multiple signals destined for a
         downlink beam into a single high-rate data stream permits
         use of high-efficiency (lower DC power consumption)
         saturated TWTA operation.
              Finally it is concluded that similar benefits of the large
         spot beam antenna aperture coverage and onboard
         processing can also be achieved in upgrading the legacy
         satellite systems operating at C and Ku-Band. The same

         AIAA_1111                                                                                                                                               7                                                     02S00729.154
                                                                                                        American Institute of Aeronautics and Astronautics

				
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