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picture1_Satellite Ppt 77148 | Ece 5233   Satellite Communications Lecture 7


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File: Satellite Ppt 77148 | Ece 5233 Satellite Communications Lecture 7
outline block diagrams of transponders satellite antenna systems examples important note slides present summary of the results detailed derivations are given in notes florida institute of page 2 technologies simplified ...

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      Outline
                 Block diagrams of transponders
                 Satellite antenna systems
                 Examples
                    Important note: Slides present summary of the results.  Detailed derivations 
                    are given in notes.
                                               Florida Institute of                            Page 2
                                                  technologies
      Simplified double conversion transponder
    Easier to make cost and power efficient filters 
      at lower frequencies
    Two step conversion:
         o From RX frequency to lower IF
         o  From lower IF to TX frequency
    Signal processing and amplification done at IF
    Two step conversion architecture common for 
      Ku band (14/11 GHz band)
    Drawback 2PAs
         o  HPAs are least reliable components
         o  Usually substantial redundancy is built – 
            typically M:N = 2:1 (i.e. one spare HPA 
            for every active one
    Strict emission requirements – highly selective 
      filters
    Filters frequently followed  by phase                            Outline of double conversion 
      equalization circuits – extremely important for                   transponder architecture
      digital communication transponders
                                                      Florida Institute of                                   Page 3
                                                         technologies
      Regenerative transponders
       On board processing
       Transponder – “switch in the sky”
       Usually deployed along with multi-beam antennas
            o  Beams are narrow – high gain
            o  Point to point communication provides link budget advantages
            o  Capacity of the link is increased – better spectrum utilization
       Used in Ka band where antenna arrays are smaller (high operating frequency)
       Switched beams, high-gain antennas increase re-use of the spectrum
       Design of the satellite more complicated due to all of the processing requirements
       On board processing increases latency
                  Simplified block diagram of a regenerative transponder                                 Page 4
                                                    Florida Institute of 
                                                       technologies
      Satellite transponders – example of frequency plan
                                                                Total of 500MHz of spectrum available
                                                                Each transponder occupies 40MHz (36MHz for signal 
                                                                  and 4MHz for guard band)
                                                                Frequency is reused through orthogonal polarization – 
                                                                  allows separation of 20MHz between two transponder 
                                                                  channels
                                                                Due to orthogonal polarization based frequency reuse 
                                                                  – 24 transponders in 500MHz  bandwidth
                                                                Each transponder is allocated a pair of frequency 
                                                                  allocations
                                                                     o Example: Transponder 3 works on horizontal 
                                                                        polarization, transmits in the range 3740-
                                                                        3780MHz and receives 5965-6005MHz
                                                                Transponder is single manageable capacity unit of a 
           Example of C-band frequency plan                       satellite
                 for IT region 2 (Americas)                     Domestically price for a transponder capacity is about 
                                                                  1.5M$-2M$/year
                                                      Florida Institute of                                   Page 5
                                                         technologies
      Antennas
    Used for TX and RX of EM waves
    Characterized by the                                                   Example of a satellite 
         o                                                                        antenna
            Antenna gain
         o  Antenna pattern
         o  Beamwidth
         o  Efficiency 
         o  Impedance
    In satellite communication – antenna is critical
         o  Light weight
         o  High gain (narrow beam)
         o  High efficiency
         o  Polarization purity
    Satellite usually has 2 antenna systems                                            Antenna pattern 
         o  Communication                                                                 parameters
         o  TTC&M
        Elements of a satellite
           Note: 2 antennas
                                                     Florida Institute of                                 Page 6
                                                        technologies
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...Outline block diagrams of transponders satellite antenna systems examples important note slides present summary the results detailed derivations are given in notes florida institute page technologies simplified double conversion transponder easier to make cost and power efficient filters at lower frequencies two step o from rx frequency if tx signal processing amplification done architecture common for ku band ghz drawback pas hpas least reliable components usually substantial redundancy is built typically m n i e one spare hpa every active strict emission requirements highly selective frequently followed by phase equalization circuits extremely digital communication regenerative on board switch sky deployed along with multi beam antennas beams narrow high gain point provides link budget advantages capacity increased better spectrum utilization used ka where arrays smaller operating switched increase re use design more complicated due all increases latency diagram a example plan total ...

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