Basic SATCOM System

patch panels. The modified SATCOM terminals were designated  “QUICKSAT”.  The  initial  introduction  of these terminals into the fleet officially marked the beginning of Phase I of the U.S. Navy’s SHF SATCOM fielding  plan  (with  everything  prior  being  referred  to  as Phase  0)  and  provided  an  immediate  operational capability. Phase II of the U.S. Navy’s SHF fielding plan, which commenced in FY 94, will replace QUICKSAT terminals on aircraft carriers with an AN/WSC-6(V)4 terminal. The U.S. Navy will also deploy an SHF Demand Assigned Multiple Access (DAMA) modem. This phase replaces the QUICKSAT terminals on aircraft carriers, and adds SHF SATCOM capabilities to more  ships. Commencing in FY97, Phase III will deploy the next AN/WSC-6 variant. The new terminal will be a modem,  modular,  open  architecture  terminal  capable  of providing a full spectrum of SHF SATCOM services and greatly expand the number of installations. The system configuration that supports Navy SHF SATCOM  consists  of  an  SHF  RF  terminal  and supporting baseband equipment. The RF terminals for shipboard use are the AN/WSC-6(V) or AN/TSC-93B (MOD) “QUICKSAT” terminal. The terminals process and convert the RF signal transmitted to or received from the space segment. The transmit frequency range is 7.9 to 8.4 GHz, and the receive range is 7.25 to 7.75 GHz.  The  OM-55(V)/USC  AJ  modems,  1105A/1106 time  division  multiple  access  (TDMA)/DAMA  modem, and  the  CQM-248A  (phase  shift  keying  (PSK) modems) are deployed on shipboard platforms. The AN/WSC-6(V) and QUICKSAT configured terminals  are  compatible  with  present  and  future  DSCS SHF  satellite  ground  terminals  and  consist  of  an antenna group, radio set group and modem group. The antenna group is configured as either a dual or single antenna system. The AN/WSC-6(V)1, with the MD- 1030A(V)  modem,  is  used  on  SURTASS  ships equipped with a single antenna. The AN/WSC-6(V)2, with  the  OM-55(V)/USC,  Frequency  Division  Multiple Access  (FDMA)  or  TDMA/DAMA  modems,  is  used  on both flag and flag-capable platforms and is configured with either a single or dual antenna. The QUICKSAT terminal is configured with an FDMA modem, single or dual  antenna,  and  deployed  on  selected  aircraft  carriers and amphibious flagships. The AN/WSC-6(V) and QUICKSAT terminals automatically track the selected satellite,   while   simultaneously   transmitting   and receiving. An antenna control unit commands the antenna to search for tracking (beacon) signals from the satellite.   Upon   satellite   acquisition,   tracking   is accomplished   automatically. BASIC SATCOM SYSTEM A  satellite  communications  system  relays  radio transmissions between Earth terminals. There are two types of communications satellites: active and passive. An active satellite acts as a repeater. It amplifies signals received and then retransmits them back to Earth. This increases the signal strength at the receiving terminal compared to that available from a passive satellite. A passive satellite, on the other hand, merely reflects radio signals  back  to  Earth. A  typical  operational  link  involves  an  active satellite  and  two  Earth  terminals.  One  terminal transmits to the satellite on the uplink frequency. The satellite  amplifies  the  signal,  translates  it  to  the downlink frequency,  and then transmits it back to Earth, where the signal is picked up by the receiving terminal. Figure 2-7 illustrates the basic concept of satellite communications  with  several  different  Earth  terminals. The  basic  design  of  a  satellite  communications system depends a great deal on the parameters of the satellite orbit. Generally, an orbit is either elliptical or circular. Its inclination is referred to as inclined, polar, or equatorial. A special type of orbit is a synchronous orbit in which the period of the orbit is the same as that of the Earth’s. Two   basic   components   make   up   a   satellite communications  system.  The  first  is  an  installed communications receiver and transmitter. The second is  two  Earth  terminals  equipped  to  transmit  and  receive signals  from  the  satellite.  The  design  of  the  overall system determines the complexity of the components and the manner in which the system operates. The   U.S.   Navy   UHF/SHF/EHF   combined communications solution allows each system to provide unique   contributions   to   the   overall   naval communications needs. The SHF spectrum is a highly desirable SATCOM medium because it possesses characteristics absent in lower  frequency  bands:  wide  operating  bandwidth, narrow  uplink  beamwidth,  low  susceptibility  to scintillation,  anti-jam  (AJ),  and  high  data  rates. Recognizing  these  characteristics,  the  U.S.  Navy developed and installed shipboard SHF terminals. These  attributes  are  discussed  in  the  following paragraphs. 2-7


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