RF Presentation

Satellite Communications Higher Application layer Data link layer Physical layer (RF Comm.)

Terminology 1.Satellite : Satellite is a repeater in a space which reflects radio signal transmitted towards it after boosting it.. 2.Transponder: A Trasnspoder is a hardware component onboard the satellite which is tuned to process some part of spectrum (Bandwidth).A Transpoder is usually 36 Mhz in Bandwidth 3.Polarization:Polariztion is actually physical orientation of RF waves in space.Today in all satellite dual polarization in used e.g Horizontal and vertical polarization.If Transmit is vertical then receive is Horizontal.Dual Polarization doubles the Bandwidth capacity of satellite.

In Ku band there are three Bands for Downlinking Ku Bands In Ku band there are three Bands for Downlinking Satellite GE-1A 12.25 - 12.75 Ghz 14.00-14.50 Ghz 10.95 - 11.45 Ghz Uplink Downlink 11.70 - 12.20 Ghz Vsat NOC Vertex (9.3 Meter)

Tx Rx HPA U/C D/C 10.95-12.75 Ghz Wide Band Amplifier LNA IF Section Tx Feeder cable Wide Band Amplifier 14.00-14.5 Ghz LNA HPA 10.95-12.75 Ghz 14.00-14.5 Ghz U/C D/C 52-88 Mhz 52-88 Mhz IF Section IF Section

a) RF section b) Tracking section RF section receives signal from satellite and converts it into IF signal and provides feed to IF section and it receives IF signal for transmitting from the IF section;upconvertes ,amplifies it and Transmit to the satellite. RF section also contains the components for Tracking of the satellite.(There is small drift in satellite path). RF section has rackmounted monitoring for section components and varions signal parameters e.g Spectrum analyzer and Health Monitor PC. a) RF section b) Tracking section

HPA A HPA B HPA Bk U/C switch (MITEQ) Horizo Pol. Vertical Pol. Coaxial feeder cables 30 dB atte. Input 10.45-12.75 Ghz output 70 Mhz Waveguide switch Bk UP U/C HPA switch U/C switch (MITEQ) Vertical Pol Tx U/C A HPA A (CPI 25 dB atte. 700 W 75dB) U/C B Vertical Tx U/C C U/C D Horizo Pol. Tx HPA B Horizo Pol. Tx Comb. Comb. HPA Bk Fixed Metal cabling

D/C switch MITEQ Horizo Rx (DC supply 26 V and control) Bk UP D/C LNA B LNA A Bk UP D/C D/C switch MITEQ D/C A Horizo Rx D/C B D/C C D/C D Vertical Rx LNA Switch Logic Controller Split. Split.

Device Operation Each and every component contains front panel for configuration and control. There are two modes of Operation Local/Remote. In local mode control is local and in remote mode component is controlled remotely by switch.Backup components must be in Remote mode. Protection Switches are used to Switch in the Backup components if some Online components goes down.Switchs keep on polling Online components for health like power supply and alarms. All switches work in either Auto or Manual mode.In Auto mode in case of failure switch would do switching automatically so switches must be in Auto mode(use front panel for setting it)

UPC Uplink power control ACU There is rain absorption in Ku Band. Uplink power control is used in Ku Band to compensate for rain absorption. BDC L band input U/C Tracking receiver ACU To U/C Channel(1-10) (There can be 10 channels and UPC can provide 20 dB Clear Sky Atte.) Splitter Receiver A UPC (Failsafe By pass) (Input 0-10 VDC) 10dB fixed atte. IF Section

2) Closed loop Operation Uplink power control Open loop Operation Rain Beacon from satellite 2) Closed loop Operation CW signal is sent by earth Station itself Signal generator Uplink to satellite UPC

Tracking ACU Drive cabinet Interface From BDC Tracking receiver POL EL (Control cables to Drive cabinet Resolvers) AZ ACU From BDC Tracking receiver (Tracking receive process the Beacon and provides input to UPC and Tracking receiver.)

Tracking 1) Step Tracking:In step tracking ACU tracks the satellite in steps in each direction step tracking is algorithm embedded in ACU as software.ACU tracks the satellite periodically.Time period can be set on the basis of satellite drift and beam width of antenna. 2) Program Tracking: In Program Tracking ACU can be pre-tuned for various satellites. Antenna can be manually tracked if required in situations like moving to new satellite and when antenna gets trapped in side lobe. If there is no Beacon visible like in rains or source failure ACU stops tracking.For normal operations ACU should be in Auto Tracking.

FEP Remote Monitoring WINNT 4.0 Workstation Running PCANYWHERE And Compass runtime. Serial cables Remote interfaces LAN connectivity FEP WINNT 4.0 Workstation running Compass runtime software for control and monitoring

Signal Monitoring Spectrum Analyzer Horizotal Rx (Signal in IF) LNA B LNA A D/C A Horizotal Rx D/C B D/C C (Signal in IF) D/C D Vertical Rx Spectrum Analyzer 9Khz to 22Ghz Split. Split. (Signal in RF)

There is difference between Uplink and Downlink Some calculations There is difference between Uplink and Downlink Frequency that is called Delta of satellite For GE-1A Delta is 1748 Mhz Uplink Frequency: 14.00-14.50 Ghz Downlink Frequency : 12.25-12.75Ghz Relation between RF and IF Frequency in RF=(Center Frequency of U/C)-70+(IF Frequency)

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