Latest Activity In Study Groups

Join Your Study Groups

VU Past Papers, MCQs and More

Satellite Communication Dated: Feb 11, 16
Dear Student,

Graded Discussion Board (GDB) of CS601 will open on Monday February 15, 2016 and close on Tuesday February 16, 2016. GDB will remain open for two days, you are required to post your comments within due date.

Discussion Topic

Satellite Communication

Suppose a MATV/SMATV (Satellite Master Antenna Television) company starts operation in the remote city of a country. They have to select satellite communication band for their satellite system. As their major business requirement is minimal interference from a severe weather condition of the city and to provide reliable, consistent service to their customers.

You are required to

a) Suggest a suitable satellite communication band, give a solid reason.

The answer should not be more than five lines.

b) Give names of frequencies polarities for LNB as per selected satellite communication band.

A concise, coherent and to the point comment is preferred over lengthy comment having irrelevant details. Your comment must not be more than 5 lines. Comments, posted on regular Lesson's MDB or sent through email will NOT be considered in any case. Any request about such an acceptance will not be catered.

Best of Luck!

Views: 5165

Replies to This Discussion

yaar mjy b part ki b smj nae a rha.please kush bta do


L-band (1–2 GHz) Global Positioning System (GPS) carriers and also satellite mobile phones, such as Iridium; Inmarsat providing communications at sea, land and air; WorldSpace satellite radio.

S-band (2–4 GHz) Weather radar, surface ship radar, and some communications satellites, especially those of NASA for communication with ISS and Space Shuttle. In May 2009, Inmarsat and Solaris mobile (a joint venture between Eutelsat and Astra) were awarded each a 2×15 MHz portion of the S-band by the European Commission.

C-band (4–8 GHz) Primarily used for satellite communications, for full-time satellite TV networks or raw satellite feeds. Commonly used in areas that are subject to tropical rainfall, since it is less susceptible to rainfade than Ku band (the original Telstar satellite had a transponder operating in this band, used to relay the first live transatlantic TV signal in 1962).

X-band (8–12 GHz) Primarily used by the military. Used in radar applications including continuous-wave, pulsed, single-polarisation, dual- polarisation, synthetic aperture radar and phased arrays. X-band radar frequency sub-bands are used in civil, military and government institutions for weather monitoring, air traffic control, maritime vessel traffic control, defence tracking and vehicle speed detection for law enforcement.

Ku-band (12–18 GHz) Used for satellite communications. In Europe, Ku-band downlink is used from 10.7 GHz to 12.75 GHz for direct broadcast satellite services, such as Astra.

Ka-band (26–40 GHz) Communications satellites, uplink in either the 27.5 GHz and 31 GHz bands, and high-resolution, close-range targeting radars on military aircraft.

communications satellite is an artificial satellite that relays and amplifies radio telecommunications signals via a transponder; it creates a communication channel between a source transmitter and a receiver(s) at different locations on Earth.

Digital signals are transmitted from the satellites on either Vertical (V) or Horizontal (H) polarity for direct bolsters, or on Right (R) and Left (L) polarity for circular(round) feeds. Standard enormous dishes are well on the way to have bolster horn that can get straight (H/V) polarity . Other systems, for example, Dish Network and Coordinate television use roundabout polarity.

If you have a big dish, most manufacturer of feed horns such as Chaparral and ADL provide what is called a "Teflon Slab" that can be added to the feed horn which would allow it to receive both linear and circular polarity signals. This will cause a loss of about 1 dB in signal level on the linear polarity signals. A Wideband Chaparral feed horn can receive both linear and circular (Ku band) polarity signals.

In order to receive the digital TV signal, you must have the feed horn set to the correct polarity.  For LNBFs, the polarity is controlled automatically by a voltage transmitted form the receiver to the LNBF via the coax cable.  The receiver will send the LNBF 18 volts for horizontal polarity, and 13 volts for vertical polarity.   For standard LNBs, the polarity is controlled by a motorized motor. In this case, odd channels represent one polarity, and even channels represent the other polarity.   Standard satellites have the even channels set the polarizer to horizontal polarity, and the odd channels set it to vertical polarity.  If the Satellite Polarity is inverse, then the even channel set it to the vertical polarity, and the odd channels set it to the horizontal polarity.  Furthermore, some LNBFs such as Dish network's DP LNBFs control the polarity change by shifting the frequency rather than using 13/18 volts.  In fact the new shifted horizontal polarity is 25600 minus the original horizontal polarity.

Each satellite sends and receives over two bands
1- Uplink: From the earth to the satellite
2- Downlink: From the satellite to the earth
BandDownlink Uplink
C 3.7-4.2 GHz             5.925-6.425 GHz
Ku 11.7-12.2 GHz       14-14.5 GHz
Ka 17.7-21 GHz          27.5-31 GHz

C band is best suit for TV Channels because of its high bandwidth other two are being used for army and intelligence companies. UHF,VHF Works with this band (Reference Page No.130,136 CS601 Handouts)

Each satellite sends and receives over two bands
–Uplink: From the earth to the satellite
–Downlink: From the satellite to the earth
Band Downlink Uplink

C 3.7-4.2 GHz 5.925-6.425 GHz
Ku 11.7-12.2 GH 14-14.5 GHz
Ka 17.7-21 GHz 27.5-31 GHz

 

C band is best suit for TV Channels because of its high bandwidth other two are being used for army and intelligence companies. UHF,VHF Works with this band.

RSS

© 2021   Created by + M.Tariq Malik.   Powered by

Promote Us  |  Report an Issue  |  Privacy Policy  |  Terms of Service