Sample Down Link Parameter

-
To receive a FTA (Free to Air) or CAS (Conditional Access) channel, an earth station engineer needs know to some parameters of that specific channel. Those are called down-link parameter of that channel.  First need the satellite orbital position. Down-link wave polarization may be horizontal or vertical. Those who use cross polarization, if their up-link polarization is vertical then down-link polarization will be horizontal and vice versa. For most the C band channel, they use cross polarization. As video compression technique MPEG-2 and MPEG-4 are generally used. As DVB system DVB-S and DVB-S2 are used. For HD channel MPGE-4 as video compression technique and DVB-S2 as DVB system are used. The main parameter to receive a channel is down-link frequency. It is related with up-link frequency. Another parameter is FEC--Forward Error Correction. It is used as error detection and correction scheme. Generally FEC value is used ¾ or 7/8.

Sample:

Satellite Name: Apstar 6
Orbital Position: 134 degree East
Frequency Band: C
Downlink Wave Polarization: Horizontal
Demodulation Technique: QPSK
DVB System Type: DVB-S
Video Decompression Technique: MPEG-2
Downlink Frequency: 4150 MHz
Modulation Rate: 9.62830 Mega Baud
FEC: ¾

Comments

Post a Comment

Popular posts from this blog

Symbol rate, Bandwidth and Bit rate Calculation

-
In satellite communication bandwidth (BW), symbol rate and bit rate are the most vital fact for proper signal transmission. There are many commercial software for BW, Symbol rate and bit rate calculation for TV signal transmission. But the equations of these parameter calculation are as follows. BW= (1+Roll of factor)* Symbol rate In general Roll of factor is 35% Symbol Rate =BW / (1+Roll of factor) and Bit Rate = Symbol rate * Modulation* FEC* (188/204)                                     [when 188 is encoder packet length] or Bit Rate = Symbol rate * Modulation* FEC* (204/188)                                     [when 204 is encoder packet length] Here, FEC = Forward Error Correction. In general FEC is in the range from 1/2 to 7/8. 188/204 = constant Unit ** BW= Hz, KHz, MHz, GHZ ** Sym...
Read more

Azimuth and Elevation Angle for Satellite tracking

-
Image
Azimuth (Az) The earth station needs to know where the satellite is in the orbit. Then the earth station engineer needs to calculate some angles to track the satellite correctly. These angles are called antenna look angle. The look angles for the ground station antenna are the azimuth and elevation angles required at the antenna so that it points directly at the satellite. With the geostationary orbit the situation is much simpler than any other orbit. As the antenna beam width is very narrow and tracking mechanism is required to compensate for the movement of the satellite about the nominal geostationary position. Three pieces of information that are needed to determine the look angles for the geostationary orbit are a. Earth station latitude b. Earth station longitude c. Satellite orbital position Using these information antenna look angle can be calculated using Napier’s rule (solving spherical triangle). Azimuth angle denotes the horizontal angle measured a...
Read more

Ethernet (UTP) Cable

-
Image
For computer networking purpose most commonly used cable is ethernet cable. Ethernet cable is mainly two types, UTP and STP. UTP stands for Unshielded Twisted Pair and STP stands for Shielded Twisted Pair. Among those UTP is used for most of the networking purpose. Depending on the network devices, UTP cable is two types- straight and cross. Here is a short description on this network cable. Figure: Network Cable (UTP - Unshielded Twisted Pair) Generally mainly used two types of UTP cable. 1. Category 5 (Cat 5)  2. Category 6 (Cat 6) In UTP, there are total eight (8) cables in four (4) pairs. Those are Internationally there are two types of standard to make straight and cross cable. 1. T-568 A (generally called  standard A) 2. T-568 B (generally called  standard B) Note: From the above design it can be observed that , if  interchange 1,3 and 2,6 then A change into B or B change into A. Or simply interchange between Green and O...
Read more

Followers