Base Band

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Integrated Receiver Decoder (IRD)

IRD: IRD stand for Integrated Receiver Decoder. This is ultimately a signal receiver. The operational  sequence of IRD is reverse than that of the earth station. The received RF signal by LNB (low noise  blocker) is converted to low band frequency that is operational for IRD.The IRD process this low  band frequency then demodulate it and then decode it according to the encoding system (while  transmitted). And thus the desired base-band signal is recovered.


Figure: Down link System of a TV Channel


A professional IRD commonly used in satellite TV channel is Proview 7000 of Harmonic brand.


 Figure: Harmonic IRD Proview 7000

Azimuth and Elevation Angle (Antenna Look Angle) for Satellite tracking

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 at the earth station antenna to north pole. Elevation is such angle denotes the vertical angle measured at the earth station antenna end from ground to satellite position.


Figure : Antenna azimuth angle


Equation for Azimuth (Az) determination

Here G = Difference between satellite orbital position and earth station antenna.
          L = Latitude of your earth station antenna. 



Elevation (El)

In the above picture Az means azimuth angle required to track the satellite horizontally. In the figure below the elevation angle has been shown.
 
Figure : Antenna elevation angle



Equation for Elevation (El) determination









Here 0.1512 is constant


Note
1) If the satellite orbital location is in east (E), then G = Antenna longitude  - Satellite orbital position.
2) If the satellite orbital location is in West (W), then G = Satellite orbital position - Antenna longitude


Online azimuth and elevation calculator

Sun Outage Problem in Satellite TV Channel


Sun Outage or Sun Transit or Sun Fade
Geostationary satellites are fantastic means of communication except for one little problem called sun outage or sun transit or sun fade. It is an interruption in or distortion of geostationary satellite signals caused by interference from solar radiation.  Because the sun is a powerful broadband microwave source and has a noise temperature. The elevated temperature of the sun causes it to transmit a high-level electrical noise signal to the receiving systems. For that reason when the sun passes directly behind the satellite (when viewed from earth) that means the sun is in direct line with a communication satellite,  reception of the relatively weak satellite signals is affected. Due to the many differences in ground station equipment, some stations may experience a complete loss of signal while others may only experience a tolerable degradation of signal.


Figure: Graphical representation of sun outage problem.

A most common video on sun outage problem


When it Occur
A sun outage typically occurs around the time of the equinoxes. This natural  illusion happens twice a year when a satellite and a receiving earth station come directly in line with the sun. In the northern hemisphere, sun outages occur before the March equinox (February, March) and after the September equinox (September and October), and in the southern hemisphere the outages occur after the March equinox and before the September equinox. The sun radiates strongly across the entire spectrum, including the microwave frequencies used to communicate with satellites (C-band, Ku band, and Ka band). So the sun swamps the signal from the satellite.

How long do they last?
For geostationary satellites, the solar outage can typically cause disruption to the received signal for a few minutes each day for a few days. It will last longer the smaller the antenna involved. A 40cm dish will have a longer period of interference than a 120cm dish. This is because a small dish has a greater signal acceptance angle than a big dish.

How do they affect watching TV?
The effects of a sun outage range from partial degradation (increase in the error rate) to total destruction of the signal. During this time interference may occur with picture quality and sound when watching television. Sun outages do not affect internet or phone service. 

Sun Outage Prediction Parameter
Time, date and duration of sun outage problem depends on some parameters.
  • Latitude of the receiving antenna
  • Latitude of the satellite
  • The diameter of the receiving antenna
  • The beam width of the receiving antenna
  • The apparent radius of the sun as seen from the Earth (about 0.25°)
  • The RF energy given off by the sun
  • The transmitter power of the satellite
  • The gain and S/N performance of the ground station receive equipment and other factors
Outage Angle
Those parameter can be used to determine the outage angle of the receive antenna. Outage angle is defined as the separation angle (measured from the ground station antenna) between the satellite and sun at the time when sun outage or signal degradation begins or ends.



Figure: sun outage angle.







Frequency = Down link Frequency in GHz.
Diameter = Dish diameter of ground station receive antenna in meters.



Connector used in TV Channel Part-1

In broadcast engineering industry, there have to use various connector and cable for different purpose. Here I will describe some connector with image and usage.

Connector # 1
Connector Name: XLR Connector
Usage: It is mainly used for audio signal connectivityBeside this it is used for stage lighting equipment,  low-voltage power supplies and other applications. It has 3 to 7 pins.
Image:
 Figure: XLR Connector

 Figure: Cable connection of 3 pin XLR Connector.



Connector # 2
Connector Name: BNC (Bayonet Neill–Concelman or British Naval Connector or Bayonet Nut Connector) Connector
Usage: BNC connector is attached to the ends of coaxial cables. It can be used for connecting RF signals, aerospace electronics and video (analog and digital) signals. It is the alternative to RCA for professional video. Home usage electronics appliance such as televisions and DVD players etc. have BNC connectors as long as RCA connector to deliver composite video.
Most commonly used BNC connector are two types depending on their impedence, 50 ohms and 75 ohms. These connector are matched with the cable of same characteristic impedance. Video (particularly HD video signals) use 75 ohm BNC connectors, whereas 50 ohm connectors are used for data and RF.


Figure:  75 ohms and 50 ohms BNC connector.

Difference between 50 and 75 Ohm BNC connectors: Dieletric material at the interface of the 75 Ohm version is absence. Another difference is 50 ohm impedance for applications up to 4 GHz and 75 ohm impedance up to 2 GHz.

 Figure: Difference betwen 75 ohms and 50 ohms BNC connector.

Image: 
 

 Figure:  BNC connector


 
  
Figure:  Various parts of BNC connector.


Connector # 3
Connector Name: BNC inline coupler video connector or BNC I connector.
Usage: To connect two BNC male connector.
Image:
  Figure: BNC I connector.




Connector # 4
Connector Name: BNC T Connector (BNC Male to BNC Double Female Splitter) 
Usage: To take video signal from one BNC male connector and transmit this same signal through two female BNC connector.
Image:

Figure: BNC T connector.


Protocols, Routing Protocols, Routed Protocols

Protocols
In a single sentence protocol is a set of rules. Protocol governs data communication to occur. It defines the format and the order of message exchanged between two or more communication entities, as well as the actions taken on the transmission and/or receipt of a message or other event. A protocol defines what is communicated, how it is communicated, and when it is communicated. Without protocol two computer can be connected but not communicate. It is essential to use same protocol for communication between two devices. When several protocols work at a time it is called protocol suit. At present three widely used protocol suits are TCP/IP, IPX/SPX and AppleTalk.

Routing Protocols
A routing protocol sends and receives routing information packets to and from other routers. Routing protocols implement algorithms that tell routers the best paths through inter-networks. Routing protocols include Border Gateway Protocol (BGP), Interior Gateway Routing Protocol (IGRP), Routing Information Protocol, and Open Shortest Path First (OSPF) to name a few. Routing protocols provide the layer 3 network state update.

Routed Protocols
A routed protocol can be routed by a router, which means that it can be forwarded from one router to another. Such as Internet Protocol (IP), Novell Inter-network Packet eXchange (IPX), and AppleTalk are  routed protocols.

In short, routing protocols route datagrams through a network. Routing is a layer 3 function, thus, routing and routed protocols are network-layer entities. Routing tables on the layer 3 switch (router) are populated by information from routing protocols. A routed protocol will enter an interface on a router, be placed in a memory buffer, then it will be forwarded out to an interface based on information in the routing table.

Routed versus Routing Protocols
Confusion often arises between routing protocols and routed protocols. While routing protocols help the router in the decision-making on which paths to send traffic, routed protocols are responsible for the actual transfer of traffic between Layer3 devices. Specifically, a routed protocol is any network protocol that provides enough information in its network layer address to allow a packet to be forwarded from one host to another host based on the addressing scheme, without knowing the entire path from source to destination. Routed protocols define the format and use of the fields within a packet. Packets generally are conveyed from end system to end system.

An Easy Explanation of Straighr and Cross Ethernet (UTP) Cable


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 Orange cable.




Cross cable or Cross over cable

When both end of a UTP cable has same type than it called straight cable. See the example below.

                         Or 
Usage of Cross Cable
It is used to connect same layer devices. As for example, if you want to connect two laptops or two PCs then you have to use Cross cable.


Straight cable or Straight through cable

When both end of a UTP cable has different type than it called cross cable. See the example below.


Usage of Straight Cable
It is used to connect different layer devices. As for example, if you want to connect one switch
(any switch) to one laptop then you have to use Straight cable.




Uplink Antenna for Transmitting TV Signal

The antenna system used by most of the TV stations is double reflected parabolic antenna. It has 3 major parts.
-    Horn antenna
-    Parabolic Sub reflector
-    Parabolic Main reflector

Horn Antenna: The waveguide has come to this portion. The certain volume of electromagnetic wave comes here with high energy. For radiation, the horn antenna acts like a radial source (theoretically unidirectional ).

Figure: Radiation sequence from the antenna system

Parabolic Sub-reflector: The high energetic volume of electromagnetic wave radiated from the horn antenna comes to the sub-reflector and reflected back to the main reflector.

Parabolic Main Reflector: The reflected electromagnetic wave from sub reflector comes to the main reflector and according to the law of reflection of the reflected parallel waves, it radiates finally for the travel to satellite.  

Station Main Matrix System or Main Video Router System of a TV Channel

Station matrix or router enhances the professionalism in baseband operational activities. The matrix system is like the digital exchange that performs signal routing. The signal routing may include analog video signal, digital video signal, analog audio signal, digital audio signal etc. Station matrix system deals with route creation in commercial broadcast operation. The route is established between the router destination and source. The main facility is to make certain sources to be available for various destinations what are connected to the station matrix. This feature decreases the number of distribution modules needed for the whole station.


The routing system is named as matrix because it performs its operational activity in such a way that follows the mechanism of cross point matrix. The matrix system has some input ports and output ports. The input ports are regarded as source of the matrix and the output port is regarded as the destination port. Video is made destined via the router’s output ports. The operational algorithm has been implemented in the matrix system. One can configure permanent or momentary route by commissioning the router’s logical module. The key thing to be reminding that a single source can be routed to multiple destinations but a single destination cannot be destined for multiple sources. 


Figure: Video routing by cross point technique (s=source, d=destination)


Most of the broadcast production vendor make video router. Evertz and Grass Valley are two renowned production vendor in broadcast world.  Evertz has introduced 64x64 matrix system which supports SD video (embedded or de-embedded).  This video router has 64 inputs and 64 outputs. All of the I/O ports support video signal of SD format. The block diagram of this router is as follows. 

 Figure: Block diagram of Evertz Xenon SD Video Router (XE4-64×64)

Down Link Parameter of TV Channel

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.

Complete down-link parameter for an anonymous channel

Satellite Name: Apstar 7
Orbital Position: 76.5 degree East
Frequency Band: C
Downlink Wave Polarization: Horizontal
Demodulation Technique: QPSK
DVB System Type: DVB-S
Video Decompression Technique: MPEG-2
Downlink Frequency: 4105 MHz
Modulation Rate: 3.3800 Mega Baud
FEC: ¾

Base band Signal Format

Different formats posse the base band signal information in different ways. So you may ask what the information in base band signal is. The signal information and their tasks are as follows.

Chrominance information: The chrominance portion of the base band signal is the collection of the colour/ hue information. This portion of base band signal says what will be the ratio of red-green-blue colour at certain position of television screen.

Luminance information: The luminance portion of the base band signal commands the brightness information of certain position of television screen.

Audio: The audio portion of the base band signal is actually the audio information of corresponding video signal.

Sync pulse: This portion of the baseband signal posses various types of synchronizing pulses for different purpose. Such as for audio-video synchronization, synchronization for scanning sequence (for horizontal and vertical scanning in television receiver), frame/field synchronization etc.

Colour coding information: There are three colour coding technology in the world. They are NTSC (National Television System Committee), PAL(Phase Alternation Line) & SECAM (Sequential Colour with Memory).

Aspect ratio information: For a particular frame of the television picture aspect ratio is width divided by the height of that frame. This may be 4:3 or 16:9 depending on the technology.


Different formats (such as SD, HD, composite) actually posse the above information of base band signals in different ways. These ways provides some special features that ensure the quality of base band signal

How DSNG system works?

DSNG stands for Digital Satellite News Gathering. DSNG system is used as mobile earth station. To perform live broadcasting from a remote place where any physical link like optical fiber, transmission wire,  radio link are not available, then the satellite link is the only way to send the raw footage to the main TV station. The DSNG system is approximately similar to the earth station system together with a mini program control system. The signal flow in the DSNG system as like as below. 

Figure: Block diagram of DSNG system workflow

TV station can use the same satellite or different satellite for main up-link and DSNG system.   After transmitting the raw footage by DSNG, main station receives that signal. Now it comes to the base band section, processed and then made ready for final on-air through the main up-link.

Figure: Up-link and down-link procedure of  DSNG system


Abbreviation in Broadcast Engineering (Base Band)

In modern television engineering most of the time we found some terms as abbreviation. To understand the broadcast engineering some one should know the elaboration of that abbreviation.
Most important abbreviation are as follows.

3PP --- 3rd-party products
ABC --- Automatic Brightness Control
ABL --- Automatic Brightness Limiter
ACC --- Automatic Color Control
ADC --- Analog to Digital Converter
ADTV --- Advanced Digital Television
AES --- Audio Engineering Society
AFT --- Automatic Fine Tuning
AGC --- Automatic Gain Control
ANSI --- American National Standards Institute
APC --- Automatic Phase Control
ATM --- Asynchronous Transfer Mode
ATSC --- Advanced Television Systems Committee
AV --- Audio/Video
AVC --- Advanced Video Coding
BNC --- Bayonet Neill Concelman
BPP --- Bits Per Pixel
CaTV --- Cable Television
CCD --- Charge Coupled Device
CCTV --- Closed Circuit Television
CCU --- Camera Control Unit
CCW --- Counter Clock Wise
CD --- Compact Disc
CE --- Consumer Electronic  
CER --- Central Equipment Room
CG --- Character Generator
Ckt --- Circuit
CRT --- Cathode Ray Tube
CSDI --- Compressed Serial Digital Interface
CW --- Clock Wise
DAC --- Digital to Analog Converter
DDR --- Digital Disk Recorder
DTA --- Digital Television Adapter
DVD --- Digital Video Disc or Digital Versatile Disc
DVE --- Digital Video Effects
DVI --- Digital Video Interactive
DVR --- Digital Video Recorder
EBU --- European Broadcasting Union
EMB --- Em-bedder
EMI --- Electromagnetic Interference
FCC --- Federal Communications Commission
FMV --- Full Motion Video
fps --- frame per second (frame rate)
FTP --- File Transfer Protocol
Genlock --- Generator Lock
GFX --- Graphics
HD --- High Definition
HDMI --- High Definition Multimedia Interface
HDTV --- High Definition Television
IC --- Integrated Circuit
IDTV --- Improved Definition Television
IEEE --- Institute of Electrical and Electronics Engineers
IPTV --- Internet Protocol Television
ISO --- International Standards Organization
ITU --- International Telecommunications Union
JPEG --- Joint Photographic Experts Group
LA --- Lighting Arrester
LCD --- Liquid Crystal Display
MCR --- Master Control Room
mic --- microphone
MOS --- Metal Oxide Semiconductor
MPEG --- Moving Picture Experts Group
NRZ --- Non Return to Zero
NRZI --- Non Return to Zero Inverted
NTSC --- National Television System Committee
OS --- Operating System
PAL --- Phase Alternating Line
PBS --- Public Broadcasting Service
PCR --- Program Control Room
PPV --- Pay Per View
PSTN --- Public Service Telephone Network
PVC --- Polyvinyl Chloride
RGB --- Red Green Blue
ROM --- Read Only Memory
RTV --- Real Time Video
SD --- Standard Definition
SDI --- Serial Digital Interface
SDTV --- Standard Definition TV
SECAM --- Sequential Color with Memory
SMPTE --- Society of Motion Picture and Television Engineers
SNV --- Satellite News Vehicle
SP --- Signal Processor
TFT --- Thin Film Transistor
TI --- Terrestrial Interference
TNC --- Threaded Neill Concelman
UCT --- Ultra Clean Technology
UHDTV --- Ultra High Definition Television
UPS --- Uninterrupted Power Supply
URC --- Universal Remote Control
VAN --- Value Added Network
VBI --- Vertical Blanking Interval
VCP --- Video Cassette Player
VCR --- Video Cassette Recorder
VDA --- Video Distribution Amplifier
VDU --- Visual Display Unit
VGA --- Video Graphics Array
VITC --- Vertical Interval Time Code
VO --- Voice Over
VOD --- Video On Demand
VTR --- Video Tape Recorder
WAN --- Wide Area Network
WFM --- Wave Form Monitor