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LNB - Low-noise Block Downconverter


LNB

­­­­­­­The box on the front of a satellite TV dish that receives the satellite signal collected by the dish, processes it, and sends it via a coaxial cable indoors to a satellite TV receiver that is connected to the TV set. The box has a scalar horn antenna (the funnel with concentric rings) which collects the microwave beam and directs it into a waveguide, a short closed metal pipe. Two small metal pins project into the waveguide from the circuit board; these serve as antennas which convert the microwaves to radio frequency alternating currents. On the circuit board (center), these are amplified by a low noise amplifier, then a local oscillator and mixer convert the block of frequencies to a lower block of frequencies, which are output to a jack on the outside of the box (black objects, right) to which a coaxial cable is connected to carry the signal inside the house.


Figure: Ku band antenna with LNB (LNB + Feed horn + Wave guide)


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A Feed Horn is basically a horn antenna that lies between the transceiver and the antenna reflector in a satellite dish system. 
When receiving a signal from the satellite, the signal is reflected from the parabolic dish to the feed horn which then passes it on to the Low Noise Block (LNB) where it is down converted and processed further. The feed horn provides some level of gain and is designed to support a particular type of polarization, this way it can filter out unwanted signals by only allowing specific polarity waves depending on the polarization of the horn antenna.


Figure: Ku band LNB

Feed Horn is always located at the focal point of the parabolic dish and is simply attached to the LNB. 

An LNB with an integrated feed horn is called as an LNBF. Normally we use LNBF but called LNB.

On the transmit side, the signal is sent from the satellite modem to the Block Up-Converter for up-conversion and then amplification and then sent out via the Feed Horn towards the dish antenna sub reflector towards the main towards the satellite.

  
Figure: LNB cutoff



Key parameters of a Feed Horn Antenna:
1.     Frequency Range: The frequency band for which the feed horn will be used – For example Ku, Ka-bands etc. The frequency band of interest will determine the waveguide size of the feed horn.
2.     Waveguide Shape: The shape of waveguide defines the sort of polarization the feed horn antenna will support. Ex. a circular waveguide supports both linear and circular polarized waveforms, while a rectangular waveguide supports linear polarization.
3.     Flange Compatibility: The flange type needed to connect the feed horn to the Low Noise Block of the Satellite system.
4.     Gain: The amount of gain the feed horn antenna provides.


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The big round “dishy” part of a satellite dish is called the “reflector” and what it does is focus all those waves like a lens. It looks something like this:

Fig: LNB at the focal point 

It focuses all of them on a point in front, where the LNB goes.


The LNB? What?

An LNB is a complex little computer that does an amazing amount of work. It consists of three parts:
  • a Block down converter, which takes the higher frequency signals which don’t travel well on wires and converts them to lower frequency signals that do;
  • a Low-Noise amplifier, which bumps up the signal power so it can travel over a wire;
  • The feed horn, which is the subject of this article.
LNBs make satellite reception possible. Once all that signal is focused in one place, it’s still not strong enough to go down a wire in its current form. The LNB takes care of that.

Finally, the feed horn

Even though the dish does a pretty good job of focusing the signal, it doesn’t do a perfect job. That’s the job of the feed horn.
A feed horn looks sort of like a funnel. It helps move those signals down the line and concentrates them even further so they land in precisely the right place. The one you see above you is just a typical one I found on the internet.
The feed horn in a satellite system is that part on the LNB (in general) that’s covered in white plastic. The plastic is invisible to satellite signals and serves to protect the electronics inside. The actual feed horn is behind the white plastic cap.


Figure: Feedhorn without LNB



Direct To Home (DTH) Service Provider In Europe.

DTH Service Providers in Europe
People tend to incline for entertainment doing anything they find fit for fun including fishing, traveling, reading books, web surfing, gossiping, cycling, writing, watching television and many more. And watching television is fun as well as recreational for most of the people of almost all the ages.  However, when we find ourselves in a mood to watch TV program, we also find ourselves in the need of a cable network or satellite tv service. For doing so, we can take help of direct-to-home service which is called DTH – a digital satellite television viewing services for subscribers directly through satellite transmission. That is why, we will now learn about direct-to-home service providers in entire Europe. Since above the earth, there are lot of satellites stationed at six key positions in orbit and DTH can make your day at home with variety of channels for fun and entertainment.      
   
In Europe, there seems to be number of DTH service providers available in the market from which you will select your preferable one which obviously meets your requirements of tv channels. We will simple begin with Canal Digital – a widely known DTH service provider for quality viewers. Established in 1997, Canal Digital goes ahead with the purpose of distributing Television programs. This remains as primary ambition for Canal Digital along with performing huge amount of activities related to broadcast and entertainment. To name few milestones of Canal Digital, it became pure subsidiary of Telenor in 2002, first Nordic Content provider to offer HDTV in 2005, Canal Digital Kabel-TV AS(Norway) becomes a part of Telenor Norway in 2010, AS is re-established fully focusing on DTH in the Nordics in 2011 and more. Canal Digital aims to reach to the customers with rich content with over 130 TV channels from where you can pick your own.  And the best thing about Canal Digital is that around 900 thousand households make their first choice to pick Canal Digital as their entertainment platform across the Nordics.

The leading DTH service provider is not only Canal Digital, the Sky is rocking high as well with endless entertainment programs and broadband. From Television to Mobile Phone, Sky is at your doorstep to entertain you with your best choice. Sky allows to explore Sky Corporate, Sky for Business, Sky Communal TV, and work for Sky. Getting bored home or anywhere in your country, just pop in Sky and enjoy the ultimate entertainment with variety of channels including Sky 1, Sky Living, Sky Atlantic, Sky Arts, Sky Cinema, Sky Sports, and Sky news as well. You will never be able to miss anything from any channel with Sky as it offers great advantage of highlighting your preferred chunks or programs or shows or sports. This is amazing for the sports lover as you can pick and choose any dedicated channels from premier league to F1 including football, cricket and golf. The opportunity of entertainment is simply enormous and quite convenient with Sky.      

Number of Choices
However, these two direct-to-home service providers are not only ruling the entire Europe, but as we will get to know about other DTH service providers and countries as well.

Albania
1. Digit-Al 


Austria 
1. Sky Osterreich


Bulgaria
1. Bulsatcom

Croatia 
1. Digi TV

Denmark 
1. Canal Digital

Franch
1. CanalSat

Finland
1. CanalDigital 

Germanya 
1. Sky Deutschland

Hungary 
1. Digi TV
2. Magyar Telekom


Ireland
 1. Sky
2. Saorsat

Italy 
1. Sky Italia

Luxembourg
1. TéléSAT Luxembourg

Netherlands
1. CanalDigitaal
2. UPC Direct 




Norway
1. Canal Digital

Poland 
1. Cyfrowy Polsat
 
Portugal
1. ZON TV Cabo

Romania
1. Orange TV
2. RCS & RDS
3. Focus Sat

Russia
1. NTV Plus
2. Tricolor TV

Serbia
1. Digi TV
2. TotalTV 

Slovakia
1. Digi TV

Spain 
1. Movistar+

Swede
1. Canal Digital

Turkey 
1. Digiturk

United Kingdom
1. Sky
2. Freesat

Ukraine
1. Xtra TV


Overall, DTH service Providers in entire Europe are extensive with endless choices to make. Out of so many, Canal Digital and Sky can be convenient as well as full of entertainment. And the rest of the DTH service providers are best based in country and specific zones. At the end, the Tv shows, programs, sports, live channels are pretty easily accessible from every single DTH Service provider.            

How to configure encoder for satellite TV signal transmission.

Encoder Configuration

Encoding  is an essential part for satellite communication. For that reason broadcast engineers need to know how to configure the encoder properly. There are a number of encoder brand in the market. Most of them have the almost same parameter to configure. So the engineers have to put some value of the parameter to the encoder to encode signal. It depends on the demand and criteria of the TV channel owner and the signal. Some of the most important and common parameter (with dummy value) are as follows.   



1) Program name: XYZ TV
2) Service ID: 101
3) Video Format: PAL/ NTSC/ SECAM
4) Video Resulation: 720*576, 1920*1080
5) Video Bit Rate Mod: CBR/ VBR
6) Video Bit Rate (kbps): 4000
7) Audio Bit Rate (kbps): 192
8) Brightness: 50
9) Contrast: 50
10) Saturation: 50
11) Hue: 50
12) Video Encode Mode: MPEG-2
13) Audio Encode Mode: MPEG-2

That parameters define the characteristic of the up-link / transmitting signal. After encoding the signal, it goes into the modulator. Then the signal is modulated for the long distance transmission. After that, the modulated signal is amplified by SSPA or HPA to increase the amplitude of the signals. Then finally it transmitted through the web guide to the satellite.  

What is the difference between symbol rate and bit rate?




A symbol can carry multiple bits (and usually does). So BPSK/BFSK has a symbol of 2 states and the bit rate is the same as the symbol. QPSK has 4 symbol states and each symbol can carry 2 bits. 8PSK has eight symbol states and each symbol can carry 3 bits. 16QAM has 16 symbol states and each symbol can carry 4 bits. I'm sure you get the drift. 

Terminology: EIRP, G/T, Input Back-Off, Output Back-Off

EIRP: Used to indicate the power transmitted from an antenna. EIRP=Power +Antenna Gain, Both EIRP and Power is expressed in dBW and Gain in dBi.

G/T: It is the figure of merit for an earth station and is expressed as dB/K (dB per K).
G/T= Antenna Gain-10*Log (System Noise Temperature) The higher the better-G/T can be raised by using a higher gain antenna or a lower temperature LNA. The earth station G/T determines the received carrier to noise ration. Increasing station G/T will increase the C/N of the received carrier.






Input Back-Off (IPBO): The level of a signal at the input of an amplifier relative to that level at the input that would result in the maximum possible output level. For example, if an input level of -20dBm causes max output and the actual input level is -25dBm, the IPBO is 5dB. Both IPBO and OPBO are commonly used to determine the operating levels in a satellite transponder TWTA.


Output Back-Off (OPBO) The level of a signal at the output of an amplifier relative to the maximum possible output level. For example, if a maximum output level is +40dBm and the measured output level is +34dBm, the OPBO is 6dB.