The DTH system of a typical model constitutes to°from six parts:
1)the head system(Headend) head system is mainly compressed coder by video frequency audio frequency and reply to constitute with machine etc..The head system main task is to carry on television signal the number coding compress and make use of a statistics to reply to use a technique and forward a machine to repeatedly take the transmission more programs in the limited satellite.DTH presses the standards MPEG-2s to carry on compression to the video frequency audio frequency signal and replies to use a technique with the dynamic state statistics, can spread hurl Chi on forwarding of a 27 MHzs machine?0 sets of television programs.DVB-T TUNER
2)deliver and up north route system(Uplink) to deliver and up north route system to include formerly carry the north bound stands of correspondence equipments and north bound equipments.Deliver a way mainly have medium keep pouring in to lose and the number radicle take to deliver 2 kinds.
3)satellite(Satellite) DTH adopt the live satellite or communications satellite of big power in the system.Because technique and cost etc. reason, some DTH systems adopted the DTH companies of big power communications satellite, the United States and Canada to adopt the big power live satellite(DBS) of the feater appropriation.DVB-T MPEG 4
4)the customer manages system(SMS) customer's managing system is DTH the heart of the system, mainly complete the following function:The small plait recommends
A.Register and management customer's data.
B.Purchase and pack a program.
C.Draw up a program to record fee standard and customer to carry on a charge.
D.The market predicts and marketing.DVB T RECEIVER
Customer's managing system is mainly managed system and solution customer's problem by the database of customer's information and the program information and provide various composings of Call Center that the customers serve.5)the condition receives system(CA)
The condition receives system to have two main functions:
A.Encrypt to the program data.
B.Carry on authorization to the program and the customer.
International top DTH condition adopted by system receives system to mainly have currently:NDS the United States, Irdeto Israel, France Via Access, Switzerland Nagra Vision etc..
Canadian company of Star Choice of the company of the United States Direct TV and adoption Direct TV technique uses of is NDS condition to receive system;The United States Dish Network(Echostar) what Canadian company of Bell ExpressVu use of the company and adoption Echostar technique is the condition of Nagra Vission to receive system.
6)the customer receives system(IRD) DTH, customer's receiving system is received antenna(Dish) by a small scaled disc form satellite and comprehensive the card(Smart Card) receiving decoding machine(IRD) and intelligence constitute.
IRD is responsible for four main functions:
A.Decode a program data to flow, and output a television.
B.Make use of intelligence card in of the airtight key(Key) carry on decrypting.
C.Receive and handle various customer's order.
D.Download and circulate various application software.
IRD in the DTH system is no longer a pure hardware equipments, it still included operate system and a great deal of of applied software.More successful IRD operate system is Open currently TV.The company of the United States Dish Network has already gradually starts IRD of getting stripe the customer as the system of Open TV.