Mar 152012
 

DTH (Direct to Home)

Direct to home (DTH)DTH means direct to home basically this service is alternative of cable TV. It is the distribution of television signals from high powered geo-stationary satellites through a small dish antenna & satellite receivers in home across the country. This service works on K U band (14/12 GHz)& are fully digital.

  • The main advantage of KU band satellite broadcasting is that it requires physically manageable smaller size of dish antenna compared to that of C band. C band requires 3.6m PDA (14db gain at 4GHz) while KU band requires 0.6m PDA (35db gain at 12GHz).

 

  • DTH reception requires a small dish antenna 60cm or 90cm, which can be easily mounted on the roof top. Feed along with low noise block converter & set top box (integrated receiver decoder, IRD) with CAS(conditional access system). A bouquet of 40to50 video programs can be simultaneously received in DTH mode.

 

  • DTH uplink chain the sources are feed to a router & output are divided into A, B&C group. Each group contain two video sources .All group are multiplexed digitally (QPSK) modulated individually at 70 MHz IF. Each group is further doubly up converted at L band (950-1450MHz) at KU band (12-14GHz). A, B&C group up converted to KU band streams RFA (13891MHz), RFB (13895MHz),& RPC(13839MHz)& are individually amplified using Klystron high power amplifier(KHPA).

 

  • DTH Downlink chain  consist of a dish, LNBF & RF cable, set top box. RF  waves (12/14GHz) from satellite are received up by a level converting into electric signal. The electric signal is amplified and down converted to L band (950-1450MHz) Feed & LNBC are combined in single unit called LNBF. The L band signal goes to indoor unit. The set top box or IRD (integrated receiver decoder) down converts the L band signal to 70MHz IF signal performs digital demodulator, demultiplexing, decoding and finally gives audio video output to TV for viewing.

 

  • The only drawback of KU band is that the signal attenuates during rains.

Direct to home (DTH)

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