3. I. INTRODUCTION (1)
1. Satellite Digital Television:
- Broadcasting television
program using signals
relayed from communication
satellites .
- Using parabolic antenna
for transmitter and receiver
station.
4. I. INTRODUCTION (2)
2. DTH:
- Direct-to-home television (DTHTV) also known as Direct-broadcast
satellite television (DBS-TV) .
- A method of receiving signals transmitted from direct-broadcast
satellites.
- Signals are transmitted using Ku band and are completely digital (high
quality).
- K-plus, VTC (vinasat-1), AnVien (NSS-6).
8. I. INTRODUCTION (4)
2. DTH- Feature:
- DTH offers better quality picture than Cable TV.
- DTH can reach remote areas where terrestrial transmission and cable TV have
failed to reach.
- DTH also allows for interactive TV services such as movie-on-demand.
- The payments will be made directly by the subscriber to the satellite company
offering the service.
9. • The frequencies for DTH vary from region to region but it lies in Ku band
of microwave .
Uplink frequency range – 17.3 to 17.8 GHz
Downlink frequency range – 12.2 to 12.7 GHz
• An electronically controlled polarizer is used at receiving terminal for
converting circularly received polarized signal to linearly polarized signal.
• Digital TV signals are transmitted as 20 Mbps QPSK signal occupying
about 27 MHz of transport bandwidth for a single channel.
• MPEG-2 format is used for video compression.
TECHNOLOGY SPECS
10. I. INTRODUCTION (3)
Quadrature phase-shift keying (QPSK)
- This is known as quadriphase PSK
- QPSK uses four points on the
- constellation diagram,
- equispaced around a circle
- QPSK can encode two bits
- per symbol, shown in the diagram
- with Gray coding to minimize
- the bit error rate (BER)
11. 1. Transmitter:
- MPEG-2 encoding :
200 Mbps -> 3 to 6Mbps.
- After MUX, Elementary
stream is compressed into 188-
byte packets.
- Adding Reed-Solomon (RS)
packets to detect erros.
- After that, Data stream is ready
to QPSK mod.
II. HOW DOES IT WORK? (1)
12. 1. Transmitter:
- Data stream are modulated QPSK.
- QPSK signal is converted frequency into Ku-band or C-band.
- Then, they are high-freq amplified to transmit into space.
II. HOW DOES IT WORK? (2)
14. a. Low Noise Block Converter:
The central element in the feed horn is low noise block-down converter.
Block-down convertor (so called because it converts a whole band or ‘block of frequencies’
to a lower band) i.e. it converts the 12.2 to 12.7 GHz band to 950 to 1450 MHz
An LNB sits on the end of an arm and faces the parabolic reflector(dish) which focuses the
signals from a satellite into the feed horn of the LNB.
II. HOW DOES IT WORK? (4)
15. Set-top box:
- An information appliance
device that generally contains a
TV-tuner input and displays
output connects to a TV-set
and an external source of
signal, turning the source
signal into content in a form
that can then be displayed on
the TV screen or other display
device
II. HOW DOES IT WORK? (8)
16. b. Disk Antenna:
Classifier:
- Axial or front feed – This is the most common type of
feed, with the feed antenna located in front of the dish
at the focus, on the beam axis, pointed back toward the
dish. A disadvantage of this type is that the feed and its
supports block some of the beam.
- Off-axis or offset feed – The reflector is an
asymmetrical segment of a paraboloid, so the focus,
and the feed antenna, are located to one side of the dish.
The purpose of this design is to move the feed structure
out of the beam path, so it does not block the beam. It is
widely used in home satellite television dishes.
- Cassegrain – In a Cassegrain antenna, the feed is
located on or behind the dish, and radiates forward,
illuminating a convex hyperboloidal secondary
reflector at the focus of the dish. The radio waves from
the feed reflect back off the secondary reflector to the
dish, which forms the outgoing beam.
- Gregorian – Similar to the Cassegrain design except
that the secondary reflector is concave, (ellipsoidal) in
shape.
II. HOW DOES IT WORK? (5)
20. Cost effective communication, information and entertainment to all.
Small size terminal can provide up to 4000 channels and 2000 radio channels
through a click of button and thus bring world’s information, news
entertainment to your home.
DTH services bypasses mediators and thus content provider comes with
customer directly.
DTH services are transparent providing digital quality video, audio, radio, and
IP to all at equal prices and other benefits with reliability.
III. ADVANTAGE (1)
21. Cost effective communication, information and entertainment to
all.
Small size terminal can provide up to 4000 channels and 2000
radio channels through a click of button and thus bring world’s
information, news entertainment to your home.
DTH services bypasses mediators and thus content provider
comes with customer directly.
DTH services are transparent providing digital quality video,
audio, radio, and IP to all at equal prices and other benefits with
reliability.
III. DEFECTIVE (2)
22. IV.SUMMARY
Direct To Home Technology connects urban , rural and
remote areas of the country and provide desire information,
communication, education and entertainment at the click of
button.
23. REFERENCE
http://en.wikipedia.org/wiki/
Ray, Justin (7 May 2002). "DirecTV-5 broadcasting satellite
launched by Proton“
“Thông tin vệ tinh” TS. Nguyễn Phạm Anh Dũng. Học viện bưu
chính viễn thông.
“Cấu trúc data trong hệ thống truyền hình số” ThS. Đặng Quang
Dũng.
http://truyenhinhanvienhd.vn/
24. Bo sung QPSK
Bo sung Set-Top Box
Down tai lieu.v.v.
Chuyen slide sang nen toi
