[Photo] Satellite TV reception technology knowledge

Editor's note:
The emergence of television has greatly enriched people's cultural life. With the continuous progress of science and technology and the continuous improvement of people's living standards, watching satellite TV programs has become a reality. In order to popularize the knowledge of satellite TV reception technology, we have invited experts to write articles and serialize related articles. There are four main parts, including basic knowledge of satellite TV reception, satellite TV reception equipment, technical parameters of TV satellites in the Asia-Pacific region, and practical technology of satellite reception. In addition, it should be noted that the installation of satellite TV receiving equipment requires the approval of the relevant units.

Before introducing practical satellite TV reception technology for home use, it is necessary to make a brief description of the satellite transmission and reception process.
1. Satellite TV program source The satellite TV program source is usually provided by the TV center. When the upstream station is close to the TV center, the TV center directly sends the program to the upstream station in video mode; when the distance is far, it is microwave or optical cable (Or both are used for mutual backup) to the upstream station, (see Figure 1).

2. The function of the upstream sending station is to send the TV and additional signals (such as broadcast teletext, etc.) to the synchronous earth satellite over the equator through the upstream channel. It is now receiving the C band (downlink frequency is 3.7 ~ 4.2GHz) To illustrate. The earth station demodulates the optical cable and microwave signal sent by the TV center to obtain multiple channels of video and audio signals, and selects a high-quality signal through the video and audio switch to send to the video and audio distributor, and its output is divided into two channels of the same signal , Sent to their respective small signal processing units, to modulate, equalize, and convert the signal, transform the baseband signal into a 6GHz high-frequency signal, send it to the feed source after high-power amplification, and send it to the satellite by the uplink antenna. There are generally two sets of small-signal and high-power amplifiers, which are backed up by the switch of the waveguide, which can improve reliability.
3. Satellites are usually equipped with multiple transponders, which change the received uplink signal 6GHz to a downlink frequency signal of about 4GHz, and perform polarization conversion, that is, if the uplink signal is vertically polarized, the downlink signal is horizontally polarized Signal, vice versa. After power amplification, the antenna on the satellite is sent to the designated service area on the earth. For example, Shandong Satellite TV, which is retransmitted by the Asia-Pacific 1A (ASTAR-1A) TV satellite located at an angle of 134 Â° (134 Â° E) above the equator in the Asia-Pacific region, has a transponder model of 10B and a downlink frequency of 4. 1GHz, the polarization mode is linear vertical polarization (V), and the satellite service areas are mainly all over China.
4. Downlink ground receiving station Downlink station can be a large collective station or a simple station for direct reception by individuals. It is generally used as a TV receiver and only needs one-way reception. Its equipment is relatively simple and consists of three parts: an antenna system, a high-frequency head (outdoor unit) and a receiver (indoor unit). The antenna is composed of a reflecting surface, a feed source, a polarizer, an antenna pointing adjustment mechanism and an antenna base. The high-frequency head includes a low-noise amplifier and a down-converter. It converts the downlink reception frequency of 4.1 GHz (Shandong Satellite TV) into a frequency signal (first intermediate frequency) of 950 to 1450 MHz to the receiver. The receiver then inputs the first intermediate frequency Signal processing is converted into video and audio signal output for user use. When the TV signal is not ideal, the antenna azimuth and elevation angle can also be adjusted through the antenna control unit and the drive control circuit, so that the picture sound achieves a satisfactory effect, and the purpose of satellite tracking and telemetry is achieved (see Figure 2).

It should also be added that there are many ways for terrestrial reception: such as direct coaxial cable reception, this method is generally used for direct reception of satellite TV in general households; in addition, cable television supplementary stations can be combined with wireless TV stations and satellite TV stations. Use cable TV to transmit; if the distance is far, you can also use the microwave antenna (transmit and receive) to transmit satellite signals, (see Figure 3).

5. Common names (Chinese-English control)
ANIMAL Animal World APT Personal Satellite Mobile Communication System BBC British Broadcasting Corporation BS Satellite Broadcasting CBTV Digital TV CCST Chinese Teletext TV CCTV Central Television Station CETV China Educational Television Station CNN American Cable News (net)
CNR carrier-to-noise ratio. It is an important technical index for satellite ground receiver terminals, generally 7-8dB
DBS live TV satellite; direct satellite reception; digital broadcasting satellite DISQQ. SWITCH satellite equipment digital control conversion DQT satellite receiving module DTH digital high-definition live TV satellite; satellite live broadcast to personal home DVB digital satellite transponder; digital broadcast TV; digital compression satellite receiver DVB-C digital cable TV DVB-C digital satellite TV Chinese standard DVB-T digital terrestrial broadcast television D2-MAC-D2 European satellite direct broadcast television standard EIRP satellite repeater station equivalent omnidirectional radiated power. It is proportional to the product of the satellite repeater's transmit antenna gain and its output power. Dbw for unit
EPG electronic program guide; electronic program menu FASH French fashion channel FEC Forward error correction method or forward error correction rate or error rate. When receiving this signal, it must be consistent with the satellite uplink coding to decode. It is an important parameter of the receiver's input signal, and the common ratio is 1/2, 2/3,
3/4, 5/6 and 7/8
H horizontal polarization; line synchronization HBO American home movie theater HDTV high-definition TV IP picture input processing IRD STB (European set-top box called STR)
IS-V International Communications Satellite LH Left-handed circularly polarized LNA low-noise preamplifier; sometimes also referred to as high-frequency head LNB high-frequency head; low-noise down-converter; low-noise amplifier and down-converter assembly MCPC multi-channel single-carrier MMDS Multi-channel microwave distribution system MPEG-2 / DVB Domestic and European satellite program standard MPEG-2 High-definition image compression standard MSY M symbol rate MTV Music TV NCC National Geographic Channel PANDA-1 Panda sound, which can transmit 6 sets of satellite sound PID ? PACKET. IDENTIFER? Digital satellites in China and Europe are based on MPEG-
2 / DVB standard, the core of MPEG-2 is to transmit "data packets", PID codes appear in a combination of 0-9 and letters A-K, thus providing convenience for manual channel selection QPSK four-phase phase shift keying; orthogonal phase Shift keying RH right-handed circularly polarized RF satellite receiver TV high-frequency signal output terminal RS-232 serial communication interface RTV Reuters TV (UK)
SATAN SATCOM satellite communication satellite antenna Satellite Satellite Satellite digital transmission of satellite digital transmission Satellite earth station in satellite earth stations Satellite of television satellite Synchronous Satellite Satellite Transponder geostationary satellite SCPC satellite transponder SCPC SIGNAL. STRENGTH. GNIDE Signal Strength Guide SMART. CARD Smart Card SMATV Satellite Common Antenna System STA. TV satellite TV STAR. MOVIES Satellite TV SYMBOL. RAT symbol rate. Or use symbol rate or symbol rate, the content of the following unit is the same: MS
Y / S; Mbit / s; MBYTE / S; MBT / S, the range of use in China is 2 ~ 30M
bit / s and 2 ï½ž 40Mbit / s
TTC Chinese teletext broadcast clock; telemetry remote control tracking station TTD Chinese teletext data TVBS satellite TV; satellite TV broadcast program TVRO ordinary single-receiving station V vertical polarization; frame synchronization VBI field blanking period; teletext transfer during field blanking TV WORLD. DNET World Television Network

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