With the rapid development of modern information technology, terrestrial digital TV has become the mainstream of the development of today's radio and television. It has been broadcast in nearly 30 provinces and cities. Its advantage is that it can achieve mobile and portable reception and meet the needs of modern society. "Request. However, due to the influence of factors such as terrain and power, it is difficult to ensure that the signal coverage of all parts of the network is in good condition, and some areas may not receive normally, such as shadowed areas of high buildings, underground parking lots, remote suburbs, rural areas, etc. Therefore, the blind area coverage of digital TV becomes the focus of the next network construction. Under this circumstance, we have developed a reliable and cheap device for solving the blind spot problem of digital TV terrestrial network coverage-digital TV repeater, also known as repeater or gap filler (GAP FILLER) .
Introduction to Digital TV Repeater
The digital TV repeater is a wireless relay amplifier device, which plays a role in signal enhancement during the transmission of digital TV. It is the most cost-effective way to expand the coverage of the established digital TV network and solve mobile communication in blind areas and remote areas. Transponders are divided into co-frequency transponders, frequency-shift transponders and optical fiber transponders according to their transmission methods.
(1) The main working principle of the same-frequency repeater (also called the same-frequency repeater) is to receive the signal from the existing coverage area through the donor antenna, and then transmit it to the area to be covered after processing such as filter amplification. Main features: simple structure and small signal forwarding delay. Isolation is the most important issue for co-frequency transponders, and it is also the most problem to be faced and solved. The construction of the project is difficult.
(2) The principle of frequency-shifting repeaters (also called difference-frequency repeaters) is basically similar to that of co-frequency repeaters, but the frequency of the signal output is moved to the specified frequency band. Main features: simple structure, small signal forwarding delay, and receiving and sending signals at different frequencies ensure isolation and will not form self-excitation. Engineering construction is the easiest.
Lihe terrestrial digital TV repeater is a brand new network optimization product designed for terrestrial digital TV system. By enhancing the received signal, and then transmitting after the same frequency or frequency conversion amplification, the coverage after forwarding reaches 0.5 to 5 kilometers, suitable for:
Coverage of suburbs, villages, and transportation;
Coverage of shadow areas (e.g. mountain areas);
Coverage of large buildings, underground mall parking lots, subway systems, etc.
Main features of digital TV repeater
√ Output power range: 1W, 2W, 5W, 10W
√ Frequency range: 470 ～ 860MHz
√ LDMOS all solid-state semiconductor technology
√ RF predistortion technology
√ Multi-level AGC control
√ Same frequency & difference frequency forwarding mode
√ High stability OCXO reference clock
√ High sensitivity
√ Low adjacent channel leakage
√ Self-excited protection
√ Small size, integrated chassis, convenient installation
√ All-weather indoor and outdoor applications
√ Local / remote monitoring
√ Comply with ISO9001 standard
√ High reliability
√ The forward signal-to-noise ratio is high, and the signal-to-noise ratio is about 10db higher than similar products.
√ The product has passed the test of the State Key Laboratory of Digital Communications of Tsinghua University and its performance has reached the level of similar foreign products.
Technical indicators of Lihe transponder
Working frequency: 470-860MHz (channel 13 to 55)
Output power: 30 ～ 40dBm (power amplifier adopts predistortion technology)
Gain: 90 ～ 100dB
Automatic gain control range: ≥40dB
Maximum allowable input power: -10dBm or 97dBuV
In-band fluctuation: ≤1.5dB
Noise figure: ≤4dB
Output standing wave ratio: ≤1.3 (open environment test)
Signal delay time: ﹤ 6uS
Out-of-band suppression: ≥60dbc (except Fc ± 20MHz)
Output shoulder: ≥40dbc
Input and output impedance: 50 / 75Ω
Monitoring function: local or remote monitoring function (user selectable)
Working temperature: -35 ℃ ～ + 65 ℃
Working humidity: 5--95% RH
Appearance size: 480 & TImes; 300 & TImes; 200mm
Power consumption: ≤30W or 80W (depending on different models)
Power supply: AC 220V
Connector form: N head
The products have a high share in China, and also used for INDUCTOTHERM,ELECTROTHERM,MEGATHERM,PILLAR,SUPERHEAT,ABP , Mitsubishi electric, Fuji, the United States Yingda equipment and other manufacturers of induction Furnace.
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