The main technical foundation for the development of China â€™s satellite live digital TV receiver chips and key modulation technology products comes from the research results of the â€œDirect Broadcast Satellite System Transmission Technology Researchâ€ project of the State Administration of Radio, Film and Television, namely the â€œAdvanced Satellite Broadcasting Systemâ€ (ABS-S) technical standard. Through close cooperation with the State Administration of Radio, Film and Television, China Unicom participated in the formulation and industrialization of ABS-S, and successfully developed the satellite TV receiver chip AVL1108 based on the ABS-S standard. ABS-S industrial chain of terminal receiving equipment.
In August 2006, the first-generation ABS-S dedicated receiver demodulation chip AVL1108 was successfully taped once, and it took only 10 months from project establishment to mass production. The advent of the chip marks the beginning of a new phase of industrialization of China's new generation satellite transmission technology (ABS-S). As the only mature and supply-capable ABS-S demodulation chip supplier, Zhongtian Lianke supplies the demodulation chip AVL1108 in batches to many domestic machine manufacturers, and fully supports the development work of domestic machine manufacturers. The satellite direct broadcast digital TV set-top box based on the AVL1108 chip developed based on ABS-S technology has basically covered the whole country, the reception quality is good, and the problem of safe reception is completely solved. After verification, AVL1108 has become the industry's most mature satellite live demodulation chip product.
Figure 1: The first generation digital TV demodulation chip AVL1108
Technical characteristics of AVL1108
The new generation of live broadcast satellite digital TV reception demodulation chip AVL1108 adopts a breakthrough innovative design, which further improves the performance of the ABS-S channel demodulation chip, reduces cost and power consumption, and its unique satellite demodulation and high-performance decoding technology is in the international leading position. The chip can perform QPSK and 8PSK demodulation and LDPC decoding functions; in 8PSK mode, it can provide 45MSps symbol rate and a maximum net code rate of 120Mbps; it fully meets the requirements of using 56MHz transponders on "Zhongxing Nine". If advanced video coding methods such as AVS or H.264 are used, a single transponder can carry 15 channels of high-definition satellite TV programs. After detailed testing, its performance fully meets the design requirements and is at the international advanced level. The measured load-to-noise ratio threshold of the receiving system based on this chip differs from the theoretical simulation result by only 0.1 ~ 0.3dB, and its data transmission capability, receiving threshold and other indicators reach or It exceeds the level of the latest generation of international satellite communication technology standard DVB-S2. At the same time, its structure is simpler, signal reception is more convenient, and its stability reaches the world's leading level.
ABS-S technology adopts advanced and efficient channel coding technology, which greatly improves the satellite spectrum utilization efficiency through high-order modulation and filter roll-off factor control, and effectively improves the satellite signal transmission capability. As China's first mature channel demodulation chip that fully complies with the ABS-S standard, AVL1108 can be applied to high-definition interactive satellite TV in addition to the government-led "Village Village" project. The innovative technology points of AVL1108, a live satellite digital TV receiver demodulation chip, are as follows:
* The main functions of AVL1108 include baseband signal demodulation and channel decoding. It is used to convert the ABS-S baseband signal output from the satellite tuner into a TS stream and provide it to the back-end decoding chip through a simple interface.
* AVL1108 is the industry's first satellite TV receiver chip in 8PSK demodulation mode, with a symbol rate of 45MSps and a net stream rate of 120Mbps, which can provide more channel reception and high-definition TV transmission.
* AVL1108 provides RF automatic gain control, and it can be connected to the front-end tuner only through a simple RC network.
* AVL1108 integrates high-performance dual-channel analog-to-digital converter (ADC), with DC elimination, IQ compensation and phase compensation functions.
* The received signal passes through matched filter, symbol clock recovery loop, carrier frequency and phase tracking loop, equalizer, forward error correction decoder, and then generates TS stream, which is sent to the back-end decoding chip.
* Through the standard two-wire bus control interface, the back-end processing chip can conveniently control the AVL1108, and configure the down converter (LNB) through the DiSEqC interface provided by the AVL1108.
* AVL1108 is specially optimized for ABS-S signal format, which can achieve perfect clock synchronization and excellent forward error correction performance. * AVL1108 has a strong ability to resist phase noise, can quickly lock the signal in the environment where the frequency deviation reaches 5MHz, and can maintain accurate clock synchronization.
Figure 2: AVL1108 internal structure diagram
AVL1108 performance index
The performance (technical) indicators of the AVL1108 are as follows: In 8PSK mode, the symbol rate is from 1MSps to 45MSps; it is fully in line with the Chinese Digital Direct Broadcast Satellite Standard (ABS-S), and supports 8PSK and QPSK modes; / 2, 3/5, 2/3, 3/4, 4/5, 5/6, 13/15, 9/10; the pulse shaping roll-off factor is 0.2, 0.25, 0.35; integrated two ADCs, with elimination Tributary, IQ compensation and phase compensation functions; signal quality monitoring and lock detection; built-in RF automatic gain control, which can be directly connected to the tuner; DiSEqC 2.0 fully compatible LNB controller; output data interface includes serial interface and parallel interface; standard Two-wire bus interface can provide four optional addresses; 100-pin LQFP-EP package.
Figure 3: AVL1108-based satellite digital TV receiver front-end design schematic
AVL1108 has a complete reference design and evaluation platform. Under the evaluation environment based on the evaluation platform, you can quickly test the functions and performance of the AVL1108 chip. At present, AVL1108 has completed preparations for large-scale industrialization. On this basis, it has supported the technical solutions of more than 30 complete machine manufacturers. Many domestic receiver equipment manufacturers have already had mass production capabilities, and have actively participated in the construction of the national "Village Village" project.
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