China’s first direct broadcast satellite, “Zhongxing No.9â€, was successfully launched on June 9, 2008 and has been officially put into operation. The “village to village†project led by the Chinese government has been opened, and the entire “village village†will be opened. More than 20 million home users are involved. With the launch of the “Village to Village†project, it is expected that China will become the world's largest direct broadcast satellite user market in the next two or three years.
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The main technical basis for the development of China's satellite live digital TV receiver chip and modulation key technology products stems from the research results of the "Research on Transmission Technology of Direct Broadcast Satellite System" by the State Administration of Radio, Film and Television, namely the "Advanced Satellite Broadcasting System" (ABS-S) technical standard. Through close cooperation with the State Administration of Radio, Film and Television, Zhongtian Lianke participated in the formulation and industrialization of ABS-S, and successfully developed the satellite TV receiver chip AVL1108 based on the ABS-S standard. Based on this, the modulator was improved. The terminal receives the ABS-S industry chain of the equipment.
In August 2006, the first generation of ABS-S dedicated receiving and demodulating chip AVL1108 was successfully streamed, and it took only 10 months from project establishment to mass production. The launch of the chip marks the beginning of a new phase in the industrialization of China's new generation of satellite transmission technology (ABS-S). As the only mature ABS-S demodulation chip supplier with availability, Zhongtian Lianke supplies the demodulation chip AVL1108 to a number of domestic machine manufacturers in batches, and fully supports the development of domestic machine manufacturers. The satellite live digital TV set-top box using the AVL1108 chip developed based on ABS-S technology has basically covered the whole country, and the receiving picture quality is good, and the problem of safe reception is completely solved. After verification, AVL1108 has become the most mature satellite live demodulation chip product in the industry.
Figure 1: First generation digital TV demodulation chip AVL1108
Technical characteristics of AVL1108
The new generation of live satellite digital TV receiver demodulation chip AVL1108 adopts a breakthrough innovative design, which further improves the performance of ABS-S channel demodulation chip, reduces cost and power consumption, and its unique satellite demodulation and high-performance decoding technology is international. leading position. The chip can complete QPSK and 8PSK demodulation and LDPC decoding functions; it can provide 45MSps symbol rate and up to 120Mbps net code rate in 8PSK mode; it fully meets the requirement of using 56MHz transponder on "Zhongxing No.9". If advanced video coding methods such as AVS or H.264 are used, a single transponder can be equipped with 15 HD satellite TV programs. After detailed testing, its performance fully meets the design requirements and ranks at the international advanced level. Based on the chip, the measured carrier-to-noise ratio threshold and the theoretical simulation result are only 0.1~0.3dB, and the data transmission capability, receiving threshold and other indicators reach or It surpasses the level of the latest generation of international satellite communication technology standard DVB-S2, and its structure is simpler, signal reception is more convenient, and its stability reaches the world 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 the first mature channel demodulation chip in China that fully complies with the ABS-S standard, the AVL1108 can be applied to high-definition interactive satellite TV in addition to the government-led “village-to-village†project. The innovative technology of the live satellite digital TV receiver demodulation chip AVL1108 is as follows:
The main functions of the AVL1108 include baseband signal demodulation and channel decoding, which are used to convert the ABS-S baseband signal output from the satellite tuner into a TS stream and provide it to the backend decoder chip through a simple interface.
The AVL1108 is the industry's first satellite TV receiver chip with a symbol rate of 45MSps and a net stream rate of 120Mbps in 8PSK demodulation mode, providing more channel reception and high definition TV transmission.
The AVL1108 provides RF automatic gain control that can be connected to the front-end tuner with a simple RC network.
The AVL1108 integrates a high performance dual analog-to-digital converter (ADC) with DC, IQ compensation and phase compensation.
The received signal passes through a matched filter, a symbol clock recovery loop, a carrier frequency and phase tracking loop, an equalizer, and a forward error correction decoder, and then a TS stream is generated and sent to the backend decoding chip.
Through the standard two-wire bus control interface, the back-end processing chip can easily control the AVL1108, and configure the down-converter (LNB) through the DiSEqC interface provided by the AVL1108.
The AVL1108 is specifically optimized for the ABS-S signal format for perfect clock synchronization and excellent forward error correction.
The AVL1108 is extremely resistant to phase noise and can quickly lock signals in environments with a frequency offset of 5MHz and maintain accurate clock synchronization.
Figure 2: Schematic diagram of the internal structure of AVL1108
AVL1108 performance indicators
The performance (technical) specifications of the AVL1108 are as follows: In 8PSK mode, the symbol rate is from 1MSps to 45MSps; it is fully compliant with the China Digital Live Satellite Standard (ABS-S), supports 8PSK and QPSK modes; and the rate correction support for the forward error correction decoder is 1 /2, 3/5, 2/3, 3/4, 4/5, 5/6, 13/15, 9/10; pulse shaping roll-off factor of 0.2, 0.25, 0.35; integrated two ADCs with elimination Tributary, IQ compensation and phase compensation; signal quality monitoring and lock detection; built-in RF automatic gain control, can be directly connected to the tuner; DiSEqC 2.0 fully compatible LNB controller; output data interface including serial interface and parallel interface; Two-wire bus interface with four selectable addresses; 100-pin LQFP-EP package.
Figure 3: Schematic diagram of front-end design of satellite digital TV receiver based on AVL1108
Summary of this article
The AVL1108 has a complete reference design and evaluation platform to quickly test the features and performance of the AVL1108 chip in an evaluation platform-based evaluation environment. At present, AVL1108 has completed preparations for large-scale industrialization. On this basis, it has supported more than 30 complete machine manufacturers' technical solutions. Many domestic receiver equipment manufacturers have already possessed mass production capabilities and actively participated in the construction of the national “village to village†project.
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