Research On Key Technology Of Digital TV Demodulation Chip

With the coming of age of the digital era, the vigorous development of digital television technologies are happening worldwide. Substitution of Color TV for black and white TV is known as the first television revolution, while substitution of Digital TV for Analog TV subsequently becomes the second revolution which will have a far-reaching influence on humans work and life. In the face of such technological changes, countries in the world set about the deployment of their own digital broadcast TV transmission networks and draw up transitional plan from Analog TV to Digital TV. The United States has stepped into overall Digital TV era since the analog TV signals was going off the air in June 2009. Some of the European countries such as the United Kingdom have accomplished the transition from Analog TV to Digital TV in 2010. Meanwhile, China recently issue the Digital Terrestrial Multimedia Broadcasting (DTMB) standard and China Multiple Media Broadcasting (CMMB) standard. It is predicted that national analog TV broadcast will be turned off and totally replaced by digital TV in 2015. At present, researches on Demodulator IC Design which is regarded as the core technology of broadcast digital TV system remain the primary priority.With in-depth research and analysis of digital TV state-of-art, this paper discussed the key factors which affect the DTV demodulation performance including sample offset, carrier offset, multipath and Doppler shift. And then the synchronization scheme using in DVB-S2 and CMMB systems is proposed to cope with the interference under the low SNR channels and multipath channel. Meanwhile, the channel estimation and equalization schemes which are suit for CMMB and DTMB are proposed. And ICI mitigation circuits and low-complexity high-performance long echo mitigation circuits were designed to eliminate the side effects produced by high speed mobile environment and single frequency networks. In addition, this work also researches the frequency domain equalization of single-carrier systems. Moreover, low complexity SC-FDE schemes were raised for both ATSC and DTMB after through studying the frequency domain equalization of single-carrier systems.The crucial research contributions of this work are listed as below:(1) The proposed fast frame synchronization algorithm for DVB-S2 demodulator considered the low SNR (-2.35dB) and large carrier frequency offset (5MHz) channel. And it was able to improve the adaptive capability of the DVB-S2 demodulator by means of frame length estimate and auto identifying the modulation modes. Furthermore, an optimal structure is applied to reduce the hardware resource consumption of the frame synchronization.(2) An anti-multipath interference integer-Frequency-Offset estimator was proposed to eliminate multipath interference with continuous data cross-correlation and thus improved the performance of carrier synchronization.(3) For single frequency network, once the guard interval of OFDM system is shorter than the length of channel response impluse, the severe inter-symbol interference will be generated. This work employed the signal reconstruction with decision feedback structure to eliminate ISI efficiently for performance improvement. An optimal structure was proposed as well for the purpose of reducing the chip area consumption.(4) To eliminate ICI in the high speed mobile channel, this work presented an adaptive ICI-mitigate scheme with iterative decision feedback structure. The scheme used efficient low-complex Doppler estimation module to make adaptively control of the ICI mitigation circuits. And also the ICI mitigate scheme with iterative decision feedback structure could eliminate ICI efficiently and improved the system performance in high speed mobile channel. In addition, the optimal structure is proposed to reduce the chip area consumption.(5) This work discussed efficient iterative decision feedback frequency domain equalizer for single-carrier systems. It raised the system performance at low hardware resource cost by comparison with the traditional single-carrier time domain equalizer. By using the proposed frequency domain equalizer, DTMB demodulator can support both the single carrier mode and multi-carrier mode with low-complexity architecture.(6) Single carrier frequency domain equalizer for ATSC systems was proposed in this paper. The proposed scheme utilized the cyclic prefix reconstruction and iterative decision feedback structure to eliminate IBI and ICI efficiently and therefore improved the system performance of both the static and dynamical channel.