摘要
随着信息技术的快速发展,电视技术正经历着从模拟到数字的转变,在未来10年间具有巨大的市场潜力,国际竞争将十分激烈。数字视频地面广播(即无线传输)是其中的重要技术。数字视频地面广播不仅能传输数字音/视频和宽带数字数据,还能实现远程教育等交互式多媒体业务。当前,数字地面广播在全球已经出现了多种不同标准,国外主要有美国的ATSC、欧洲的DVB-T和日本的ISDB-T;我国迄今已有5种标准提案,其中地面数字多媒体电视广播传输协议(TDS-OFDM based DMB-T)和高级数字电视广播系统传输标准(ADTB-T)为两大主流方向。
本文研制的数字视频地面广播射频接收前端模块是DVB-T接收系统的一个关键部件,它关系到整个接收系统性能指标的优劣。此模块不仅适用于DVB-T标准的接收系统,还适用于DMB-T、ADTB-T等其他各种标准的接收系统以及有线电视数字机顶盒和线缆调制解调器。该模块采用具有高镜像抑制能力的二次变频接收方案,能在50MHz~878MHz的带宽内接收-90dBm~-10dBm的RF信号,并提供80dB的增益控制范围,噪声系数小于5dB;双环频率合成器产生两种本地振荡器(LO)频率,相位噪声优于-82dBc/Hz@1kHz,第一中频滤波器使调谐器具有50dBc的镜像抑制能力。本文还研制了适用于DVB-T射频接收前端模块的宽带锁相环,它能锁定900MHz~1800MHz的频率范围,其稳定性和相位噪声均能满足DVB-T系统指标的要求。
本文中首先介绍了设计方案,然后用EDA软件对调谐器模块和宽带锁相环的各项指标进行了仿真,依据仿真结果设计制作了硬件实物,最后对硬件系统进行了测试。与市场现有芯片相比较,本文设计的模块有较低的噪声系数,更大的增益控制范围,性能良好,达到了预期的设计指标。
With the promotion of information technology, analog TV will be substituted with digital TV in the next 10 years. International competition come with this upgrade will be extremely intense, especially in the field of Digital Television Terrestrial Broadcasting namely wireless transmission technology. Digital Television Terrestrial Broadcasting (DTTB) can not only receive digital video/audio and transmit broadband datum, but also implement interaction multimedia including long-distant education. Currently, there are three DTTB transmission standards abroad. They are ATSC in the USA, DVB-T in Europe and ISDB-T in Japan. Nowadays, 5 standard resolutions are available in China, and TDS-OFDM based DMB-T as well as ADTB-T are two competitive standards.
This paper focuses on the research of RF receiver front-end module, which is a key component of DVB-T receiving system. This module can suitable not only for any digital video broadcasting-terrestrial Receivers or CATV system, but also for Cable Modems and Digital Set-Top Boxes.
This paper presents a design of low-cost, broadband RF receiver front-end module which adopts dual-conversion topology bearing high image rejection. This module can process RF signal with amplitude from–90dBm to -10dBm, and the operating frequency range extends from 50MHz to 878MHz while providing over 80dB gain-control range and its noise figure is below 5dB. A dual synthesizer generates both local oscillator (LO) frequencies, providing superior phase noise performance of -82dBc/Hz at 1kHz. The HI-IF filter achieves over 50dBc of image rejection. A broadband PLL based on this tuner is implemented. This PLL can lock the frequency between 900MHz and 1800MHz and its stability and phase noise can satisfy the system specifications.
The design scheme is presented first. According to the system specifications, the simulation of the tuner and PLL are realized with EDA software. Then the RF board hardware design is completed and finally excellent test results are given. All measurement results have good agreement with the simulation results, which satisfy the system requirements.
引文
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