摘要
在20世纪70年代初期,联邦德国开发了一种为汽车驾驶人员服务的广播信息服务(RIS),RIS附加在调频广播中,可识别各米波调频广播,以解决在驾车旅途中由于调频发射机服务区比较小而经常需要重调收音机的问题。由于功能很有限,远不能满足需要。不久,欧洲广播联盟组织成立,开发了广播数据系统(RDS),并于1984年公布了首份RDS系统的技术规范。经过20多年的发展,目前RDS技术已经成熟,RDS及相关产品在全球已经形成了年销售上百亿欧元的产业规模。美国也制订了相类似的RBDS。
RDS接收机的调频波段在87.5~108.0MHz范围,相邻电台波段间隔至少100kHz,在57kH上加载副载波数据。数据内容包括电台类型、节目类型、交通公告、广告信息、标准时间、天气预报等,同时提供了开放式数据接口,为特殊要求用户提供数据文本应用通道。
本论文主要内容是做一块处理RDS/RDBS信号的前端处理器芯片。从高频头接受电台信号,通过滤波器分离出57kHz载波信号,再从57kHz的载波信号解调出RDS/RBDS,再对信号进行编译。处理完的数据就可以用DSP芯片进行处理,处理完的数据再通过D/A转换,再经过功放就可以听到完美的广播信息。第一章回顾RDS/RBDS技术的发展,什么是RDS/RBDS,具体的用途在何处,整体上如何工作的;第二章研究如何芯片的基准源,芯片基准源是在电压变化和温度变化的情况下为整块芯片电路提供稳定的电流源;第三章研究如何设计前端抗混淆滤波器,抗混淆滤波器将无用高频部分滤除,消除高频部分对有用信号的干扰;第四章讨论如何设计57kHz的开关电容带通滤波器,这是这块芯片的关键部分,芯片的主要模拟性能指标都在这开关电容滤波器中,因此本论文花大量时间分析研究开关电容滤波器,论述开关电容电路工作的基础,分析开关电容电荷放大器,开关电容积分器,研究开关电容电路的z域分析,并分析由这些基础的结构组成的二级开关电容电路:第五章总结全文。
在标准cmos工艺中电容的相对精度相当高。开关电容电路的主要优点是与cmos工艺兼容;高精度的时间常数;良好的电压线性度;良好的稳定特性。主要的缺点:时钟馈通;需要不重叠的时钟信号;信号的宽度必须小于时钟频率。
German made an air information system for drivers in 1970s.AIS can distinguish all meter lengths in FM broadcasting, so the problem of tuning radios again because of the small transmitters' service during driving cars is well done. The function of this system is very small, and can not be satisfied well. European broadcasting league was founded and made the radio data system (RDS). In the following it promulgated the first technology rules of RDS. The RDS technology is mature, and RDS and involving products have formed tens of billion sell scale in a year. America has established the similar of radio broadcasting data system (RBDS).
FM lengths of the receiver are from 87.5 to 108.0MHz. The nearing radio length is at least 100 KHz. The data of RDS is included in 57 KHz. The RDS/RBDS system offers a large range of applications by its many functions to be implemented. For car radios the most important are: program service name, traffic program identification, traffic announcement signal, alternative frequency list, program identification, enhanced other networks information.
The thesis introduces a chip of RDS/RDBS pre-processor. The high frequency receiver receives radio signal. Compared with standard radio systems, RDS/RBDS controlled radio systems additional require an RDS/RBDS demodulator with a 57KHz switched capacitor band-pass filter information about the current reception situation (reception quality, multi-path disturbance etc.),and additional microcontroller power for RDS/RBDS data processing, decoding and radio control.
The new RDS/RBDS pre-processor includes all these specific functions and meets all requirements of a high end RDS/RBDS radio. Moreover the timing requirements of the set controller, regarding RDS/RBDS data processing are reduced due to the integration of decoder functions, so that the development of radio control software can be concentrated specifically on radio set features.
引文
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