一种可编程振荡器的设计

【作者】 马静恒；

【导师】 黄显核；

【作者基本信息】 电子科技大学 ， 检测技术与自动化装置， 2008， 硕士

【摘要】 晶体振荡器以其高稳定度而著称,不同性能的晶体振荡器,满足工程上不同的需要,但其一般工作在固定频率中。而可编程晶振的最大特点就是短时间内就能定置一系列高稳定的频率。以单个多用途可编程晶振来代替库存几百种固定晶振的方式将为设计者、加工厂和其他从事大批量生产的电子公司带来巨大的灵活性,其便于集成能创造出巨大的节约效果。本设计通过采用基于锁相环的方式,以晶体振荡器为频率源进行频率合成,实现频率输出的可编程。虽然这对晶振的高稳定度有一定的负面影响,但已完全能够满足一般的工业需求。本论文首先对基于锁相环路的频率合成原理作了详细的介绍,然后对压控振荡器(VCO)进行分析和设计,并运用ADS实现仿真;接着设计了频率合成器的核心部件环路滤波器(LPF),最后给出了可编程晶振的总体设计方案和软件编码的设定,并进行了相关的实验验证。本设计具有频率范围广、分辨率高、稳定性好、可程控性强、步进率小、结构简单、成本低等优点,有很强的实用性和经济性,便于推广。设计所采用的是National Semiconductor公司所生产高稳定、低功耗的锁相环芯片LMX2306;VCO电路采用西勒振荡电路分立元件拓扑结构和芯片式两种方式,通过性能的比较最终选择后者;LPF通过直接计算获得元件值;而可编程数据通过软件codeloader载入芯片内部,最终得到期望的频率输出(70MHz～150MHz),其最小步进可达到5kHz,输出功率为-10dBm。更多还原

【Abstract】 The crystal oscillator, which generally works at fixed frequency, is famous for its high stability. And different kinds of crystal oscillators fulfill the different engineering. The major characteristic of the programmable crystal oscillator is to set a series frequencies of high stability at short notice. Then several hundred kinds of fixed crystal oscillators in stock are substituted by a multi-purpose programmable crystal oscillator. It is flexible for designers, factories and companies, moreover it’s convenience for integration will bring the latent frugal effects.Based on the phase-locked loop and the crystal oscillator as the source, a programmable oscillator is designed. Although it brings certain negative influence on the high stability of the crystal oscillator in this way, it is enough for general industry requirement. Moreover, it is advantageous for the frequency control.First, the basic principle of frequency synthetic technology is introduced in detailed in this paper. Second, the discussion and improvement of the design of the Voltage Controlled Oscillator (VCO), which is simulated by ADS, is presented; and another component loop passed filter (LPF), which is the core of PLL, is designed. Finally, a total solution and the coding are given at the end of this paper. There are has many merits in the design, such as wide rang frequencies, high resolution ratio, high stability, programming. And, as its strong practicability and economy, it is easy to make it popular.We use the phase locked loop chip LMX2306 in this design. In its peripheral circuits, we calculated the components of LPF directly, and choosed the better VCO after comparing the performances between Seiler common collector VCO and MAX2606. At last, the programmable date which is used to set dividing frequency sequence is loaded by codeloader. The output of this device is between 70MHz and 150MHz according to the VCO’s inductor, and the minimum step can achieves 5kHz, the power is -10dBm.更多还原