GNSS射频芯片中小数分频技术研究  

Research on fractional frequency division technology in GNSS RF chip

作　　者：李鑫[1] 黄海生[1] 

机构地区：[1]西安邮电大学电子工程学院,陕西西安710121

出　　处：《现代电子技术》2016年第5期55-57,62,共4页Modern Electronics Technique

基　　金：陕西省科技统筹创新工程计划项目(2012KTCQ01-06);陕西省教育厅产业化培育项目(2013JC10);西安邮电大学青年教师科研基金项目(101-0490);陕西省科技统筹创新工程计划战略性新兴产业重大产品(群)项目":北斗授时型接收机芯片组及产业化"项目(2014KTCQ01-21)

摘　　要：针对GNSS射频前端PLL频率综合器中的低杂散小数分频问题,提出了分别基于累加器结构和MASH1-1-1Δ-∑结构的两种小数分频调制器实现方案。进而选取3.996 MHz为GNSS射频前端模拟中频频率,16.368 MHz为PLL频率综合器参考频率,在GPS L1和BD-2 B1频点上对30级累加器级联结构和MASH1-1-1Δ-∑结构的输出功率谱进行分析,并在此基础上对它们的小数杂散特性进行了对比研究。结果表明,MASH1-1-1Δ-∑结构具有噪声整形功能,可将小数杂散由低频段推至高频段,从而在低频段获得更优的杂散特性。由于高频段的杂散可被PLL环路滤波器滤除,故MASH1-1-1Δ-∑结构更适合用在基于PLL的频率综合器中。In view of the low-spurious fractional frequency division problem in PLL frequency synthesizer of GNSS RF front- end, two implementation schemes of fractional frequency division modulator respectively based on accumulator structure and MASH1-1-1Δ-Σ structure are proposed. The 3.996 MHz is chosen as the intermediate frequency of GNSS RF front-end, and 16.368 MHz as the reference frequency of PLL frequency synthesizer. The output power spectrums of cascade structure with 30- grade accumulator and MASH1-1-1Δ-Σ structure are analyzed at the frequency points of GPS L1 and BD-2 B1. On this basis, the fractional spur characteristics of the two structures are compared and studied. The comparison results show that the MASH1-1-1Δ-Σ structure has noise shaping function, and can push the fractional spurs from low-frequency band to high-frequency band to obtain better spur characteristics at low-frequency band. Since the spurs at high-frequency band can be filtered out by the PLL loop filter, the MASH1-1-1Δ-Σ structure is more suitable to use in the frequency synthesizer based on PLL.

关 键 词：小数分频 累加器 MASH1-1-1 Δ-Σ调制器 小数杂散 

分 类 号：TN402-34[电子电信—微电子学与固体电子学]