{"title":"A new Fractional-N frequency synthesizer using Nested-PLL architecture","authors":"Mohammadreza Jamali, Emad Ebrahimi","doi":"10.1109/IRANIANCEE.2017.7985408","DOIUrl":null,"url":null,"abstract":"Delta-sigma modulators (DSM) in conventional Fractional-N PLLs produce quantization noise and can't remove fractional spurs around the main frequency well. In order to reduce the spurs in Fractional-N synthesizers, a new Nested-PLL has been presented in this work. The proposed Fractional-N PLL consists of a conventional PLL as a frequency multiplier (*M) in feedback path that make fraction M/N along divider (N). In the other words the fraction M/N is achieved by a Nested-PLL instead of delta-sigma modulator. Therefore, spurs caused by delta-sigma modulator or pulse swallower is removed. The proposed Nested-PLL and its stability issues are addressed in this paper. Also to verify the proposed structure a prototype of the synthesizer with Fref=100MHz and Fout=1GHz–1.3GHz designed and simulated systematically, and no fractional spurs are observed.","PeriodicalId":161929,"journal":{"name":"2017 Iranian Conference on Electrical Engineering (ICEE)","volume":"64 1","pages":"0"},"PeriodicalIF":0.0000,"publicationDate":"2017-05-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"1","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"2017 Iranian Conference on Electrical Engineering (ICEE)","FirstCategoryId":"1085","ListUrlMain":"https://doi.org/10.1109/IRANIANCEE.2017.7985408","RegionNum":0,"RegionCategory":null,"ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"","JCRName":"","Score":null,"Total":0}
引用次数: 1
Abstract
Delta-sigma modulators (DSM) in conventional Fractional-N PLLs produce quantization noise and can't remove fractional spurs around the main frequency well. In order to reduce the spurs in Fractional-N synthesizers, a new Nested-PLL has been presented in this work. The proposed Fractional-N PLL consists of a conventional PLL as a frequency multiplier (*M) in feedback path that make fraction M/N along divider (N). In the other words the fraction M/N is achieved by a Nested-PLL instead of delta-sigma modulator. Therefore, spurs caused by delta-sigma modulator or pulse swallower is removed. The proposed Nested-PLL and its stability issues are addressed in this paper. Also to verify the proposed structure a prototype of the synthesizer with Fref=100MHz and Fout=1GHz–1.3GHz designed and simulated systematically, and no fractional spurs are observed.