Design Of Wide-band High Precision Digital Controlled Oscillator In All Digital Phase Locked Loop For NB-IoT

With the development of communication technology and semiconductor technology,the transmission of information is more and more convenient,modern communication makes the connection between people very close,the interconnection of all things has become the goal of ”Internet of Things”.Narrowband Io T is a fast-growing Io T protocol that can be upgraded and deployed on LTE networks,with higher requirements for RF transceivers and frequency synthesizers.Under the advanced technology,wideband all digital phase locked loop is more suitable for Io T application scenarios.As the core module of ADPLL frequency synthesizer,digital controlled oscillator have an important influence on the performance of ADPLL system.Therefore,the design of wide-band high precision digital controlled oscillator has great theoretical significance and engineering application value.In this thesis,the principle of all digital PLL frequency synthesizer is expounded.Based on the analysis of the NB-Io T protocol,the specific requirement of digital controlled oscillator is figured out.40 nm CMOS technology has been choosen to design a low band DCO with a frequency range of 3122-4400 MHz and a high band DCO working in 4194-5364 MHz.In order to improve the accuracy of capacitor array in designed DCOs,a capacitor array with middle node is proposed,and the linearity of capacitor array is optimized.DCOs work at 0.9V power supply,with the structure of complementary differential coupled LC oscillator,the tail current source is eliminated to adapt low voltage supply and improve phase noise,the inverter chain buffer is used,and the frequency range has a certain margin compared with the specific requirement.The circuit design,layout design and post simulation results are given.Post simulation result shows that under room temperature,the low band DCO has a frequency range of 2926-4406 MHz,with a frequency gain of 44 k Hz/LSB at the intermediate frequency,the average current consumption less than 3.516 m A,and the phase noise in the full band is better than-114.981 d Bc/ Hz@1MHz and-146.035 d Bc/Hz@30MHz.The high band DCO has a frequency range of 3797-5514 MHz,the frequency gain at the intermediate frequency is 52 k Hz/LSB,the average current consumption less than 4.158 m A,and the phase noise of the entire band is better than that of 111.585 d Bc/Hz@1MHz and-145.011 d Bc/Hz@30MHz.The wide-band high precision DCOs designed in this thesis meet the requirements and can be applied to all digital phase locked loop frequency synthesizer for NB-Io T.