A Study Of Key Technology Of Low Spur And Wideband Frequency Synthesizer

With the rapid development of modern mobile communications,mobile communication chip design's requirements are also increasing.Wideband wireless communications due to its low average power,high spectrum efficiency,security and good and strong multipath resolution capability,has gradually become a mainstream way of modern communication.Wideband frequency synthesizer is the core module of wideband mobile communications chip,which is a hot research field in both academic and industrial fields.In this paper,the wideband frequency synthesizer key technology is the main research content.Firstly,I introduce the basic principles and structures of the frequency synthesizer composition.And then focuses on the influence of wideband frequency synthesizer spurious factors and improving methods,as well as wideband LC-VCO's design methods.Finally,the core module circuit structure of wideband frequency synthesizer are analysised and designed.In order to solve the current mismatch,I design a charge pump circuit with a virtual branch.In order to solve the change of tuning gain of broadband LC-VCO.I design a switched capacitor array and switches with a variable capacitor array.In order to provide a stable power supply for analog modules,I design a cap-less low dropout linear regulator supply circuit.The circuit is designed and simulationed by Global Foundry 0.18/?m CMOS RF process.Simulation results show that the charge pump current's mismatch is less than 0.25%.The VCO control voltage is 0.5Mv/?s.The oscillation frequency of the VCO is 1.23GHz-2.57 GHz,with a frequency coverage of 70% and tuning gain of 17-30MHz/V.The phase noise at 2.57 GHz is 136dBc/Hz@1MHz.After taping out and testing,the test results basically meet the design specifications,proving the correctness and feasibility of the design.