| The frequency dividers in Phase-locked loops(PLLs)are often implemented by the combination of prescalers and digital swallow counters.As one of the blocks which work at the highest frequency,the circuit optimization of prescalers is significant to the system performance.Since injection-locked frequency divider(ILFD)has excellent performance of simple structure,high operating frequency,low noise and low power,it has gradually become a hot research in high frequency application.However,the injection-locked models are too complicated to guide design and optimization of ILFD circuit effectively due to some instinct problems such as the nonlinearity and frequency conversion;Because there are different requirements for the quality factor of the loop,bandwidth and other parameters,it is difficult to improve locking range,reduce power consumption and enlarge division simultaneously in ILFD circuit design.This paper firstly analyses the essence of the injection-locked phenomenon.Based on this,a comprehensive exploration of its circuit operating principle can be concluded.Combining with the existing theoretical models and the circuit topologies and its structure characteristics,we intend to study the mechanism of interaction between different parameters in ILFD.Secondly,based on the theory conclusions,ILFDs were designed in this paper aiming to realize wide locking range,low power and large division.The proposed ILFDs were based on direct-injection,including current-reused topology,body-biased technique,dual-injection and harmonic-enhancement technique.Finally,by utilizing Chartered 0.18?m 2P5 M RF CMOS process,the proposed ILFDs have been validated by two MPWs,which were tested to further prove the conclusions.The experimental results reveal that the three proposed injection-locked frequency dividers can realize the multi-mode division function with low power consumption,and each kind of these division modes has a wide locking range. |
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