This article presents a set of ring oscillators design using three types of inverters. Symbolical delay calculations are performed and dependency on the supply voltage is investigated for each inverter. Based on delay descriptions, combined structures show the potential to behave more stable than simple structures. Mostly combined structures reduce speed as the cost of realizing less sensitive circuits. The analysis yields more robust ring oscillators vs noisy conditions, specifically supply voltage ripples and temperature deviations. Based on calculations, seven possible structures are simulated exploiting TSMC 0.18 μm CMOS. Additionally, combined ring oscillators are more robust against supply voltage ripples and temperature variations. The cost of this robustness is reduced oscillation frequency value. Based on the structure, in CMOS technology expresses 3% oscillation frequency deviation against 30% supply variation. The new combined structures demonstrate high potential to be used in larger circuits and systems like phase loops and clock generator.

中文翻译：

---

鲁棒的组合环形振荡器：延迟描述方法

本文介绍了一组使用三种类型的逆变器的环形振荡器设计。执行符号延迟计算，并研究每个逆变器对电源电压的依赖性。根据延迟描述，组合结构显示出比简单结构更稳定的性能。由于实现敏感性较低的电路的成本，多数情况下组合结构会降低速度。与噪声条件相比，该分析得出的环形振荡器更加鲁棒，特别是电源电压纹波和温度偏差。基于计算，利用TSMC 0.18μmCMOS模拟了七个可能的结构。此外，组合式环形振荡器在电源电压纹波和温度变化方面更强大。这种鲁棒性的代价是降低了振荡频率值。根据结构，CMOS技术中的误差表示3％的振荡频率偏差相对于30％的电源变化。新的组合结构展示了在较大的电路和系统（如相位环和时钟发生器）中使用的巨大潜力。