This paper presents a detailed study of phase noise of an LC Quadrature Voltage-Controlled Oscillator (QVCO). This QVCO is made of coupling two identical cross-connected Colpitts oscillators as core oscillators. MOSFETs are used as varactors, the substrates of which are used for coupling the two core Colpitts oscillators. Phase noise improvement resulted from substrate coupling is not only due to elimination of noise sources (as no extra passive or active coupling devices are used) but also due to lower effective thermal noise of the substrates. To verify this, a rigorous phase noise analysis of the circuit using the Linear Time Variant (LTV) model is performed for the 1/f² region. It indicates that the improvement is not only due to lower thermal noise of the substrate, but also a better noise modulating factor (NMF). The proposed QVCO was designed and simulated in a 0.18 ​μm RF-CMOS Technology at frequency of 5.35 ​GHz with a power consumption of 8 ​mW, tuning range of 18% and phase noise of −142.8 ​dBc/Hz at 5 ​MHz frequency offset. The presented analysis indicates a phase noise of −143 ​dBc/Hz at an offset of 5 ​MHz, which shows a good agreement with the simulation. The difference between the simulated and calculated phase noise at high frequency offsets is less than 0.2 ​dB.

本文对LC正交压控振荡器（QVCO）的相位噪声进行了详细研究。该QVCO由耦合两个相同的交叉连接的Colpitts振荡器作为核心振荡器组成。MOSFET用作变容二极管，其衬底用于耦合两个核心Colpitts振荡器。基板耦合导致的相位噪声改善不仅是由于消除了噪声源（因为没有使用额外的无源或有源耦合设备），而且还由于基板的有效热噪声较低。为了验证这一点，针对1 / f ²使用线性时变（LTV）模型对电路进行了严格的相位噪声分析。地区。这表明改进不仅是由于基板的热噪声较低，而且是由于噪声调制因子（NMF）更好。拟议的QVCO在0.18μmRF-CMOS技术中以5.35 GHz的频率进行设计和仿真，功耗为8 mW，调谐范围为18％，在5 MHz时的相位噪声为−142.8 dBc / Hz频偏。提出的分析表明，在5 MHz的偏移量处的相位噪声为-143 dBc / Hz，这与仿真显示出良好的一致性。高频偏移处仿真和计算的相位噪声之间的差异小于0.2 dB。