부산대학교 도서관

Voltage-controlled-oscillators (VCOs) with simultaneous low phase noise and wide frequency tuning range (FTR) spanning from tens GHz to millimeter-wave (mm-wave) bands are required for various standardized applications, such as 5G wireless communication, software-defined radios, and emerging high-speed wireline data links. However, due to the limited quality factor of on-chip passive components, increasing parasitics, and the tight capacitance budget, it is still very challenging for a single VCO to meet the wide FTR requirement while maintaining the phase-noise performance, especially in mm-wave bands. A recent development has proven that, when compared with enlarging switched-capacitor arrays or using switched inductors/transformers, multimode multicore techniques [1–5] are more efficient. This is because no RF current ideally flows through the lossy mode switches (assuming symmetrical cores), thereby relaxing the trade-off between on-resistance and off-capacitance of switches. In [1], a four-port dual-mode VCO with a 41.2% FTR is proposed. The parallel-inductor floorplan can achieve small inductance with high Q, favoring mm-wave operations. However, the dual-mode FTR is insufficient for many applications. The off-state negative G m pairs contribute large parasitic capacitance, which reduces the FTR. An EM mixed-coupling quad-mode quad-core VCO was reported in [2], which achieved an FTR of 73.2%. The quad-core topology theoretically improves the phase noise by 6dB. However, the quad-mode VCO has only two effective inductance values, while the other two modes are generated by introducing additional coupling capacitor pairs. On the one hand, the large coupling capacitors introduce non-negligible parasitic capacitance. On the other hand, two modes sharing the same inductance limit the design space, making it difficult to optimize both modes simultaneously. A triple-mode dual-core VCO with an 80.6% FTR using a compact inductor topology was proposed in [3]. However, the third mode was achieved by switching on and off negative G m pairs. The off-state negative G m pairs inevitably contribute to large parasitic capacitance. In addition, the asymmetrical compact-inductor topology sacrifices the Q and, consequently, the phase noise. The measured 186.3dBc/Hz average FoM at a 10MHz offset is inferior to the state-of-the-art narrow-band VCOs at similar frequency points.