A 196.2 dBc/Hz FOMT 16.8-to-21.6 GHz Class-F23 VCO with Transformer-Based Optimal Q-factor Tank in 65-nm CMOS

Abstract

For the increasing demand of high data rate and wide coverage in high-quality satellite communication, the frequency synthesizer is expected to deliver wide tuning range (TR) and pure spectrum with low power consumption. In order to lower the phase noise (PN), transformer-based, trifilar-coil, and multi-core VCO topologies have emerged in recent years [1–4]. However, at millimeter-wave (mm-Wave) bands, TR becomes narrow and the Q-factor of resonance tank becomes low as the parasitic effect increases, especially for complicated trifilar-coil tank. It severely restricts VCOs’ figure-of-merit (FOM) as shown in Fig. 1. In terms of low power design, single-core VCO utilizing high-order tank to realize waveform shaping exhibits low PN, such as the Class-F topology. Figure 1 shows the conventional two-port Class-F VCO in [1]. The employment of the 1$:\mathrm{n}(\mathrm{n}\gt1)$ transformer amplifies voltage at gate, resulting in transistor entering triode region deeply. Thick-oxide devices are used to withstand large voltage swing, which may decrease switching speed and introduce additional noise. Besides, Q-factor of multi-turn transformer deteriorates at mm-Wave bands.