Divide-by-2 Transformer-Based Injection-Locked Frequency Dividers with Two Active Cores

This letter presents a high-performance wide-band divide-by-2 injection-locked frequency divider (ILFD) in the 0.18 μm CMOS process. The ILFD uses transformer-coupled resonator with two resonant frequencies based on the lumped inductor model, and it consists of two sub-ILFDs coupled by inductive coupling. The sub-ILFD can be switched on/off to aid the circuit analysis, thus the ILFD can operate in three modes. At low input power, the two sub-ILFDs act as an independent ILFDs with a high-band locking range and a low-band locking range. At high input power, the ILFD has two non-overlapped locking ranges indicating that the dual-resonance resonator plays the role and will lead to a wide overlapped locking range. At the power consumption of 1.83 mW and at the input power of 0 dBm, the low-band locking range is 3.3 GHz from 2.3 to 5.6 GHz. The optimal bias condition at low power yields wide locking range and high figure of merit. Measurement data shows the designed ILFD has employed the property of a dualresonance resonator.