A 24.4∼39.6 GHz Wide Locking Range Divide-by-4 Injection-Locked Frequency Divider With High Harmonic Rejection Ratio

In this brief, an innovative divide-by-4 injection-locked frequency divider (ILFD) is hereby proposed to expand the locking range (LR) and improve the harmonic rejection ratio (HRR). Specifically, a fourth-order transformer-based resonator is adopted to improve the LR without any additional tuning capacitors, and a dual-tank network is proposed to optimize the harmonic rejection. To implement the proposed techniques, two chips with different networks are analyzed, designed, and fabricated in a 28-nm CMOS technology. The chip with the dual-tank network is proven to achieve the bandwidth from 24.4 to 39.6 GHz, i.e., 47.5% with the second and third harmonic rejection ratios of better than 32 dBc and 11 dBc, while the other chip achieves the bandwidth from 30.8 to 42.6 GHz, i.e., 32.2%. Additionally, the ILFD with the dual-tank network is confirmed to possess differential output power from -17.5 to -19.8 dBm, consuming only 7.4 mW dc power under a 0.5-V supply.