Colpitts Injection-Locked Frequency Divider Implemented With a 3-D Helical Transformer

This letter proposes a wide locking range and low power complementary Colpitts injection-locked frequency divider (ILFD) employing a 3-D helical transformer. The proposed ILFD consists of two single-ended complementary Colpitts oscillators coupled by a 3-D transformer to form a differential oscillator. The aim of using the 3-D transformer is to reduce chip size. The divide-by-2 LC-tank ILFD is implemented by adding an injection nMOS between the differential outputs of the voltage controlled oscillator. The measurement results show that at the supply voltage of 1.8 V, the divider free-running frequency is tunable from 4.24 to 4.8 GHz. At the incident power of 0 dBm, vtune=0.9 V, and V _DD=1.5 V, the locking range is about 2.4 GHz (26.9%), from the incident frequency 7.7 to 10.1 GHz. The core power consumption is 3.9 mW. The die area is 0.548times 0.656 mm².