AbstractThis article presents a wide‐locking range injection‐locked frequency divider (ILFD), using a tunable active inductor (TAI), which is used to extend the locking range and to reduce die area. The CMOS ILFD is based on a new Colpitts voltage‐controlled oscillator (CVCO) with TAI‐C tank and was fabricated in the 0.18‐μm 1P6M CMOS technology. The ILFD is performed by adding injection MOSFETs between the differential outputs of the CVCO. At the supply voltage of 1.9 V, the free‐running ILFD tuning range is from 2.25 GHz to 1.26 GHz, whereas the tuning bias of active inductor is tuned from 0.88 V to 1.04 V. At the incident power of 0 dBm, the operation‐locking range is from the incident frequency 1.25–5.85 GHz. The phase noise of the ILFD can track with the injection source. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2376–2379, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23650