This paper presents a quadrature injection locked frequency divider (ILFD) employing tunable active inductors (TAIs), which are used is to extend the locking range and to reduce die area. The CMOS ILFD is based on a new quadrature voltage-controlled oscillator (VCO) with cross-coupled switching pairs and TAI-C tanks, and was fabricated in the 0.18-μm 1P6M CMOS technology. The divide-by-2 LC-tank ILFD is performed by adding injection MOSFETs between the differential outputs of the VCO. Measurement results show that at the supply voltage of 1.8V, the divider free-running frequency is tunable from 1.34GHz to 3.07GHz, and at the incident power of 0dBm the locking range is about 6GHz (137%), from the incident frequency 1.37GHz to 7.38GHz. The core power consumption is 22.8mW. The die area is 0.63×0.55mm².