Implementation of 6-Port 3D transformer in injection-locked frequency divider

This paper proposes a 6-port 3-dimensional (3-D) transformer used to improve the performance of injection-locked frequency divider (ILFD). The aim of the 3-D transformer is to reduce chip size and to reduce power consumption. The CMOS LC-tank ILFD is implemented using the direct injection nMOS between the differential outputs of an nMOS-core cross-coupled VCO. At the supply voltage of 0.6 V, the free-running frequency of ILFD is tunable from 4.81 GHz to 5.3 GHz. At the incident power of 0 dBm and VDD = 0.6 V, the total locking range is about 3 GHz, from the incident frequency 8.9 to 11.9 GHz for the ILFD in the divide-by-2 mode. The core power consumption is 1.02 mW. The die area is 0.394 × 0.623 mm2.