A Frequency Divider Implemented With a Subharmonic Mixer and a Divide-by-Two Divider

This letter proposes a divide-by-four injection-locked frequency divider (ILFD) with the use of a subharmonic mixer and a divide-by-two frequency divider (D2FD). The D2FD circuit consists of a two-stage differential CMOS ring oscillator with n-MOS switches directly coupled to its differential outputs, the measured phase noise of the D2FD is -97 dBc/Hz at 1-MHz offset from the free running frequency of 1.08GHz. The low-voltage CMOS divide-by-four FD (D4FD) has been implemented with the UMC 0.18-mum 1P6M CMOS technology and the power consumption is 9 mW at the supply voltage of 1.2 V. At the input power of 0 dBm, the D4FD can function properly with about 330-MHz locking range from 4.15 to 4.48GHz