CMOS 40 GHz divide-by-5 injection-locked frequency divider

A 40 GHz divide-by-5 injection-locked frequency divider fabricated in a CMOS 0.18 μm process is presented. By utilising a series-LC bandpass filter that is connected to the common-mode node of the differential injection pair to bypass the unwanted second harmonic and produce high impedance for the desired fourth-order harmonic, the fourth-order harmonic (4f₀) is peaked and mixed with input signals (at 5f₀) to achieve the output frequency f₀ (=5f₀ - 4f₀). With an injection power of -3 dBm, the measured maximum locking range is 735 MHz at a tuning voltage of 0.8 V. The total locking range covers 39.36-42.1 GHz as the tuning voltage rises from 0 to 1.8 V. This divider consumes 18 mW at 1 V supply voltage.