A 66% Tuning-Range, 60-GHz Quadrature Ring Oscillator Using Current-Combining for Frequency Multiplication

This letter introduces a wide tuning range voltage-controlled oscillator with quadrature outputs, which uses current-combining for four times frequency multiplication from 15 to 60 GHz. The oscillator is based on an eight-stage interleaved ring oscillator (RO), where the supply currents of the oscillator stages are reused for frequency multiplication and quadrature signal generation within two transformers. For this purpose, the RO is supplied through the primary center taps of the transformers. That results in an alternating current in the transformer with a frequency of four times the RO frequency. The secondary sides of the transformers provide the frequency multiplied quadrature-phase output signals. The oscillator (area: 0.135 mm
²
) was fabricated in a 28-nm CMOS process. The measurement results show that it achieves a very wide tuning range of 66% and has a power demand of 15.3 mW at 60 GHz (PN: −63.5 dBc/Hz, FOM: −163.6 at 1-MHz offset).