Transformer Design for Transformer- Coupled Multi-phase Voltage-controlled Oscillators (VCOs)

This This paper presents transformer design for voltage-controlled oscillators (VCOs). It first presents a quadrature voltage-controlled oscillator (QVCO), which consists of four symmetric complementary cross-coupled sub-VCOs coupled by a loop inductor through magnetic coupling. The circuit design uses the concept of traveling wave and standing wave oscillators. The first proposed CMOS QVCO has been implemented with the TSMC 0.18μu 1P6M technology and the die area is $1.2 \times 1.2$mm
²
. At the supply voltage of 1.3 V, the total power consumption is 23.66 mW. The free-running oscillation frequency of the QVCO is tuneable from 3.67 to 4.25 GHz GHz as the tuning voltage is varied from 0.0V to 2.5V. The measured phase noise at 1MHz frequency offset is −125.34 dBc/Hz at the oscillation frequency of 3.67 GHz and the figure of merit (FOM) of the proposed QVCO is -182.89 dBc/Hz. The second QVCO uses 2.5:2.5 transformer.