Low-voltage/low-power 7-GHz transformer-coupled current-reused CMOS QVCO with wide tuning range

In this article, we report the design of a transformercoupled current-reused quadrature voltage-controlled oscillator (QVCO) having low-voltage operation, low-power consumption, and a wide tuning range. An improved trifilar transformer that is fabricated by symmetrically interlacing two half circle secondary coils between the turns of the primary coil is proposed to provide a higher magnetic coupling factor. A QVCO integrated with such a trifilar transformer is implemented using 0.18-lm RF CMOS technology. When the QVCO is operated at a supply voltage of 1V at 7.263 GHz, the measured phase noise is -111.4 dBc/Hz at a 1-MHz offset. Further, the QVCO core draws only 1.58 mW. The total tuning range is -510 MHz over the whole tuning range (from 0 to 1.8 V). The calculated figure of merit is 186.6 dB and the power-frequency-tuning-normalized factor is -9.4 dB. As compared to the reported data in a previous study, a 28.2% reduction in power consumption and a 54.5% increase in tuning range can be achieved.