This paper presents a 7 GHz differential current-reused voltage-controlled oscillator (CR-VCO) with low power consumption and low phase noise using 0.18-µm CMOS technology. The output power of this CR-VCO is enhanced by utilizing a trifilar-transformer-feedback technique. The lower phase noise is achieved by the more symmetric voltage swings resulting from the improved balance of switching current. At a 1.5-V DC supply voltage, the power dissipation is only 3.4 mW. The total tuning range is 1.4 GHz (17.9%) as the tuning voltage ranges from 0 V to 1.8 V. The optimum phase noise is around -117.3 dBc/Hz at a frequency offset of 1 MHz from the center frequency of 7.07 GHz. The corresponding output power is around -6.8 dBm. For the proposed CR-VCO, the calculated figures-of-merit, FOM and FOMT , are -188.9 and -193.9 dBc/Hz, respectively.

In this paper, a fully integrated 5 GHz voltage controlled oscillator (VCO) is presented. The VCO is designed with 0.18 µm silicon complementary metal oxide semiconductor (Si-CMOS) process. To achieve low phase noise, a novel varactors pair circuit is proposed to cancel effects of capacitance fluctuation that makes harmonic currents which increase phase noise of VCO. The VCO with the proposed varactor circuit has tuning range from 5.1 GHz to 6.1 GHz (relative value of 17.9%) and phase noise of lower than -110.8 dBc/Hz at 1 MHz offset over the full tuning range. Figure-of-merit-with-tuning-range (FOMT) of the proposed VCO is -182 dBc/Hz.

This paper presents a wide tuning range VCO with an automatic frequency, gain, and two-step amplitude calibration loop for Digital TV (DTV) tuner applications. To cover the wide tuning range, the fully digital automatic frequency calibration (AFC) loop is used. In addition to the AFC loop, a two-step negative-Gm tuning loop is proposed to provide the optimum negative-Gm to the LC tank in a wide frequency range with a fine resolution. In the coarse negative-Gm tuning loop, the number of active negative-Gm cells is selected digitally based on the target frequency. In the fine negative-Gm tuning loop, the negative-Gm is tuned finely with the bias voltage of the VCO. Also, the digital VCO gain calibration scheme is proposed to compensate for the gain variation in a wide tuning range. The VCO tuning range is 2.6 GHz, from 1.7 GHz to 4.3 GHz, and the power consumption is 2 mA to 4 mA from a 1.8 V supply. The measured VCO phase noise is -120 dBc/Hz at 1 MHz offset.