94 GHz VCO Using Negative Capacitance Technique

A 94 GHz voltage-controlled oscillator (VCO) using both LC-source-degeneration-based (LCSD-based) negative capacitance technique and series-peaking gain enhancement technique is demonstrated in a 90 nm CMOS process. The LCSD-based negative capacitance is made by adding two tunable LC tanks, which use NMOSFET varactors as the needed capacitors, to the source terminals of the crosscoupled transistor pair of the VCO. Compared with the traditional cross-coupled transistor pair, the proposed one significantly decreases the tunable equivalent parallel capacitance (CEQ) to zero and even a negative value. This in turn results in the increase of both the operation frequency and the tuning range of the VCO. The VCO draws 8.3 mA current from a 1 V power supply, i. e. it only consumes 8.3 mW. The VCO achieves a tuning range of 91 similar to 96 GHz. In addition, the VCO achieves an excellent low phase-noise of. 98.3 dBc/Hz at 1 MHz offset from 95.16 GHz. The corresponding FOM is. 188.5 dBc/ Hz, one of the best results ever reported for a V-or W-band CMOS VCO. The circuit occupies a small chip area of 0.75x0.42 mm(2), i. e. 0.315 mm(2), excluding the test pads.