94 GHz VCO using negative capacitance technique

Abstract

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 cross-coupled transistor pair of the VCO. Compared with the traditional cross-coupled transistor pair, the proposed one significantly decreases the tunable equivalent parallel capacitance (C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">EQ</sub> ) 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 91~96 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 0.75×0.42 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , i.e. 0.315 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , excluding the test pads.