A 122-GHz SiGe-Based Signal-Generation Chip Employing a Fundamental-Wave Oscillator With Capacitive Feedback Frequency-Enhancement

This paper presents a highly integrated and fully balanced signal generation block comprising a fundamental-wave voltage-controlled oscillator (VCO), an output buffer, and a configurable frequency divider stage (prescaler). The VCO introduces a negative resistance structure in conjunction with capacitive cross-coupling. This compound structure allows fundamental oscillation to be sustained at high frequencies while providing wide tuning ranges. The capabilities of the capacitive feedback were analyzed using a linear transistor model, and boundary conditions, which support the early design phase, were derived. The chip was fabricated in a SiGe technology with 300-GHz f_max HBTs. The output frequency of the monolithic microwave integrated circuit is centered at 122 GHz and provides a tuning range of 16 GHz at an average single-sideband phase noise of -95 dBc/Hz at 1 MHz offset frequency. Possible applications include ISM applications at 122 GHz and short-range radar systems with wide tuning ranges.