A Varactor-Less DCO With $7~GHz$ Tuning Range for $77~GHz$ Automotive Radars

The generation of precise linear frequency modulation is a critical requirement for millimeterwave automotive radars. This paper presents the analysis and design of a CMOS 75.5 - 82.5 GHz monotonically linear digitally controlled oscillator (ML-DCO) fulfilling the requirements of the 77 GHz automotive radar. Non-linear large varactors are avoided. Linear coarse, intermediate, and fine-tuning ranges are achieved by arranging the available minimum Metal-Oxide-Metal (MoM) capacitor in unique configurations. Moreover, a new tuning mechanism derived from a Colpitts topology is discussed to meet the wide tuning requirements without losing linearity. The new arrangement results in a minimal amplitude variation while the ML-DCO is tuned. The coarse, intermediate, and fine-tuning steps from the post-layout simulation are 0.22, 10, and 346 KHz, respectively. The power consumption is 14 mW from a 1.2 V supply. The achieved phase-noise is -98.53 dBc/Hz at a 1 MHz offset when oscillating at 77 GHz. The ML-DCO demonstrates -185 Figure of Merit and -184 Figure of Merit for Tuning.