A Varactor-Less DCO with 7 GHz Tuning Range for 77 GHz Automotive Radars

Abstract

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.