A New Boosted Active-Capacitor With Negative-Gm for Wide Tuning Range VCOs

A new boosted active-capacitor (BAC) architecture using LC-tuned active-impedance-conversion is presented. In the chosen frequency range, the proposed BAC acts as a tunable capacitance multiplier and negative-transconductance, but where the positive-transconductance is not multiplied. The BAC is used as a low-loss tunable capacitor bank element for designing a wide tuning range voltage-controlled oscillator (VCO). A current-reuse technique is used to lower power consumption and suppress potential parasitic oscillation modes. A zero-capacitance-variation biasing is proposed for a BAC-VCO robust against process, voltage, and temperature variations. The BAC designed in a 65 nm bulk CMOS process achieves a capacitance tuning ratio of 7.8 with a quality factor of higher than 20 across VCO's tuning range. The BAC-VCO prototype has a tuning range of 8.3-14.3 GHz using less than 5 mW core power and achieves FoMT of up to -202.4 dBc/Hz.

I. Introduction

High-performance digital-circuits driven by CMOS scaling have led to an increased interest in the integration of multi-standard radios to meet the high data-rate demands with low-cost [1], [2]. Increasing data-rate demands are also driving the development of wideband low-power millimeter-wave radios in CMOS technology, which utilize the vast and largely unoccupied region of the frequency spectrum for higher throughput [3], [4]. These wireless communication systems require a high-performance wide tuning range LC VCO to generate the desired carrier frequencies either directly or by using frequency dividers [2], or sub-harmonic injection-locked oscillators [3], [4], or multipliers [5].