Switched Substrate-Shield-Based Low-Loss CMOS Inductors for Wide Tuning Range VCOs

A switched substrate-shield inductor (SSI) topology in bulk CMOS is proposed which minimizes parasitic capacitance and substrate losses, while tuned magnetically induced currents facilitate inductor tunability. The high frequency behavior of the induced current is analyzed, resulting in intuitive insights and design guidelines for a high-performance SSI. An SSI prototype in 65-nm bulk CMOS achieves 34% inductance tunability with a quality factor of >10.3. A voltage-controlled oscillator (VCO) using SSI achieves 40.3% tuning range, from 21 to 31.6 GHz, and a phase noise of -119.1 ± 3.7 dBc/Hz at 10-MHz offset frequencies. The VCO core consumes 4.3 ± 0.2 mW from a 1-V supply.

I. Introduction

With a rapid adoption of wireless mobile devices, the demand for high data rate will continue to grow. To meet such demands, wireless communication is expanding toward millimeter-wave (mm-wave) frequencies where a larger spectrum range is available [1]–[6]. Voltage-controlled oscillators (VCOs) with wide frequency tuning range (TR) are required to support larger bandwidth at mm-wave frequencies, and to compensate for the process-voltage-temperature (PVT) variations in bulk CMOS technologies. VCOs operating at mm-wave frequency demonstrate relatively poor TR and phase noise (PN) performance due to low-quality factor ( of the passive components and large parasitics [4], [6]. Instead, mm-wave carrier signals can be synthesized by the frequency-multiplication of a high-frequency signal [3], [7].