A 5-mW, 1.2–3.5-GHz Capacitive Degeneration in LC-Digitally-Controlled Oscillator for Nano-Satellite Frequency Synthesizers in 90-nm CMOS

Abstract

This paper proposes an 8-bit LC tuned digitally-controlled oscillator (DCO) that exploits a new tunable active inductor (TAI) with a high [Formula: see text]-factor. This TAI achieves a maximum [Formula: see text]-factor value of 98 over a frequency range of 1770[Formula: see text]MHz. It tunes from 3.55[Formula: see text]nH to 15.2[Formula: see text]nH. The proposed TAI is used in the resonator of a wide tunable low-phase-noise DCO-LC oscillator. The tuning circuitry of the DCO with an additional resistance contributes to better effective capacitance characteristics as compared to the basic topology. Thanks to the capacitive degeneration network formed by a resistance connected in parallel with a capacity, the achieved frequency resolution is between 3[Formula: see text]kHz and 16[Formula: see text]kHz without any dithering. The proposed DCO with capacitive degeneration oscillates at a frequency that can be tuned from 1.22 to 3.52[Formula: see text]GHz with 65% tuning range. It consumes 5.2-mA current from a 1.0-V voltage supply, achieves a phase noise of [Formula: see text]105.8[Formula: see text]dBc/Hz at 1-MHz offset and exhibits a figure of merit (FoM) of [Formula: see text]178[Formula: see text]dBc/Hz. The proposed digitally-controlled oscillator was implemented in TSMC 90-nm CMOS MS/RF technology.