A Low-Phase-Noise Wide-Tuning-Range Oscillator Based on Resonant Mode Switching

Abstract

In this paper we will present a low-phase-noise wide-tuning-range oscillator suitable for scaled CMOS processes. It switches between the two resonant modes of a high-order LC resonator that consists of two identical LC tanks coupled by capacitor and transformer. The mode switching method does not add lossy switches to the resonator and thus doubles frequency tuning range without degrading phase noise performance. Moreover, the coupled resonator leads to 3 dB lower phase noise than a single LC tank, which provides a way of achieving low phase noise in scaled CMOS process. Finally, the novel way of using inductive and capacitive coupling jointly decouples frequency separation and tank impedances of the two resonant modes, and makes it possible to achieve balanced performance. The proposed structure is verified by a prototype in a low power 65 nm CMOS process, which covers all cellular bands with a continuous tuning range of 2.5-5.6 GHz and meets all stringent phase noise specifications of cellular standards. It uses a 0.6 V power supply and achieves excellent phase noise figure-of-merit (FoM) of 192.5 dB at 3.7 GHz and 188 dB across the entire tuning range. This demonstrates the possibility of achieving low phase noise and wide tuning range at the same time in scaled CMOS processes.Index Terms-Coupled oscillator, dual band, low phase noise, mode switching, VCO, wide tuning range oscillator.

A 2.7 GHz to 7 GHz Fractional-N LC-PLL Utilizing Multi-Metal Layer SoC Technology in 28 nm CMOS

“…13 is used. The impedance, of the loop filter is given by (6) where , . Assuming , it makes and the unity gain bandwidth with, where is the divider ratio and is the gain of the PFD along with the CP.…”

“…Increasing the switch size to compensate for the resistive loss limits the VCO tuning range due to the large parasitic capacitance associated with the switches. In another approach, a coupled resonant tank using a switch-less inductor is introduced [6], [7]. It occupies a larger silicon area in order to realize the transformer effect, and requires many overlapping frequency sub-ranges to cover the required frequency range continuously [6].…”

“…In another approach, a coupled resonant tank using a switch-less inductor is introduced [6], [7]. It occupies a larger silicon area in order to realize the transformer effect, and requires many overlapping frequency sub-ranges to cover the required frequency range continuously [6]. In [7], two LC tanks, one active and one inactive, are coupled together to achieve a wider tuning range.…”

A dual-band CMOS LC-VCO with highly linear frequency tuning characteristics

“…From the well-known phase noise model for an oscillator is Leeson's equation, the phase noise LðΔf Þ p 1=Q 3 , where the Q is the quality factor of the LC tank [8]. The quality factor is desired to be maximized to obtain a low phase noise and reduce the current consumption.…”

A 0.3-V power supply 2.4-GHz-band Class-C VCO IC with amplitude feedback loop in 65-nm CMOS

“…Several LC-VCOs were reported to improve the performance such as low phase noise [2], linear Kvco [3], ultra-wide band operation [4], and low DC power consumption [1,5]. A transformer-feedback VCO topology reported in [1] provides a good solution for the low voltage application.…”