Switched-inductor VCO based on tapped vertical solenoid inductors

Abstract

A new switched-inductor voltage controlled oscillator (VCO) scheme based on tapped vertical solenoid inductors is presented. With tapping ports, various effective inductances are selected by switches for multi-band operation. As a proof of concept, two VCOs, with one and two tapping ports separately, are implemented in a 0.18 mm 1P6M standard CMOS. Because of the vertical structure of the inductors, the new scheme consumes much less area than the conventional switch-inductor VCOs. The measured frequency bands of the VCOs are located between 1.96 and 3.49 GHz, and the measured phase noise at 1 MHz offset is between 2115.4 and 2118.5 dBc/Hz across all bands under power consumption of 14.4 mW (8 mA, 1.8 V).Introduction: With the increasing demand on low-cost multi-standard, multi-band wireless and wireline systems, voltage controlled oscillators (VCOs) that are able to cover multiple frequency bands attract more attention. Owing to the stringent phase noise performance requirement, LCVCOs are preferred. Because the on-chip inductors are usually fixed, the tuning range of the VCO is therefore limited by the low C max /C min ratio of varactors. Many researches have been devoted to inductance tuning schemes, such as the fourth-order resonator [1], the transformerbased resonator [2], magnetically tuning architecture [3], and so forth, which are employed along with conventional capacitance tuning to enhance frequency range and lower the VCO gain variation. Among them, the switched-inductor structure [4-6] is relatively simple, but considered as an inferior structure because of the negative effects of the 'real' switches. Though the parasitic on-resistances of the switches degrade the phase noise performance, it was concluded that the on-resistances and other losses associated with the switches can be made sufficiently low [6]. However, two additional planar inductors are used in previous works, because on-chip inductors are always the most area-consuming devices, and this scheme consumes large chip area. In this Letter, the tapped vertical solenoid inductors are used for switched-inductor VCOs, which benefit from the multilayer structure and help to reduce chip area and cost. Moreover, the vertical solenoid inductors are considered to have higher peak quality factor and self-resonance frequency than planer inductors [7].

A high output power and low phase noise GaN HEMT VCO with array of switchable inductors

“…However, an LC resonator using varactors cannot provide a wide TR . Several researches implement a wide TR VCO by using switched‐capacitor arrays or switched inductors techniques. Compared with switched‐capacitor array VCO, the cross‐coupled VCO involving array of switchable inductors can operate at higher oscillation frequency because the switchable inductors may be connected in parallel.…”

“…According to the Barkhausen criteria, the switchable inductor VCO was easily satisfied start‐up condition with a fixed bias current because of higher equivalent parallel loss resistance of LC‐tank . Therefore, inductive switching methods such as switch‐inductor , self‐inductive switching and switched‐coupled inductors have been proposed to improve TR of LC‐tank VCOs. This paper presents and analyzes cross‐coupled VCOs involving array of switchable inductors.…”

High-performance cost-efficient dual-band CMOS LC VCO

“…Many high-performance signal processings call for the employment of LC voltagecontrolled oscillators (VCOs) [1,2,3,4,5,6,7,8,9]. Dual-band VCOs [1,3,6,7] find usages in many multi-standard multi-band wireless/wireline communication/ sensor systems.…”

“…Dual-band VCOs [1,3,6,7] find usages in many multi-standard multi-band wireless/wireline communication/ sensor systems. A theoretical study of the design constraints of fourth-order dualband LC VCOs is recently conducted [10].…”

CMOS 1.98–5.58 GHz transformer‐based VCO with current‐reused topology

“…Owing to the low phase noise performance, LC-VCOs are preferred rather than ring oscillators and relaxation oscillators, but their achievable FTR is usually limited owing to the low C max /C min ratio of the varactor. To enhance the desired FTR, most LC-VCOs use switched capacitors [1] or inductors [2,3]. However, these approaches suffer from the channel resistance and parasitic capacitance of the switch, which tend to degrade the phase noise performance and the FTR of the LC-VCO.…”