Voltage-controlled oscillator

About: Voltage-controlled oscillator is a research topic. Over the lifetime, 23896 publications have been published within this topic receiving 231875 citations. The topic is also known as: VCO.

A Subthreshold Low Phase Noise CMOS LC VCO for Ultra Low Power Applications

Abstract: A subthreshold low power, low phase-noise voltage controlled oscillator (VCO) is demonstrated in a commercial 0.18 mum CMOS process. In subthreshold regime, MOS drain current is dominated by diffusion mechanism resulting in a high ratio of transconductance to drain current and suppressed phase noise. Therefore, low power and low phase noise characteristics are achieved without using nonconventional high passive components. The VCO measures a phase noise of -106 dBc/Hz at 400 kHz offset from 2.63 GHz oscillation frequency with 0.43 mW power dissipation drawn from 0.45 V power supply. Figures of merit for this VCO (power-frequency-normalized of 12 dB and power frequency-tuning-normalized of -10 dB) are among the best reported for CMOS oscillators.

Method and apparatus providing a dual mode VCO for an adaptive receiver

Abstract: An RF VCO (260A) forms, in the preferred embodiment, a part of a dual mode mobile station (100). Also disclosed is a method for operating the VCO. The VCO is operated in a first frequency band using a first inductance (300A) that forms part of a first resonant circuit (parallel resonance), and the VCO is switched for operation to a second frequency band by the closing a switch (M5) that causes a second resonant circuit (serial resonance) to be inductively coupled to the first resonant circuit. The second resonant circuit includes a second inductance (300B), and preferably includes at least one frequency tunable component, such as a varactor (VR3, VR4), for adjusting the resonant frequency of the second resonant circuit. The second inductance is center tapped, and the switch, such as a MOS transistor, is coupled in series between two ends of the center tapped inductance. The first frequency band may include 3.6 GHz (a double frequency GSM band) and the second frequency band may include 4.3 GHz (a double frequency WCDMA band). Additional operational bands can be also be used. In the preferred embodiment the first inductance forms part of a transformer primary fabricated in an integrated circuit, and the second inductance forms part of the transformer secondary that is fabricated in the integrated circuit so as to underlie the first inductance. A signal detector (D1, D2) may be provided that is responsive to a signal induced in the transformer secondary, and the signal detector has an output coupled to a closed loop control circuit (310) for controlling a magnitude of a signal output from the VCO. A further input to the closed loop control circuit may be a signal that is indicative of communication channel conditions, and the current consumption of the VCO circuit is maintained at a level that is adequate to ensure operation with the communication channel conditions. A passive buffering circuit (320) is provided for coupling an output of the VCO circuit to a further circuit, such as a mixer, thereby reducing the total VCO current considerably.

Temperature stabilized voltage controlled oscillator

Abstract: An integrated circuit Voltage Controlled Oscillator (VCO) in a battery-powered device, such as a cellular phone, can be configured to tune across a fairly wide frequency range using a relatively narrow control voltage range. The frequency response of the VCO can be temperature compensated by applying a temperature variable voltage source to varactors (310a-310b) that form part of a VCO resonant circuit. The reference ends of the varactors can be supplied with a temperature dependent voltage source (370, 380) that has a temperature dependence that substantially compensates for varactor temperature dependence. The temperature dependent voltage source (370, 380) can be a Proportional To Absolute Temperature (PTAT) device. The VCO includes a CMOS oscillator manufactured on the substrate, an LC resonant tank on the substrate and at least a pair of varacters (310a, 310b; 320a, 320b) having a common anode connection.

LC-VCO Design Optimization Methodology Based on the $g_m/I_D$ Ratio for Nanometer CMOS Technologies

Abstract: In this paper, an LC voltage-controlled oscillator (LC VCO) design optimization methodology based on the gm/ID tech nique and on the exploration of all inversion regions of the MOS transistor (MOST) is presented. An in-depth study of the com promises between phase noise and current consumption permits optimization of the design for given specifications. Semiempirical models of MOSTs and inductors, obtained by simulation, jointly with analytical phase noise models, allow to get a design space map where the design tradeoffs are easily identified. Four LC-VCO designs in different inversion regions in a 90-nm CMOS process are obtained with the proposed methodology and verified with electrical simulations. Finally, the implementation and measurements are presented for a 2.4-GHz VCO operating in moderate inversion. The designed VCO draws 440 μA from a 1.2-V power supply and presents a phase noise of -106.2 dBc/Hz at 400 kHz from the carrier.

An optimally coupled 5 GHz quadrature LC oscillator

Abstract: A 5 GHz quadrature LC oscillator is realized which is based on a new architecture for multi-phase LC oscillators. Each section in the oscillator is coupled with an explicit phase shift of 180 degrees divided by the number of sections. Analysis on behavioral level shows that this maximizes the quality factor, and as a result, the carrier-to-noise ratio and robustness. An effective quality factor is derived which quantizes the degradation in phase noise performance if the sections of a multiphase LC oscillator are non-optimally coupled. The realized 5 GHz quadrature LC oscillator demonstrates that even at high frequencies the additional complexity of the proposed architecture yields a CNR improvement. The oscillator is realized in a BiCMOS process with a cut-off frequency of 30 GHz using an LC resonator with a quality factor of 4. A tuning range from 4.91 to 5.23 GHz is obtained with a CNR better than 113 dBc/Hz at 2 MHz offset. The VCO core power dissipation is only 21.2 mW at 2.7 V supply voltage.