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.

Class-C VCO With Amplitude Feedback Loop for Robust Start-Up and Enhanced Oscillation Swing

Abstract: We propose a feedback class-C voltage-controlled oscillator (VCO) that has robust start-up and a large oscillation amplitude. It initially starts oscillating as a conventional cross-coupled LC-VCO for robust start-up and subsequently transforms automatically into an amplitude-enhanced class-C VCO when it reaches steady-state to give improved noise performance. Detailed analysis of the start-up conditions, enhanced oscillation swing, and amplitude stability provides valuable insight into oscillator design considerations. The proposed VCO is implemented in a 0.18-μm CMOS process. The measured phase noise at room temperature is - 125 dBc/Hz at 1 MHz offset with a power dissipation of 3.4 mW at an oscillation frequency of 4.84 GHz. The figure-of-merit is -193 dBc/Hz.

A 2.7 V GSM RF transceiver IC

Abstract: A 2.7-V RF transceiver IC is intended for small, low-cost global system for mobile communications (GSM) handsets. This chip includes a quadrature modulator (QMOD) and an offset phase locked loop (OPLL) in the transmit path and a dual IF receiver that consists of a low noise amplifier (LNA) with an active-bias circuit, two Gilbert-cell mixers, a programmable gain linear amplifier (PGA), and a quadrature demodulator (QDEM). The IC also contains frequency dividers with a very high frequency voltage controlled oscillator (VHF-VCO) to simplify the receiver design. The system evaluation results are the phase error of 2.7/spl deg/ r.m.s. and the noise transmitted in the GSM receiving band of -163 dBc/Hz for transmitters and the reference sensitivity of -105 dBm for receivers. Power-control functions are provided for independent transmit and receive operation. The IC is implemented by using bipolar technology with f/sub T/=15 GHz, r'/sub bb/=150 /spl Omega/, and 0.6-/spl mu/m features.

A Self-Sustained CMOS Microwave Chemical Sensor Using a Frequency Synthesizer

Abstract: In this paper, a CMOS on-chip sensor is presented to detect dielectric constant of organic chemicals. The dielectric constant of these chemicals is measured using the oscillation frequency shift of an LC voltage-controlled oscillator (VCO) upon the change of the tank capacitance when exposed to the liquid. To make the system self-sustained, the VCO is embedded inside a frequency synthesizer to convert the frequency shift into voltage that can be digitized using an on-chip analog-to-digital converter. The dielectric constant is then estimated using a detection procedure including the calibration of the sensor. The dielectric constants of different organic liquids have been detected in the frequency range of 7-9 GHz with an accuracy of 3.7% compared with theoretical values for sample volumes of 10-20 μL. The sensor is also applicable for binary mixture detection and estimation of the fractional volume of the constituting materials with an accuracy of 1%-2%.

A 6.5 GHz monolithic CMOS voltage-controlled oscillator

Abstract: Phase noise and frequency tuning range are key performance parameters of high-frequency voltage-controlled oscillators (VCOs). To achieve low phase noise, LC sinusoidal oscillators with high quality factor (Q) are preferred to other topologies, such as inverter-based ring oscillators. The frequency tuning of LC oscillators can be readily achieved with varactor diodes either on-chip or external. The frequency tuning range is often limited by low supply voltage and maximum variable capacitance available to varactors at high frequencies when on-chip inductors are used. Other frequency tuning approaches include varying current in the resonator to alter effective capacitance, or varying relative weighting between two different LC resonators. While the former approach varies loop gain in addition to the phase, the latter requires careful choice of the resonators and their Qs for stable oscillations. This VCO architecture incorporates two coupled fixed-frequency LC oscillators to generate a variable-frequency output by varying the coupling between two oscillators.

High-Gain Fully Printed Organic Complementary Circuits on Flexible Plastic Foils

Abstract: We present several fully printed organic complementary circuits using n- and p-type organic thin-film transistors. n-Type and p-type devices are developed on a flexible polyethylene-naphthalate substrate. All organic layers are deposited using a low-cost screen-printing technique. The inverters show a high gain and a switching point at exactly VDD/2. A seven-stage voltage-controlled oscillator (VCO) is designed with an organic output buffer, using the n- and p-type organic transistors. This VCO oscillates at a frequency of 186 Hz. Finally, two complementary differential amplifiers with high gain and large bandwidth are presented. The amplifiers only draw a 1-μA current from a 40-V power supply.