Quadrature voltage controlled oscillator

Abstract

In a quadrature voltage controlled oscillator, a first oscillator includes a first resonant circuit for generating a preset first resonant frequency and a first pair of cross-coupled transistors for supplying energy to the first resonant frequency to generate first and second signals having a phase difference of 180°. A second oscillator includes a second resonant circuit for generating a preset second resonant frequency and a second pair of cross-coupled transistors for generating third and fourth signals for supplying energy to the second resonant frequency having a phase difference of 180°. A first current source is connected between a first common node of the first cross-coupled transistor pair and a ground. A second current source is connected between a second common node of the second cross-coupled transistor pair and the ground. A differential load is connected between a third common node of the first and second current sources and the ground.

Description

[0001] priority statement [0002] This application claims priority from Korean Patent Application No. 2005-86519 filed in the Korean Intellectual Property Office on September 15, 2005, the contents of which are incorporated herein by reference. technical field [0003] The present invention relates to a quadrature voltage controlled oscillator employed in an RF transceiver performing quadrature modulation / demodulation. More particularly, the present invention relates to a quadrature voltage controlled oscillator that configures a common node as an inductor to differentiate quadrature signals without using active devices, thereby enabling improved phase noise performance and reduced power consumption. Background technique [0004] In recent years, the demand for wireless communication has increased worldwide. But the limited availability of frequencies raises the royalty fees for specific frequencies. As a result, companies and organizations are looking for more complex m...

AI Technical Summary

Problems solved by technology

[0009] Specifically, first, in the case of using a VCO and a frequency divider, the duty cycle of the VCO is less than 50% so that the I / Q signal is inaccurate

Here, the load of the frequency divider typically acts as a resistor, however, its size varies so as to compromise the accuracy of the IQ signal

[0010] Second, in the case of VCOs and polyphase filters, amplifiers must be added due to significant signal loss, thus resulting in significant additional power dissipation

[0011] Third, in the case of two separate VCOs coupled, use a coupling transistor to couple the VCOs, increasing phase noise

[0018] However, disadvantageously, the coils Ls1 and Ls2 need to be integrated inside the IC of the conventional quadrature VCO

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