US 2011/0032044 A1 · THE DIFFERENTIAL VCO AND QUADRATURE VCO USING CENTER-TAPPED CROSS-COUPLING OF TRANSFORMER

Abstract

Provided are a differential voltage-controlled oscillator (VCO) and a quadrature VCO using center-tapped cross-coupling of a transformer. The differential VCO and the quadrature VCO can be driven by low power through a current reuse structure and have an excellent phase noise characteristic by center-tapped cross-coupling through a transformer. Further, variable capacitance units for frequency variation are divided into variable capacitance units for coarse tuning and variable capacitance units for fine tuning. Therefore, it is possible to obtain a wide tuning range while voltage oscillation gain is reduced. Further, the differential VCO and the quadrature VCO are configured in such a manner that the respective variable capacitance units operate linearly throughout the entire capacitance region due to control voltage distribution by resistors. Accordingly, it is possible to obtain a linear control voltage-oscillation frequency characteristic. The quadrature VCO according to the present invention can output four-phase quadrature signals while having an excellent phase noise characteristic, without substrate loss and current consumption caused by the switching transistors.

Claims15

Dependent claims

A differential voltage-controlled oscillator (VCO) using center-tapped cross-coupling of a transformer, comprising:

a resonant circuit including:
a transformer having a primary coil connected between a first node and a third node, and a secondary coil connected between a second node and a fourth node;
first and second variable capacitance units connected between a first control voltage and the first and second nodes, respectively;
and third and fourth variable capacitance units connected between a second control voltage and the third and fourth nodes, respectively, wherein the resonant circuit oscillates a frequency depending on the first and second control voltages;
a first amplification circuit including first and second PMOS transistors connected between a power supply and the first node and between the power supply and the second node, respectively, and differentially amplifying and outputting the oscillation frequency output from the resonant circuit;
and
a second amplification circuit including first and second NMOS transistors connected between the third node and a fifth node and between the fourth node and the fifth node, respectively, and differentially amplifying and outputting the oscillation frequency output from the resonant circuit,
wherein the first NMOS transistor and the second NMOS transistor are differentially cross-coupled to the second PMOS transistor and the first PMOS transistor, respectively, through the transformer.

5 more elements

A quadrature VCO using center-tapped cross-coupling of a transformer, comprising:

first and second differential VCOs that are connected to each other through first to fourth switching transistors so as to output four-phase quadrature signals, wherein the sources of the first and second switching transistors connected to the first differential VCO are connected to body gates of first and second NMOS transistors or body gates of first and second PMOS transistors composing an amplification circuit of the first differential VCO, respectively, and
the sources of the third and fourth switching transistors connected to the second differential VCO are connected to body gates of first and second NMOS transistors or body gates of first and second PMOS transistors composing an amplification circuit of the second differential VCO, respectively.

Dependencies are inferred from the claim text.

The differential vco and quadrature vco using center-tapped cross-coupling of transformer

Life of this patent

The differential vco and quadrature vco using center-tapped cross-coupling of transformer

Life of this patent

Abstract

Claims15