# US 7,609,120 B2 · Voltage-controlled oscillator using LC resonator

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- Number: US 7,609,120 B2
- Document ID: US7609120B2
- Status: Granted
- Kind: B2
- Application number: 11/574,041
- Filed: 2005-08-26
- Published: 2009-02-26
- Granted: 2009-10-27
- Earliest claimed: 2004-08-30
- Assignees: Fci
- Inventors: Yu Jin Chung; Bum Man Kim; Jong Ryul Lee; Kwang Jun Yun
- Web page: https://patentgrep.com/patent/US7609120B2

## CPC

- H03B 5/1228: {the amplifier comprising one or more field effect transistors}
- H03B 5/1215: {the current source or degeneration circuit being in common to both transistors of the pair, e.g. a cross-coupled long-tailed pair}
- H03B 5/1243: {the means comprising voltage variable capacitance diodes}
- H03B: GENERATION OF OSCILLATIONS, DIRECTLY OR BY FREQUENCY-CHANGING, BY CIRCUITS EMPLOYING ACTIVE ELEMENTS WHICH OPERATE IN A NON-SWITCHING MANNER; GENERATION OF NOISE BY SUCH CIRCUITS (generators adapted for electrophonic musical instruments G10H; masers or lasers H01S; generation of oscillations in plasma H05H)

## Abstract

Provided is a voltage-controlled oscillator (VCO) using an LC resonator circuit which includes a first resonance circuit in which two serially connected varactor diodes and an inductor are connected in parallel, a second resonance circuit in which one or more inductor L1 and one or more capacitor C1 are connected in parallel, the second resonance circuit being serially connected to a port of the first resonance circuit, and a third resonance circuit in which one or more inductor L2 and one or more capacitor C2 are connected in parallel, the third resonance circuit being serially connected to the other port of the first resonance circuit.

## Claims

### Claim 1

A voltage-controlled oscillator (VCO) using an LC resonator comprising a first differential amplifier, a second differential amplifier, a LC resonator connected to output of the first and second differential amplifier and a current source which supplies current to the first and second differential amplifier and the LC resonator, the LC resonator comprising:
a first resonance circuit in which two serially connected varactor diodes and an inductor are connected in parallel;
a second resonance circuit in which one or more inductor L1 and one or more capacitor C1 are connected in parallel, the second resonance circuit being serially connected to a port of the first resonance circuit; and
a third resonance circuit in which one or more inductor L2 and one or more capacitor C2 are connected in parallel, the third resonance circuit being serially connected to the other port of the first resonance circuit.

### Claim 2 (depends on 1)

The voltage-controlled oscillator (VCO) using an LC resonator of claim 1, wherein the LC resonator is a harmonic tuned LC resonator circuit which exhibits a characteristic of opening at an oscillation frequency and a third harmonic wave and being short-circuited at a second harmonic wave and changes an output voltage waveform of an oscillator to have a sharp inclination, and wherein the LC resonator plays a role in a filter in order to minimize a noise of current source.

### Claim 3 (depends on 1)

The voltage-controlled oscillator using LC resonator of claim 1, wherein the first differential amplifier and the second differential amplifier are latch circuits that include cross-coupled transistors.