Varactor voltage controlled oscillator (VCO) providing independent coarse and fine frequency tuning

• US 8,786,376 B2
• Filed: 12/13/2011
• Issued: 07/22/2014
• Est. Priority Date: 12/13/2011
• Status: Active Grant

• Current Assignee: Peraso Technologies Inc. (Peraso, Inc.)
• Original Assignee: Peraso Technologies Inc. (Peraso, Inc.)
• Inventors: Voinigescu, Sorin, Laksin, Ekaterina
• Primary Examiner(s): Johnson, Ryan
• Application Number:
  US13/324,556
• Publication Number:
  US 20130147566A1
• Time in Patent Office: 952 Days
• Field of Search: 331/177.V, 331/117.FE, 331/36.C, 331/117.R, 331/167, 331/177.R, 331/34, 331/16
• US Class Current: 331/117.R
• CPC Class Codes: H03B 2200/0008 Colpitts oscillator
• CPC Class Codes: H03B 2200/0034 including a buffer amplifier
• CPC Class Codes: H03B 5/1203 the amplifier being a single transistor
• CPC Class Codes: H03B 5/1218 the generator being of the balanced type
• CPC Class Codes: H03B 5/1231 the amplifier comprising one or more bipolar transistors
• CPC Class Codes: H03B 5/1253 the transistors being field-effect transistors
• CPC Class Codes: H03B 5/1265 switched capacitors

Abstract

A voltage controlled oscillator, includes a tank circuit including an inductor having a value L, interconnected with first and second variable capacitors, having values C_VAR1 and C_VAR2, and a fixed capacitor C_FIXED, to cause oscillation of the oscillator at a controlled frequency

$f_{\mathrm{osc}}={\left(2\pi \right)}^{-1}{\left(L\left\{C_{\mathrm{VAR}2}+\frac{C_{\mathrm{FIXED}}{C}_{\mathrm{VAR}1}}{C_{\mathrm{FIXED}}+C_{\mathrm{VAR}1}}\right\}\right)}^{-1/2}$
C_VAR1 controls coarse frequency tuning of the oscillator, and C_VAR2 may control fine tuning of the oscillator. The variable capacitors may be formed using accumulation-mode MOS varactors.

Claims

1. A voltage controlled oscillator, comprising:

a transistor;

a tank circuit interconnecting said transistor in feedback, said tank circuit including an inductor having a value L, interconnected with first and second variable capacitors, having values C_VAR1 and C_VAR2, and a fixed capacitor C_FIXED, to cause oscillation of said oscillator at a controlled frequency

2. The voltage controlled oscillator of claim 1, wherein C_VAR1 controls coarse frequency tuning of said oscillator, and wherein C_VAR2 controls fine tuning of said oscillator.

3. The voltage controlled oscillator of claim 1, wherein said second variable capacitor is formed of two back-to-back connected MOS varactors.

4. The voltage controlled oscillator of claim 3, wherein a capacitance of said second variable capacitor is controlled by an analog voltage applied to a node connecting said two back-to-back MOS varactors.

5. The voltage controlled oscillator of claim 1, wherein the capacitance of each capacitor of said bank is controlled using a binary control signal applied to a node connecting respective two back-to-back MOS varactors.

6. The voltage controlled oscillator of claim 1, wherein said transistor is a heterojunction transistor.

7. The voltage controlled oscillator of claim 1, wherein said fixed capacitor is connected between a base and emitter of said transistor.

8. The voltage controlled oscillator of claim 1, wherein said transistor is connected in common collector.

9. The voltage controlled oscillator of claim 1, wherein first and second variable capacitors are formed using accumulation-mode MOS varactors.

10. The voltage controlled oscillator of claim 1, further comprising

a second transistor, and wherein said transistor and said second transistor are connected to provide a differential output signal.

11. The voltage controlled oscillator of claim 1, wherein said second variable capacitor C_VAR2 further comprises an additional bank of parallel variable capacitors, the capacitance of each of which may be selectively adjusted by a control signal.

12. The voltage controlled oscillator of claim 11, wherein a control signal used to control capacitance of a capacitor in said bank of capacitors forming said first variable capacitor further controls capacitance of a capacitor said additional bank of parallel variable capacitors of said second variable capacitor.

13. A method of producing an oscillating voltage at a desired frequency, comprising:

providing a transistor;

providing a tank circuit interconnecting said transistor in feedback, said tank circuit including an inductor having a value L, interconnected with first and second variable capacitors, having values C_VAR1 and C_VAR2, and a fixed capacitor C_FIXED, to cause oscillation of said transistor at a controlled frequency

14. The method of claim 13, wherein C_VAR1 controls coarse frequency tuning of said oscillator, and wherein C_VAR2 controls fine tuning of said oscillator.

15. A voltage controlled oscillator, comprising:

a transistor;

a tank circuit interconnecting said transistor in feedback, said tank circuit including an inductor having a value L, interconnected with first and second variable capacitors, having values C_VAR1 and C_VAR2, and a fixed capacitor C_FIXED, to cause oscillation of said oscillator at a controlled frequency