System and method for a voltage controlled oscillator

Patent metadata

Field	Value
Publication number	US-9537447-B2
Application number	US-201514808867-A
Country	US
Kind code	B2
Filing date	Jul 24, 2015
Priority date	Sep 30, 2013
Publication date	Jan 3, 2017
Grant date	Jan 3, 2017

Abstract

In accordance with an embodiment, a voltage controlled oscillator (VCO) includes a VCO core having a plurality of transistors, a bias resistor coupled between collector terminals of the VCO core and a first supply node, and a varactor circuit coupled to emitter terminals of the VCO core. The bias resistor is configured to limit a self-bias condition of the VCO core.

First claim

What is claimed is:

1. A voltage controlled oscillator (VCO) comprising:
a VCO core;
a tunable capacitance element having a first terminal coupled to an emitter node of the VCO core and a second terminal coupled to a tuning node;
a VCO frequency coupling circuit coupled between the emitter node of the VCO core and the tunable capacitance element, the VCO frequency coupling circuit configured to provide a signal path at a frequency of oscillation, wherein the VCO frequency coupling circuit comprises a first capacitor having a first terminal coupled to an emitter terminal of the VCO core, and a first transmission line element having a first terminal coupled to a second terminal of the first capacitor; and
a VCO harmonic coupling circuit coupled between the emitter node of the VCO core and a reference node, the VCO harmonic coupling circuit configured to provide a signal path at a harmonic of the frequency of oscillation of the VCO.

2. The VCO of claim 1 , further comprising a self-biasing limiting circuit coupled between a collector terminal of the VCO core and a supply node of the VCO.

3. The VCO of claim 2 , wherein the self-biasing limiting circuit comprises a resistor.

4. The VCO of claim 1 , wherein the VCO harmonic coupling circuit comprises an RF choke circuit coupled between a second terminal of the first capacitor and the reference node.

5. The VCO of claim 4 , wherein:
the first transmission line element comprises a length of at least 100 μm; and
the RF choke circuit has a quarter wavelength at about twice a frequency of operation of the VCO.

6. The VCO of claim 4 , wherein the RF choke circuit comprises:
a second transmission line element having a first terminal coupled to the first terminal of the first transmission line element;
a third transmission line element having a first node coupled to a second terminal of the second transmission line element; and
a second capacitor coupled between the first node of the first transmission line element and the reference node.

7. The VCO of claim 4 , wherein the tunable capacitance element comprises a first terminal coupled to a second terminal of the first transmission line element and a second terminal coupled to the tuning node.

8. The VCO of claim 1 , wherein the tunable capacitance element comprises a diode.

9. A voltage controlled oscillator (VCO) comprising:
a VCO core comprising a plurality of transistors; and
a varactor circuit coupled to emitter terminals of the VCO core, wherein the varactor circuit comprises
a first capacitor having a first terminal coupled to an emitter node of the VCO core,
a first transmission line element having a first terminal coupled to a second terminal of the first capacitor,
a tunable capacitance element having a first terminal coupled to a second terminal of the first transmission line element and a second terminal coupled to a tuning node, and
an RF choke circuit coupled between a second terminal of the first capacitor and a second reference node.

10. The VCO of claim 9 , wherein the tunable capacitance element comprises a diode.

11. The VCO of claim 9 , wherein the RF choke circuit comprises:
a second transmission line element having a first terminal coupled to the first terminal of the first transmission line element,
a third transmission line element having a first node coupled to a second terminal of the second transmission line element, and
a second capacitor coupled between the first node of the first transmission line element and a second reference node.

12. The VCO of claim 9 , wherein the first transmission line element comprises a length of at least 100 μm.

13. The VCO of claim 9 , wherein the RF choke circuit has a quarter wavelength at about twice a frequency of operation of the VCO.

14. The VCO of claim 9 , further comprising a resistor coupled between a common supply node of the VCO core and a power supply input terminal of the VCO.

15. The VCO of claim 14 , wherein the resistor has a resistance between about 1 ohm and about 20 ohms.

16. A method of operating a voltage controlled oscillator (VCO), the method comprising:
applying a supply voltage to a collector terminal of a transistor of a VCO core;
tuning the VCO comprising applying a tuning voltage to a varactor circuit coupled to an emitter terminal of the transistor of the VCO core;
providing a signal path at a frequency of oscillation of the VCO between a tuning node and the emitter terminal of the transistor of the VCO core using a first transmission line element; and
coupling harmonics of the VCO to a reference node via an RF choke circuit coupled between the emitter terminals of the VCO core and the reference node.

17. The method of claim 16 , wherein:
applying the supply voltage to the VCO core comprises applying the supply voltage via a resistor coupled to collector terminal of the transistor of the VCO core; and
the method further comprises limiting a self-biasing condition of the VCO core via the resistor.

18. The method of claim 16 , wherein the RF choke has a quarter wavelength of about two times the frequency of oscillation of the VCO.

19. The method of claim 16 , further comprising filtering the tuning node using a second transmission line element coupled between a tuning terminal of the VCO and the tuning node.

20. The method of claim 19 , wherein the second transmission line element has a quarter wavelength of about four times the frequency of oscillation of the VCO.

Assignees

• Infineon Technologies Ag

Inventors

• Trotta Saverio

Classifications

• H03B5/1847

  the active element in the amplifier being a semiconductor device · CPC title

• H03B5/1243

  the means comprising voltage variable capacitance diodes · CPC title

• H03B5/1218

  the generator being of the balanced type · CPC title

• H03B1/00

  Details · CPC title

• H03B5/1206 Primary

  using multiple transistors for amplification · CPC title