Variable inductor for integrated circuit and printed circuit board

• US 20050068146A1
• Filed: 09/25/2003
• Published: 03/31/2005
• Est. Priority Date: 09/25/2003
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Jessie, Darryl
• Granted Patent: US 7,460,001 B2
• Time in Patent Office: Days
• US Class Current: 336/200
• CPC Class Codes: H01F 17/0006 Printed inductances printed coils for dynamo-electric machines H02K3/26; printed circuits H05K
• CPC Class Codes: H01F 2021/125 Printed variable inductor with taps, e.g. for VCO
• CPC Class Codes: H01F 21/12 discontinuously variable, e.g. tapped
• CPC Class Codes: H01L 23/5227 Inductive arrangements or effects of, or between, wiring layers other inductive arrangements H01L23/645
• CPC Class Codes: H01L 27/08 including only semiconductor components of a single kind
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/0002 Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
• CPC Class Codes: H01L 2924/3011 Impedance
• CPC Class Codes: H03J 2200/35 Inductance tunable by switching in/out parts of the inductor

Abstract

A variable inductor can be formed on an integrated circuit with a primary conductor, a secondary conductor, and a switch. The primary conductor implements an inductor and may be formed in various patterns (e.g., a spiral). The secondary conductor forms a loop in proximity to (e.g., on the outside of) the primary conductor. The switch couples in series with the secondary conductor and opens or closes the loop. The inductance of the inductor is varied by closing and opening the loop with the switch. A current source may also be coupled in series with the secondary conductor and used to control the current flow in the secondary conductor to either increase or decrease the inductance. Multiple loops may be formed to change the inductance in more than two discrete steps. The variable inductor may be used for various applications such as filters, VCOs, and impedance matching networks.

Claims

1. An integrated circuit (IC) comprising:

a primary conductor for an inductor;

a secondary conductor forming a loop in proximity to the primary conductor; and

a switch coupled in series with the secondary conductor and operable to open or close the loop, wherein inductance of the inductor is varied by closing and opening the loop with the switch.

2. The integrated circuit of claim 1, wherein the primary conductor is formed in a spiral pattern.

3. The integrated circuit of claim 1, further comprising:

a current source coupled in series with the secondary conductor and the switch.

4. The integrated circuit of claim 3, wherein the current source is operable to direct current to flow in a first direction in the secondary conductor to reduce inductance of the inductor.

5. The integrated circuit of claim 3, wherein the current source is operable to direct current to flow in a second direction in the secondary conductor to increase inductance of the inductor.

6. The integrated circuit of claim 1, wherein the secondary conductor is located outside of the primary conductor.

7. The integrated circuit of claim 1, wherein the secondary conductor is located inside of the primary conductor.

8. The integrated circuit of claim 1, wherein the secondary conductor is located on a layer on top of the primary conductor.

9. The integrated circuit of claim 1, wherein the secondary conductor is located on a layer underneath the primary conductor.

10. The integrated circuit of claim 1, further comprising:

a third conductor forming a second loop in proximity to the primary conductor; and

a second switch coupled in series with the third conductor and operable to open or close the second loop.

11. The integrated circuit of claim 1, further comprising:

a capacitor coupled in series with the secondary conductor and the switch.

12. The integrated circuit of claim 1, further comprising:

a reactive circuit element coupled in series with the secondary conductor and the switch.

13. The integrated circuit of claim 1, wherein the primary conductor is fabricated with a low-loss metal.

14. The integrated circuit of claim 1, wherein the secondary conductor is fabricated with a low-loss metal.

15. The integrated circuit of claim 1, wherein the switch is implemented with a metal-oxide semiconductor (MOS) transistor.

16. The integrated circuit of claim 1, wherein the secondary conductor is placed at a predetermined distance away from the primary conductor, the predetermined distance being selected based on a particular amount of change in inductance with the loop opened and closed.

17. The integrated circuit of claim 1, further comprising:

a capacitor coupled to two ends of the primary conductor, wherein the capacitor and the inductor form a resonator tank.

18. The integrated circuit of claim 1, wherein the inductor is part of a voltage controlled oscillator (VCO).

19. The integrated circuit of claim 1, wherein the inductor is part of a filter.

20. The integrated circuit of claim 1, wherein the inductor is part of an impedance matching network.

21. A device comprising:

a primary conductor for an inductor;

a secondary conductor forming a loop in proximity to the primary conductor; and

a switch coupled in series with the secondary conductor and operable to open or close the loop, wherein inductance of the inductor is varied by closing and opening the loop with the switch.

22. The device of claim 21, further comprising:

a capacitor coupled to two ends of the primary conductor, wherein the capacitor and the inductor form a resonator tank.

23. An integrated circuit (IC) comprising:

a primary conductor for an inductor;

a secondary conductor forming a loop in proximity to the primary conductor;

a switch coupled in series with the secondary conductor and operable to open or close the loop, wherein inductance of the inductor is varied by closing and opening the loop with the switch; and

a capacitor coupled to two ends of the primary conductor, wherein the capacitor and inductor form a resonator tank for a voltage controlled oscillator (VCO), and wherein the VCO is operable at two frequencies corresponding to the loop being closed and opened.

24. The integrated circuit of claim 23, wherein the capacitor is a variable capacitor.

25. A method of fabricating an integrated circuit (IC), comprising:

forming a primary conductor for an inductor;

forming a secondary conductor in a loop in proximity to the primary conductor; and

forming a switch in series with the secondary conductor, wherein the switch is operable to open or close the loop to vary inductance of the inductor.

26. The method of 25, further comprising:

forming a current source in series with the secondary conductor and the switch.

27. The method of 25, further comprising:

forming a capacitor in series with the secondary conductor and the switch.

28. The method of 25, further comprising:

forming a third conductor in a second loop in close proximity to the primary conductor; and

forming a second switch in series with the third conductor and operable to open or close the second loop.