Variable integrated inductor

• US 20060033602A1
• Filed: 08/29/2005
• Published: 02/16/2006
• Est. Priority Date: 08/16/2004
• Status: Active Grant

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Mattsson, Thomas
• Granted Patent: US 7,432,794 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: Y10T 29/4902 Electromagnet, transformer or inductor

Abstract

A variable integrated inductor is described herein which has an inductance value that can be switched between two or more values. In the preferred embodiment, the variable integrated inductor includes a multi-loop primary inductor which is electromagnetically coupled to a pair of secondary inductors. The secondary inductors are connected to one another to form a closed circuit within which the secondary inductors have a changeable topology that can be switched between a series connection and a parallel connection in order to change an inductance value which is output by the multi-loop primary inductor. In one application, the variable integrated inductor is used in a voltage controlled oscillator (VCO) which is of the type that can be used in a multi-band RF radio transceiver (e.g., wireless communication device). In other applications, the variable integrated inductor can be used in a tuned amplifier load, an impedance matching network, a digitally controlled oscillator or any other type of frequency selective LC-network.

Claims

1. A variable integrated inductor, comprising:

a multi-loop primary inductor; and

a pair of secondary inductors, electromagnetically coupled to said multi-loop primary inductor, said secondary inductors are connected to one another to form a closed circuit within which said secondary inductors have a changeable topology that can be switched between a series connection and a parallel connection to change an inductance value output by said multi-loop primary inductor.

2. The variable integrated inductor of claim 1, wherein when said pair of secondary inductors have the series connection then there is no change in the inductance value output by said multi-loop primary inductor.

3. The variable integrated inductor of claim 1, wherein when said pair of secondary inductors have the parallel connection then there is a decrease in the inductance value output by said multi-loop primary inductor.

4. The variable integrated inductor of claim 1, wherein said pair of secondary inductors include one secondary inductor that has a predetermined inductance and a positive coupling coefficient k and another secondary inductor that has a predetermined inductance and a negative coupling coefficient −

k.

5. The variable integrated inductor of claim 1, wherein said multi-loop primary inductor is a symmetric multi-loop primary inductor.

6. The variable integrated inductor of claim 1, wherein said multi-loop primary inductor is a single turn figure-8 shaped inductor that has two sub-loops of which the first sub-loop has a magnetic field in one direction and the second sub-loop has a magnetic field in an opposite direction.

7. The variable integrated inductor of claim 1, wherein said multi-loop primary inductor is a cloverleaf shaped inductor.

8. The variable integrated inductor of claim 1, wherein said multi-loop primary inductor is a two turn figure-8 shaped inductor.

9. The variable integrated inductor of claim 1, further comprising multiple pairs of secondary inductors which are used to increase a number of possible inductance values which can be output by said multi-loop primary inductor.

10. The variable integrated inductor of claim 1, wherein said multi-loop primary inductor and said pair of secondary inductors are used in a selected one of the following devices:

a voltage controlled oscillator;

a tuned amplifier load;

a digitally controlled oscillator;

an impedance matching network; and

a frequency selective LC-network.

11. A method for manufacturing a switched integrated inductor, said method comprising the steps of:

forming a multi-loop primary inductor on a chip;

forming a pair of secondary inductors on the chip such that;

said pair of secondary inductors are electromagnetically coupled to said multi-loop primary inductor; and

said pair of secondary inductors form a closed circuit which has a switchable topology; and

forming a switch on said chip, said switch is used to change the switchable topology of said pair of secondary inductors to either a series connection or a parallel connection to change an inductance value which is output by said multi-loop primary inductor.

12. The method of claim 11, wherein when said switch is in an open position then said pair of secondary inductors have the series connection which does not cause a change to the inductance value output by said multi-loop primary inductor.

13. The method of claim 11, wherein when said switch is in a closed position then said pair of secondary inductors have the parallel connection which causes a decrease in the inductance value output by said multi-loop primary inductor.

14. The method of claim 11, wherein said pair of secondary inductors include one secondary inductor that has a predetermined inductance and a positive coupling coefficient k and another secondary inductor that has a predetermined inductance and a negative coupling coefficient −

k.

15. The method of claim 11, wherein said multi-loop primary inductor is a symmetric multi-loop primary inductor.

16. The method of claim 15, wherein said multi-loop primary inductor is a single turn figure-8 shaped inductor that has two sub-loops of which the first sub-loop has a magnetic field in one direction and the second sub-loop has a magnetic field in an opposite direction.

17. A multi-band radio transceiver, comprising:

a receive path incorporating a first voltage controlled oscillator which includes;

a first variable capacitor; and

a first variable integrated inductor, wherein said first variable integrated inductor includes;

a first multi-loop primary inductor; and

a first pair of secondary inductors, electromagnetically coupled to said first multi-loop primary inductor, said first pair of secondary

inductors are connected to one another to form a closed circuit within which said first pair of secondary inductors have a changeable topology that

can be switched between a series connection and a parallel connection to change an inductance value output by said first multi-loop primary inductor; and

a transmit path incorporating a second voltage controlled oscillator which includes;

a second variable capacitor; and

a second variable integrated inductor, wherein said second variable integrated inductor includes;

a second multi-loop primary inductor; and

a second pair of secondary inductors, electromagnetically coupled to said second multi-loop primary inductor, said second pair of secondary inductors are connected to one another to form a closed circuit within which said second pair of secondary inductors have a changeable topology that

can be switched between a series connection and a parallel connection to change an inductance value output by said second multi-loop primary inductor.

18. The multi-band radio transceiver of claim 17, wherein said first variable integrated inductor has a symmetrical multi-loop layout which reduces electromagnetic coupling to said second variable integrate inductor and vice versa.

19. The multi-band radio transceiver of claim 17, wherein when one of said pairs of secondary inductors have the series connection then there is no change in the inductance value which is output by the corresponding multi-loop primary inductor.

20. The multi-band radio transceiver of claim 17, wherein when one of said pairs of secondary inductors have the parallel connection then there is a decrease in the inductance value which is output by the corresponding multi-loop primary inductor.

21. A wireless communication device, comprising:

a receive path incorporating a first voltage controlled oscillator which includes;

a first variable capacitor; and

a first symmetric variable integrated inductor, wherein said first symmetric variable integrated inductor includes;

a first multi-loop primary inductor; and

a first pair of secondary inductors, electromagnetically coupled to said first multi-loop primary inductor, said first pair of secondary

inductors are connected to one another to form a closed circuit within which said first pair of secondary inductors have a changeable topology that

can be switched between a series connection and a parallel connection to change an inductance value output by said first multi-loop primary inductor; and

a transmit path incorporating a second voltage controlled oscillator which includes;

a second variable capacitor; and

a second symmetric variable integrated inductor, wherein said second symmetric variable integrated inductor includes;

a second multi-loop primary inductor; and

a second pair of secondary inductors, electromagnetically coupled to said second multi-loop primary inductor, said second pair of secondary inductors are connected to one another to form a closed circuit within which said second pair of secondary inductors have a changeable topology that

can be switched between a series connection and a parallel connection to change an inductance value output by said second multi-loop primary inductor.