Notch filter with differential split inductor

• US 9,893,702 B2
• Filed: 07/27/2015
• Issued: 02/13/2018
• Est. Priority Date: 07/27/2015
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Rajendran, Gireesh, Joshi, Alok Prakash, Sivadas, Apu
• Primary Examiner(s): Patel, Rakesh
• Application Number:
  US14/810,166
• Publication Number:
  US 20170033757A1
• Time in Patent Office: 932 Days
• Field of Search: 333 4, 333175, 333186, 333188, 333174, 333176, 333185, 361271, 336200, 336147, 336180
• CPC Class Codes: H01F 2038/146 in combination with capacitive coupling
• CPC Class Codes: H01F 38/14 Inductive couplings for wireless supply or distribution of electric power using inductive coupling H02J50/10
• CPC Class Codes: H03F 3/191 Tuned amplifiers H03F3/193, H03F3/195 take precedence
• CPC Class Codes: H03F 3/195 in integrated circuits
• CPC Class Codes: H03H 11/52 simulating negative resistances
• CPC Class Codes: H03H 2007/013 Notch or bandstop filters
• CPC Class Codes: H03H 7/0115 comprising only inductors and capacitors H03H7/075, H03H7/09, H03H7/12, H03H7/13 take precedence
• CPC Class Codes: H03H 7/0153 Electrical filters; Controlling thereof

Abstract

A notch filter including an inductor-capacitor tuning circuit is disclosed. The inductor-capacitor tuning circuit may determine a frequency response of the notch filter in accordance with an associated resonant frequency. In some exemplary embodiments, the inductor-capacitor circuit may include a differential inductor divided at a symmetry point and a variable capacitor coupled to the differential inductor at the symmetry point.

Claims

1. A method, comprising:

coupling, via a differential inductor, a first terminal to a second terminal, the differential inductor comprising a first inductor section, a second inductor section separate from the first inductor section, and a common-mode point; and

tuning, via a variable capacitor, a resonant frequency associated with the differential inductor, wherein the variable capacitor is encircled by the differential inductor and serially directly connects the first inductor section to the second inductor section.

2. The method of claim 1, further comprising:

coupling the first terminal to the common-mode point via the first inductor section of the differential inductor; and

coupling the second terminal to the common-mode point via the second inductor section of the differential inductor.

3. An apparatus comprising:

a differential inductor comprising a first inductor section, a second inductor section separate from the first inductor section, and a common-mode point; and

a variable capacitor encircled by the differential inductor, wherein the variable capacitor is configured to serially directly connect the first inductor section to the second inductor section and tune a resonant frequency associated with the differential inductor.

4. The apparatus of claim 3, wherein the first inductor section has an inductance value substantially the same as the second inductor section.

5. The apparatus of claim 3, the variable capacitor comprising a plurality of metal oxide silicon (MOS) devices coupled to the common-mode point.

6. The apparatus of claim 3, the variable capacitor being from the group consisting of a microelectomechanical system (MEMS) capacitor, a varactor, a diode-based variable capacitor and a switched capacitor array.

7. The apparatus of claim 3, the variable capacitor comprising:

a plurality of drain bias circuits; and

a plurality of source bias circuits, the drain bias circuits and the source bias circuits configured to control a capacitance value associated with the variable capacitor.

8. The apparatus of claim 7, wherein the drain bias circuits and the source bias circuits are configured to control the capacitance value in response to a capacitance control signal.

9. The apparatus of claim 3, further comprising:

a capacitance selector coupled to the variable capacitor and configured to control a capacitance value of the variable capacitor.

10. The apparatus of claim 9, wherein the capacitance selector is further configured to drive a capacitance control signal to the variable capacitor to control the capacitance value.

11. The apparatus of claim 3, wherein:

the first inductor section and the second inductor section are coupled to the common-mode point.

12. An apparatus comprising:

means for coupling a first terminal to a second terminal via a differential inductor comprising a first inductor section, a second inductor section separate from the first inductor section, and a common-mode point; and

means for tuning a resonant frequency associated with the differential inductor via a variable capacitor, the variable capacitor serially directly connecting the first inductor section to the second inductor section, wherein the means for tuning the resonant frequency is encircled by the means for coupling the first terminal to the second terminal.

13. The apparatus of claim 12, the means for coupling the first terminal to the second terminal comprising:

means for coupling the first terminal to the common-mode point via the first inductor section of the differential inductor; and

means for coupling the second terminal to the common-mode point via the second inductor section of the differential inductor.

14. The apparatus of claim 12, wherein an inductance value of the first inductor section of the differential inductor is substantially the same as the second inductor section of the differential inductor.

15. The apparatus of claim 12, the means for tuning the resonant frequency comprising:

means for generating a varying capacitance of the variable capacitor via a plurality of metal oxide silicon (MOS) devices.

16. The apparatus of claim 12, the means for tuning the resonant frequency comprising:

means for controlling a capacitance value of the variable capacitor via drain bias circuits and source bias circuits.

17. The apparatus of claim 16, the means for controlling the capacitance value comprising:

means for responding to a capacitance control signal.

18. The apparatus of claim 12, the means for tuning the resonant frequency comprising:

means for driving a capacitance control signal to tune the resonant frequency.