Tunable bandpass filter integrated circuit

• US 9,123,983 B1
• Filed: 07/20/2012
• Issued: 09/01/2015
• Est. Priority Date: 07/20/2012
• Status: Active Grant

• Current Assignee: Hittite Microwave, LLC (Analog Devices, Inc.)
• Original Assignee: Hittite Microwave Corporation (Analog Devices, Inc.)
• Inventors: Oran, Ekrem
• Primary Examiner(s): Pascal, Robert
• Assistant Examiner(s): STEVENS, GERALD D
• Application Number:
  US13/553,952
• Time in Patent Office: 1,138 Days
• Field of Search: 333/208, 333/209, 333/212, 333/219, 333/235, 333/206, 333/207
• US Class Current: 1/1
• CPC Class Codes: H01P 1/205 Comb or interdigital filters; Cascaded coaxial cavities H01P1/203 takes precedence
• CPC Class Codes: H01P 1/208 Cascaded cavities; Cascaded resonators inside a hollow waveguide structure H01P1/205 takes precedence
• CPC Class Codes: H01P 1/2088 Integrated in a substrate
• CPC Class Codes: H01P 1/219 Evanescent mode filters

Abstract

A tunable bandpass filter integrated circuit includes a filter core including at least two spaced conductor layers, a plurality of peripherally spaced backside vias extending between the conductor layers defining a resonator cavity, at least one internal backside via, and a tunable impedance connected in series with the internal backside via between the conductor layers for adjusting the resonance of the cavity.

Claims

1. A tunable bandpass filter integrated circuit comprising:

at least two spaced conductor layers;

a plurality of peripherally spaced backside vias extending between said two spaced conductor layers defining a resonator cavity;

at least one internal backside via comprising a first internal backside via; and

a tunable impedance connected in series with said first internal backside via between said two spaced conductor layers, wherein a center frequency of the tunable bandpass filter is based at least partly on an impedance of said first internal backside via and an impedance of the tunable impedance, and wherein adjusting the impedance of the tunable impedance causes the center frequency of the tunable bandpass filter to be adjusted.

2. The tunable bandpass filter integrated circuit of claim 1 in which said bandpass filter integrated circuit is a microwave monolithic integrated circuit (MMIC).

3. The tunable bandpass filter integrated circuit of claim 1 in which said bandpass filter integrated circuit operates at and above millimeter wavelengths (mmW).

4. The tunable bandpass filter integrated circuit of claim 1 in which a semiconductor material is disposed between the two spaced conductor layers.

5. The tunable bandpass filter integrated circuit of claim 4 in which said semiconductor material includes a low conductivity silicon.

6. The tunable bandpass filter integrated circuit of claim 4 in which said semiconductor material includes gallium arsenide.

7. The tunable bandpass filter integrated circuit of claim 4 in which a dielectric layer is disposed between said two spaced conductor layers.

8. The tunable bandpass filter integrated circuit of claim 7 in which said dielectric layer includes SiN.

9. The tunable bandpass filter integrated circuit of claim 7 in which said dielectric layer includes SiO₂.

10. The tunable bandpass filter integrated circuit of claim 1 in which said two spaced conductor layers are disposed on a top and a bottom of a filter core.

11. The tunable bandpass filter integrated circuit of claim 1 in which said tunable impedance includes a varactor.

12. The tunable bandpass filter integrated circuit of claim 1 in which said tunable impedance includes a MEMS device.

13. The tunable bandpass filter integrated circuit of claim 1 in which said tunable impedance includes a ferroelectric dielectric.

14. The tunable bandpass filter integrated circuit of claim 1 in which at least one of said peripherally spaced backside vias is omitted in at least two locations to form input and output ports.

15. The tunable bandpass filter integrated circuit of claim 14 further comprising a second tunable impedance element, wherein said at least one internal backside via comprises a second internal backside via, wherein said second internal backside via and the second tunable impedance are disposed in series between said two spaced conductor layers, said second internal backside via being separated from said first internal backside via, wherein a secondary metallization member extends between one of said input and output ports and at least one of said tunable impedance and said first internal backside via.

16. The tunable bandpass filter integrated circuit of claim 1 further comprising a second tunable impedance, wherein said at least one internal backside via comprises a second internal backside via, wherein said first internal backside via is separated from said second internal backside via, and wherein said second internal backside via and the second tunable impedance are connected in series between said two spaced conductor layers, wherein said first internal backside via and said tunable impedance are included in a first resonator, and wherein said second internal backside via and the second tunable impedance are included in a second resonator.

17. The tunable bandpass filter integrated circuit of claim 16 in which the first resonator and the second resonator each function as a filter.

18. The tunable bandpass filter integrated circuit of claim 16 in which the bandpass filter is configured as an evanescent mode filter.

19. The tunable bandpass filter integrated circuit of claim 16 in which there is an opening in a conductor layer of said two spaced conductor layers with a bridging secondary metallization element for coupling between the first resonator and the second resonator.

20. The tunable bandpass filter integrated circuit of claim 19 in which extremities of the bridging secondary metallization element are short circuited at a frequency of operation.

21. The tunable bandpass filter integrated circuit of claim 16 in which there is an inter-resonator tunable capacitance between the first and second resonators for controlling inter-resonator coupling.

22. The tunable bandpass filter integrated circuit of claim 16 in which there is coupling between the first resonator and a non-adjacent resonator to establish asymmetrical bandpass response with one or more finite frequency nulls.

23. The tunable bandpass filter integrated circuit of claim 16 in which the first and second resonators are in a line.

24. The tunable bandpass filter integrated circuit of claim 16 in which the first and second resonators are in a folded path.

25. The tunable bandpass filter integrated circuit of claim 1 in which said tunable impedance includes back-to-back connected varactors for mitigating large signal distortions.

26. The tunable bandpass filter integrated circuit of claim 25 in which said back-to-back connected varactors include a resistance for controlling the slope of amplitude equalization associated with the bandpass filter integrated circuit.

27. The tunable bandpass filter integrated circuit of claim 1 in which said integrated circuit includes bump pads for flip chip mounting.