Electronically tunable RF diplexers tuned by tunable capacitors

• US 6,683,513 B2
• Filed: 10/24/2001
• Issued: 01/27/2004
• Est. Priority Date: 10/26/2000
• Status: Expired due to Term

• Current Assignee: NXP USA, Inc. (NXP Semiconductors NV)
• Original Assignee: Paratek Microwave Incorporated (Blackberry Limited)
• Inventors: Xu, Jian, Shamsaifar, Khosro
• Primary Examiner(s): Pascal, Robert
• Assistant Examiner(s): TAKAOKA, DEAN O
• Application Number:
  US10/000,471
• Publication Number:
  US 20020053954A1
• Time in Patent Office: 825 Days
• Field of Search: 333/135, 333/209, 333/202, 333/132, 333/134, 333/205, 333/208
• US Class Current: 333/135
• CPC Class Codes: H01P 1/213 combining or separating two or more different frequencies H01P1/215 takes precedence

Abstract

A diplexer includes a first tunable bandpass filter connected to a first port, a second tunable bandpass filter connected to a second port, and a coupling element for coupling the first bandpass filter and the second bandpass filter to a third port. Each of the tunable bandpass filters includes a tunable capacitor, wherein a control signal applied to the tunable capacitor controls the transmission characteristic of the filter. The tunable capacitor can be a tunable dielectric varactor or a microelectromechanical variable capacitor. The coupling element can include one of: a circulator, a T-junction, and an orthomode transducer. Each of the first and second filters can comprise a fin line filter including a plurality of tunable dielectric capacitors mounted within a waveguide for controlling the filter transmission characteristics. Fixed bandpass filters can be inserted between each of the tunable bandpass filters and the coupling element.

Claims

1. A diplexer comprising:

a first tunable bandpass filter including a first tunable capacitor and connected to a first port;

a second tunable bandpass filter including a second tunable capacitor and connected to a second port; and

means for coupling the first bandpass filter and the second bandpass filter to a third port, wherein the means for coupling the first bandpass filter and the second bandpass filter to a third port comprises one of;

a circulator, a T-junction, and an orthomode transducer.

2. A diplexer according to claim 1, wherein the first and second tunable capacitors each comprise:

a tunable dielectric varactor.

3. A diplexer according to claim 1, wherein the first and second tunable capacitors each comprise:

a microelectromechanical variable capacitor.

4. A diplexer comprising:

a first tunable bandpass filter including a first tunable capacitor and connected to a first port;

a second tunable bandpass filter including a second tunable capacitor and connected to a second port; and

means for coupling the first bandpass filter and the second bandpass filter to a third port, wherein;

the first tunable bandpass filter comprises a first plurality of resonators, wherein the first tunable capacitor couples a signal between two of the resonators in the first plurality of resonators; and

the second tunable bandpass filter comprises a second plurality of resonators, wherein the second tunable capacitor couples a signal between two of the resonators in the second plurality of resonators.

5. A diplexer comprising:

a first tunable bandpass filter including a first tunable capacitor and connected to a first port;

a second tunable bandpass filter including a second tunable capacitor and connected to a second port; and

means for coupling the first bandpass filter and the second bandpass filter to a third port, wherein the first tunable bandpass filter comprises;

a first waveguide; and

a first septum position along an axis of the first waveguide; and

wherein the first tunable capacitor is mounted on the septum.

6. A diplexer according to claim 5, wherein the first tunable capacitor comprises:

a substrate having a first dielectric constant and having generally a planar surface;

a tunable dielectric layer positioned on the generally planar surface of the substrate, the tunable dielectric layer having a second dielectric constant greater than said first dielectric constant; and

first and second electrodes positioned on a surface of the tunable dielectric layer opposite the generally planar surface of the substrate, said first and second electrodes being separated to form a gap therebetween.

7. A diplexer according to claim 6, wherein the first tunable capacitor further comprises:

an insulating material in said gap.

8. A diplexer according to claim 6, wherein the tunable dielectric layer in the first tunable dielectric varactor has a permittivity in a range from about 20 to about 2000, and a tunability in a range from about 10% to about 80% at a bias voltage of about 10 V/μ

m.

9. A diplexer according to claim 5, wherein the second tunable bandpass filter comprises:

a second waveguide; and

a second septum position along an axis of the second waveguide; and

wherein the second tunable capacitor is mounted on the second septum.

10. A diplexer according to claim 9, wherein the second tunable capacitor comprises:

a substrate having a first dielectric constant and having generally a planar surface;

a tunable dielectric layer positioned on the generally planar surface of the substrate, the tunable dielectric layer having a second dielectric constant greater than said first dielectric constant; and

first and second electrodes positioned on a surface of the tunable dielectric layer opposite the generally planar surface of the substrate, said first and second electrodes being separated to form a gap therebetween.

11. A diplexer according to claim 10, wherein the second tunable capacitor further comprises:

an insulating material in said gap.

12. A diplexer according to claim 9, wherein the tunable dielectric layer in the second tunable capacitor has a permittivity in a range from about 20 to about 2000, and a tunability in a range from about 10% to about 80% at a bias voltage of about 10 V/μ

m.

13. A diplexer according to claim 10, further comprising:

a first fixed bandpass filter connected between the first tunable bandpass and the means for coupling the first bandpass filter and the second bandpass filter to a third port; and

a second fixed bandpass filter connected between the second tunable bandpass and the means for coupling the first bandpass filter and the second bandpass filter to a third port.

14. A diplexer according to claim 13, wherein:

each of the first and second fixed bandpass filters has a larger passband than each of the first and second tunable filters.

15. A diplexer according to claim 13, wherein:

the first tunable filter has a passband that can be tuned within a passband of the first fixed bandpass filter; and

the second tunable filter has a passband that can be tuned within a passband of the second fixed bandpass filter.

16. A diplexer comprising:

a first tunable bandpass filter including a first tunable capacitor and connected to a first port;

a second tunable bandpass filter including a second tunable capacitor and connected to a second port; and

means for coupling the first bandpass filter and the second bandpass filter to a third port, wherein;

the first tunable bandpass filter comprises a first plurality of resonators, wherein the first tunable capacitor is positioned within one of the resonators in the first plurality of resonators; and

the second tunable bandpass filter comprises a second plurality of resonators, wherein the second tunable capacitor is positioned within one of the resonators in the second plurality of resonators.

17. A diplexer according to claim 16, wherein the first and second tunable capacitors each comprise:

a microelectromechanical variable capacitor.

18. A diplexer according to claim 16, wherein the first and second tunable capacitors each comprise:

a tunable dielectric varactor.