Tunable dual-band ferroelectric antenna

• US 6,329,959 B1
• Filed: 06/16/2000
• Issued: 12/11/2001
• Est. Priority Date: 06/17/1999
• Status: Expired due to Term

• Current Assignee: Penn State Research Foundation
• Original Assignee: Penn State Research Foundation
• Inventors: Teo, Peng Thian, Varadan, Vijay K.
• Primary Examiner(s): Ho, Tan
• Application Number:
  US09/595,933
• Time in Patent Office: 543 Days
• Field of Search: 343/700.MS, 343/702, 343/787, 343/788, 343/815, 501/137
• US Class Current: 343/787
• CPC Class Codes: H01Q 1/364 using a particular conducting material, e.g. superconductor
• CPC Class Codes: H01Q 1/38 formed by a conductive layer on an insulating support patch antennas H01Q9/0407; microstrip dipole antennas H01Q9/065; microstrip slot antennas H01Q13/106; transmission line microstrip antennas H01Q13/206; manufacturing reflecting surfaces using insulating material for supporting the reflecting surface H01Q15/142
• CPC Class Codes: H01Q 15/02 Refracting or diffracting devices, e.g. lens, prism
• CPC Class Codes: H01Q 21/30 Combinations of separate antenna units operating in different wavebands and connected to a common feeder system
• CPC Class Codes: H01Q 3/44 varying the electric or magnetic characteristics of reflecting, refracting, or diffracting devices associated with the radiating element
• CPC Class Codes: H01Q 9/0407 Substantially flat resonant element parallel to ground plane, e.g. patch antenna dipole H01Q9/285; monopole H01Q9/40
• CPC Class Codes: H01Q 9/0414 in a stacked or folded configuration
• CPC Class Codes: H01Q 9/0442 with particular tuning means
• CPC Class Codes: H01Q 9/14 Length of element or elements adjustable telescopic elements H01Q1/10

Abstract

A multilayer tunable ferroelectric antenna assembly that includes two superimposed substrate layers. A first substrate layer consists of a low dielectric material carrying on one face an electrically ground plane, and on its opposite face an electrically conductive patch serving as an active feeder-resonator. A second substrate includes a ferroelectric material having one face positioned on top of the feeder-resonator and carrying on the opposite face an electrically conductive patch acting as a director. The upper director patch is fed through capacitve coupling of energy from the feeder-resonator. Application of bias voltage between the director and the feeder-resonator changes the permittivity of the ferroelectric substrate, thereby causing a shift in resonance frequency. A radiation null, corresponding to energy absorption, could be tuned into the resonance frequency at which the antenna is previously exhibiting a radiation characteristic. This provides the antenna a means to behave either as a radiator or an absorber at particular frequency.

Claims

1. A tunable dual band antenna comprising:

a stacked assembly that includes;

a layer of ferroelectric material disposed on an electrically conductive feeder-resonator;

an electrically conductive director disposed above said layer of ferroelectric material, wherein electromagnetic energy received by said feeder-resonator is capacitively coupled via said layer of ferroelectric material to said director; and

wherein said stacked assembly exhibits two resonant frequencies that are tunable in response to a bias voltage applied to said layer of ferroelectric material.

2. The tunable dual band antenna of claim 1, wherein said director is disposed on top of said layer of ferroelectric material.

3. The tunable dual band antenna of claim 2, further comprising a ground plane and a layer of dielectric material disposed between said layer of ferroelectric material and said ground plane.

4. The tunable dual band antenna of claim 3, wherein said layer of ferroelectric material has a permittivity value much higher than that of said layer of dielectric material.

5. The tunable dual band antenna of claim 4, wherein said feeder-resonator has a larger surface area compared with that of said second substrate layer of ferroelectric material and that of said director.

6. The tunable dual band antenna of claim 4, wherein said feeder-resonator acts as a ground reference for said layer of ferroelectric material and said director when a DC biasing voltage is applied to said layer of ferroelectric material.

7. The tunable dual band antenna of claim 6, further comprising means for applying said bias voltage across said layer of ferroelectric material to tune said antenna, and wherein said bias voltage is variable.

8. The tunable dual band antenna of claim 7, wherein said bias voltage is variable.

9. The tunable dual band antenna of claim 4, wherein said ferroelectric material includes barium strontium titanate.

10. A method for transforming an antenna into an absorber for electromagnetic energy at a particular frequency comprising the steps of.

providing a layer of ferroelectric material disposed on a feeder-resonator;

providing a director-resonator disposed above said layer of ferroelectric material; and

providing a bias voltage across said layer of ferroelectric material.

11. The method of claim 10, further comprising:

providing an electrically conductive ground plane; and

providing a layer of low dielectric material between said layer of ferroelectric material and said ground plane.

12. The method of claim 11, wherein said layer of ferroelectric material has a permittivity value much higher than that of said layer of dielectric material.

13. The method of claim 12, further comprising providing a resistive layer defining a predetermined broken pattern above said director resonator.

14. The method of claim 13, wherein the bias voltage is varied until a radiation null is generated or tuned into a resonance frequency at which the antenna previously exhibited a radiation.

15. A tunable dual band antenna assembly comprising:

an electrically conductive ground plane;

a first substrate layer having a bottom surface overlying said ground plane and an opposing upper surface, wherein said first substrate layer includes a low dielectric material;

an electrically conductive sheet overlying said opposing upper surface of said substrate layer;

said electrically conductive sheet including a patch radiator and a microstrip feed therefor;

wherein said patch radiator serves as a feeder radiator;

a second substrate layer having one face positioned on top of said feeder radiator and an opposing face, said second substrate layer including a thin film ferroelectric material having a permittivity value much higher than that of said first substrate layer;

an electrically conductive patch overlying said opposing face of said second substrate layer, wherein said electrically conductive patch is operable as a director and is fed through capacitive coupling of energy from said patch radiator; and

means for applying a bias voltage across said second substrate layer.

16. The tunable dual band antenna assembly of claim 15, wherein said feeder radiator has a larger surface area compared with that of said thin-film ferroelectric substrate layer and said director, wherein said feeder radiator and said director are dimensioned for different frequencies.

17. The tunable dual band antenna assembly of claim 15, wherein said feeder radiator is operable to excite electromagnetic energy for said director element and to serve as a ground plane for said second substrate layer and said director.

18. The tunable dual band antenna assembly of claim 15, wherein said bias voltage is variable to tune said antenna.

19. A method for providing adaptive nulling at a particular frequency in a radiation pattern of an antenna comprising the steps of:

providing an electrically conductive ground plane;

providing a first substrate layer of dielectric material over the ground plane;

providing a first electrically conductive sheet overlying a top of said first substrate layer, wherein said first electrically conductive sheet includes a feeder patch resonator and a microstrip feed therefor;

providing a second substrate layer over said feeder patch resonator, wherein said second substrate layer inclues a tunable thin-film ferroelectric material;

providing a second electrically conductive sheet overlying a top of said second substrate layer, wherein said second electrically conductive sheet includes a director-patch resonator;

providing a bias voltage between said second electrically conductive sheet and said firt electrically conductive sheet; and

providing a resistive layer defining a predetermined broken pattern thereon over said director-patch resonator.

20. The method of claim 19, wherein said bias voltage is varied until a radiation null is generated or turned into a resonance frequency at which the antenna previously exhibiting a radiation.