Method and apparatus for electrically tuning a resonating device

• US 6,097,263 A
• Filed: 06/27/1997
• Issued: 08/01/2000
• Est. Priority Date: 06/28/1996
• Status: Expired due to Fees

• Current Assignee: Robert M. Yandrofski, Y. Development, LLC
• Original Assignee: Robert M. Yandrofski
• Inventors: Zhang, Zhihang, Mueller, Carl H., Koepf, Gerhard A.
• Primary Examiner(s): Lee, Benny T.
• Application Number:
  US08/884,362
• Time in Patent Office: 1,131 Days
• Field of Search: 333/219.1, 333/227, 333/231, 333/235, 333/99 S, 333/17.1, 505/210, 505/700, 505/701, 505/866
• US Class Current: 333/17.1
• CPC Class Codes: H01P 1/20336 Comb or interdigital filters
• CPC Class Codes: H01P 1/20381 Special shape resonators
• CPC Class Codes: H01P 1/2039 Galvanic coupling between Input/Output
• CPC Class Codes: H01P 7/06 Cavity resonators
• CPC Class Codes: H01P 7/082 Microstripline resonators H01P7/088 takes precedence
• CPC Class Codes: H01P 7/088 Tunable resonators
• CPC Class Codes: H01P 7/10 Dielectric resonators
• CPC Class Codes: Y10S 505/701 Coated or thin film device, i.e. active or passive
• CPC Class Codes: Y10S 505/866 Wave transmission line, network, waveguide, or microwave storage device

Abstract

The present invention provides an electronically tunable resonating apparatus which uses a tunable dielectric material which is biased by an electric field to alter the resonant frequency in a resonating cavity. The electrodes which apply the electric field are connected to a variable voltage source. The electrodes can therefore apply a plurality of electric field strengths and provide a range of resonant frequencies in the resonating apparatus. The resonating apparatus is particularly useful for microwave and millimeterwave electromagnetic energy.

Claims

1. A tunable electromagnetic resonating apparatus, comprising:

a cavity for resonating at a cavity resonant frequency in response to electromagnetic energy received by said cavity;

an input for inputting said electromagnetic energy into said cavity;

an output for outputting said electromagnetic energy from said cavity;

a resonator coupled to said cavity for altering the cavity resonant frequency, said resonator comprising a dielectric material having an electric permittivity that is a variable function of a voltage applied to said dielectric material, and a pair of spaced-apart conductors, said pair of spaced-apart conductors being located on a common surface of a substrate, the dielectric material being located in a gap between the conductors;

a biasing circuit for applying said voltage to said dielectric material;

a leakage controller for inhibiting coupling of the electromagnetic energy to said biasing circuit, said leakage controller being operatively connected to said biasing circuit;

a sensing device operatively connected to the cavity for determining the cavity resonant frequency and generating a signal in response thereto;

a variable power source connected to said biasing circuit for appylying power thereto; and

a control device connected to the variable power source and sensing device for receiving the signal and generating a control signal in response thereto, wherein the variable power source applies power to the biasing circuit in response to said control signal, wherein said cavity resonant frequency is altered by altering said electric permittivity in response to altering of the applied voltage.

2. The apparatus, as claimed in claim 1, wherein:

said cavity comprises a second dielectric material having a substantially constant permittivity during operation of said apparatus.

3. The apparatus, as claimed in claim 1, wherein:

said cavity has a quality factor of no less than about 300.

4. The apparatus, as claimed in claim 1, wherein:

at least a portion of said resonator is positioned inside of said cavity.

5. The apparatus, as claimed in claim 1, wherein:

said biasing circuit applies to said dielectric material a direct current electric field having an electric field strength of no more than about 500 kv/cm.

6. The apparatus, as claimed in claim 1, wherein:

said resonator comprises at least one voltage node, said biasing circuit comprises a conductor, and said leakage controller comprises a connection for said conductor located at substantially the same position as said voltage node.

7. The apparatus, as claimed in claim 1, wherein:

said biasing circuit comprises a biasing conductor and said leakage controller comprises a shunt capacitor connected to said conductor, the shunt capacitor being located one-quarter wavelength of the electromagnetic energy from one of the spaced-apart conductors.

8. The apparatus, as claimed in claim 1, wherein:

a dielectric impedance of said dielectric material is less than a substrate impedance of said substrate.

9. The apparatus, as claimed in claim 1, wherein:

said electromagnetic energy has a frequency ranging from about 3×

10⁸ to about 1×

10¹¹ Hz.

10. The apparatus, as claimed in claim 1, wherein:

said dielectric mateial is one of Ba, Sr_1-x TiO₃ where 0≦

x≦

1;

PbZr_1-x Ti_x O₃ where 0≦

x≦

1;

LaTiO₃, PbZrO₃ ;

LaZrO₃ ;

PbMgO₃ ;

PbNbO₃ ; and

KTaO₃.

11. The apparatus, as claimed in claim 1, further comprising:

a second dielectric matcrial, including at least one of a paraelectric and ferroelectric material, positioned in the cavity at a distance from said dielectric material, said second dielectric material having a second electric permittivity altered by a second biasing circuit for biasing said second dielectric material and altering the second electric permittivity to yield a selected cavity resonant frequency in said cavity.

12. The apparatus, as claimed in claim 11, wherein:

said substrate supports said dielectric material and said second dielectric material.

13. The apparatus, as claimed in claim 1, further comprising:

a dielectric puck located in said cavity and at least a portion of said resonator is supported by said dielectric puck.

14. The tunable electromagnetic resonating apparatus, as claimed in claim 1, wherein:

said dielectric material is a bulk or thin film ferroelctric or paraelectric material.

15. A tunable electromaagnetic resonating apparatus, comprising:

a cavity for resonating at a cavity resonant frequency in response to electromagnetic energy received by said cavity;

an input for inputting said electromagnetic energy into said cavity;

an output for outputting said electromagnetic energy from said cavity;

a resonator positioned inside of said cavity for altering the cavity resonant frequency, said resonator comprising a dielectric material having an elcctric permittivity that is a variable function of a voltage applied to said dielectric material and a pair of spaced-apart conductors, said pair of spaced-apart conductors being located on a common surface of an insulating substrate and each of said pair of spaced-apart conductors being located on opposing sides of said dielectric material, said insulating substrate having a substrate impedance that is greater than a dielectric impedance of said dielectric material;

a biasing circuit for applying said voltage to said dielectric material;

a sensor operatively connected to the cavity for determining the cavity resonant frequency and generating a signal in response thereto;

a variable power source connected to the biasing circuit for applying power thereto; and

a controller connected to the variable power source and sensor for receiving the signal and generating a control signal in response thereto, wherein the variable power source applies power to the biasing circuit in response to the control signal, wherein said cavity resonant frequency is altered by altering said electric permittivity in response to altering of the applied voltage.

16. The apparatus, as claimed in claim 15, wherein said substrate impedance is at least about 200% of the dielectric impedance.

17. The apparatus, as claimed in claim 15, wherein said substrate is composed of at least one of LaAlO₃, MgO, Al₂ O₃, and NdGaO₃.

18. The apparatus, as claimed in claim 15, further comprising:

a leakage coatoller for inhibiting coupling of the electromagnetic energy to said biasing circuit, said leakage controller being operatively connected to said biasing circuit.

19. A tunable electromagnetic resonating apparatus, comprising:

a cavity means for resonating at a cavity resonant frequency in response to electromagnetic energy received by said cavity means;

an input means for inputting said electromagnetic energy into said cavity means;

an output means for outputting said electromagnetic energy from said cavity means;

resonating means coupled to said cavity means for altering the cavity resonant frequency, said resonating means comprising a dielectric material having an electric permittivity that is a variable function of a voltage applied to said dielectric material and first and second spaced-apart conductors, the dielectric material being located between said first and second spaced-apart conductors and said first and second spaced-apart conductors each being located on a common surface of a substrate;

biasing means for applying said voltage to said dielectric material;

sensing means operatively connected to the cavity means for determining the cavity resonant frequency and generating a signal in response thereto;

a variable power source connected to the biasing means for applying power thereto; and

control meeans connectcd to the variable power source and sensing means for receiving said signal and generating a control signal in response thereto, wherein said variable power source applies power to the biasing means in response to the control signal, wherein said cavity resonant frequency is altered by altering said electric permittivity in response to altering of the applied voltage.

20. The tunable electromagnetic resonating apparatus, as claimed in claim 19, further comprising:

a second resonating means coupled to said cavity means for altering the cavity resonant frequency, the resonating means having a first resonant frequency and the second resonating means a second resonant frequency, the first resonating frequency being less than the cavity resonant frequency and the second resonant frequency being more than the cavity resonant frequency.

21. The tunable electromagnetic resonating apparatus, as claimed in claim 19, wherein at least a portion of said resonating means is positioned in a gap between said first and second spaced-apart conductors.

22. The tunable electromagnetic resonating apparatus, as claimed in claim 19, wherein:

said resonating means comprises a ground conductor also supported by said substrate and wherein at least one of said first and second conductors are connected to said ground conductor.

23. The tunable electromagnetic resonating apparatus, as claimed in claim 19, wherein:

said resonating means has a resonant frequency and said resonant frequency is no less tha about 65% of said cavity resonant frequency and no more than about 135% of said cavity resonant frequency.

24. Thc tunable electromagnetic resonating apparatus, as claimed in claim 19, wherein:

said first and second spaced-apart conductors are not in physical contact with one another.

25. The tunable electromagnetic resonating apparatus, as claimed in claim 19, wherein:

said first and scond spaced-apart conductors are configured as one of a microstrip line, slot line, and coplanar waveguide.

26. The tunable electromagnetic resonating apparatus, as claimed in claim 19, wherein:

at least one of said first and second spaced-apart conductors has a minimum thickness and said minimum thickness is at least about 3 times the skin depth at the operating frequency for the conductive material in the conductors.

27. A method for altering a cavity resonant frequency in an electromagnetic resonating apparatus, comprising:

(a) providing (i) a cavity for resonating at a cavity resonant frequency in response to electromagnetic energy received by the cavity, the cavity having an input for inputting the electromagnetic energy into the cavity and an output for outputting the electromagnetic energy from the cavity, (ii) a resonator coupled to the cavity for altering the cavity resonant frequency, the resonator including a dielectric material having an electric permittivity that is a variable function of a voltage applied to the dielectric material and a pair of spaced-apart conductors, said pair of conductors are located on a common surface of a substrate, (iii) a biasing circuit for applying the voltage to the dielectric material, and (iv) a leakage controller for inhibiting coupling of the electromagnetic energy to the biasing circuit, the leakage controller being operatively connected to the biasing circuit;

passing at least a portion of the electromagnetic energy through the cavity and through the dielectric material;

measuring the cavity resonant frequency;

generating a signal based on the measured cavity resonant frequency;

generating a control signal in response to the signal; and

altering a voltage applied to the dielectric material by the biasing circuit in response to the control signal to alter the electric permittivity and thereby alter the cavity resonant frequency.

28. The method of claim 27, wherein a dielectric puck is located within the cavity and at least a portion of the resonator is supported by the dielectric puck.

29. The method of claim 27, wherein the cavity includes a second dielectric material having a substantially constant electric permittivity during the passing step and wherein the second dielectric material and the dielectric material are supported by the substrate.