Slotted surface scattering antennas

• US 9,882,288 B2
• Filed: 06/30/2015
• Issued: 01/30/2018
• Est. Priority Date: 05/02/2014
• Status: Active Grant

• Current Assignee: The Invention Science Fund I, L.L.C. (Intellectual Ventures LLC)
• Original Assignee: The Invention Science Fund I, L.L.C. (Intellectual Ventures LLC)
• Inventors: Black, Eric J., Deutsch, Brian Mark, Katko, Alexander Remley, Machado, Melroy, McCandless, Jay Howard, Urzhumov, Yaroslav A.
• Primary Examiner(s): DUONG, DIEU HIEN
• Application Number:
  US14/755,579
• Publication Number:
  US 20150380828A1
• Time in Patent Office: 945 Days
• CPC Class Codes: H01H 59/0009 making use of micromechanics
• CPC Class Codes: H01Q 13/206 Microstrip transmission line antennas
• CPC Class Codes: H01Q 23/00 Antennas with active circuits or circuit elements integrated within them or attached to them
• CPC Class Codes: H01Q 3/443 varying the phase velocity along a leaky transmission line frequency scanning H01Q3/22; non-resonant leaky-waveguide or transmission-line aerials H01Q13/20
• CPC Class Codes: H01Q 9/0407 Substantially flat resonant element parallel to ground plane, e.g. patch antenna dipole H01Q9/285; monopole H01Q9/40

Abstract

Surface scattering antennas with lumped elements provide adjustable radiation fields by adjustably coupling scattering elements along a waveguide. In some approaches, the scattering elements include slots in an upper surface of the waveguide, and the lumped elements are configured to span the slots provide adjustable loading. In some approaches, the scattering elements are adjusted by adjusting bias voltages for the lumped elements. In some approaches, the lumped elements include diodes or transistors.

Claims

1. An antenna, comprising:

a waveguide;

a plurality of subwavelength radiative elements coupled to the waveguide; and

a plurality of lumped element circuits directly coupled to the subwavelength radiative elements and configured to adjust radiation characteristics of the subwavelength radiative elements;

wherein the waveguide includes a bounding surface, and the plurality of subwavelength radiative elements includes a plurality of unit cells each containing a slot in the bounding surface;

wherein the waveguide defines a propagation direction, and the subwavelength radiative elements have inter-element spacings along the propagation direction that are substantially less than a free-space wavelength corresponding to an operating frequency band of the antenna; and

wherein the inter-element spacings are less than or equal to one-third of the free-space wavelength.

2. The antenna of claim 1, wherein the waveguide is a stripline waveguide.

3. The antenna of claim 2, wherein the plurality of subwavelength radiative elements includes:

a first plurality of subwavelength radiative elements coupled to a left edge of the stripline waveguide; and

a second plurality of subwavelength radiative elements coupled to a right edge of the stripline waveguide.

4. The antenna of claim 3, wherein the first plurality and the second plurality are positioned at equal positions along a length of the stripline waveguide.

5. The antenna of claim 3, wherein the first plurality and the second plurality are positioned at first and second staggered positions along a length of the stripline waveguide.

6. The antenna of claim 5, wherein the second staggered positions are midpoints between adjacent first positions.

7. The antenna of claim 1, wherein the inter-elements spacings are less than or equal to one-fourth of the free-space wavelength.

8. The antenna of claim 1, wherein the inter-elements spacings are less than or equal to one-fifth of the free-space wavelength.

9. The antenna of claim 1, wherein each slot defines a slot width dimension and a slot length dimension, and the slot length dimension is substantially equal to one-half of the free-space wavelength.

10. The antenna of claim 9, wherein the slot length dimension corresponds to a direction perpendicular to the propagation direction.

11. The antenna of claim 1, wherein the lumped circuit elements include, for each of the plurality of unit cells, a three-port element with a first port connected to one side of the slot and a second port connected to another slide of the slot.

12. The antenna of claim 11, further comprising, for each of the plurality of unit cells:

a bias voltage line connected to a third port of the three-port element.

13. The antenna of claim 11, wherein each three-port element is a transistor.

14. The antenna of claim 1, wherein the lumped circuit elements include, for each of the plurality of unit cells, a pair of two-port elements connected in series across the slot.

15. The antenna of claim 14, wherein the pair of two-port elements is a diode and a blocking capacitor.

16. The antenna of claim 14, further comprising, for each of the plurality of unit cells:

a bias voltage line connected between a node common to the pair of two-port elements.

17. The antenna of claim 14, wherein each pair of two-port elements is a pair of nonlinear variable-impedance devices.

18. The antenna of claim 17, wherein each pair of nonlinear variable-impedance devices is a matched pair of nonlinear variable-impedance devices.

19. The antenna of claim 17, wherein the nonlinear variable-impedance devices include MEMS switched capacitors or MEMS varactors.

20. The antenna of claim 14, wherein the pair of two-port elements is a pair of diodes.

21. The antenna of claim 20, wherein each diode in the pair of diodes has a cathode connected to the slot and an anode connected to the other diode in the pair of diodes.

22. The antenna of claim 20, wherein each diode in the pair of diodes has an anode connected to the slot and a cathode connected to the other diode in the pair of diodes.

23. The antenna of claim 20, wherein the pair of diodes is a pair of varactors.

24. The antenna of claim 14, wherein the pair of two-port elements is a pair of oppositely-oriented two-port elements.

25. The antenna of claim 24, wherein the pair of oppositely-oriented two-port elements is a pair of identical, oppositely-oriented two-port elements.

26. The antenna of claim 14, wherein the pair of two-port elements is configured so that a first 2nd harmonic generated by a first element in the pair of two-port elements is substantially cancelled by a second 2nd harmonic generated by a second element in the pair of two-port elements.

27. The antenna of claim 1, wherein the lumped circuit elements include, for each of the plurality of unit cells, a first lumped element connected at or near an upper end of the slot and a second lumped element connected at or near a lower end of the slot.

28. The antenna of claim 27, wherein the lumped circuit elements further include one or more additional lumped elements connected at one or more additional positions along the slot between the first lumped element and the second lumped element.

29. The antenna of claim 27, wherein:

the radiation characteristics of the subwavelength radiative elements include, for each unit cell, a scattering parameter having a frequency variation at an operating frequency band of the antenna; and

positions of the first and second lumped elements are selected to reduce or minimize the frequency variation of the scattering parameter.

30. The antenna of claim 27, wherein:

the radiation characteristics of the subwavelength radiative elements include, for each unit cell, a scattering parameter having a frequency variation at an operating frequency band of the antenna; and

the first and second lumped elements have respective first and second impedances that vary with frequency, the first and second variable impedances being selected to reduce or minimize the frequency variation of the scattering parameter.

31. The antenna of claim 27, wherein:

the radiation characteristics of the subwavelength radiative elements include, for each unit cell, a total scattering parameter that includes contributions from a first scattering parameter corresponding to the first lumped element and a second scattering parameter corresponding to the second lumped element;

wherein a frequency variation of the first scattering parameter is substantially complementary to a frequency variation of the second scattering parameter.

32. The antenna of claim 27, wherein the first lumped element is a first varactor and the second lumped element is a second varactor.

33. The antenna of claim 27, wherein the first lumped element is a first transistor and the second lumped element is a second transistor.

34. The antenna of claim 27, wherein the first lumped element is a varactor and the second lumped element is a transistor.

35. The antenna of claim 1, wherein the waveguide is a stripline waveguide, the bounding surface is an upper ground plane of the stripline, and each slot includes an opening sufficient to admit a bias line for the lumped element circuit of that unit cell.

36. The antenna of claim 35, wherein each slot includes narrow first portion that extends from the opening and towards the stripline and a narrow second portion that extends from the opening and away from the stripline.

37. The antenna of claim 36, wherein the opening is a circular antipad enclosing a pad for the bias line.

38. The antenna of claim 35, wherein each slot has a total length equal to about one-half of a free-space wavelength corresponding to an operating frequency band of the antenna, where the total length equals a length of the narrow first portion plus a length of the narrow second portion plus a diameter of the opening.

39. The antenna of claim 35, wherein the stripline waveguide includes a lower ground plane and each bias line extends through both the upper ground plane and the lower ground plane.

40. The antenna of claim 39, further comprising:

for each unit cell, a stub choke for the bias line.

41. The antenna of claim 40, wherein each stub choke is configured to provide a high impedance of the bias line at an operating frequency band of the antenna.

42. The antenna of claim 40, wherein each stub choke is positioned on a metal layer positioned below the lower ground plane of the stripline waveguide.

43. The antenna of claim 39, wherein each unit cell includes an arrangement of vias enclosing both the stripline and the slot.

44. The antenna of claim 43, wherein the upper ground plane, the lower ground plane, and the arrangement of vias define a cavity volume for the unit cell.

45. The antenna of claim 35, further comprising:

a dielectric layer positioned above the upper ground plane, where each bias line extends through the dielectric layer to connect to the lumped element circuit on the upper surface of the dielectric layer.