MICROSTRIP ANTENNA

• US 20090140927A1
• Filed: 11/30/2007
• Published: 06/04/2009
• Est. Priority Date: 11/30/2007
• Status: Active Grant

• Current Assignee: Harada Industry of America, Incorporated (Harada Industry Company Limited)
• Original Assignee: Harada Industry of America, Incorporated (Harada Industry Company Limited)
• Inventors: Maeda, Hiroyuki, Dai, Yingcheng
• Granted Patent: US 7,994,999 B2
• Time in Patent Office: Days
• US Class Current: 343/700.MS
• CPC Class Codes: H01Q 5/40 Imbricated or interleaved structures; Combined or electromagnetically coupled arrangements, e.g. comprising two or more non-connected fed radiating elements
• 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 9/0428 radiating a circular polarised wave
• CPC Class Codes: H01Q 9/0435 using two feed points
• CPC Class Codes: H01Q 9/045 with particular feeding means for circular polarisation H01Q9/0428

Abstract

A microstrip antenna that can be linear, co-circular, or dual-circularly polarized having co-planar radiating elements and operating at dual frequency bands wherein an inner radiating element is surrounded by and spaced from an outer radiating element. Each radiating element resonates at a different frequency. In one embodiment of the invention a feed network has a single, cross-shaped, feed line that is positioned between the inner and outer radiating elements and capacitively coupled to the inner and outer radiating elements. In another embodiment of the present invention, the radiating elements are fed separately by first and second feed networks each having a plurality of feed points. The radiating elements each have one active feed point that is either directly or indirectly coupled to its respective feed network.

Claims

1. A microstrip antenna comprising:

a ground plane;

a dielectric material having a predetermined thickness disposed on the ground plane;

an inner radiating element disposed on the dielectric material, the inner radiating element having a predetermined outer perimeter and a first resonating frequency;

an outer radiating element disposed on the dielectric material, co-planar with and at least partially surrounding the inner radiating element, the outer radiating element being spaced from the predetermined outer perimeter of the inner radiating element by a predetermined distance, the outer radiating element having a predetermined inner perimeter, a predetermined outer perimeter and a second resonating frequency different from the first resonating frequency of the inner radiating element;

a first plurality of radiating apertures between a top edge of the predetermined outer perimeter of the inner radiating element and the ground plane;

a second plurality of radiating apertures between a top edge of the predetermined inner and outer perimeters of the outer radiating element and the ground plane;

a cross-shaped microstrip feed network disposed between and coplanar with the inner and outer radiating elements, the cross-shaped microstrip feed network being separated from the inner and outer radiating elements by a predetermined distance, the cross-shaped microstrip feed network being capacitively coupled to the inner and outer radiating elements and having a coupling capacitance between the feed network and the inner and outer radiating elements that is proportional to the predetermined distance between the cross-shaped microstrip feed network and the inner and outer radiating elements.

2. The microstrip antenna as claimed in claim 1 wherein the cross-shaped feed network further comprises four segments, each interconnected and having a predetermined length wherein the length of each of the four segments is directly proportional to the coupling capacitance.

3. The microstrip antenna as claimed in claim 2 further comprising;

a single feed pin located in the cross-shaped feed network; and

an RF feed connected to the single feed pin and the ground plane.

4. The microstrip antenna as claimed in claim 1 further comprising:

a first plurality of slits in the predetermined outer perimeter of the inner radiating element; and

a second plurality of slits in at least one of the predetermined inner and outer perimeters of the outer radiating element,

wherein the first and second plurality of slits tune the microstrip antenna to first and second resonating frequencies.

5. The microstrip antenna as claimed in claim 1 further comprising:

the inner radiating element having a square predetermined perimeter;

a first corner of the square predetermined perimeter of the inner radiating element having a blunt edge; and

a second corner of the square predetermined perimeter of the inner radiating element having a blunt edge, the second corner being diagonally opposite the first corner;

wherein the first and second blunt edge corners of the inner radiating element provide a circular polarization for the inner radiating element.

6. The microstrip antenna as claimed in claim 1 further comprising:

the outer radiating element having a square ring predetermined perimeter;

a first outer corner of the square perimeter of the outer radiating element having a blunt edge; and

a second outer corner of the square ring perimeter of the outer radiating element having a blunt edge, the second outer corner being diagonally opposite the first outer corner thereby defining a circular polarization for the outer radiating element.

7. The microstrip antenna as claimed in claim 5 further comprising:

the outer radiating element having a square predetermined perimeter;

a first outer corner of the square ring perimeter of the outer radiating element having a blunt edge; and

a second outer corner of the square ring perimeter of the outer radiating element having a blunt edge, the second outer corner being diagonally opposite the first outer corner thereby defining a circular polarization for the outer radiating element.

8. The microstrip antenna as claimed in claim 7 further comprising:

the blunt edge of the first corner of the inner radiating element and the blunt edge of the first outer corner of the outer radiating element being in similar corner locations;

the blunt edge of the second corner of the inner radiating element and the blunt edge of the second outer corner of the outer radiating element being in similar corner locations; and

wherein the circular polarization of the inner radiating element is in the same direction as the circular polarization of the outer radiating element thereby defining co-circular polarization of the microstrip antenna.

9. The microstrip antenna as claimed in claim 7 further comprising:

the blunt edge of the first corner of the inner radiating element and the blunt edge of the first outer corner of the outer radiating element being in diagonally opposite corner locations relative to each other;

the blunt edge of the second corner of the inner radiating element and the blunt edge of the second outer corner of the outer radiating element are in diagonally opposite corner locations relative to each other; and

wherein the circular polarization of the inner radiating element is a direction opposite to the circular polarization of the outer radiating element thereby defining dual-circular polarization of the microstrip antenna.

10. A microstrip antenna comprising:

a ground plane;

a dielectric material having a predetermined thickness disposed on the ground plane;

an inner radiating element disposed on the dielectric material, the inner radiating element having a predetermined outer perimeter, a first resonant frequency and a first polarization;

an outer radiating element disposed on the dielectric material, co-planar with and at least partially surrounding the inner radiating element, the outer radiating element having a predetermined inner perimeter being spaced a predetermined distance from the predetermined outer perimeter of the inner radiating element, a predetermined outer perimeter, a second resonant frequency and a second polarization;

a cross-shaped microstrip feed line disposed between and coplanar with the inner and outer radiating elements, the cross-shaped microstrip feed line being separated from the inner and outer radiating elements by a space having a predetermined size and defining a coupling capacitance between the cross-shaped microstrip feed line and the inner and outer radiating elements.

11. The microstrip antenna as claimed in claim 10 wherein the cross-shaped microstrip feed line further comprises four intersecting segments, each segment having a predetermined length wherein the length of each of the four segments is directly proportional to the coupling capacitance.

12. The microstrip antenna as claimed in claim 11 wherein the cross-shaped microstrip feed line further comprises a single feed pin.

13. The microstrip antenna as claimed in claim 12 wherein the single feed line is fed by a coaxial cable having inner and outer conductors, the inner conductor being connected to the microstrip patch feed line and the outer conductor being connected to the ground plane.

14. The microstrip antenna as claimed in claim 12 wherein the single feed pin is located at a point of intersection of the four intersecting segments.

15. The microstrip antenna as claimed in claim 10 wherein the inner radiating element has a predetermined shape and the outer radiating element has a predetermined shape at least partially surrounding the inner radiating element wherein the predetermined shape of the inner and outer radiating elements are selected from the group consisting of:

a circle and a polygon.

16. The microstrip antenna as claimed in claim 10 wherein the first polarization and the second polarization are the same.

17. The microstrip antenna as claimed in claim 16 wherein the first and second polarizations are linear.

18. The microstrip antenna as claimed in claim 16 wherein the first and second polarizations are circular.

19. The microstrip antenna as claimed in claim 18 wherein the first polarization is a circular polarization in a first direction and the second polarization is a circular polarization in a second direction that is opposite the first direction.

20. The microstrip antenna as claimed in claim 10 wherein the first polarization is a linear polarization and the second polarization is a linear polarization perpendicular to the first polarization.

21. A microstrip antenna comprising:

a ground plane;

a dielectric material having a predetermined thickness disposed on the ground plane;

an inner radiating element disposed on the dielectric material and having a predetermined outer perimeter, the inner radiating element having a first resonant frequency and a first polarization;

a first feed network coupled to the inner radiating element, the first feed network having a plurality of feed points;

an outer radiating element disposed on the dielectric material, co-planar with and at least partially surrounding the inner radiating element, the outer radiating element being spaced a predetermined distance from the outer perimeter of the inner radiating element, the outer radiating element having a predetermined inner perimeter and a predetermined outer perimeter, the outer radiating element having a second resonant frequency and a second polarization;

a second feed network coupled to the outer radiating element, the second feed network having a plurality of feed points; and

wherein a single feed point of the first feed network is actively fed and wherein a single feed point of the second feed network is actively fed.

22. The antenna as claimed in claim 21 wherein the plurality of feed points for the first and second feed networks further comprises:

a feed point on a vertical side of the inner radiating element;

a feed point on a horizontal side of the inner radiating element;

a feed point on a vertical side of the outer radiating element; and

a feed point a horizontal side of the outer radiating element.

23. The antenna as claimed in claim 22 further comprising the actively fed feed point in the first feed network is located on an opposite side of the actively fed feed point in the second feed network.

24. The antenna as claimed in claim 21 further comprising each of the feed points in either the first or second feed network being surrounded by a space thereby creating a feed point island capacitively coupled to either the inner or outer radiating elements.

25. The antenna as claimed in claim 21 further comprising each of the feed points in the first and second feed networks being surrounded by a space thereby creating a feed point island capacitively coupled to each of the inner and outer radiating elements respectively.

26. The antenna as claimed in claim 24 further comprising:

the actively fed feed point in the first feed network being physically coupled to the inner radiating element; and

the actively fed feed point in the second feed network being capacitively coupled to the outer radiating element.

27. The antenna as claimed in claim 24 further comprising:

the actively fed feed point in the first feed network being capacitively coupled to the inner radiating element; and

the actively fed feed point in the second feed network being physically coupled to the outer radiating element.

28. The antenna as claimed in claim 21 further comprising;

a first circular polarization for the inner radiating element defined by the inner radiating element having a square perimeter, a first corner of the inner radiating element having a blunt edge and a second corner of the inner radiating element, diagonally opposite the first corner, having a blunt edge; and

a second circular polarization for the outer radiating element defined by the outer radiating element having square inner and outer perimeters, a first outer corner of the outer radiating element having a blunt edge and a second outer corner of the outer radiating element, diagonally opposite the first outer corner, having a blunt edge.

29. The antenna as claimed in claim 28 further comprising the first circular polarization being a same direction as the second circular polarization defined by the first and second corners of the inner radiating element and the first and second outer corners of the outer radiating element being at similar corner locations respectively.

30. The antenna as claimed in claim 28 further comprising the first circular polarization being circular in a direction opposite to the second circular polarization defined by the first and second corners of the inner radiating element and the first and second outer corners of the outer radiating element being at diagonally opposite corner locations respectively.

31. The antenna as claimed in claim 21 wherein the plurality of feed points further comprises feed points for the inner and outer radiating elements being on a center line of the antenna.

32. The antenna as claimed in claim 21 wherein the plurality of feed points further comprises feed points for the inner and outer radiating elements being on a diagonal line of the antenna.

33. A microstrip antenna comprising:

a ground plane;

a dielectric material having a predetermined thickness disposed on the ground plane;

an inner radiating element disposed on the dielectric material and having a predetermined outer perimeter, the inner radiating element having a first resonant frequency and a first polarization;

a first feed network coupled to the inner radiating element, the first feed network having at least one feed point;

an outer radiating element disposed on the dielectric material, co-planar with and at least partially surrounding the inner radiating element, the outer radiating element being spaced a predetermined distance from the outer perimeter of the inner radiating element, the outer radiating element having a predetermined inner perimeter and a predetermined outer perimeter, the outer radiating element having a second resonant frequency and a second polarization;

a second feed network capacitively coupled to the outer radiating element, the second feed network having at least one feed point wherein the at least one feed point is surrounded by a space thereby creating at least one feed point island within the outer radiating element; and

wherein a single feed point of the at least one feed point on the inner radiating element is actively fed by a first supply and wherein a single feed point island of the at least one feed point for the outer radiating element is actively fed by a second supply.

34. The antenna as claimed in claim 33 further comprising the at least one feed point in the first feed network being surrounded by a space thereby creating at least one feed point island within the inner radiating element.

35. The antenna as claimed in claim 33 wherein the at least one feed point for the inner and outer radiating elements further comprises:

a feed point on a vertical side of the inner radiating element;

a feed point on a horizontal side of the inner radiating element;

a feed point on a vertical side of the outer radiating element; and

a feed point a horizontal side of the outer radiating element.

36. The antenna as claimed in claim 35 wherein an active feed is connected to at least one feed point on the inner radiating element defining an active feed and the active feed is located on an opposite side of an active feed connected to the at least one feed point for the outer radiating element.

37. The antenna as claimed in claim 33 further comprising;

a first circular polarization for the inner radiating element defined by the inner radiating element having a square perimeter, a first corner of the inner radiating element having a blunt edge and a second corner, diagonally opposite the first corner having a blunt edge; and

a second circular polarization for the outer radiating element defined by the outer radiating element having a square perimeter, a first outer corner of the outer radiating element having a blunt edge and a second outer corner of the outer radiating element, diagonally opposite the first outer corner, having a blunt edge.

38. The antenna as claimed in claim 37 further comprising the first circular polarization for the inner radiating element being co-circular with the second circular polarization for the outer radiating element defined by the first and second corners of the inner radiating element and the first and second outer corners of the outer radiating element being at similar corner locations respectively.

39. The antenna as claimed in claim 37 further comprising the first circular polarization for the inner radiating element being circular in a direction opposite the second circular polarization for the outer radiating element defined by the first and second corners of the inner radiating element and the first and second outer corners of the outer radiating element being at diagonally opposite corner locations respectively.