WO2002065583A1

WO2002065583A1 - Magnetic dipole and shielded spiral sheet antennas structures and methods

Info

Publication number: WO2002065583A1
Application number: PCT/US2002/004228
Authority: WO
Inventors: Eli Yablonovitch; Laurent Desclos; Sebastian Rowson
Original assignee: Ethertronics, Inc.
Priority date: 2001-02-12
Filing date: 2002-02-11
Publication date: 2002-08-22
Also published as: KR20100037168A; KR20030084925A; KR100945124B1; EP1371111B1; EP1371111A4; EP1371111A1; KR20080064907A; DE60229503D1; ATE412259T1; KR20090016491A

Abstract

The spiral sheet antenna (10) allows a small efficient antenna structure that is much smaller than the electromagnetic wavelength. It achieves the small size by introducing a high effective dielectric constant through geometry rather than through a special high dielectric constant material. It typically includes a rectangular cylinder-like shape, with a seam. The edges of the seam can overlap to make a high capacitance, or they can make a high capacitance by simply having the edges of the seam very close to each other. The highcapacitance serves the same role as a high dielectric constant material in a conventional compact antenna.

Description

Magnetic Dipole and Shielded Spiral Sheet Antennas Structures and Methods

CROSS REFERENCE TO RELATED APPLICATIONS

This application relates to concurrently filed, co-pending application U.S. patent application Ser. No. 09/781,720, entitled "Magnetic Dipole Antenna Structure and Method" by Eli Yablonovitch et al., owned by the assignee of this application and incorporated herein by reference, filed on February 12, 2001.

This application relates to concurrently filed, co-pending application U.S. patent application Ser. No. 09/781,779, entitled "Spiral Sheet Antenna Structure and Method" by Eli Yablonovitch et al., owned by the assignee of this application and incorporated herein by reference, filed on February 12, 2001.

This application relates to concurrently filed, co-pending application U.S. patent application Ser. No. 09/781,780, entitled "Shielded Spiral Sheet Antenna Structure and Method" by Eli Yablonovitch et al., owned by the assignee of this application and incorporated herein by reference, filed on February 12, 2001.

This application relates to concurrently filed, co-pending application U.S. patent application Ser. No. 09/781,723, entitled "Internal Circuit Board in an Antenna Structure and Method Thereof by Eli Yablonovitch et al., owned by the assignee of this application and incorporated herein by reference, filed on February 12, 2001.

BACKGROUND INFORMATION

Field of the Invention

The present invention relates generally to the field of wireless communication, and particularly to the design of an antenna.

Description of Related Art

Small antennas are required for portable wireless communications. To

produce a resonant antenna structure at a certain radio frequency, it is usually

necessary for the structure to be of a size equal to one-half of the electromagnetic

wavelength, or for some designs, one-quarter of the electromagnetic wavelength. This is usually still too large. A conventional solution, to reduce the size further, is to reduce the effective

wavelength of the electromagnetic waves, by inserting a material of a high dielectric

constant. Then, the internal wavelength is reduced by the square root of the dielectric

constant. This requires special high dielectric constant materials that add cost, weight and cause an efficiency penalty. Accordingly, the present invention addresses these

needs.

SUMMARY OF THE INVENTION

The present invention provides an effective increase in the dielectric constant

purely by geometry, using a spiral sheet configuration. The dielectric material can have a dielectric constant >1, or it can simply be air with dielectric constant=l.

Therefore cheaper dielectric materials can be used. Indeed there is nothing cheaper

than air.

In a first aspect of the invention, an antenna comprises a first plate and a second plate, the combination of the first and second plates serving as a capacitive

structure; and a third metallic structure, coupled to the first and second plates, thereby

producing a cylindrical or substantially cylindrical current distribution, with two

openings or holes at either end of the cylinder-like shape. Although a cylindrical

current distribution is described, other shapes of current distribution can be practiced provided that the current is distributed around two openings or holes, that would

construct an antenna without departing from the spirit of the present invention. In

effect, the overlap between the first and second plates, on the edge of the cylinder,

forms a seam between the two holes at the ends of the cylinder-like structure.

In a second aspect of the invention, an antenna structure produces a spiral current distribution by forming three plates in which a first plate overlaps with a

second plate, a second plate overlaps with a third plate, or any combination thereof. The overlapping regions between the first and second plates, and between the second and third plates create two holes that result in the spiral current distribution. The two holes, significantly, operate for the inflow and outflow of magnetic field. The three

plates organized in this structure reflect a jelly-rolls configuration that produces

spiral-type of current distribution. Although the spiral current distribution is described, other shapes of current distribution, such as circular, can be practiced

which utilizes two holes in constructing an antenna without departing from the spirits

in the present invention.

In a third aspect of the invention, a metallic border has a width comparable to

the thickness of a spiral sheet antenna which provides an effective shield, as measured by the front-to-back radiation ratio. The spiral sheet antenna structure can

be readily shielded from an absorber on one side by providing a metallic border,

asymmetrically on one face of the spiral sheet antenna. For example a front-to-back

ratio of 5dB can be achieved by an asymmetric shield structure. The form of asymmetric structure is mathematically and geometrically specified by a geometrical

procedure. Significantly, two holes or openings are asymmetrically placed so that they tend to face in the same direction, and away from the absorber. In one

embodiment, both openings are facing in the same direction.

In a fourth aspect of the invention, a spiral sheet antenna forms the outer

housing of a system, like a cellphone. The antenna is designed with at least two holes

or openings for the radio frequency magnetic field to enter and to exit. System components are in the form of a double sided circuit board, but a complete integrated

system can reside inside the antenna volume of a wireless system. The antenna comprises a metallic structure with two or more openings, at least one seam

connecting between the two or more openings; and one or more metal sheets, coupled to the metallic structure, for providing radio shielding; and a circuit board or other

electronic elements inside the antenna structure.

Advantageously, the present invention discloses an antenna structure that is

more compact, reducing the overall size of a wireless device. The present invention further advantageously reduces the cost of building an antenna by using air as the

dielectric. Moreover, the present invention provides a shield to block radio energy

from being absorbed in a body, which potentially could be harmful to a person's

health. The present invention also designs an antenna structure in which radio energy tends to flow in the direction away from a person. Furthermore, the present invention

efficiently uses the available internal space in an antenna to maximize the space utility

in an antenna and cellphone. Therefore, the dimension of a cellphone becomes even

more compact.

Other structures and methods are disclosed in the detailed description below. This summary does not purport to define the invention. The invention is defined by

the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a pictorial diagram illustrating a cross-sectional view of a spiral sheet

antenna for producing a spiral sheet current distribution in accordance with the present invention. The overlapping plates 11 and 12 form a seam between the two openings

at the ends.

FIGS. 2A-2B are pictorial diagrams illustrating a perspective view of two similar antenna structures having different aspect ratio in length and width, respectively, of a spiral sheet antenna for producing a spiral sheet current distribution in accordance with the present invention. FIG. 3 is a pictorial diagram illustrating a first possible drive configuration for a spiral sheet antenna in accordance with the present invention.

FIG. 4 is a pictorial diagram illustrating a second possible drive configuration

for a spiral sheet antenna in accordance with the present invention.

FIG. 5 is a pictorial diagram illustrating a first embodiment of a cylinder-like

antenna having two holes at the ends, with a seam between the two holes for producing a circular current distribution with a double parallel plate in accordance

with the present invention.

FIG. 6 is a pictorial diagram illustrating a perspective view of a cylinder-like

with the present invention.

FIGS. 7A-7B are pictorial diagrams illustrating a perspective view and a cross-

section view, respectively, of a third drive configuration of the cylinder-like antenna shown in FIG. 6 for exciting a circular current distribution with a double parallel plate

seam in accordance with the present invention.

FIG. 8 is a pictorial diagram illustrating a third embodiment of a magnetic

dipole sheet antenna having two holes at the ends, with a slot seam between the two

holes, allowing a circular current distribution in accordance with the present

invention.

FIGS. 9A-9B are pictorial diagrams illustrating a perspective view and a side

cross-section view, respectively, of a first embodiment of a shielded spiral sheet antenna having two holes at the ends and an overlapping seam between the holes,

providing shielding from absorbers adjacent to the antenna. . FIGS. 10A-10B are pictorial diagrams illustrating side views of an operational

mathematical technique for determining shielding effectiveness in a shield spiral sheet antenna in accordance with the present invention.

FIG. 11 is a pictorial diagram illustrating an operational procedure for

determining the center of a hole in a shielded spiral sheet antenna in accordance with

the present invention.

FIGS. 12A-12B are pictorial diagrams illustrating a second embodiment of a shielded spiral sheet antenna with overlapping capacitive seam structure in

accordance with the present invention. FIG. 12B is a side cross-section view showing

the path 128-129 followed by magnetic field lines B.

FIG. 13 is a pictorial diagram illustrating a multi-frequency, multi-tap antenna

with spring contacts Wl and W2 in accordance with the present invention.

FIG. 14 is a pictorial diagram illustrating the placement of internal circuit boards inside an antenna m accordance with the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT(S)

antenna 10, resembling a rectangular cylindrical shape, with two holes at the ends, and a capacitive seam connecting the two holes, for producing a cylindrical current

distribution. The spiral sheet antenna 10 can be constructed with three plates, a first

plate 11, a second plate 12, and a third plate 13. The variable d 14 represents the

spacing between the first plate 11 and the second plate 12, and the variable t 15

represents the thickness of all three plates. A vertical connection 16 connects between the third plate 13 and the first plate 11, while the third plate 13 connects to the second plate 12 via a vertical connection 17. The length of the third plate 13, between vertical connections 16 and 17 is selected to be less than a quarter wavelength, λ/4n,

where n is the square root of the dielectric constant.

The structure of the spiral sheet antenna 10 increases the effective dielectric

constant by a factor of t/d. Effective increase in capacitance is due to overlapping

plates between the plate 11 and the plate 12. . In effect, the spiral antenna 10

produces a large dielectric constant, without the need for a high dielectric constant

material, just from electrode geometry alone, i.e. ε_relative = t d. Effectively, treating the

spiral sheet antenna as a patch type antenna, the required length of the patch then

becomes a is the relative dielectric constant of the capacitor

dielectric.

FIGS. 2A is a pictorial diagram illustrating a perspective view of a spiral

sheet antenna 20 for producing a cylinder-like current distribution. The spiral sheet

antenna 20 has a first hole 21 and a second hole 22, at the ends, and a capacitive seam

connecting the two holes. The alternating current (AC) magnetic field vector B , is

shown entering hole 21 and exiting hole 22.

FIG. 2B is a pictorial diagram illustrating a spiral sheet antenna 25 for

producing a cylinder-like current distribution with a different aspect ratio, with a first

hole 26 and a second hole 27. The structure shape in FIG. 2B is the same as the

structure shape in FIG. 2A. However, the aspect ratio, in FIG. 2B, is different from the aspect ratio in FIG. 2 A. The curved vector I represents the general direction of the

AC currents.

The spiral antennas 20 and 25 in FIGS. 2 A and 2B operate like a single-turn

solenoids. A single-turn solenoid consists of a cylinder-like current distribution. A 2A. However, the aspect ratio, in FIG. 2B, is different from the aspect ratio in FIG. 2A. The curved vector I represents, (he general direction of the AC currents.

The spiral antennas 20 and 25 in FIGS. 2A and 2B operate like a single-turn solenoids. A single-tum solenoid consists of a cytinder like current distribution. A significant portion of the electromagnetic radiation produced by the spiral antennas 20

and 25 arises from the altemating current (AC) magnetic field vector B that enters and exits.from the holes at the end of the single turn solenoid.

Advantageously, the antennas 20 and 25 do not require a high dielectric constant ceramic to attain a small dimensional size. The inherent capacitance in the structure of the antennas 20 and 25 allows a low frequency operation according to the formula:

ωa , where ω is the frequency in radians/second, L is the inductance of the single

V •W -' turn solenoid formed by 11, 16, 13, 17 and 12 in FIG. 1., and C is the capacitance from the thin overlapping region labeled as the thickness d 15, or the spacing 14.

FIG. 3 is a pictorial diagram illustrating a first drive or feed configuration 30 for a spiral sheet antenna producing a cylindrical current distribution. The first drive configuration 30 has a first plate 31, a second plate 32, a third plate 33, a first hole 34, and a second hole 35. A drive cable 36 attaches and drives the spiral sheet antenna 20. In this embodiment, the co-axial drive cable 36 matches any desired input impedance. An optional vertical short circuit wire, 37, can assist in providing an impedance matching shunt to the spiral εhθβt antenna 20.

FIG. 4 is a pictorial diagram illustrating a second drive configuration 40 of a spiral sheet antenna for producing a rectangular cylinder-like current distribution. The antenna might have a high electrical conductivity, e.g. copper depending on the

required antenna Q-factor.

FIGS. 3 and 4 illustrate two sample drive configurations applied to the spiral

sheet antenna 20, and are not meant to be an exhaustive listing since many possibilities abound. One of ordinary skill in the art should recognize that there are

numerous other similar, equivalent, or different drive configurations that can be practiced without departing from the spirit of the present invention. A spiral sheet

antenna 20 produces an AC magnetic field that radiates efficiently in a structure that is

λ smaller than that is a typical restriction for a patch antenna, where λ is the

electromagnetic wavelength in vacuum, and

index.

The antenna being described here can be regarded as a rectangular metallic enclosure with two openings, (at the ends of the rectangle), and a seam connecting the

two holes. The seam functions as a capacitor and can be implemented in several different ways. First, the seam can be constructed as an overlapping region as shown in 20. Second, a seam can be constructed as slot between to metal sheets as shown in

80. where two edges meet. Third, a seam can be constructed with a slot under which

there is an additional metal sheet underneath as shown in 60.

FIG. 5 is a pictorial diagram 50 illustrating a first embodiment of a rectangular

cylindrical sheet antenna with an opening at each end of the rectangular cylinder, and

with a seam 54 connecting the two holes at the ends. The seam 54 comprises of a slot over a double parallel plate. The rectangular cylindrical current distribution structure

50 has a second plate 52 overlapping with a first plate 51 in two areas on either side

of the slot or seam 54 to provide capacitance. The third plate 53 is far from the first and second plates 51 and 52, and therefore contributes little to the capacitance. The rectangular cylindrical cuπent distribution structure 50 thus yields the benefit of a

large dielectric constant, without the need for a special dielectric material. However,

the capacitance is diminished by a factor 4 due to the two capacitors in series from the overlap of the first and second plates 51 and 52,compared to the same two plates in parallel.

FIG. 6 is a pictorial diagram 60, a perspective view illustrating the second

embodiment of a seam configuration in a rectangular cylindrical sheet antenna.. A first hole 61 is positioned in the front of the pictorial diagram 60, while a second hole

62 is positioned at the back of the pictorial diagram 60.The rectangular cylindrical

sheet antenna may be driven in a number of different ways. A possible approach is to

place a wire parallel to the long axis, but off-center to drive cuπents across the slot.

FIG. 7A is a pictorial diagram 70 illustrating this, the second type of drive configuration (of the third seam example, illustrated in FIG. 6) for the rectangular

cylindrical sheet antenna. A co-axial feed cable 74 extends and connects through a

third plate 73, a second plate 72, and a first plate 71, to an off-center drive wire 75.

FIG. 7B is a pictorial diagram 76 illustrating a side view of this second type of drive

configuration. A drive wire 77 is shown in cross-section in FIG. 7B.

FIG. 8 is a pictorial diagram 80 illustrating a third embodiment of a

rectangular cylindrical sheet antenna with a slot seam for producing a magnetic

dipole current distribution. The pictorial diagram 80 will not operate at as low a

frequency as the spiral sheet structure, all other things being equal, since the capacitance of a slot seam is less than the capacitance of the over-lapping sheets in the spiral sheet structure. FIG. 9A is a pictorial diagram illustrating a perspective view, and FIG. 9B illustrating a side view, of a first embodiment of a shielded spiral sheet antenna 90 for

producing a cylinder-like cuπent distribution. The structure in the shielded spiral

sheet antenna 90 is similar to the structure in the spiral sheet antenna 20. A first hole

91 is at one end of the rectangle, and a second hole 92 is at the other end of the rectangle. An over-lapping seam 93, connects the two holes together. In the case of a

cellphone the pair of holes 91 and 92 is positioned to face away from a user's ear. A

base plate 94, of the shielded spiral sheet antenna 90, is positioned facing the human

body, extending 94a beyond the third plate 13 at one end and extending 94b beyond the third plate 13 at the other end. The shielded spiral sheet antenna 90 therefore faces

away from the human body. The width of the border w and w' determines the degree

of front-to-back shielding ratio. If w « t and w'« t, then a shielding ratio of 3dB or

better can be achieved.

FIGS. 10A and 10B are pictorial diagrams illustrating side views of a operational mathematical technique for defining a shielded spiral sheet antenna. To define the shielded spiral sheet antenna 100, two center points are chosen, a

geometrical center point of a top opening 101 and a geometrical center point of a

bottom opening 102. A path 103, L_s, represents the shortest path between the

geometrical center point of a top opening 101 and the geometrical center point of a bottom opening 102 on the short side. A path 104, L_e, represents the longest path between the geometrical center point of a top opening 101 and the geometrical center

point of a bottom opening 102 on the longer side. The path 103 is shorter than the

path 104 that faces a user. The mathematical relationship between the different variables should be

governed by the following inequality, L_s - L_e > at, Eq. (1), in order to provide a

good shielding, front-to-back. A value of α « 1 provides some good degree of

shielding.

FIG. 11 is a pictorial diagram 110 illustrating an operational procedure for

determining the center of a hole for the purposes of our operational mathematical

technique for defining a shielded spiral antenna. The geometrical center of the top

and bottom openings can be defined as a type of geometrical "center-of-gravity":

∑(R -Ro) = 0 Eq. edges of opening

(2)

where R is the set of position vectors at the edges of the opening, and Ro is

the center-of-gravity center point that satisfies the Eq. (2).

This equation defines the center point for use in the mathematical specification

in Eq (1). The point around which all the vectors sum to zero, defines the center of

the hole, or opening. The type of metallic shielding specified FIGS. 9A, 9B, 10A, and 10B, are useful for shielding cell phone antennas from the user.

FIG. 12A is a pictorial diagram 120 illustrating a perspective view of a second embodiment of a shielded spiral sheet antenna (with overlapping capacitive structure).

A first hole 124 and a second hole 125 are positioned to face away from the user. In

effect, both the first and second holes 124 and 125 are facing the front. A seam 126

connects between the first hole 124 and the second hole 125.

FIG. 12B is a pictorial diagram 127 illustrating a side cross-sectional view of

FIG. 12A, with AC magnetic field illustrated. The structure diagram has two holes

for the magnetic field entering 128 and exiting 129 the antenna. The rectangular openings shown, may be smaller than the width of the rectangle. A rectangular container is intended as an illustration. The rectangular container may be in a shape

resembling a cell phone body instead.

FIG. 13 is a pictorial diagram illustrating a dual frequency, dual-tap antenna

130 with a first hole 131, a second hole 132, and a third hole 133. A first seam 135

connects between the first hole 131 and the third hole 133. A second seam 136 connects between the hole 132 and the hole 133. Spring contacts w, and w₂ can

connect to different circuits on a circuit board, such as for operating with main cell

phone bands including Personal Communication System (PCS) at 1900 MHz, Global Positioning Systems (GPS) at 1575 MHz, bluetooth, Advanced mobile phone system

(amps) at 850 MHz, and 900 MHz cell phone bands. The spring contacts are only an example. The concept is to use multiple taps for the different frequencies that might

be needed in a wireless system. The multi-taps would be derived from a single

antenna structure.

In general, the antenna structure consists of a metallic enclosure, with holes, or openings. For each independent antenna, or for each frequency band, an additional

hole or opening must be provided on the metallic enclosure. For the example in FIG.

13, two frequencies, require 3 holes. Likewise n-frequencies would require (n+1)

holes or openings, connected by n seams. Some of the n-frequencies might be

identical, for the purpose of space or polarization diversity.

FIG. 14 is a pictorial diagram 140 illustrating the placement of one or more

internal circuit boards 143 inside an antenna. Radio Frequency Magnetic fields enter

a first hole 141 and exit through a second hole 142. The internal volume in an antenna can be wisely utilized as not to waste any unused empty space. The extra

space can be filled with one or more active circuit boards 143 for operation of a cell phone. The internal circuit boards do not interfere much with the internal AC RF

magnetic fields inside the antenna structure. This allows the antenna volume to be put

to good use in a small volume cell phone.

The above embodiments are only illustrative of the principles of this

invention and are not intended to limit the invention to the particular embodiments

described. For example, the basic concept in this invention teaches a metallic

structure with at least two holes, and a seam. One of ordinary skill in the art should

recognize that any type of antenna structure, which possesses these types of characteristics, is within the spirit of the present invention. Furthermore, although

the term "holes" are used, it is apparent to one of ordinary skill in the art that other

similar or equivalent concepts may be used, such as opening, gaps, spacing, etc.

Accordingly, various modifications, adaptations, and combinations of various features of the described embodiments can be practiced without departing from the scope of the invention as set forth in the appended claims.

Claims

CLAIMS WE CLAIM:

1. An antenna, comprising: a metallic structure with two or more openings/holes; and at least one seam connecting between the two or more openings/holes.

2. The antenna of Claim 1, wherein the two or more holes are on the same side of the metallic structure.

3. The antenna of Claim 1 , wherein the position of the two or more holes are

facing in the same direction.

4. The antenna of Claim 1, wherein the at least one seam comprises a capacitive structure of the spiral sheet type.

5. The antenna of Claim 1, wherein the at least one seam comprises a capacitive structure of the slot type.

6. The antenna of Claim 1, wherein the at least one seam comprises a capacitive structure of the double parallel plate type

7. The antenna of Claim 1, wherein the at least one seam comprises a capacitive structure

8. The antenna of Claim 1, further comprising a pair of wires coupled to the antenna, the pair of wires providing energy to the antenna.

9. The antenna of Claim 1, further comprising a wire and a ground, the wire and the ground coupled to the antenna for providing energy to the antenna.

10. The antenna of Claim 1, wherein an electrical length of the antenna is less than one-quarter wavelength.

11. An antenna comprising: a metallic enclosure with a number of openings or holes, each opening or hole coπesponding to a different frequency band; and capacitive seams connecting the openings together, the capacitive seams including slots in the metal or allow for overlap of metal at the seam, to provide more capacitance.

12. An antenna, comprising: a first plate and a second plate, the combination of the first and second plates serving as a capacitive structure; and a metallic structure, coupled to the first and second plates, thereby producing a circular or substantially circular cuπent distribution.

13. The antenna of Claim 12, wherein the third means comprises a metallic

structure.

14. The antenna of Claim 12, further comprising a pair of wires coupled to the antenna, the pair of wires providing energy to the antenna.

15. The antenna of Claim 12, further comprising a wire and a ground, the wire and the ground coupled to the antenna for providing energy to the antenna.

16. The antenna of Claim 12, wherein an electrical length of the antenna is less than one-quarter wavelength.

17. An antenna, comprising: a first plate; a second plate; a third plate, wherein the first, second, third plates are electrically connected to produce a circular or substantially circular cuπent distribution.

18. The antenna of Claim 17, further comprising a pair of wires coupled to the antenna, the pair of wires providing energy to the antenna.

19. The antenna of Claim 17, further comprising a wire and a ground, the wire and the ground coupled to the antenna for providing energy to the antenna.

20. The antenna of Claim 17, wherein an electrical length of the antenna is less than one-quarter wavelength.

21. An antenna, comprising: a first plate; a second plate; and a third plate, wherein the first, second, third plates are electrically connected to produce a spiral or substantially spiral cuπent distribution.

22. The antenna of Claim 21, wherein an electrical length of the antenna is less than one-quarter wavelength.

23. The antenna of Claim 21 , further comprising a pair of wires coupled to the antenna, the pair of wires providing energy to the antenna.

24. The antenna of Claim 21, further comprising a wire and a ground, the wire and the ground coupled to the antenna for providing energy to the antenna.

25. The antenna of Claim 21, wherein an electrical length of the antenna is

less than one-quarter wavelength.

26. An antenna, comprising: a first means and a second means, the combination of the first and second means serving as a capacitive structure; a third means, coupled to the first and second means, thereby producing a circular or substantially circular ciurent distribution.

27. An antenna, comprising: a metallic structure with two or more openings; at least one seam connecting between the two or more openings; and one or more metal sheets, coupled to the metallic structure, for providing radio shielding.

28. The antenna of Claim 27, wherein the two or more holes are on the same

side of the metallic structure.

29. The antenna of Claim 27, wherein the position of the two or more holes are facing in the same direction.

30. The antenna of Claim 27, wherein the at least one seam comprises a capacitive structure of a spiral sheet type.

31. The antenna of Claim 27, wherein the at least one seam comprises a capacitive structure of a slot type.

32. The antenna of Claim 27, wherein the at least one seam comprises a capacitive structure of a double parallel plate type.

33. The antenna of Claim 27, wherein the at least one seam comprises a capacitive structure.

34. The antenna of Claim 27, further comprising a pair of wires coupled to the antenna, the pair of wires providing energy to the antenna.

35. The antenna of Claim 27, further comprising a wire and a ground, the wire and the ground coupled to the antenna for providing energy to the antenna.

36. The antenna of Claim 27, wherein an electrical length of the antenna is less than one-quarter wavelength.

37. An antenna, comprising: a first plate and a second plate, the combination of the first and second plates serving as a capacitive structure; a metallic structure, coupled to the first and second plates, thereby producing a circular or substantially circular current distribution; and

one or more metal sheets, coupled to the first plate, the second plate, or the metallic structure, for providing radio shielding.

38. The antenna of Claim 37, further comprising a pair of wires coupled to the antenna, the pair of wires providing energy to the antenna.

39. The antenna of Claim 37, further comprising a wire and a ground, the wire and the ground coupled to the antenna for providing energy to the antenna.

40. The antenna of Claim 37, wherein an electrical length of the antenna is

less than one-quarter wavelength.

41. An antenna, comprising: a first means and a second means, the combination of the first and second means serving as a capacitive structure; a third means, coupled to the first and second means, thereby producing a circular or substantially circular cuπent distribution; and one or more metal sheets, coupled to the first, second, or third means, for providing radio shielding.

42. The antenna of Claim 41, wherein the third means comprises a metallic structure.

43. The antenna of Claim 41, further comprising a pair of wires coupled to the antenna, the pair of wires providing energy to the antenna.

44. The antenna of Claim 41, further comprising a wire and a ground, the wire and the ground coupled to the antenna for providing energy to the antenna.

45. The antenna of Claim 41, wherein an electrical length of the antenna is

less than one-quarter wavelength.

46. An antenna, comprising: a first plate and a second plate, the combination of the first and second

plates serving as a capacitive structure; and a third plate, wherein the first, second, third plates are electrically connected to produce a circular or substantially circular cuπent distribution.

47. The antenna of Claim 46, further comprising a pair of wires coupled to the antenna, the pair of wires providing energy to the antenna.

48. The antenna of Claim 46, further comprising a wire and a ground, the wire and the ground coupled to the antenna for providing energy to the antenna.

49. The antenna of Claim 46, wherein an electrical length of the antenna is

less than one-quarter wavelength.

50. An antenna, comprising: a first plate; a second plate; and a third plate, wherein the first, second, third plates are electrically connected to produce a spiral or substantially spiral cuπent distribution.

51. The antenna of Claim 50, further comprising a pair of wires coupled to the antenna, the pair of wires providing energy to the antenna.

52. The antenna of Claim 50, further comprising a wire and a ground, the wire and the ground coupled to the antenna for providing energy to the antenna.

53. The antenna of Claim 50, wherein an electrical length of the antenna is less than one-quarter wavelength.

54. A system, comprising:

an antenna, comprising: a metallic structure with two or more openings; at least one seam connecting between the two or more openings; and one or more metal sheets, coupled to the metallic structure, for providing

radio shielding; and a circuit board or other electronic elements inside the antenna structure.

55. The antenna of Claim 54, further comprising a pair of wires coupled to the antenna, the pair of wires providing energy to the antenna.

56. The antenna of Claim 54, further comprising a wire and a ground, the wire and the ground coupled to the antenna for providing energy to the antenna.

57. A system, comprising:

an antenna, comprising: a metallic structure with two or more openings; and at least one seam connecting between the two or more openings; and a circuit board or other electronic elements inside the antenna structure.

58. The antenna of Claim 57, wherein the two or more holes are on the same side of the metallic structure.

59. The antenna of Claim 57, wherein the position of the two or more holes are facing in the same direction.

60. The antenna of Claim 57, wherein the at least one seam comprises a capacitive structure of the spiral sheet type.

61. The antenna of Claim 57, wherein the at least one seam comprises a capacitive structure of the slot type.

62. The antenna of Claim 57, wherein the at least one seam comprises a capacitive structure of the double parallel plate type

63. The antenna of Claim 57, wherein the at least one seam comprises a capacitive structure.

64. The antenna of Claim 57, further comprising a pair of wires coupled to the antenna, the pair of wires providing energy to the antenna.

65. The antenna of Claim 57, further comprising a wire and a ground, the wire and the ground coupled to the antenna for providing energy to the antenna.

66. The antenna of Claim 57, wherein the electrical length of the antenna is less than one-quarter wavelength.

67. A system, comprising:

an antenna, comprising: a first plate and a second plate, the combination of the first and second plates serving as a capacitive structure; a metallic structure, coupled to the first and second plates, thereby producing a circular or substantially circular cuπent distribution; and a circuit board or other electronic elements inside the antenna structure.

68. A system, comprising: an antenna, comprising: a first means and a second means, the combination of the first and second means serving as a capacitive structure; a third means, coupled to the first and second means, thereby producing a circular or substantially circular cuπent distribution; and a circuit board or other electronic elements inside the antenna structure.

69. The antenna of Claim 68, wherein the third means comprises a metallic structure.

70. The antenna of Claim 68, further comprising a pair of wires coupled to the antenna, the pair of wires providing energy to the antenna.

71. The antenna of Claim 68, further comprising a wire and a ground, the wire and the ground coupled to the antenna for providing energy to the antenna.

72. The antenna of Claim 68, wherein an electrical length of the antenna is

less than one-quarter wavelength.

73. A system, comprising: an antenna, comprising: a first plate; a second plate; and a third plate, wherein the first, second, third plates are electrically connected to produce a circular or substantially circular cuπent distribution; and a circuit board or other electronic elements inside the antenna structure.

74. The antenna of Claim 73, further comprising a pair of wires coupled to the antenna, the pair of wires providing energy to the antenna.

75. The antenna of Claim 73, further comprising a wire and a ground, the wire and the ground coupled to the antenna for providing energy to the antenna.

76. The antenna of Claim 73, wherein the electrical length of the antenna is less than one-quarter wavelength.

77. A system, comprising: an antenna, comprising: a first plate; a second plate; a third plate, wherein the first, second, third plates are electrically connected to produce a spiral or substantially spiral cuπent distribution; and a circuit board or other electronic elements inside the antenna structure.

78. The antenna of Claim 77, wherein an electrical length of the antenna is less than one-quarter wavelength.

79. The antenna of Claim 77, further comprising a pair of wires coupled to the antenna, the pair of wires providing energy to the antenna.

80. The antenna of Claim 77, further comprising a wire and a ground, the wire and the ground coupled to the antenna for providing energy to the antenna.

81. The antenna of Claim 77, wherein an electrical length of the antenna is less than one-quarter wavelength.

82. A system, comprising: an antenna, comprising a metallic structure with two or more openings; at least one seam connecting between the two or more openings; one or more metal sheets, coupled to the metallic structure, for providing

83. The antenna of Claim 82, wherein the two or more holes are on the same side of the metallic structure.

84. The antenna of Claim 82, wherein the position of the two or more holes are facing in the same direction.

85. The antenna of Claim 82, wherein the at least one seam comprises a capacitive structure of the spiral sheet type.

86. The antenna of Claim 82, wherein the at least one seam comprises a capacitive structure of the slot type.

87. The antenna of Claim 82, wherein the at least one seam comprises a capacitive structure of the double parallel plate type

88. The antenna of Claim 82, wherein the at least one seam comprises a capacitive structure.

89. The antenna of Claim 82, further comprising a pair of wires coupled to the

antenna, the pair of wires providing energy to the antenna.

90. The antenna of Claim 82, further comprising a wire and a ground, the wire

and the ground coupled to the antenna for providing energy to the antenna.

91. The antenna of Claim 82, wherein an electrical length of the antenna is less than one-quarter wavelength.

92. A system, comprising: an antenna, comprising: a first plate and a second plate, the combination of the first and second plates serving as a capacitive structure; and a metallic structure, coupled to the first and second plates, thereby producing a circular or substantially circular cuπent distribution; one or more metal sheets, coupled to the first plate, the second plate, or the

metallic structure, for providing radio shielding; and a circuit board or other electronic elements inside the antenna structure.

93. The antenna of Claim 92, further comprising a pair of wires coupled to the antenna, the pair of wires providing energy to the antenna.

94. The antenna of Claim 92, further comprising a wire and a ground, the wire and the ground coupled to the antenna for providing energy to the antenna.

95. The antenna of Claim 92, wherein an electrical length of the antenna is less than one-quarter wavelength.

96. A system, comprising: an antenna, comprising: a first means and a second means, the combination of the first and second means serving as a capacitive structure; a third means, coupled to the first and second means, thereby producing a circular or substantially circular cuπent distribution; one or more metal sheets, coupled to the first, second, or third means, for providing radio shielding; and a circuit board or other electronic elements inside the antenna structure.

97. The antenna of Claim 96, wherein the third means comprises a metallic structure.

98. The antenna of Claim 96, further comprising a pair of wires coupled to the antenna, the pair of wires providing energy to the antenna.

99. The antenna of Claim 96, further comprising a wire and a ground, the wire and the ground coupled to the antenna for providing energy to the antenna.

100. The antenna of Claim 96, wherein an electrical length of the antenna is less than one-quarter wavelength.

101. A system, comprising: an antenna, comprising: a first plate and a second plate, the combination of the first and second plates serving as a capacitive structure; a third plate, wherein the first, second, third plates are electrically connected to produce a circular or substantially circular cuπent distribution; and a circuit board or other electronic elements inside the antenna structure.

102. The antenna of Claim 101, further comprising a pair of wires coupled to the antenna, the pair of wires providing energy to the antenna.

103. The antenna of Claim 101, further comprising a wire and a ground, the wire and the ground coupled to the antenna for providing energy to the antenna.

104. The antenna of Claim 101, wherem an electrical length of the antenna is less than one-quarter wavelength.

105. A system, comprising: an antenna, comprising: a first plate; a second plate; a third plate, wherein the first, second, third plates are electrically connected to produce a spiral or substantially spiral current distribution; and a circuit board or other electronic elements inside the antenna structure.

106. The antenna of Claim 101, further comprising a pair of wires coupled to the antenna, the pair of wires providing energy to the antenna.

107. The antenna of Claim 101, further comprising a wire and a ground, the wire and the ground coupled to the antenna for providing energy to the antenna.

108. The antenna of Claim 101, wherein an electrical length of the antenna is less than one-quarter wavelength.

109. An antenna having a multiplicity of bands, comprising: a first electrical connection for connecting to a first frequency band; and a second electrical connection for connecting to a second frequency band or bands.

110. The antenna of Claim 109, further comprising additional electrical connection or connections for a multiplicity of bands.

111. The antenna of Claim 109, wherein the first electrical connection comprises two wires.

112. The antenna of Claim 109, wherein the first electrical connection comprises one wire and one ground connection.

113. The antenna of Claim 109, further comprising a pair of wires coupled to the antenna, the pair of wires providing energy to the antenna.

114. The antenna of Claim 109, further comprising a wire and a ground, the wire and the ground coupled to the antenna for providing energy to the antenna.