Fractal antenna ground counterpoise, ground planes, and loading elements

• US 6,140,975 A
• Filed: 11/07/1997
• Issued: 10/31/2000
• Est. Priority Date: 08/09/1995
• Status: Expired due to Term

• Current Assignee: Fractal Antenna Systems Inc.
• Original Assignee: Nathan Cohen
• Inventors: Cohen, Nathan
• Primary Examiner(s): Wimer, Michael C.
• Application Number:
  US08/967,375
• Time in Patent Office: 1,089 Days
• Field of Search: 343/752, 343/829, 343/830, 343/846, 343/848, 343/792.5, 343/899
• US Class Current: 343/846
• CPC Class Codes: H01Q 1/243 with built-in antennas
• CPC Class Codes: H01Q 1/246 specially adapted for base stations
• CPC Class Codes: H01Q 1/36 Structural form of radiating elements, e.g. cone, spiral, umbrella; Particular materials used therewithH01Q1/08, H01Q1/14 take precedence
• 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 21/061 Two dimensional planar arrays
• CPC Class Codes: H01Q 21/205 providing an omnidirectional coverage turnstile aerials H01Q21/26
• CPC Class Codes: H01Q 21/28 Combinations of substantially independent non-interacting antenna units or systems multiple beam H01Q25/00
• CPC Class Codes: H01Q 9/26 with folded element or elements, the folded parts being spaced apart a small fraction of operating wavelength resonant loop antennas H01Q7/00
• CPC Class Codes: H01Q 9/36 with top loading
• CPC Class Codes: H01Q 9/38 with counterpoise with counterpoise comprising elongated elements coplanar with the active element H01Q9/44

Abstract

An antenna system includes a ground counterpoise or a top-hat located load assembly having at least one element whose physical shape is at least partially defined as a first or higher iteration deterministic fractal. The resultant ground counterpoise may rely upon an opening angle for performance, and produces a more compact antenna system relative to prior art non-Euclidean ground counterpoise elements. A vertical antenna system may be fabricated with fractal ground elements and a vertical element that may also be a fractal. Gain characteristics of antenna systems utilizing a fractal ground counterpoise are no worse than prior art, larger, systems, and exhibit improved vertical polarization characteristics, and a termination impedance of about 30Ω. A vertical antenna system preferably includes vertically spaced-apart fractal conductive and passive elements, and one or more fractal ground elements. The resultant antenna system may be tuned by rotating the vertical elements relative to each other, and/or by varying the spaced-apart distance therebetween. Fractalized ground counterpoise elements may be fabricated on a flexible printed circuit substrate, and/or placed within the support mount of a cellular telephone car antenna. A vertical antenna having a fractalized top-hat loading assembly advantageously reduces resonant frequency, size and area of the loading assembly, without substantial penalty in performance.

Claims

1. An antenna system including:

a driven element, and

a fractal counterpoise element having a portion that includes at least a first motif and a first replication of said first motif and a second replication of said first motif such that a point chosen on a geometric figure represented by said first motif will result in a corresponding point on said first replication and on said second replication of said first motif;

wherein there exists at least one non-straight line locus connecting each said point;

wherein a replication of said first motif is a change selected from a group consisting of (a) a rotation and change of scale of said first motif, (b) a linear displacement translation and a change of scale of said first motif, and (c) a rotation and a linear displacement translation and a change of scale of said first motif; and

wherein said fractal counterpoise element has a perimeter compression parameter (PC) defined by;

space="preserve" listing-type="equation">PC=(full-sized antenna element length)/(fractal-reduced antenna element length)

in which PC=A·

log(N(D+C)). A and C are constant coefficients for said first motif, N is an iteration number, and D is a fractal dimension given by log(L)/log(r), where L and r are one-dimensional fractal counterpoise element lengths before and after fractalization, respectively.

2. The antenna system of claim 1, wherein said first motif is selected from a group consisting of (i) Koch, (ii) Minkowski, (iii) Cantor, (iv) torn square, (v) Mandelbrot, (vi) Caley tree, (vii) monkey'"'"'s swing, (viii) Sierpinski gasket, and (ix) Julia.

3. The antenna system of claim 1, wherein said driven element includes an element having a portion that includes at least a second motif and a first replication of said second motif and a second replication of said second motif such that a point chosen on a geometric figure represented by said second motif will result in a corresponding point on said first replication and on said second replication of said second motif;

wherein there exists at least one non-straight line locus connecting each said point; and

wherein a replication of said second motif is a change selected from a group consisting of (a) a rotation and change of scale of said second motif, (b) a linear displacement translation and a change of scale of said second motif, and (c) a rotation and a linear displacement translation and a change of scale of said second motif.

4. The antenna system of claim 1, wherein said driven element includes a spaced-apart second element having a portion that includes at least a third motif and a first replication of said third motif and a second replication of said third motif such that a point chosen on a geometric figure represented by said third motif will result in a corresponding point on said first replication and on said second replication of said third motif;

wherein there exists at least one non-straight line locus connecting each said point; and

wherein a replication of said third motif is a change selected from a group consisting of (a) a rotation and change of scale of said third motif, (b) a linear displacement translation and a change of scale of said third motif, and (c) a rotation and a linear displacement translation and a change of scale of said third motif.

5. The antenna system of claim 3, wherein at least one of said first motif and said second motif is selected from a group consisting of (i) Koch, (ii) Minkowski, (iii) Cantor, (iv) torn square, (v) Mandelbrot, (vi) Caley tree, (vii) monkey'"'"'s swing, (viii) Sierpinski gasket, and (ix) Julia.

6. The antenna system of claim 1, wherein said first motif has x-axis, y-axis coordinates for a next iteration N+1 defined by x_N+1 =f(x_N, y_N) and y_N+1 =g(x_N, y_N), where x_N, y_N are coordinates for iteration N, and where f(x,y) and g(x,y) are functions defining said first motif.

7. The antenna system of claim 4, wherein at least one of said first motif and said third motif is selected from a group consisting of (i) Koch, (ii) Minkowski, (iii) Cantor, (iv) torn square, (v) Mandelbrot, (vi) Caley tree, (vii) monkey'"'"'s swing, (viii) Sierpinski gasket, and (ix) Julia.

8. The antenna system of claim 1, in which said fractal counterpoise element is fabricated in a manner selected from a group consisting of (i) shaping conductive wire to form said fractal counterpoise element, (ii) forming upon an insulator substrate a conductive layer defining traces shaped to form said fractal counterpoise element, (iii) forming upon a flexible insulator substrate conductive traces shaped to form said fractal counterpoise element, and (iv) forming upon a semiconductor substrate a layer of conductive material shaped to form said fractal counterpoise element.

9. The antenna system of claim 1, wherein:

said antenna system is a vertical antenna system;

said fractal counterpoise element includes three dendrite elements that each have an overall length approximating 0.087 λ

where λ

is wavelength at a resonant frequency of interest; and

wherein gain of said antenna system is within at least 1 dB of unity.

10. A fractal antenna coupleable to a transceiver unit, the fractal antenna comprising:

a driven element, and

a ground counterpoise system including at least one fractal counterpoise element having a portion that includes at least a first motif and a first replication of said first motif and a second replication of said first motif such that a point chosen on a geometric figure represented by said first motif will result in a corresponding point on said first replication and on said second replication of said first motif;

wherein there exists at least one non-straight line locus connecting each said point;

wherein a replication of said first motif is a change selected from a group consisting of (a) a rotation and change of scale of said first motif, (b) a linear displacement translation and a change of scale of said first motif, and (c) a rotation and a linear displacement translation and a change of scale of said first motif; and

wherein said first motif is selected from a group consisting of (i) Koch, (ii) Minkowski, (iii) Cantor, (iv) torn square, (v) Mandelbrot, (vi) Caley tree, (vii) monkey'"'"'s swing, (viii) Sierpinski gasket, and (ix) Julia.

11. The fractal antenna of claim 10, wherein said fractal counterpoise element is fabricated in a manner selected from a group consisting of (i) shaping conductive wire to form said fractal counterpoise element, (ii) forming upon an insulator substrate a conductive layer defining traces shaped to form said fractal counterpoise element, (iii) forming upon a flexible insulator substrate conductive traces shaped to form said fractal counterpoise element, and (iv) forming upon a semiconductor substrate a layer of conductive material shaped to form said fractal counterpoise element.

12. The fractal antenna of claim 10, wherein said first motif has x-axis, y-axis coordinates for a next iteration N+1 defined by x_N+1 =f(x_N, y_N) and y_N+1 =g(x_N, y_N), where x_N, y_N are coordinates for iteration N, and where f(x,y) and g(x,y) are functions defining said first motif.

13. The fractal antenna of claim 10, wherein said ground counterpoise system has a perimeter compression parameter (PC) defined by:

##EQU6## where;

space="preserve" listing-type="equation">PC=A·

log[N(D+C)]

in which A and C are constant coefficients for said first motif, N is an iteration number, and D is a fractal dimension given by log(L)/log(r), where L and r are one-dimensional fractal counterpoise system lengths before and after fractalization, respectively.

14. The fractal antenna of claim 10, wherein:

said transceiver unit is hand holdable in size;

said antenna is mounted within a housing of said transceiver unit; and

said fractal counterpoise element is fabricated in a manner selected from a group consisting of (i) shaping conductive wire to form said fractal counterpoise element, (ii) forming upon an insulator substrate a conductive layer defining traces shaped to form said fractal counterpoise element, (iii) forming upon a flexible insulator substrate conductive traces shaped to form said fractal counterpoise element, and (iv) forming upon a semiconductor substrate a layer of conductive material shaped to form said fractal counterpoise element.

15. The fractal antenna of claim 10, wherein said transceiver includes a plurality of such fractal antennas arrayed in at least one configuration selected from a group consisting of (i) an array of substantially identical said fractal antennas coupled to an electronic circuit that dynamically selects a chosen one of said fractal antennas to be electronically coupled to said transceiver unit, (ii) an array of substantially identical such fractal antennas coupled to an electronic circuit that dynamically selects a chosen one of said fractal antennas to be electronically coupled to said transceiver unit wherein at least two fractal antennas in said array differ in antenna orientation from other fractal antennas in said array, (iii) a plurality of said fractal antennas wherein at least two said fractal antennas have elements that differ from elements in other said fractal antennas.

16. The antenna of claim 10, wherein said driven element has a portion that includes at least a second motif provided by a fractal generator, and a conductive element spaced-apart from said driven element by a distance Δ

chosen to vary at least one characteristic of said antenna, at a desired frequency c/λ

where λ and

wavelength at a frequency of interest and c is velocity of light, selected from the group consisting of (i) resonant frequency, and (ii) bandwidth.

17. The antenna of claim 16, wherein said antenna is tunable by varying at least one parameter selected from a group consisting of (a) said distance Δ

, (b) relative rotation between at least a part of said ground counterpoise system and said portion of said driven element, (c) location at which a feedline center lead is coupled to said portion of said driven element, (d) location of a cut in said portion of said driven element, and (e) size of a cut-away region of said portion of said driven element.

18. A top-hat loaded antenna, comprising:

a vertical element having an upper end and a lower end; and

a top-hat assembly electrically coupled to said upper end of said vertical element;

wherein said top-hat assembly includes a top-hat element having a portion that includes a first motif and a first replication of said first motif and a second replication of said first motif such that a point chosen on a geometric figure represented by said first motif will result in a corresponding point on said first replication and on said second replication of said first motif;

wherein there exists at least one non-straight line locus connecting each said point;

wherein a replication of said first motif is a change selected from a group consisting of (a) a rotation and change of scale of said first motif, (b) a linear displacement translation and a change of scale of said first motif, and (c) a rotation and a linear displacement translation and a change of scale of said first motif; and

wherein said top-hat element has a perimeter compression parameter (PC) defined by;

space="preserve" listing-type="equation">PC=(full-sized antenna element length)/(fractal-reduced antenna element length)

in which PC=A·

log(N(D+C)), A and C are constant coefficients for said first motif, N is an iteration number, and D is a fractal dimension given by log(L)/log(r), where L and r are one-dimensional fractal top-hat element lengths before and after fractalization, respectively.

19. The antenna of claim 18, wherein said first motif is selected from a group consisting of (i) Koch, (ii) Minkowski, (iii) Cantor, (iv) torn square, (v) Mandelbrot, (vi) Caley tree, (vii) monkey'"'"'s swing, (viii) Sierpinski gasket, and (ix) Julia.