US 3787871 A
A spiral antenna wherein its radiating elements terminate in Archimedean spirals.
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Description (OCR text may contain errors)
United States Patent 1 1 1111 3,787,871
Reese v Jan. 22, 1974  TERMINATOR FOR SPIRAL ANTENNA 3,618,114 11/1971 343/895 2,863,145 12/ 43/895  Inventor: Joe Reese, China Lake, Calif. v
 Assignee: The United States of America as 1 represented y h Secretary of the Primary Examiner-Eli Lieberman Navy, Washington, DC Attorney, Agent, or Firm-R. S. Sciascia; Roy Miller; 221 Filed: Mar. 3, 1971 Adams  Appl. No.: 121,606
 US. Cl. 343/895 57 ABSTRACT  Int. Cl. H0111 H36  Field of Search 343/895 A spu'al antenna wherem lts radlatlng elements terml- 5 Referenc'es Cited nate in Archimedean spirals.
UNITED STATES PATENTS l 5/1962 343/895 Claims, 1 Drawing Figure INVENTOR.
JOE REESE BYZ ROY MILLER ROBERT W. ADAM S ATTORNEYS.
TERMINATOR FOR SPIRAL ANTENNA STATEMENT OF GOVERNMENT INTEREST The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.
BACKGROUND OF THE INVENTION In order to achieve an equiangular spiral direction finding antenna which is frequency independent and will operate for any polarization, the antenna radiating elements must be so loaded as to simulate an infinite radiating plane. In prior devices loading is accomplished by physically mounting radio frequency resistive material to the radiating surface of the antenna.
The material is often ferrite filled epoxy, machined to close tolerances in an annular shape, and attached to the antenna at its outermost part. Viewed in cross section, the material is seen as attached at the full diameter of the antenna substrate, and sloping away from the surface of the antenna, in a covering relationship, toward its center. That is, the material is a ferrite loaded epoxy washer having a wedge shaped cross section, wherein the thickest portion of the wedge is attached to the antenna substrate at its outer edge and the thinnest portion of the wedge extends toward the center of the antenna in covering relationship to the radiators, in order to provide gradual resistive coupling to the antenna.
As a result, the antennas physical dimension and weight are increased. Its depth is increased by the thickness of the material. Its diameter by the surface outside the radiating area required for mounting the material; and its weight by the weight of the resistive material, which is primarily iron. Additionally, because of the proximity of the material to the radiating surface the antenna frequency band is limited and its sensitivity is reduced.
SUMMARY OF THE INVENTION The present invention is a means for loading the antenna by encircling the radiating elements with a plurality of interlocking spirals, wherein each of the spirals is attached to a radiating element. These spirals are, in general, Archimedean spirals consisting of elements having constant width, and spacing between adjacent element equal to the elements width.
BRIEF DESCRIPTION OF THE DRAWING The FIGURE is a diagrammatical view of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT The present invention which is a means for terminating the radiating elements of a spiral antenna is shown in the FIGURE. Although the spiral antenna shown is composed of two radiating elements 10 and 12, the present invention can be used with spiral antennas having any number of radiators.
is equal to the width of arm 16, and the spacing between adjacent arms 14 and 16 is equal to the arm width. By interlocking, arms 14 and 16 couple and provide resistive loading for radiators l0 and 12, which simulates an infinite radiating plane.
The present invention is implemented as follows: at the radius determined by the parameters defining the intended use (frequency range, etc.), the width of radiating elements 10 and 12 are decreased and converted into interlocking Archimedean spirals 14 and 16, wherein the spacing between adjacent arms 14 and 16 equal the arm width. Although the arms may be of any length, approximately four revolutions by each arm provides satisfactory results'for at least some applications.
The spiral antenna and terminating means may be produced by etching copper clad epoxy glass board. The negative used for etching may be a photocopy of a spiral drawing wherein the design is determined by the antennas intended use. In the alternative, as an example, the terminating means may be constructed from wires wound in the preferred spirals and soldered to the ends of radiators 10 and 12.
As mentioned above, the present invention is not limited to the embodiment shown, but may be utilized with spiral antennas having any number of radiating elements.
What is claimed is:
1. An antenna array comprising;
a plurality of interwound spiral radiators, and
radiator termination means having at least a separate spiral member coupled to each said radiator and encircling said plurality of radiators for simulating an infinite radiating plane.
2. The antenna of claim I wherein each said member is an electrically conductive material in the shape of an Archimedean spiral fixedly attached to each said radiator, such that each said radiator has one electrically conductive Archimedean spiral arm attached thereto.
3. The antenna of claim 2 wherein the Archimedean spiral arms interlock such that the spiral arms attached to adjacent radiators are adjacent.
4. The antenna of claim 3 wherein the width of each said spiral arm is equal to the width of the separation between adjacent spiral arms.
5. The antenna of claim 4 wherein said antenna comprises a copper clad epoxy glass board wherein said radiators and said spiral arms are etched.
6. The antenna of claim 4 wherein said antenna comprises a copper clad epoxy glass board wherein said radiators are etched, and electrically conductive wire in the shape of an Archimedean spiral attached to each radiator.
7. The antenna of claim 4 wherein the length of said arms is such that each said arm encircles said radiators four times.