Method and apparatus for matched impedance feeding of microstrip-type radio frequency antenna structure

• US 4,613,868 A
• Filed: 02/03/1983
• Issued: 09/23/1986
• Est. Priority Date: 02/03/1983
• Status: Expired due to Fees

• Current Assignee: Ball Corporation
• Original Assignee: Ball Corporation
• Inventors: Weiss, Michael A.
• Primary Examiner(s): Lieberman, Eli
• Application Number:
  US06/463,588
• Time in Patent Office: 1,328 Days
• Field of Search: 343/700 MS, 343/767, 343/746, 343/860-862
• US Class Current: 343/700.0MS
• 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

The center region of a dual slot microstrip-type antenna radiator "patch" structure is forced to take on a controlled non-zero radio frequency impedance by the provision of a slot formed therein at the center region. By controlling the dimension of such an impedance-matching slot in the radiator patch, a feedpoint connection may be made at the center region of the radiator patch and still achieve matched impedance feed. Because the feedpoint can thus be centrally located within the antenna structure, any spurious radiation which occurs from the feedpoint connection or associated feedlines does not tend to skew the overall or composite radiation antenna of the pattern as much as when such feedpoints are asymmetrically disposed on the radiator patch with respect to the primary radiating apertures.

Claims

1. A radio frequency antenna structure comprising a symmetrically fed dual-slotted half-wavelength microstrip radiator patch and including:

a linearly polarized radiator patch having a resonant half-wavelength dimension along its direction of linear polarization and a low impedance centerline transverse to said resonant dimension, said patch being disposed above a reference surface and defining a resonant cavity with a pair of spaced-apart radiating slots or apertures therebetween;

an r.f. feedpoint connection disposed substantially within said radiator patch; and

an impedance matching slot having an entirely closed boundary perimeter of less than one wavelength formed within said radiator patch substantially along said low impedance centerline transverse to said resonant dimension and also having predetermined location and dimensions for producing a corresponding predetermined r.f. impedance at said r.f. feedpoint connection.

2. A symmetrically fed dual-slotted half wavelength microstrip antenna structure comprising:

a conductive ground or reference surface;

a conductive dual radiating slot half wavelength radiator patch disposed above said reference surface;

an impedance matching slot formed in said patch at approximately the center thereof and having a closed perimeter of less than one wavelength for providing a predetermined r.f. impedance substantially greater than zero impedance at said feedpoint; and

wherein said impedance matching slot is substantially parallel to the dual radiating slots formed by opposing edges of the patch and the underlying reference surface and also transverse to a one-half wavelength resonant dimension of said patch.

3. A symmetrically fed dual-slotted half wavelength microstrip radio frequency radiator patch antenna structure comprising:

a conductive ground or reference surface;

a conductive patch disposed above said reference surface and thereby defining a resonant cavity in the volume included therebetween with one resonant dimension of the cavity being approximately one-half wavelength long at an intended antenna operating frequency and also defining a pair of radiating slots or apertures between opposing edges of said patch and the underlying reference surface with said radiating apertures each being oriented substantially transverse to said resonant dimension;

at least one r.f. feedpoint connection disposed on said patch substantially midway between said radiating apertures; and

said patch including a slot formed therein and disposed at the patch mid portion substantially adjacent said feedpoint connection, said slot extending substantially transverse to said resonant dimension for a predetermined distance thereby providing a corresponding predetermined r.f. impedance at said feedpoint connection.

4. A radio frequency antenna structure as in claim 3 including r.f. feed means having one feed conductor electrically connected to said feedpoint on said patch and another feed conductor electrically connected to said reference surface.

5. A symmetrically fed dual-slotted half-wavelength microstrip radio frequency radiator patch antenna structure comprising:

a conductive ground or reference surface;

a conductive path disposed above said reference surface and thereby defining a resonant cavity in the volume included therebetween with one resonant dimension of the cavity being approximately one-half wavelength long at an intended antenna operating frequency and also defining a pair of radiating slots or apertures between opposing edges of said patch and the underlying reference surface with said radiating apertures each being oriented substantially transverse to said resonant dimension;

at least one r.f. feedpoint connection disposed on said patch substantially midway between said radiating apertures;

said patch including a slot formed therein and disposed at the patch mid portion substantially adjacent said feedpoint connection, said slot extending substantially transverse to said resonant dimension for a predetermined distance thereby providing a corresponding predetermined r.f. impedance at said feedpoint connection; and

r.f. feed means having one feed conductor electrically connected to said feedpoint on said patch and another feed conductor electrically connected to said reference surface;

wherein said another feed conductor is electrically connected to said patch at at least one reference point disposed on the opposite side of said slot from said feedpoint connection.

6. A symmetrically fed dual-slotted half-wavelength microstrip radio frequency radiator patch antenna structure comprising:

a conductive ground or reference surface;

a conductive patch disposed above said reference surface and thereby defining a resonant cavity in the volume included therebetween with one resonant dimension of the cavity being approximately one-half wavelength long at an intended antenna operating frequency and also defining a pair of radiating apertures between opposing edges of said patch and the underlying reference surface with said radiating apertures each being oriented substantially transverse to said resonant dimension;

at least one r.f. feedpoint connection disposed on said patch substantially midway between said radiating apertures; and

said patch including a slot formed therein and disposed at the patch mid portion substantially adjacent said feedpoint connection, said slot extending substantially transverse to said resonant dimension for a predetermined distance thereby providing a corresponding predetermined r.f. impedance at said feedpoint connection;

wherein said patch is substantially rectilinear in shape and wherein said radiating apertures and said slot are each of substantially straight line linear shapes.

7. A radio frequency antenna structure as in claim 6 wherein said patch is of substantially rectangular shape having a width dimension approximately equal to one-half wavelength at an intended operating frequency and having a length dimension less than one wavelength at said operating frequency.

8. A radio frequency antenna structure as in claim 7 wherein said slot is of substantially rectangular shape having a perimeter slightly different from one wavelength at said operating frequency.

9. A radio frequency antenna structure as in claim 8 wherein said slot has a closed boundary wholly contained within the outer patch boundaries.

10. A method of obtaining matched impedance feeding of a symmetrically fed dual-slotted linearly polarized half-wavelength microstrip radio frequency radiator patch antenna structure having a conductive ground or reference surface, a conductive radiator patch disposed above said reference surface and defining a resonant cavity with a pair of spaced-apart radiating slots or apertures therebetween and an r.f. feedpoint connection disposed substantially within said radiator patch, said method comprising the step of:

forming an impedance matching slot having an entirely closed boundary perimeter of less than one wavelength within said radiator patch and substantially transverse to the resonant dimension of said linearly polarized antenna structure and also having predetermined location and dimensions for producing a corresponding predetermined r.f. impedance at said r.f. feedpoint connection.

11. A method of obtaining matched impedance feeding of symmetrically fed dual-slotted half-wavelength microstrip radiator patch antenna structure having a conductive ground or reference surface, and a conductive dual raidating slot half wavelength radiator patch disposed above said reference surface, said method comprising the steps of:

forming an impedance matching slot in said patch at approximately the center thereof having a closed perimeter of less than one wavelength for providing a predetermined r.f. impedance substantially greater than zero impedance at said feedpoint; and

wherein said impedance matching slot is formed substantially parallel to the dual radiating slots defined by opposing edges of the patch and the underlying referecne surface and also formed transverse to a one-half wavelength resonant dimension of said patch.