Microstrip antenna structures and arrays

Abstract

A microstrip antenna structure formed from a unitary conducting surface separated from a ground plane by a dielectric film where the r.f. radiator and feedlines form a generally planar arrangement of unitary integrally formed electrical conductors. The r.f. radiators are fed from an outside edge to selectively produce linearly and/or circularly polarized radiation at a selected resonant frequency(s). Necessary fixed phase shifting circuits are integrally formed by printed circuit techniques in the generally planar arrangement of electrical conductors for the circularly polarized radiators. A plurality of such antenna elements are also formed into a phased antenna array to achieve substantially ideal array gain thus producing an extremely high gain antenna with inexpensive printed circuit board construction techniques. Furthermore, appropriately controlled phase shifting networks may be integrally formed within the generally planar array of electrical conductors in combination with switchable diode elements to achieve any desired relative phase shifts between the array elements and thus to steer the array beam in a desired direction.

What is claimed is: 
     
       1. An antenna structure comprising: an electrically conducting ground surface,   a single layer electrically conducting surface comprising both an r.f. radiator conducting area and an r.f. feedline conducting area integrally connected thereto,   a dielectric sheet disposed between said ground surface and the single layer electrically conducting surface, and   said r.f. feedline being connected at the outside edge of said r.f. radiator conducting area to at least one predetermined point on the periphery of said radiator conducting area to achieve an r.f. radiation pattern having predetermined polarization characteristics from said radiator,   said r.f. feedline conducting area including: a first section connected to only a first point on the outside edge of said r.f. radiator conducting area,   a second section connected to only a second point on the outside edge of said r.f. radiator conducting area,   said first and second points being separated by a predetermined amount along the outside edge of said r.f. conducting area to define two intersecting axes of current flow, each such axis passing through a corresponding one of said first and second points, and   phase shifting means connected between said first and second sections and a common r.f. input/output point whereby the relative phases of r.f. signals on said first and second sections are controlled with respect to the phase at said common r.f. input/output to produce an r.f. radiation pattern having circular polarization characteristics.     
     
     
       2. An antenna structure as in claim 1 wherein said phase shifting means comprises means for introducing a 90° relative phase shift thereby producing circular r.f. polarization. 
     
     
       3. An antenna structure as in claim 2 wherein said phase shifting means comprises: a closed rectilinear conductive path having four corners,   said first and second sections being connected to respectively associated adjacent ones of said corners, and   said common r.f. input/output comprising one of the remaining two corners for right-hand circular r.f. polarization and comprising the other one of the remaining two corners for left-hand circular r.f. polarization.   
     
     
       4. An antenna structure as in claim 2 wherein: said r.f. radiator conducting area is a square shaped area.   
     
     
       5. An antenna structure as in claim 2 wherein: said r.f. radiator conducting area is a circularly shaped area.   
     
     
       6. An antenna array comprising: an electrically conducting ground surface,   a single layer arrangement of electrical conductors comprising both a plurality of r.f. radiators and a corporate structure r.f. feedline having a common input/output connected thereto,   a dielectric sheet disposed between said ground surface and the single layer arrangement of electrical conductors,   each of said r.f. radiators comprising an elongated unitary conducting area separate from said dielectric sheet, each of said areas having a width substantially equal to one-half wavelength at an anticipated operating frequency and a length of more than one such wavelength with a plurality of spaced feed points along one of the longer sides located at intervals of no more than one such wavelength apart,   said plural r.f. radiators being spaced from one another by substantially one-half such wavelength in a direction perpendicular to the longer sides of the r.f. radiators, and   said corporate structure r.f. feedline being connected to said spaced feed points at the outer edge of said r.f. radiators.   
     
     
       7. An antenna array as in claim 6 wherein said corporate structure r.f. feedline comprises predetermined different r.f. transmission lengths between the common input/output and the various r.f. radiators to produce a tapered amplitude distribution over the aperture of the array thereby reducing sidelobes in the r.f. radiation pattern of the array. 
     
     
       8. A phased antenna array structure comprising: an electrically conducting ground surface,   a single layer arrangement of electrical conductors comprising a plurality of r.f. radiators and a respectively corresponding plurality of r.f. feedline antenna structures respectively connected thereto and also connected to a common r.f. input/output point,   a dielectric sheet disposed between said ground surface and the single layer arrangement of electrical conductors,   each of said r.f. feedlines being connected at the outer edge of its correspondingly associated r.f. radiator to at least one predetermined point to achieve an r.f. radiation pattern from each r.f. radiator having predetermined polarization characteristics,   controllable phase shifters being interposed in said r.f. feedlines to control the relative phase of r.f. energy associated with each r.f. radiator and thereby to control the beam direction of the overall radiation pattern of said array,   said phase shifters being an integral part of said single layer arrangement of electrical conductors, and   each of said phase shifters including switchable diodes for controlling the phase shift to be produced thereby.   
     
     
       9. An antenna array comprising: an electrically conducting ground surface,   a single layer electrically conducting surface comprising both a plurality of r.f. radiator conducting areas and a plurality of r.f. feedline conducting areas integrally connected thereto,   a dielectric sheet disposed between said ground surface and the single layer electrically conducting surface,   each of said r.f. feedlines being connected at the outside edge of its correspondingly associated r.f. radiator conducting area to at least one predetermined point on the periphery of said radiator conducting area to achieve an r.f. radiation pattern having predetermined polarization characteristics from said radiator,   said plurality of separate r.f. radiators and respectively corresponding r.f. feedlines being arranged in a phased array including interconnections between said plurality of r.f. feedlines to connect all of the plurality of r.f. radiators with a common r.f. input/output point, and   wherein the interconnected r.f. feedlines comprise predetermined different r.f. transmission lengths between the common input/output and the various r.f. radiators to produce a tapered amplitude distribution over the aperture of the array thereby reducing sidelobes in the r.f. radiation pattern of the array.   
     
     
       10. An antenna structure comprising: an electrically conducting ground surface,   a single layer electrically conducting surface comprising both an r.f. radiator conducting area and an r.f. feedline conducting area integrally connecting thereto,   a dielectric sheet disposed between said ground surface and the layer electrically conducting surface, and   said r.f. feedline being connected at the outside edge of said r.f. radiator conducting area to at least one predetermined point on the periphery of said radiator conducting area to achieve an r.f. radiation pattern having predetermined polarization characteristics from said radiator,   said r.f. radiator being formed in a rectangular shaped area,   the longer side of the rectangular area being substantially equal to but slightly less than one-half wavelength long at a first anticipated operating frequency when r.f. is to be fed into a shorter side of the area, and   the shorter side of the rectangular area being substantially equal to but slightly less than one-half wavelength long at a second anticipated operating frequency when r.f. is to be fed into a longer side of the area.   
     
     
       11. An antenna structure comprising: an electrically conducting ground surface,   a single layer electrically conducting surface comprising both an r.f. radiator conducting area and an r.f. feedline conducting area integrally connected thereto,   a dielectric sheet disposed between said ground surface and the single layer electrically conducting surface,   said r.f. feedline being connected at the outside edge of said r.f. radiator conducting area to at least one predetermined point on the periphery of said radiator conducting area to achieve an r.f. radiation pattern having predetermined polarization characteristics from said radiator,   said r.f. feedline being connected to only one point on the outside edge of said r.f. radiator conducting area to produce an r.f. radiation pattern having circular polarization characteristics,   said r.f. radiator conducting area including means dimensioned differently in two mutually orthogonal directions, said means providing two corresponding complex-valued electrical impedances along said directions at the intended r.f. operating frequency, which two complex-valued impedances are complex conjugates of each other thus facilitating the desired circular r.f. polarization characteristic.   
     
     
       12. An antenna structure comprising: an electrically conducting ground surface,   a single layer electrically conducting surface comprising both an r.f. radiator conducting area and an r.f. feedline conducting area integrally connected thereto,   a dielectric sheet disposed between said ground surface and the single layer electrically conducting surface,   said r.f. feedline being connected at the outside edge of said r.f. radiator conducting area to at least one predetermined point on the periphery of said radiator conducting area to achieve an r.f. radiation pattern having predetermined polarization characteristics from said radiator,   said r.f. feedline conducting area comprising: a first feedline connected only to a first point on the outside edge of said r.f. radiator conducting area to produce a linear r.f. polarization characteristics; and   a second feedline connected only to a second point on the outside edge of said r.f. radiator conducting area to produce a circular r.f. polarization characteristic,     said r.f. radiator conducting area including means dimensioned differently in two mutually perpendicular directions, said means providing two corresponding complex-valued electrical impedances along said directions at the intended r.f. operating frequency, which two complex-valued impedances are complex conjugates of each other thus facilitating the desired circular r.f. polarization characteristic. .Iadd. 13. An antenna structure comprising:   an electrically conducting ground surface,   a single layer electrically conducting surface comprising both an r.f. radiator conducting area and an r.f. feedline conducting area integrally connected thereto,   a dielectric sheet disposed between said ground surface and the single layer electrically conducting surface, and   said r.f. feedline being connected at the outside edge of said r.f. radiator conducting area to at least one predetermined point on the periphery of said radiator conducting area to achieve an r.f. radiation pattern having predetermined polarization characteristics from said radiator,   said r.f. feedline conducting area including: a first section connected to only a first point on the outside edge of said r.f. radiator conducting area,   a second section connected to only a second point on the outside edge of said r.f. radiator conducting area,   said first and second points being separated by a predetermined amount along the outside edge of said r.f. conducting area to define two intersecting axes of current flow, each such axis passing through a corresponding one of said first and second points, and   phase shifting means connected between said first and second sections and a common r.f. input/output point whereby the relative phases of r.f. signals on said first and second sections are controlled with respect to the phase at said common r.f. input/output to produce an r.f. radiation pattern having predetermined polarization characteristics. .Iaddend..Iadd. 14. An antenna structure as in claim 13 wherein said phase shifting means comprises means for introducing an approximately 90°  relative phase shift thereby producing approximately circular r.f. polarization. .Iaddend..Iadd. 15. An antenna structure as in claim 14 wherein said phase shifting means comprises:     a closed rectilinear conductive path having four corners,   said first and second sections being connected to respectively associated adjacent ones of said corners, and   said common r.f. input/output comprising one of the remaining two corners for right-hand circular r.f. polarization and comprising the other one of the remaining two corners for left-hand circular r.f. polarization. .Iaddend..Iadd. 16. An antenna structure as in claim 14 wherein:   said r.f. radiator conducting area is an approximately square shaped area. .Iaddend..Iadd. 17. An antenna structure as in claim 14 wherein:   said r.f. radiator conducting area is an approximately circularly shaped area. .Iaddend. .Iadd. 18. An antenna structure comprising:   an electrically conducting ground surface,   a single layer electrically conducting surface comprising both an r.f. radiator conducting area and an r.f. feedline conducting area integrally connected thereto,   a dielectric sheet disposed between said ground surface and the single layer electrically conducting surface,   said r.f. feedline being connected at the outside edge of said r.f. radiator conducting area to only one predetermined point on the periphery of said radiator conducting area to achieve an r.f. radiation pattern having predetermined circular or elliptical polarization characteristics from said radiator,   said r.f. radiator conducting area including means dimensioned differently in two mutually orthogonal directions, said means providing two corresponding predetermined complex-valued electrical impedances along said directions at the intended r.f. operating frequency, which two complex-valued impedances are interrelated so as to produce the desired predetermined circular or elliptical r.f. polarization characteristic. .Iaddend. .Iadd. 19. An antenna structure comprising:   an electrically conducting ground surface,   a single layer electrically conducting surface comprising both an r.f. radiator conducting area and an r.f. feedline conducting area integrally connected thereto,   a dielectric sheet disposed between said ground surface and the single layer electrically conducting surface,   said r.f. feedline being connected at the outside edge of said r.f. radiator conducting area to at least one predetermined point on the periphery of said radiator conducting area to achieve an r.f. radiation pattern having predetermined polarization characteristics from said radiator,   said r.f. feedline conducting area comprising: a first feedline connected only to a first point on the outside edge of said r.f. radiator conducting area to produce a linear r.f. polarization characteristic; and   a second feedline connected only to a second point on the outside edge of said r.f. radiator conducting area to produce an approximately circular r.f. polarization characteristic,     said r.f. radiator conducting area including means dimensioned differently in two mutually perpendicular directions, said means providing two corresponding complex-valued electrical impedances along said directions at the intended r.f. operating frequency, which two complex-valued impedances are approximately complex conjugates of each other thus facilitating the desired approximate circular r.f. polarization characteristic. .Iaddend.