Cavity-backed slot antenna

Claim 2

An antenna, comprising: (a) a dielectric substrate having an adherent electrically conductive sheet forming a directionally-radiating elongated slot and means forming a microwave cavity backing said elongated slot; (b) a dielectric layer composed of material having a dielectric constant of twenty or more overlying said conductive sheet and coupled to said slot to effect reduction of the resonant frequency of said antenna and permit a reduction in the size of the means forming a microwave cavity; and (c) r.f. transmission means electrically coupled to said conductive sheet across and on opposite sides of said slot and adapted to carry r.f. energy.

Claim 3

The antenna as recited in claim 1, further comprising: electrically reactive means mounted across said slot and electrically coupled to said conductive sheet on opposite sides of said slot and being variable for fine tuning the resonant frequency of said antenna.

Claim 4

The antenna as recited in claim 2, wherein said reactive means is in the form of a pair of capacitive elements mounted across said slot and electrically coupled to said conductive sheet on opposite sides of said slot and at symmetrical locations therealong, said capacitive elements being variable for fine tuning the resonant frequency of said antenna.

Claim 5

The antenna as recited in claim 1, wherein the dielectric layer is composed of an iron-loaded dielectric, and the dielectric constant of said dielectric layer is between approximately 20 and 80.

Claim 6

The antenna is recited is claim 1, wherein said dielectric layer has a thickness between about 40 and 80 mils.

Claim 7

The antenna as recited in claim 1, wherein said elongated slot is contained within the perimeter of said conductive sheet and has a configuration in the shape of an unconnected square.

Claim 8

The antenna as recited in claim 1, wherein said elongated slot is contained within the perimeter of said conductive sheet and has a configuration in the shape of a straight line.

Claim 9

The antenna as recited in claim 1, wherein said elongated slot is contained within the perimeter of said conductive sheet and has a configuration in the shape of an unconnected triangle.

Claim 10

The antenna as recited in claim 1, wherein said elongated slot is contained within the perimeter of said conductive sheet and has a configuration in the shape of an unconnected circle.

Claim 11

A cavity-backed slot antenna, comprising: (a) an electrically conductive sheet having an elongated slot of a given length formed therein; (b) an electrically conductive housing electrically connected to said conductive sheet and defining a cavity of a given size therein which encloses said slot at one side of said sheet; (c) a dielectric layer composed of an iron-loaded dielectric material having a high dielectric constant of about 10 to about 80, said dielectric layer being disposed over at least said slot defined in said conductive sheet so as to effect a reduction of the resonant frequency of said antenna below that otherwise associated with said given cavity size and slot length permitting said antenna to be characterized as electrically small; (d) r.f. transmission means electrically coupled to said conductive sheet across and on opposite sides of said slot and adapted to carry r.f. energy; and (e) electrically reactive means mounted across said slot and electrically coupled to said conductive sheet on opposite sides of said slot and being adjustable for fine tuning the resonant frequency of said antenna.

Claim 12

A cavity-backed slot antenna, comprising: (a) an electrically conductive sheet having an elongated slot of a given length formed therein; (b) an electrically conductive housing electrically connected to said conductive sheet and defining a cavity of a given size therein which encloses said slot at one side of said sheet; (c) a dielectric layer composed of an iron-loaded dielectric material having a high dielectric constant of about 10 to about 80, said dielectric layer being disposed over at least said slot defined in said conductive sheet so as to effect a reduction of the resonant frequency of said antenna below that otherwise associated with said given cavity size and slot length permitting said antenna to be characterized as electrically small; (d) r.f. transmission means electrically coupled to said conductive sheet across and on opposite sides of said slot and adapted to carry r.f. energy; and (e) electrically reactive means mounted across said slot and electrically coupled to said conductive sheet on opposite sides of said slot and being adjustable for fine tuning the resonant frequency of said antenna.

Claim 13

The slot antenna as recited in claim 10, further comprising: a protective cover of electrically transparent material overlying said dielectric layer.

Claim 14

The slot antenna as recited in claim 10, wherein said conductive sheet includes; a dielectric plate composed of material having a dielectric constant of less than three, said dielectric plate extending across said housing; and a conductive layer of electrically conductive material covering an interior side of said dielectric plate and electrically contacting said housing, said conductive layer having said slot defined therein so as to wholly contained within the perimeter of said conductive layer.

Claim 15

The slot antenna as recited in claim 10, wherein the high dielectric constant of said dielectric layer is about 20.

Claim 16

The slot antenna as recited in claim 10, wherein said dielectric layer has a thickness between about 40 and 80 mils.

Claim 17

The slot antenna as recited in claim 10, wherein said dielectric layer has a thickness greater than about 30 mils.

Claim 18

The slot antenna as recited in claim 10, wherein said cavity has a depth substantially less than one-quarter wavelength.

Claim 19

The slot antenna as recited in claim 10, wherein said elongated slot is contained within the perimeter of said conductive sheet and has a configuration in the shape of an unconnected square.

Claim 20

The slot antenna as recited in claim 10, wherein said elongated slot is contained within the perimeter of said conductive sheet and has a configuration in the shape of a straight line.

Claim 21

The slot antenna as recited in claim 11, wherein said elongated slot is contained within the perimeter of said conductive sheet and has a configuration in the shape of an unconnected triangle.

Claim 22

The slot antenna as recited in claim 10, wherein said elongated slot is contained within the perimeter of said conductive sheet and has a configuration in the shape of an unconnected circle.

Claim 23

The slot antenna as recited in claim 10, wherein said reactive means is in the form of a pair of capacitive elements mounted across said slot and electrically coupled to said conductive sheet on opposite sides of said slot and at symmetrical locations therealong, said capacitive elements being variable for fine tuning the resonant frequency of said antenna.

Claim 24

An electrically-small, cavity-backed slot antenna, comprising: (a) an electrically conductive housing having a side and bottom and an open top so as to define a cavity of a given size therein; (b) support means extending across and connected to said housing to close the same and having a conductive portion of electrically conductive material electrically contacting said housing, said conductive portion having an elongated slot of a given length formed therein which is contained within the perimeter of said conductive portion, said elongated slot having unconnected ends and a configuration selected from a group consisting of an unconnected square, unconnected circle, unconnected triangle and straight line; (c) a dielectric layer composed of material having a dielectric constant of ten or greater, said dielectric layer being attached to said support means and disposed over at least said slot defined in said conductive portion so as to effect a reduction of the resonant frequency of said antenna below that otherwise associated with said given cavity size and slot length permitting said antenna to be characterized as electrically small; (d) a protective cover of electrically transparent material overlying said dielectric layer; (e) r.f. transmission means electrically coupled to said conductive portion across said slot and adapted to carry r.f. energy; and (f) a plurality of capacitive elements mounted across said slot and electrically coupled to said conductive portion on opposite sides of said slot and at symmetrical locations therealong, said capacitive elements being variable for fine tuning the resonant frequency of said antenna.

Claim 25

An electrically-small, cavity-backed slot antenna, comprising: (a) an electrically conductive housing having a side and bottom and an open top so as to define a cavity of a given size therein; (b) support means extending across and connected to said housing to close the same and having a conductive portion of electrically conductive material electrically contacting said housing, said conductive portion having an elongated slot of a given length formed therein which is contained within the perimeter of said conductive portion, said elongated slot having unconnected ends and a configuration selected from a group consisting of an unconnected square, unconnected circle, unconnected triangle and straight line; (c) a dielectric layer composed of material having a dielectric constant of ten or greater, said dielectric layer being attached to said support means and disposed over at least said slot defined in said conductive portion so as to effect a reduction of the resonant frequency of said antenna below that otherwise associated with said given cavity size and slot length permitting said antenna to be characterized as electrically small; (d) a protective cover of electrically transparent material overlying said dielectric layer; (e) r.f. transmission means electrically coupled to said conductive portion across said slot and adapted to carry r.f. energy; and (f) a plurality of capacitive elements mounted across said slot and electrically coupled to said conductive portion on opposite sides of said slot and at symmetrical locations therealong, said capacitive elements being variable for fine tuning the resonant frequency of said antenna.

Claim 26

The slot antenna as recited in claim 22, wherein the dielectric layer is composed of an iron-loaded dielectric material and the dielectric constant of said dielectric layer is between approximately 10 and 80.

Claim 27

The slot antenna as recited in claim 23, wherein the dielectric constant of said dielectric layer is about 20.

Claim 28

The slot antenna as recited in claim 22, wherein said material of said dielectric layer is a member selected from the group consisting of alumina ceramic, silicone resin/ceramic powder-filled, boron nitride, gallium arsenide, aluminum oxide, and cross linked polystyrene/ceramic powder-filled.

Claim 29

The slot antenna as recited in claim 22, wherein said dielectric layer has a thickness between about 40 and 80 mils.

Claim 30

The slot antenna as recited in claim 25, wherein said cavity has a depth substantially less than one-quarter wavelength.

Claim 31

The slot antenna as recited in claim 22, wherein said elongated slot is contained within the perimeter of said conductive portion and has a configuration in the shape of an unconnected square.

Claim 32

The slot antenna as recited in claim 25, wherein said elongated slot is contained within the perimeter of said conductive portion and has a configuration in the shape of a straight line.

Claim 33

The slot antenna as recited in claim 22, wherein said elongated slot is contained within the perimeter of said conductive portion and has a configuration in the shape of an unconnected triangle.

Claim 34

The slot antenna as recited in claim 22, wherein said elongated slot is contained within the perimeter of said conductive portion and has a configuration in the shape of an unconnected circle.