Ridge scan antenna

Claim 2

A radar antenna system for radiating a fan shaped beam in a vertical plane and scanning the beam through a given azimuth angle, comprising, in combination: a. an elongated horizontally disposed waveguide for receiving electro-magnetic energy in one end and having a series of holes in one longitudinal side wall dimensional below cut-off so as to be non-resonant, said holes coupling energy out from the waveguide in a manner defining said fan shaped beam, the non resonant characteristic of said holes rendering the shape of said beam substantially insensitive to frequency variations over approxiMately a frequency octave; b. an elongated ridge member co-extensive with the length of said waveguide arranged to extend wholly within the guide along its length; and, c. means for maintaining the leading edge of the ridge in parallel relation with the longitudinal axis of the waveguide while moving the ridge towards and away from the opposite side wall of the waveguide to thereby vary the phase velocity of energy propagated along the waveguide in a manner to effect scanning of said fan shaped beam through said given azimuth angle.

Claim 3

A radar antenna system for radiating a fan shaped beam in a vertical plane and scanning the beam through a given azimuth angle, comprising, in combination: a. an elongated horizontally disposed waveguide for receiving electro-magnetic energy in one end and having a series of holes in one longitudinal side wall dimensioned below cut-off so as to be non-resonant, said holes coupling energy out from the waveguide in a manner defining said fan-shaped beam; b. an elongated ridge member co-extensive with the length of said waveguide arranged to extend wholly within the guide along its length; and, c. means for maintaining the leading edge of the ridge in parallel relation with the longitudinal axis of the waveguide while moving the ridge towards and away from the opposite side wall of the waveguide to thereby vary the phase velocity of energy propagated along the waveguide in a manner to effect scanning of said fan shaped beam through said given azimuth angle, said series of holes being arranged in first and second groups disposed alternately above and below the longitudinal center line of said one longitudinal side wall, each group comprising a given number of holes in closely spaced side-by-side relation along a given longitudinal distance to define a given length for the group, the spacing between successive groups being of the same order as said given length whereby energy is coupled out of the waveguide in such a manner that said given azimuth angle of scan passes through and on either side of a vertical plane bisecting the waveguide at its mid-point and oriented perpendicularly to the longitudinal axis of the waveguide.

Claim 4

A radar antenna system for radiating a fan shaped beam in a vertical plane and scanning the beam through a given azimuth angle, comprising, in combination: a. an elongated horizontally disposed waveguide for receiving electro-magnetic energy in one end and having a series of holes in one longitudinal side wall dimensioned below cut-off so as to be non-resonant, said holes coupling energy out from the waveguide in a manner defining said fan-shaped beam; b. an elongated ridge member co-extensive with the length of said waveguide arranged to extend wholly within the guide along its length; and, c. means for maintaining the leading edge of the ridge in parallel relation with the longitudinal axis of the waveguide while moving the ridge towards and away from the opposite side wall of the waveguide to thereby vary the phase velocity of energy propagated along the waveguide in a manner to effect scanning of said fan shaped beam through said given azimuth angle, said series of holes being arranged in first and second groups disposed alternately above and below the longitudinal center line of said one longitudinal side wall, each group comprising a given number of holes in closely spaced side-by-side relation along a given longitudinal distance to define a given length for the group, the spacing between successive groups being of the same order as said given length whereby energy is coupled out of the waveguide in such a manner that said given azimuth angle of scan passes through and on either side of a vertical plane bisecting the waveguide at its mid-point and oriented perpendicularly to the longitudinal axis of the waveguide.

Claim 5

An antenna according to claim 2, in which said one longitudinal side wall includes recessed areas to define reduced thickness portions surrounding the given number of holes making up the groups to increase the efficiency of coupling of energy out of the waveguide through the holes.

Claim 6

An antenna according to claim 3, in which said elongated waveguide constitutes an integral extrusion in the form of a T in cross section, the stem of the T accomodating at least a portion of said ridge, the broad side wall opposite the ridge constituting said one longitudinal side wall having recessed areas and said series of holes, said extrusion further defining integral upper and lower longitudinal flanges extending forwardly from the upper and lower edges of the said longitudinal side wall to define extended conductive surfaces guiding the coupled out radiant energy in a forward direction and further defining securing means for facilitating the mounting of the waveguide in the leading edge of an aircraft wing, the entire extrusion minimizing any leakage of electromagnetic energy in portions of the waveguide other than the holes.

Claim 7

An antenna according to claim 4, including an elongated plastic means extending longitudinally between said upper and lower flanges in surface contact with said one longitudinal side wall, said plastic means including portions filling said recessed areas, the dielectric constant of the plastic means having a value to effect an optimum coupling of the energy passing from the waveguide to free space.

Claim 8

An antenna according to claim 4, in which said extrusion further defines longitudinal lightening passages running parallel to and on either exterior side of the narrow sides defined by the rectangular waveguide, whereby when said waveguide is mounted in the leading Edge of an aircraft wing, hot air can be passed through said passages to heat said extrusion and serve as a de-icing means for the wing.

Claim 9

An antenna according to claim 5, in which said elongated plastic means includes a conductive path following a circuitous route to pass between said portions filling said recessed areas on either side of a center line from one end of the plastic means towards the other such that current can be passed through the conductive path to heat the extrusion and serve as a de-icing means for the wing.

Claim 10

An antenna according to claim 1, in which said waveguide is T shaped in cross section, said one longitudinal side wall having the series of holes constituting a broad side wall, said ridge member being positioned in the stem of said T shape for movement towards and away from said broad side wall, said means for maintaining the leading edge of the ridge member in parallel relation with the longitudinal axis of the waveguide while moving the ridge towards and away from the broad side wall, including: a. a series of rods rigidly secured at first ends to the trailing edge of the ridge member at evenly spaced longitudinal points, the other ends of the rods passing through bearing openings in the stem of the T shape; and b. a driving means coupled to said other ends of the rods for reciprocating them in unison back and forth in the housing to thereby move the ridge towards and away from said broad side wall, the ridge member itself and rods being held out of physical contact with the T shaped waveguide other than at the bearing openings so that it is ''''floating.''''

Claim 11

An antenna according to claim 8, in which the stem of the T shape is sufficiently long that said ridge member can move freely within the stem to a ''''negative'''' ridge position with respect to a conventional rigid ridged waveguide shape.

Claim 12

An antenna according to claim 8, in which said driving means includes means for reciprocating said rods to follow a linear motion over a major portion of their travel in each direction.

Claim 13

An antenna according to claim 1, having an input energy transition structure for passing said electromagnetic energy into said one end of said waveguide, said input transition structure including: a. an input waveguide section having a transition ridge section pivoted at one end to the co-extensive end of said ridge member in the waveguide, and having its other end coupled to be flush with one wall of said input waveguide section such that a gradual diminution of the effect of the ridge member is provided for any given position of the ridge member; and b. an expanding waveguide coupling section with its converging end coupled to the input waveguide section, and its expanded end receiving input electromagnetic energy.

Claim 14

An antenna according to claim 1, having a termination transition structure for providing a proper termination impedance for energy passing towards the other end of said waveguide, said termination transition structure including: a. a termination waveguide section having a closed end and a transition ridge section pivoted at one end to the end of the ridge member co-extensive with said other end of the waveguide, and having its other end coupled to be flush with one wall of said termination waveguide section such that a gradual diminution of the effect of the ridge member is provided for any given position of the ridge member; and b. a wedge-shaped section of ferrite material on the wall of the termination waveguide section opposite to the transition ridge section to minimize reflections of energy at said other end of the waveguide.

Claim 15

An antenna according to claim 1, having an input energy transition structure for passing said electromagnetic energy into said one end of said waveguide, said input transition structure including: an input waveguide section including a transition ridge section constituting an integral extension of the ridge member, said extension having itS upper edge tapering towards its lower edge and including a plurality of slots to define ridge projections decreasing successively in height, the floor of said waveguide section including a series of windows through which said ridge projections extend when said ridge member is moving in the waveguide to thereby provide a gradual diminution of the effect of the ridge member for any given position of the ridge member.

Claim 16

An antenna according to claim 13, in which said input energy transition structure includes an expanding waveguide coupling section with its converging end connected to said input waveguide section and its expanded end receiving input electromagnetic energy.

Claim 17

An antenna according to claim 13, in which said input waveguide section expands in size from its end coupled to the waveguide to its end receiving input electromagnetic energy.

Claim 18

An antenna according to claim 1, having a termination transition structure for providing a proper termination impedance for energy passing towards the other end of said waveguide, said termination transition structure including: a termination waveguide section having a closed end and a transition ridge section constituting an integral extension of the ridge member, said extension having its upper edge tapering towards its lower edge and including a plurality of slots to define ridge projections decreasing successively in height, the floor of said termination waveguide section including a series of windows through which said ridge projections extend when said ridge member is moving in the waveguide; and a wedge-shaped section of ferrite material on the wall of the termination waveguide section opposite to the transition ridge section to minimize reflections of energy at said other end of the waveguide.

Claim 19

An antenna according to claim 1, having an input structure for passing electromagnetic energy into said one end of said waveguide including: an input waveguide section including a ridge section constituting an integral extension of said ridge member, the upper wall of the waveguide section opposite said ridge section having a coaxial line connected thereto, the outer conductor of the line terminating at the wall and the inner conductor extending into the waveguide towards the top edge of said ridge section, said inner conductor terminating short of the ridge section; movable tuning probe means extending into said wall of the waveguide section between the inner conductor and the point of connection of the waveguide section to said waveguide; and means mechanically connecting the tuning probe means to said ridge member for movement with the ridge member whereby input electromagnetic energy in said coaxial line is transferred to said waveguide with maximum coupling efficiency for every position of the ridge member.

Claim 20

An antenna according to claim 1, having a termination transition structure for providing a proper termination impedance for energy passing towards the other end of said waveguide, said termination transition structure including: a wedge shaped section of ferrite material on the wall of said other end of said waveguide opposite the co-extensive end portion of said ridge member; and a metallic end wall closing the said other end of the waveguide, the wedge shaped section minimizing reflections of energy at said other end of the waveguide.

Claim 21

A radar antenna system for radiating a fan shaped beam in a vertical plane and scanning the beam through a given azimuth angle, comprising, in combination: a. an elongated horizontally disposed waveguide for receiving electro-magnetic energy in one end and having a series of holes in one longitudinal side wall dimensioned below cut-off so as to be non-resonant, said holes coupling energy out from the waveguide in a manner defining said fan-shaped beam; b. an elongated ridge member co-extensive with the length of said waveguide arranged to extend wholly within the guide along its length; and, c. means for maintaining the leading edge of tHe ridge in parallel relation with the longitudinal axis of the waveguide while moving the ridge towards and away from the opposite side wall of the waveguide to thereby vary the phase velocity of energy propagated along the waveguide in a manner to effect scanning of said fan shaped beam through said given azimuth angle, said series of holes extending longitudinally between the longitudinal center line and one edge of said one longitudinal wall in closely spaced side-by-side relationship, the portion of the wall through which the holes pass being recessed to provide a reduced thickness portion to increase the efficiency of coupling of energy out of the waveguide.

Claim 22

A radar antenna system for radiating a fan shaped beam in a vertical plane and scanning the beam through a given azimuth angle, comprising, in combination: a. an elongated horizontally disposed waveguide for receiving electro-magnetic energy in one end and having a series of holes in one longitudinal side wall dimensioned below cut-off so as to be non-resonant, said holes coupling energy out from the waveguide in a manner defining said fan-shaped beam; b. an elongated ridge member co-extensive with the length of said waveguide arranged to extend wholly within the guide along its length; and, c. means for maintaining the leading edge of tHe ridge in parallel relation with the longitudinal axis of the waveguide while moving the ridge towards and away from the opposite side wall of the waveguide to thereby vary the phase velocity of energy propagated along the waveguide in a manner to effect scanning of said fan shaped beam through said given azimuth angle, said series of holes extending longitudinally between the longitudinal center line and one edge of said one longitudinal wall in closely spaced side-by-side relationship, the portion of the wall through which the holes pass being recessed to provide a reduced thickness portion to increase the efficiency of coupling of energy out of the waveguide.

Claim 23

A radar antenna system for radiating a fan shaped beam in a vertical plane and scanning the beam through a given azimuth angle, comprising, in combination: a. an elongated horizontally disposed waveguide for receiving electro-magnetic energy in one end and having a series of holes in one longitudinal side wall dimensioned below cut-off so as to be non-resonant, said holes coupling energy out from the waveguide in a manner defining said fan-shaped beam; b. an elongated ridge member co-extensive with the length of said waveguide arranged to extend wholly within the guide along its length; and, c. means for maintaining the leading edge of the ridge in parallel relation with the longitudinal axis of the waveguide while moving the ridge towards and away from the opposite side wall of the waveguide to thereby vary the phase velocity of energy propagated along the waveguide in a manner to effect scanning of said fan shaped beam through said given azimuth angle, said series of holes being arranged in groups serially extending between the longitudinal center line and one edge of said one longitudinal wall, each group comprising a given number of holes in closely spaced side-by-side relation along a given longitudinal distance to define a given length for the group, the spacing between successive groups being of the same order as said given length, the longitudinal wall including recessed areas to define reduced thickness portions surrounding the given number of holes making up the groups to increase the efficiency of coupling of energy out of the waveguide.

Claim 24

A radar antenna system for radiating a fan shaped beam in a vertical plane and scanning the beam through a given azimuth angle, comprising, in combination: a. an elongated horizontally disposed waveguide for receiving electro-magnetic energy in one end and having a series of holes in one longitudinal side wall dimensioned below cut-off so as to be non-resonant, said holes coupling energy out from the waveguide in a manner defining said fan-shaped beam; b. an elongated ridge member co-extensive with the length of said waveguide arranged to extend wholly within the guide along its length; and, c. means for maintaining the leading edge of the ridge in parallel relation with the longitudinal axis of the waveguide while moving the ridge towards and away from the opposite side wall of the waveguide to thereby vary the phase velocity of energy propagated along the waveguide in a manner to effect scanning of said fan shaped beam through said given azimuth angle, said series of holes being arranged in groups serially extending between the longitudinal center line and one edge of said one longitudinal wall, each group comprising a given number of holes in closely spaced side-by-side relation along a given longitudinal distance to define a given length for the group, the spacing between successive groups being of the same order as said given length, the longitudinal wall including recessed areas to define reduced thickness portions surrounding the given number of holes making up the groups to increase the efficiency of coupling of energy out of the waveguide.

Claim 25

An antenna according to claim 20, including short waveguide stubs surrounding each of the groups of holes and extending normally from said one longitudinal wall, said waveguide stubs constituting fixed phase shifters having different electrical lengths whereby the angular relationship of the limits of the azimuth angle through which the fan shaped beam is scanned by movement of said ridge member, relative to a vertical plane perpendicularly bisecting the waveguide, can be changed.

Claim 26

An antenna according to claim 1, in which said elongated ridge member is periodically segmented to structurally relieve stresses in the ridge member when moved towards and away from said opposite side wall of the waveguide.

Claim 27

A radar antenna system comprising: an elongated horizontally disposed waveguide for receiving electromagnetic energy in one end and having a series of holes in one longitudinal side wall dimensioned below cut-off so as to be non-resonant and substantially insensitive to wave length, said holes being arranged in first and second groups disposed alternately above and below the longitudinal center line of said one longitudinal side wall, each group comprising a given number of holes in closely spaced side by side relation along a given longitudinal distance to define a given length for the group, the spacing between successive groups being of the same order as said given length whereby energy is coupled out of the waveguide to provide a fan shaped beam lying in a vertical plane including broadside.

Claim 28

A radar antenna system comprising: an elongated horizontally disposed waveguide for receiving electromagnetic energy in one end and having a series of holes in one longitudinal side wall dimensioned below cut-off so as to be non-resonant and substantially insensitive to wave length, said holes being arranged in first and second groups disposed alternately above and below the longitudinal center line of said one longitudinal side wall, each group comprising a given number of holes in closely spaced side by side relation along a given longitudinal distance to define a given length for the group, the spacing between successive groups being of the same order as said given length whereby energy is coupled out of the waveguide to provide a fan shaped beam lying in a vertical plane including broadside.

Claim 29

A radar antenna according to claim 23, in which said waveguide has a T shape in cross section; a ridge member in the stem portion of the T shape; and means for moving the ridge member partially into and completely out of that portion of The waveguide defined by the cross of the T shape, the stem of the T shape being sufficiently long that said ridge member is moved into the stem so that its leading edge is moved below the cross of the T shape to a ''''negative'''' ridge position, the movement of the ridge member effecting a scanning of said fan shaped beam, through an azimuth angle on either side of broadside.