Gte Government Systems Corporation

Gte Products Corporation

Gte Sylvania Incorporated

US Government as Represented by the Secretary of the Army

Samuel C Kuo

Normand Barbano

William D Rosser

Warren M Shelton

Robert E Davis

Craig G Roberts

Gustavo E Bird

A foreshortened log periodic antenna comprising variously configured dipole elements and a tapered feedline is further size reduced with an improved configuration of the dipole with the lowest resonant frequency. By substantially increasing the thickness of that dipole, the overall length of the already size-reduced dipole is further decreased by 8% to 10%.

Foreshortened log-periodic dipole antenna

A foreshortened log-periodic antenna which includes variously configured dipole elements and a tapered feedline is disclosed. The dipole elements are arranged in four regions. A first region, located nearest to a feed end of the antenna, includes solid triangular dipoles having constant base-to-height ratios. A second region, adjacent to the first region, includes solid triangular dipoles having decreasing base-to-height ratios. A third region, located adjacent to the second region, includes a single linear dipole. A fourth region, located adjacent to the third region and nearest to a low frequency end of the antenna, includes foreshortened dipoles. The feedline may be implemented either in coaxial or microstrip form so that a lower characteristic impedance is pressed at the feed end of the antenna than at the low frequency end of the antenna. Specifically, for a coaxial feedline having individual conductors separated by a distance 'd' at the feed end of the antenna, the individual conductors taper relative to each other so that they are separated by a distance of 2d-5d at the low frequency end of the antenna.

Foreshortened dipole antenna with triangular radiating elements and

The foreshortened dipoles of the antenna described in U.S. Pat. No. 3,732,572 are further substantially shortened with a new construction in which each radiating element comprises two portions. A planar rectangular body electrically connects to the feed point by a stem portion which attaches to the rectangular body at the farthest point from the feed point and is spaced slightly from the plane of the body to electrically isolate the two portions.

Foreshortened antenna structures

A crossed log-periodic dipole antenna having a unique feedline/boom structure providing improved antenna performance. The antenna is assembled from a pair of orthogonally displaced log-periodic antennas each having a pair of half-dipole structures, each structure having a half-dipole assembly and a central feed boom. The half-dipole assembly comprises a single sheet of conducting material formed to provide a central boom portion and a plurality of half-dipole elements projecting radially from opposite sides of the boom. The boom portion has a reduced thickness, a shape which complements that of the outer surface of the boom, and is press-fitted against and bonded to the boom exterior to form an integrated rigid unit. This configuration minimizes the force required to connect each half-dipole assembly with the adjacent boom, decreases the offset distance between the two dipole halves of each antenna, and reduces the electrical shadowing effect of the booms on the antennas. The invention also comprehends a method of making such an antenna.

Crossed log-periodic dipole antenna and method of making same

In a log-periodic monopole antenna array of the type described in U.S. Pat. No. 3,286,268, each antenna of the array having active elements spaced over the top surface of a ground structure and grounded parasitic elements interspersed between the active elements, the improvement of means for mechanically and electrically connecting the parasitic elements to a non-solderable ground structure comprising an elongated block compressed into a correspondingly shaped groove in the structure. Screw means threadedly engage the ground structure in a direction transversely of the top surface thereof and abut against the block. The lower strip portion of the parasitic elements is disposed in the groove between the block and a groove side wall and is compressed therebetween when the screw means is tightened into the structure and against the block. In one embodiment, one side of the block and the adjacent side of the groove are tapered toward the opposite side of the groove so as to force the block against the strip when the screw means is tightened. In another embodiment the block abutting surface of the head of the screw means is tapered and forces the block against the strip when the screw means is tightened. A tight mechanical and electrical connection of the parasitic element strip portions in the array of antennas is thus achieved in a minimum of space.

Log-periodic monopole antenna array

The foreshortened dipoles of the antenna described in U.S. Pat. No. 3,732,572 are further substantially shortened without performance impairment with a new construction in which each radiating element comprises a planar rectangular body electrically connected to the feed line by a stem attached to the body remotely from the feed line and spaced slightly from the plane of the body.

Log periodic antenna with foreshortened radiating elements

A foreshortened log periodic antenna includes variously configured dipole elements which are arranged in four regions along the axis of the array. The first region includes a series of solid, triangular dipoles characterized by substantially constant base/height ratios. The second region similarly includes a series of solid, triangular dipoles. However, these elements are characterized by decreasing base/height ratios so as to afford a gradual transition into the third region, which includes a single linear dipole. The fourth region includes a series of solid or hollow rectangular elements connected by respective stems to the antenna feedline. In a manner set forth in U.S. Pat. No. 3,732,572, entitled 'Log Periodic Antenna with Foreshortened Dipoles', the rectangular elements effect a reduction in the width of the array without a substantial affect on electrical performance.

Foreshortened dipole antenna with triangular radiators

A log-periodic antenna comprises two arrays of dimensionally tapered radiating elements disposed in the E-plane and each fed by a balanced line consisting of the inner conductors of two coaxial cables. In one embodiment the elements of each array are dipoles and in another embodiment are formed of continuous conductive strips in zig-zag patterns on non-conductive support members. Each array preferably has two sets of elements disposed in planes, respectively, which converge toward the smaller end of the array with vertically aligned radiating elements of each set projecting in opposite directions from the array axis. Periodic gain dropout anomalies across the antenna operating band are eliminated by use of a shielded feed line.

Log-periodic antenna

A log-periodic antenna comprises two arrays of dimensionally tapered radiating elements disposed in the E-plane and each fed by a balanced line consisting of the inner conductors of two coaxial cables. In one embodiment the elements of each array are dipoles and in another embodiment are formed of continuous conductive strips in zig-zag patterns on non-conductive support members. Each array preferably have two sets of elements disposed in planes, respectively, which converge toward the smaller end of the array with vertically aligned radiating elements of each set projecting in opposite directions from the array axis. Periodic gain dropout anomalies across the antenna operating band are eliminated by use of a shielded feed line.

A log-periodic antenna comprises two arrays of dimensionally tapered radiating elements disposed in the E-plane and each fed by a balanced line consisting of the inner conductors of two coaxial cables. In one embodiment the elements of each array are dipoles and in an other embodiment are formed of continuous conductive strips in zig-zag patterns on non-conductive support members. Each array preferably has two sets of elements disposed in planes, respectively, which converge toward the smaller end of the array with vertically aligned radiating elements of each set projecting in opposite directions from the array axis. Periodic gain dropout anomalies across the antenna operating band are at least substantially reduced by use of shielded feed lines. In another embodiment which has particular advantage at HF frequencies, a single array is operated over a ground plane which provides a mirror image thereof. In yet another embodiment which has advantage in direction finding, the sets of elements of each array are located on associated opposite sides of a right rectangular pyramid. A pair of these pyramidal arrays, with some of the element sets being coplanar, are employed for direction finding.

Groundplane mounted log-periodic antenna

A log-periodic antenna comprises two arrays of dimensionally tapered radiating elements disposed in the E-plane and each fed by a balanced line consisting of the inner conductors of two coaxial cables. In one embodiment the elements of each array are dipoles and in another embodiment are formed of continuous conductive strips in zig-zag patterns on non-conductive support members. Each array preferably has two sets of elements disposed in planes, respectively, which converge toward the smaller end of the array with vertically aligned radiating elements of each set projecting in opposite directions from the array axis. Periodic gain dropout anomalies across the antenna operating band are eliminated by use of a shielded feed line. In another embodiment having advantage in direction finding, the sets of elements of each array are located on associated opposite sides of a right rectangular pyramid. These pyramidal arrays are used in pairs for direction finding.

A vertically-polarized log-periodic monopole antenna comprises two closely spaced arrays of elements over a ground plane and connected to a balanced feed source, i.e, the arrays are separately excited out of phase by the source. The elements of each array taper from minimum dimensions at the feed end to maximum at the other end in progressive increments of a predetermined ratio .tau. and are open at their inner ends proximate to the ground plane. Each array preferably comprises an electrically continuous wire-like conductor configured to define the profile of the elements and to constitute the interelement connecting lines. Preferred shapes of the elements are trapezoidal, pseudo-trapezoidal and triangular. The antenna provides very broadband (20 to 750 MHz) frequency independent performance at minimum VSWR (&lt;2.0 to 1) and has non-critical design parameters.

Log-periodic monopole antenna

A log-periodically loaded monopole antenna comprises a plurality of longitudinally log-periodically spaced longitudinally tapering linear radiating elements in a vertical plane, a meander transmission line (meanderline) in a second plane perpendicular to the vertical plane and extending longitudinally on opposite sides of the plane of the elements and intersecting successive elements at the cross-over points, and a straight transmission line or shunt in the second plane interconnecting the junctions of the elements and the meanderline. The addition of this shunt substantially eliminates the large gain drop-out characteristic of this antenna, the voltage standing wave ratio being reduced from an average of 6:1 to less than 1.6:1. In one embodiment the elements are pivotally connected to the transmission line for pivoting in the vertical plane to permit collapsing of the elements toward the plane of the transmission line when required due to space limitations.

Periodically loaded antenna structure

The basic log periodic zig zag antenna is made of one continuous conductor herein vertical wires function as radiators when they are in resonance. Horizontal wires of the antenna are the phasing stubs, which provide the proper phase shift for the radiating elements. Efficiency of the antenna is enhanced by effectively shortening the path between adjacent elements in the active region with a single conductor. Additionally, a vertical conductor between the shortened path conductor and the respective radiating elements reduces the resonance Q of the vertical radiators and functions as a mechanical support for the radiators.

Log periodic zig zag monopole antenna

A broadband (8-18 GHz) radomed horn antenna system comprises a conical horn having broadband slots on the inner surface and a radome having a frusto-conical side wall and a spherically shaped transverse wall inserted into the horn. The radome wall is thin relative to operating wavelength. The radome side wall fits snugly against the inner surface of the horn wall so that transverse wall is proximate to the horn feed port with its convex side facing toward the horn aperture. The cylindrical feed guide contains a higher order hybrid mode suppressor which maintains a substantially uniform radiation pattern over the operating band with an acceptable insertion loss.

Growing community of inventors

Saratoga, CA, United States of America

Samuel C Kuo