Modulated impedance feeding system for log-periodic antennas

Claim 2

In log-periodic antennas having a series of substantially log-periodically scaled antenna elements including a feeder periodically coupled to said antenna elements to form loaded and unloaded portions along said feeder, the improvement comprising: modulated impedance matching means for modulating the characteristic impedance of said feeder in the region near said antenna elements relative to the characteristic impedance of said feeder away from said antenna elements, said modulated impedance matching means thereby matching the image impedances of said loaded feeder portions at said antenna elements with the adjacent unloaded feeder portions.

Claim 3

In log-periodic antennas having a series of substantially log-periodically scaled antenna elements including a feeder periodically coupled to said antenna elements to form loaded and unloaded portions along said feeder, the improvement comprising: impedance-matching means coupled to said feeder for matching the image impedances of said loaded feeder portions to said antenna elements with the adjacent unloaded feeder portions; said antenna elements comprising a series of monopole elements projecting transversely above a ground plane and periodically coupled to said feeder, said impedance-matching means including means for increasing the characteristic impedance of said feeder in the region near said monopoles above the characteristic impedance of said feeder away from said monopoles.

Claim 4

In log-periodic antennas having a series of substantially log-periodically scaled antenna elements including a feeder periodically coupled to said antenna elements to form loaded and unloaded portions along said feeder, the improvement comprising: impedance-matching means coupled to said feeder for matching the image impedances of said loaded feeder portions to said antenna elements with the adjacent unloaded feeder portions; said antenna elements comprising a series of monopole elements projecting transversely above a ground plane and periodically coupled to said feeder, said impedance-matching means including means for increasing the characteristic impedance of said feeder in the region near said monopoles above the characteristic impedance of said feeder away from said monopoles.

Claim 5

The improvement of claim 2, wherein said impedance-matching means comprises means for supporting said feeder in the region near said monopoles a greater distance above said ground plane than the distance between said ground plane and the remaining portion of the feeder away from the monopoles.

Claim 6

In log-periodic antennas having a series of substantially log-periodically scaled antenna elements including a feeder periodically coupled to said antenna elements to form loaded and unloaded portions along said feeder, the improvement comprising: impedance-matching means coupled to said feeder for matching the image impedances of said loaded feeder portions at said antenna elements with the adjacent unloaded feeder portions; said antenna elements comprising a ground plane and a series of slots therein, and wherein said feeder is spacially separated from said slots on one side of said ground plane, said impedance-matching means modulating the characteristic impedance of said feeder in the vicinity of said slots.

Claim 7

In log-periodic antennas having a series of substantially log-periodically scaled antenna elements including a feeder periodically coupled to said antenna elements to form loaded and unloaded portions along said feeder, the improvement comprising: impedance-matching means coupled to said feeder for matching the image impedances of said loaded feeder portions at said antenna elements with the adjacent unloaded feeder portions; said antenna elements comprising a ground plane and a series of slots therein, and wherein said feeder is spacially separated from said slots on one side of said ground plane, said impedance-matching means modulating the characteristic impedance of said feeder in the vicinity of said slots.

Claim 8

The improvement of claim 4, wherein said impedance-matching means includes means for supporting said feeder above said slots closer to the ground plane than the distance between the ground plane and the remaining portion of the feeder away from the slots.

Claim 9

The improvement of claim 5, including a series of log-periodically scaled cavity sections associated with each of said slots to form a log-periodic cavity backed slot array.

Claim 10

In log-periodic antennas having a series of substantially log-periodically scaled antenna elements extending from a feed point, the improvement comprising a log-periodically scaled directional coupler feed line, said feed line including: a first transmission line having oppositely disposed conducting line elements extending from said feed point at one end of said series of antenna elements towards the opposite end; a second transmission line having oppositely disposed conducting line elements respectively coupled to said first line along the length thereof; a series of transposition elements interconnecting the conducting line elements of said second transmission line at substantially log-periodically spaced distances along said line; and means for connecting said antenna elements to said respective transposition elements along said line, whereby an electromagnetic wave traveling from said feed point on said firSt transmission line towards said opposite end, is coupled to said second transmission line and travels thereon back towards said feed point to excite said antenna elements.

Claim 11

In log-periodic antennas having a series of substantially log-periodically scaled antenna elements extending from a feed point, the improvement comprising a log-periodically scaled directional coupler feed line, said feed line including: a first transmission line having oppositely disposed conducting line elements extending from said feed point at one end of said series of antenna elements towards the opposite end; a second transmission line having oppositely disposed conducting line elements respectively coupled to said first line along the length thereof; a series of transposition elements interconnecting the conducting line elements of said second transmission line at substantially log-periodically spaced distances along said line; and means for connecting said antenna elements to said respective transposition elements along said line, whereby an electromagnetic wave traveling from said feed point on said firSt transmission line towards said opposite end, is coupled to said second transmission line and travels thereon back towards said feed point to excite said antenna elements.

Claim 12

The improvement of claim 7, wherein said first transmission line comprises a coaxial cable having a center conductor and a concentric outer conductor, said coaxial cable extending from said feed point toward said opposite end of said series of antenna elements, the outer conductor of said coaxial cable defining one of said first transmission line elements, and the center conductor of said coaxial cable electrically extending from said feed point toward the opposite end of said series of antenna elements to define the other of said first transmission line elements.

Claim 13

The improvement of claim 7, wherein said antenna elements comprise a series of V dipole elements each connected to a respective one of said transposition elements to form an array of V dipoles connected across said second transmission line.