The Helical Antenna

Helical Antennas in Satellite Radio Channel

“…It is found (Kraus, 1949) that, although (3) and (4) are different in form, the patterns (1) and (2) for entire helix are nearly the same, and the similar could also be stated for the dielectrically loaded antenna. Furthermore, the main lobes of E θ and E ϑ patterns are very similar to the array factor pattern.…”

“…Ideally, applying (6)-(8), the radiation characteristics of the helical antenna and the antenna geometry can be directly connected by single variable, the velocity v of the surface wave (Kraus, 1949;Maclean & Kouyoumjian, 1959;Nakano et al, 1986;Wong & King, 1979). As the wave velocities in a finite helix are hard to calculate, those calculated for the infinite www.intechopen.com helix can be applied as a fair approximation.…”

“…We may observe three regions: the exponential decaying region away from the source, the surface wave region after the first minimum and the standing wave due to reflection of the outgoing wave at the open antenna end. The works of (Klock, 1963;Kraus, 1948Kraus, , 1949Marsh, 1950) showed that the approximate current distribution can be estimated assuming two main current waves, one with a complex valued phase constant settled in the region of normal mode (m = 0) that forms a standing wave deteriorating antenna radiation pattern, and one with real phase constant in the region of the axial mode (m = -1) that contributes to the beam radiation. The analytical procedure of a satisfying accuracy for determining the relationship between the powers of the surface waves traversing the arbitrary sized helical antenna may still be sought using a variational technique, assuming the existence of only two principal propagation modes (normal and axial), and a sinusoidal current distributions for each of them taking into account the velocities calculated for the infinite helical waveguide, as shown by (Klock, 1963).…”

Multiband Multimode Arched Bow-Shaped Fractal Helix Antenna

“…The low impedances (solid-R in = 35 Ω-65 Ω, dash-X in = −20 Ω-+20 Ω) are very approximate to 50 Ω in quad-bands, which means four matched bands can be obtained easily with 50 Ω coaxial feeding. Compared with the empirical formula Z in = R in ≈ 140 · C λ given by Kraus [24] for a side-fed CHA, K 2 ABFH antenna has lower value due to impedance transformation of fractal geometry and coaxial cable. Z in can be further tuned to 50 Ω with an extra quarter wavelength of impedance transformer beneath the ground plate or tapering initial segment of the fractal helix wire.…”

“…Cylindrical helix antenna (CHA) was invented by Kraus in 1946 [23][24][25]. It has two operation modes of circular polarization: normal mode [26] and axial mode.…”