A bent, crossed‐wire antenna with vertical parasitic elements: Formation of a circularly polarized conical beam

Abstract

SUMMARYA novel crossed-wire antenna backed by a ground plane is proposed and analyzed using the method of moments. Two wires are crossed and fed in phase at the crossing point to radiate a conical beam. To make the conical beam circularly polarized, the crossed wires are bent and four vertical parasitic elements (PE) are added. The antenna is characterized by its simple feed and CP radiation at low elevation angles. First, the effects of the PE location on the radiation characteristics are investigated for crossed wires of a half wavelength. When the PE location is appropriately chosen, the antenna radiates a CP conical beam. Next, attention is paid to CP radiation in a wide range of elevation angle. Calculations show that the angle range where the axial ratio is less than 3 dB increases to 65° from 15° for a changed crossed-wire length. The maximum CP radiation is obtained at an elevation angle of 35°. Finally, the frequency characteristics are studied and the bandwidth for a 3-dB axial ratio criterion is found to be 8%.

Modified Crossed-Wire Antennas Radiating a Circularly Polarized Conical Beam

“…Four bent arms symmetrical with respect to the cross point o′ are backed by a ground plane at height h. e arms are fed at the cross point o′ through a vertical wire o′-o of length h, as shown in Figure 1(c), and the bottom end o is excited by a coaxial line. To obtain CP radiation, four parasitic elements of length h and radius ρ are added symmetrically with respect to the cross point o′ [7]. e location (x, y) of the parasitic element is designated as (d x , d y ), as shown in Figure 1(b).…”

“…e antenna is designed to radiate a CP wave in the maximum beam direction. For this, the parasitic element location (d x , d y ) is appropriately selected [7] using the method of moments [8]. To enhance the CP wave bandwidth, the bent arm length is taken to be twice (2l x + 2l y ) as long as that (l x + l y = 3λ 0 /8) of the original antenna, as shown in Figures 1(b) and 1(d), where l x and l y are element lengths in the x and y directions of the bent arm in the first quadrant, respectively, and λ 0 is the free-space wavelength at a test frequency of f 0 .…”

“…A crossed-wire antenna shown in Figure 1(a)is in a class with the nonplanar antennas having a monopole radiator [7]. e antenna has an advantage over a conventional one [2][3][4][5][6] in that the maximum radiation can be obtained at a lower elevation-angle direction.…”

“…For this, two types of antennas with increased wire length are analyzed using the method of moments [8]; one is a bent-type antenna shown in Figure 1(b) and the other is a spiral-type antenna shown in Figure 1(e), each having wire o-o′ shown Figure 1(c) as a monopole radiator. e radiation characteristics including the axial ratio, beam direction, input impedance, and radiation pattern are discussed and compared with those of the original antenna [7] shown in Figure 1…”

Double‐loop antennas for a circularly polarized tilted beam

“…Since the beam is tilted in the elevation direction of the satellite, there is no need to tilt the antenna plane toward the satellite, leading to full use of a low-profile advantage of the planar antenna. In addition, the antenna has a higher gain than that for a CP conical beam [10][11][12][13], since the beam is formed in the azimuth direction of the satellite. The beam azimuth direction is controlled by two methods; one is an electronic control of the antenna excitation and the other is a mechanical control of the antenna rotation.…”