The low-profile hemispherical helical antenna with circular polarization radiation over a wide angular range

Abstract

Fig. 3(a) displays the measured return loss characteristic for thex-cut version of the LiNbO 3 hi-lo antenna. A measured bandwidth of 9.2% centered at approximately 12.8 GHz was observed, which is slightly lower than the z-cut antenna, but still adequate for most wireless communication systems.The far field radiation patterns at 12.75 GHz for the x-cut LiNbO 3 hi-lo antenna are given in Fig. 3(b). As the LiNbO3 wafer and the brass mounting block were approximately the same dimensions as in the z-cut case, the slight ripple in the patterns is still evident. The F/B ratio was measured to be approximately 26 dB, and a wide 3 dB beamwidth is again observed. The cross-polarization level in each plane of the x-cut LiNbO 3 hi-lo stacked patch was more than 30 dB below the copolarization level at broadside. The gain of the x-cut LiNbO3 hi-lo antenna was approximately 7 dBi. The computed gain differed by less than 1 dB from the directivity for both of the LiNbO 3 antenna structures, illustrating the efficiency of the hi-lo architecture, and implying low surface wave activity. IV. CONCLUSIONTwo hi-lo stacked patch antenna structures have been constructed employing z-cut/x-cut LiNbO3 wafers and a low permittivity foam dielectric. The use of the LiNbO 3 material enables the full integration of the antenna with electro-optic photonic devices. This can reduce the size, complexity and cost of base stations or remote antenna units in applications such as hybrid fiber-radio systems at high microwave and millimeter-wave frequencies. The LiNbO3 hi-lo configuration yields very good impedance and radiation characteristics. The simple nature of the hi-lo structure is compliant with the package requirements for OEICs, facilitating the realization of combined antenna/photonic/ microwave modules. ACKNOWLEDGMENTThe authors would like to thank Y. Visagathilagar, C. P. Wu, and S. Donovan for their assistance in the processing of the LiNbO3 wafers, and D. Welch for the mounting structures. REFERENCES[1] Y. Furuhama, "Research and developments of millimeter-wave technologies for advanced communications," in Proc. 3rd RIEC Symp.Abstract-The low-profile hemispherical helical antenna is studied experimentally and theoretically. This antenna can produce circular polarization radiation over a wide angular range of 90 . The current distribution, the input impedance, the axial ratio, the power gain, and the radiation pattern are rigorously studied. The 3-dB axial ratio bandwidth of a five-turn hemispherical helical antenna is found to be 14.6. In the range of 1 0 1 3, a relatively stable power gain of more than 9 dB is obtained. The radiation patterns typically consist of a large smooth main lobe with almost no sidelobes. These new antenna characteristics have a potential application in mobile satellite communications.

A small hemispherical helical antenna array for two‐dimensional GPS beam‐forming

“…[5] The antenna array was designed using four hemispherical helical antennas [Hui et al, 2003]. The reason to choose the hemispherical helical antenna is that it can produce circular polarization over a wide scanning angle.…”

“…The four antenna elements are placed in a square lattice as shown in Figure 3 to form a planar array with dimensions dx = dy = 0.7l (l is the wavelength at 1.575 GHz) and d 1 = [Hui et al, 2004]. Although hemispherical helical antennas have good circular polarization characteristic, their original design is not matched [Hui et al, 2003]. Here we introduce a slight modification to the original design.…”

“…By adjusting L 1 = 2 mm, L 2 = 37.5 mm, and L 3 = 5 mm, significant improvement in return loss can be obtained. The matching section is to neutralize the large capacitive reactance of the hemispherical part [Hui et al, 2003] by introducing an inductive reactance. The dimensions of this section were found by trial and error using computer simulations.…”

“…Four beams spanning in a two-dimensional (2-D) directional space are produced by the Butler matrix. The use of hemispherical helical antennas as array elements provides circular polarization over a wide scanning angular range [Hui et al, 2003]. The original design of the hemispherical helical antenna is not matched.…”

Analysis on two novel spherical helical antennas

“…The impedance and circular polarization were studied by Safaai-Jazi [2]. A hemispherical helical antenna was proposed by Hui [3,4]. It provides a more robust and low-profile structure.…”