A novel method for a single-feed circularly polarized (CP) loop antenna with both broad impedance bandwidth and axial ratio (AR) bandwidth is presented based on characteristic mode analysis (CMA). The circular polarization characteristics are generated by exciting two orthogonal degenerate modes (DMs) via single feeding simultaneously. The 90 phase difference is achieved by loading the lumped inductors or capacitors. The wide bandwidth characteristics are generated by splitting a pair of DMs. Consequently, the two overlapping resonance points are split. The positions of feeding and loadings are determined with the aid of CMA. Compared with conventional methods, the presented method can simplify the feeding structure and provided a compact antenna. Based on this method, a loop antenna with two inductors is demonstrated for circular polarization application. The measured results show an impedance bandwidth of 47% and 3 dB AR bandwidth of 8.3% at 2.4 GHz wireless local area network (WLAN) bands. Both the simulated and measured results agree well.

Abstract-A hybrid method is developed to compute the radiation pattern of antennas on large complex three-dimension carriers. The hybrid method involves computing the radiation fields of the antenna in free space with FEM, characterizing the reflection and diffraction of the carrier to the radiation fields with CRE (Complex Ray Expansion) and UTD (Uniform Theory of Diffraction). The ray technique of SBR using traditional hybrid method is employed by CRE. The shortcomings of the SBR, such as great number of ray trace, distortion and partly shadowing of the rays etc., are overcome by the use of CRE, and the time consuming physical-optics-type integration is replaced by the paraxial approximation of the complex rays. A dipole placed on different carriers are taken as the examples to show the validity of the hybrid method, and the radiation patterns computed by the proposed method are in good agreement with those by FEM. By using the proposed method, the computation of the three dimension radiation pattern of an antenna in a large ship is finished by a PC in 1671.20 seconds.

In this paper, a new method based on characteristic mode analysis for designing wide-beam antennas is proposed. According to theory of characteristic modes, the total radiation pattern is the linear combination of modal currents. The phase of the excitation coefficient is demonstrated to be the characteristic angle. To get a wide-beam pattern, a fundamental mode and an even mode are selected to be excited and combined. The method is verified by the proposed antenna. First, two modes are selected based on characteristic mode analysis. Then the modes are excited separately using different feeding networks. Lastly, a 1-to-3 power divider is proposed to combine the feeding networks. The proposed antenna has a 3-dB beamwidth of over 200∘ in both 45∘ and 135∘ planes. The results have shown that the proposed antenna is suitable for a wide range of detection applications.

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