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A helix whose arm is composed of a uniform section and a tapered section, referred to as a UT helix, has been analyzed using the method of moments [1]. The analysis shows that the tapered section contributes to the reduction of the reverse current traveling toward the feed point. This reduction generates a radiation beam with almost purely circular polarization. It has also been revealed that the...
The antenna characteristics of helices for the normal and axial modes [1] have been theoretically revealed using numerical techniques. However, little theoretical analysis has been performed for revealing the antenna characteristics of the conical mode [2][3]. With this background, this paper presents the antenna characteristics of the conical mode helix. The antenna characteristics presented here...
The authors' papers [1][2] have revealed that a monofilar helix antenna radiates a circularly polarized wave. The diameter of this helix is increased from the bottom to the top. In contrast with this structure, this paper presents a monofilar helix whose diameter is decreased from the bottom to the top [3]. This antenna is called a conical helix antenna.
A dual-band metahelical antenna that has a negative phase constant for the current on the helical arm is realized. A left-handed circularly polarized (CP) wave is obtained within a specific frequency band and a right-handed CP wave is obtained within a different frequency band. The antenna characteristics, including the radiation pattern, gain, and input performance (VSWR) are presented and discussed.
A novel helical antenna, designated as the metahelical antenna, is proposed, where the helical arm has electromagnetic right-handed (RH) and left-handed (LH) properties. The antenna design process is described. It is found that the metahelical antenna radiates a circularly polarized (CP) wave within two frequency bands. The rotational sense of the CP wave within one of the frequency bands is opposite...
A wire composite helical-spiral (CHES) antenna fed from the central point of its bottom is investigated, where the number of helical turns is selected to be extremely small (one turn). The CHES is designed such that it radiates a circularly-polarized tilted beam under the condition that the diameter of the CHES is smaller than that of a corresponding tilted-beam spiral antenna. It is found that the...
This paper presents a spiral antenna backed by a mushroom-shaped EBG reflector. The antenna characteristics are investigated on the basis of the electric and magnetic fields obtained by using the finite-difference time-domain method. The investigation reveals that removing some patches from the EBG reflector improves the axial ratio.
A circularly polarized (CP) wave radiation beam tilted from the direction normal to an antenna plane can be obtained using spiral [1][2] and loop antennas [3]. However, little theoretical analysis for the tilted beam from a helical antenna has been performed. This paper fills this gap and a CP tilted beam is obtained using a tapered short helical antenna. The frequency responses of the axial ratio...
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