The Helical Antenna
The Helical Antenna
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DOI：
10.1109/jrproc.1949.231279
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发表时间：
1949-03
期刊：
影响因子：
--
通讯作者：
J. Kraus
中科院分区：
文献类型：
--
作者：
J. Kraus
螺旋线是天线的一种基本形式，其中环形和直线是极限情况。当螺旋线与波长相比很小时，辐射最大垂直于螺旋轴。根据螺旋几何形状，辐射在理论上可以是椭圆偏振、平面偏振或圆偏振的。当螺旋周长约为1个波长时，辐射在螺旋轴的方向上可以是最大的，并且是圆偏振的或接近圆偏振的。这种辐射模式，称为轴向或波束模式，在实践中非常容易产生，并且可以在具有期望的图案、阻抗和极化特性的宽频率范围内占主导地位。由于螺旋线上波传播的相速度的自然调整，辐射图案在宽频率范围内保持在轴向模式中。终端阻抗在相同的频率范围内是相对恒定的，因为波在螺旋线上的初始衰减很大。分析了圆极化的条件，讨论了阵列因子在决定长螺旋线辐射方向图中的重要性。
The helix is a fundamental form of antenna of which loops and straight wires are limiting cases. When the helix is small compared to the wavelength, radiation is maximum normal to the helix axis. Depending on the helix geometry, the radiation may, in theory, be elliptically, plane, or circularly polarized. When the helix circumference is about 1 wavelength, radiation may be maximum in the direction of the helix axis and circularly polarized or nearly so. This mode of radiation, called the axial or beam mode, is generated in practice with great ease, and may be dominant over a wide frequency range with desirable pattern, impedance, and polarization characteristics. The radiation pattern is maintained in the axial mode over wide frequency ranges because of a natural adjustment of the phase velocity of wave propagation on the helix. The terminal impedance is relatively constant over the same frequency range because of the large initial attenuation of waves on the helix. The conditions for circular polarization are analyzed, and the importance of the array factor in determining the radiation pattern of a long helix is discussed.