Both voltage and current baluns can be derived from the shunt-series, equal-delay hybrid, but the voltage balun is known to be superior for broadband dipole antennas. To understand this behavior, it is necessary to distinguish between balance and symmetry. Both voltage and current baluns exhibit the appropriate balancing behavior as is shown here. However, the current balun lacks symmetry when driving high impedance loads. This is shown for the general case using analytical models, and for a representative shunt-series, equal-delay-hybrid configured as both balun types using numerical simulation and measurements. Additionally, it is shown that while the voltage balun provides symmetry it does not provide true voltage balance when the constituent transmission lines are not electrically short. While the current balun provides poor symmetry, it provides ideal current balancing action throughout a midband region, even if the constituent transmission lines are not electrically short. A broadband dipole antenna exhibits a high input impedance below its fundamental resonance. For this reason, the voltage balun topology provides better symmetry than does the current balun with antennas such as a 1.4-m biconical. The asymmetry manifests itself in vertical polarization measurements and is demonstrated with a vertical polarization inversion test using two 1.4-m biconical antennas.

中文翻译：

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源自并联、等延迟混合的平衡网络的性能

电压巴伦和电流巴伦都可以从并联串联、等延迟混合器中获得，但众所周知，电压巴伦更适合宽带偶极子天线。要理解这种行为，有必要区分平衡和对称。电压和电流巴伦都表现出适当的平衡行为，如图所示。然而，电流巴伦在驱动高阻抗负载时缺乏对称性。这显示了使用分析模型的一般情况，以及使用数值模拟和测量配置为两种巴伦类型的代表性并联串联、等延迟混合。此外，还表明，虽然电压巴伦提供对称性，但当组成传输线不短路时，它不会提供真正的电压平衡。虽然当前的巴伦提供较差的对称性，它在整个中频带区域提供理想的电流平衡作用，即使组成传输线没有电气短路。宽带偶极天线表现出低于其基本谐振的高输入阻抗。出于这个原因，电压巴伦拓扑结构比具有天线（例如 1.4 米双锥）的电流巴伦提供更好的对称性。这种不对称性在垂直极化测量中表现出来，并通过使用两个 1.4 米双锥形天线的垂直极化反转测试来证明。电压巴伦拓扑结构比带有天线（如 1.4 米双锥）的电流巴伦提供更好的对称性。这种不对称性在垂直极化测量中表现出来，并通过使用两个 1.4 米双锥形天线的垂直极化反转测试来证明。电压巴伦拓扑结构比带有天线（如 1.4 米双锥）的电流巴伦提供更好的对称性。这种不对称性在垂直极化测量中表现出来，并通过使用两个 1.4 米双锥形天线的垂直极化反转测试来证明。