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端射天线基本上是一种线性的连续系统或天线阵,其绩电过程使沿着天线轴流动的相速此光速稍低。这就是行波天线的特殊情况。沿着天线表面传播的延迟波具有几种特点,并被称为表面波。因此,端射天线是表面波天线。本文不可能讨论属于这一类的各种天线。其中某些天线是独立研制的,并已从另一角度予以研究。而另一些天线有其具体的特性,宜做个别研究。第一组天线包括“波道型”天线,尤其是八木-宇田天线。这种天线是作为多偶极子天线来研究的。第二组天线包括螺线天线,它们是典型的旋转极化天线。然而,表面波天线所共有的因素,同样地适用于这些天线。线性的连续系统或端射天线阵的方向性特性取决于延迟α_z/k和天线的长度L。然而,却不能把实际的表面波天线和理想的线性连续系统等同起来。其原因是有几种其它因素影响着天线的特性;这些因素包括表面波馈电和天线末端反射波。这些因素的影响主要表现在方向图所出现的显著的旁瓣状态上(高达有关功率的30～40%)。为了给激发表面波创造良好条件,在天线的有规则部分和馈电点之间做成一个平滑的圆锥体。为了消除天线两端的反射波,延迟结构逐渐减小到零或减至uφ≈C的程度。结果,正
The endfire antenna is basically a linear, continuous system or array of antennas whose performance causes the phase velocity at the antenna axis to be slightly lower than the speed of light. This is a special case of traveling wave antennas. Delay waves propagating along the antenna surface have several characteristics and are called surface waves. Therefore, the endfire antenna is a surface wave antenna. This article can not discuss the various antennas belonging to this category. Some of these antennas are independently developed and have been studied from another perspective. While other antennas have their own specific characteristics, should be done individually. The first set of antennas includes the “channel” antenna, especially the Yagi-Uda antenna. This antenna is studied as a multi-dipole antenna. The second group of antennas includes spiral antennas, which are typical rotating polarization antennas. However, the factors common to surface wave antennas are equally applicable to these antennas. The directivity of a linear continuous system or end-fired antenna array depends on the delay α_z / k and the length L of the antenna. However, actual surface wave antennas can not be equated with ideal linear continuous systems. The reason for this is that there are several other factors that affect the characteristics of the antenna; these include surface wave feeds and antenna tip reflections. The impact of these factors is mainly manifested in the significant sidelobe state of the pattern (up to 30-40% of the power). In order to create good conditions for the excitation of SAW, a smooth cone is made between the regular part of the antenna and the feed point. In order to eliminate the reflected wave at both ends of the antenna, the delay structure is gradually reduced to zero or reduced to the extent of uφ≈C. The result is positive