机箱内天线匹配：理论与原理

　　机箱内天线匹配：理论与原理

　　开发无线产品可能是一项艰巨的任务。在设计和开发过程中，有许多陷阱、陷阱和常见的错误。将天线的实现保存到最后是很常见的。事实是，天线使你的产品无线。它是发射信号进入太空的最关键部件。通常很少考虑天线位置以及附近的物体如何影响它。这不仅对产品的性能，而且对进度和成本都是毁灭性的。

　　天线是其环境的函数。无论是坐在办公桌上，在制造商的开发板上，还是在产品中，所有这三种情况都会导致不同的性能。与设计中的大多数元件不同，它可以在电路上产生预期的效果，天线受到周围所有事物的影响。天线的辐射电磁场与附近的材料相互作用，可以改变其工作频率。天线必须放置在其最终环境中，阻抗匹配，使其工作在所需频带内。一个不匹配的天线可以降低你的链路预算10-30分贝和严重减少范围。所有天线，不管是现成的还是实验室设计的，都可能需要匹配。

　　To understand why an antenna is affected by objects near it， how an antenna radiates must be reviewed. First， forget about what is happening to the antenna or what is nearby. What is important is the input impedance to the antenna. Examining the dipole in Figure 1， when a potential is applied to the antenna inputs， there is opposite charge buildup on the ends. Essentially the dipole ends can be viewed as open circuits， with a high voltage and no current. Due to the charge buildup at either end of the dipole， current begins to flow. As you move from the end of the dipole inwards towards the feed point， the voltage falls and the current rises. At the feed point， the current reaches its peak along with some now reduced voltage. The ratio between the voltage and current at the feed point is the input impedance to the antenna. This is the impedance that drives the antenna performance. Additionally， since there is current flow on the antenna， electromagnetic fields are radiating.