雷达发展的早期,频率大多远低于毫米波波段,问题主要集中在从地面对飞机的探测和定位上。在几乎所有情况下,干扰都来自雷达接收机的热噪音。在某种程度上,这可以用更大的功率,较长的积分时间和窄带宽加以克服。此外,作用距离一般都很远(50～300英里),对飞机分类也被认为是十分困难的。由于这些原因,早期雷达都倾向于简单的设计。它们的设计特点是大功率脉冲源, The early development of radar, the frequency is much lower than the millimeter wave band, the problem is mainly focused on the ground from the plane’s detection and positioning. In almost all cases, the interference comes from the thermal noise of the radar receiver. To some extent, this can be overcome with greater power, longer integration time and narrow bandwidth. In addition, the range of action is usually very far (50 ~ 300 miles), the classification of the aircraft is also considered very difficult. For these reasons, early radars tended to be simple designs. Their design is characterized by high-power pulse source,