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已研制成一种地下探测雷达,它采用6毫微秒单周期脉冲,具有甚高频频谱。这种雷达能从地表面上非接触地探测地下情况,并通过天线的扫描,显示出大地断面的彩色图象。本文研究了这种地下探测雷达的探测能力,并给出了试制样机的实验结果。首先是在关东地区肥泥土层的地下进行了电磁脉冲穿透性实验,结果证明电磁波在地下的传播速度大约为大气中的1/6(5.4厘米/毫微秒)。其次是用这种雷达探测地下埋设的钢管(直径10厘米),它能清晰地显示达3米的深度。由这个实验也知道了大地的衰减率为6分贝/米左右。同时表明,钢管即使是铺设在柏油路下,也能探测到。混在雷达图象中的噪声和杂波信号可用简单的信号处理电路除去。最后,本文还给出了即使在大地的电气常数为未知的场合下,也能算出物标的位置、深度和电磁脉冲在地下传播的速度的方法。
A ground-based detection radar has been developed that uses 6 nanosecond single-cycle pulses with very high frequency spectrum. The radar detects ground conditions non-contactly from the ground surface and shows a color image of the earth’s cross-section through the scanning of the antenna. This paper studies the detection ability of this underground detection radar and gives the experimental results of the prototype. The first experiment of electromagnetic pulse penetrating underground in the clay soil layer in the Kanto region showed that the propagation velocity of electromagnetic waves in the ground was about 1/6 of the atmosphere (5.4 cm / nanosecond). The second is the use of such radar to detect buried steel pipe (10 cm in diameter), it can clearly show the depth of 3 meters. It is also known from this experiment that the decay rate of the earth is about 6 dB / m. At the same time, it shows that steel pipes can be detected even if they are laid under the asphalt road. The noise and clutter signals mixed in the radar image can be removed with a simple signal processing circuit. Finally, the paper also gives a method of calculating the position, depth and speed of electromagnetic pulses propagating in the ground even when the electrical constant of the earth is unknown.