对于矩形孔径，空间谱是一个三角形函数，具有两倍孔径的支撑区间。

For the rectangularaperture, it is a triangle function with a support of twice the aperture width.

其原因很容易看出：单程电压方向图只是孔径函数的反傅立叶变换，对于均匀辐射来说，它是孔径宽度的矩形脉冲。

The reason is easy tosee: the one-way voltage pattern is just the inverse Fourier transform of theaperture function, which for uniform illumination is a rectangular pulse of thewidth of the aperture.

当该方向图被平方为双程方向图时，该平方方向图的傅立叶变换是未平方方向图的傅立叶变换的自卷积。

When that pattern issquared to get the two way pattern, the Fourier transform of the squaredpattern is the self-convolution of the Fourier transform of the unsquaredpattern.

因此，矩形孔径函数与其自身进行的卷积运算得到一个两倍孔径宽度的三角函数。

Thus, the rectangularaperture function is convolved with itself to give a triangle of twice theaperture width.

圆形孔径的空间谱具有相同的宽度，但比较平滑。

The spectrum for thecircular aperture has the same width but is somewhat smoother.

这些理想但典型的天线方向图的空间谱是低通函数。

The spatial spectraof these idealized, but typical, antenna patterns are lowpass functions.

因此，观测数据的空间频谱中的高频部分将被强烈地衰减，实际上表现为被有效地滤除。

Thus, the upperfrequencies in the spatial spectrum of the observed data will be stronglyattenuated and in fact effectively removed.

由于分辨率与带宽成正比，式（2.121）和图2.28表明，天线方向图由于具有强低通空间频谱特性而降低了分辨率。

Since resolution isproportional to bandwidth, Eq. (2.121) and Fig. 2.28 show that the antennapattern reduces resolution because it has a strongly lowpass spatial spectrum.

2.7.3. 随距离变化

2.7.3. Variation with Range

——本文译自Mark A. Richards所著的《Fundamentals of Radar Signal Processing（Second edition）》

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