球面上共焦点之椭圆、双曲线，在球心投影中仍投影成共焦椭圆、双曲线。

The cofocal ellipse and hyperbola of spherical surface will also be projected into the cofocal ellipse and hyperbola in gnomonic projection.

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在共焦椭圆情况下，当频率较低时，本文结果与准TEM波分析结果趋于一致。

The results of this method are in agreement with those calculated in quasi-TEM case in low frequency for confocal ellipses.

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该文从能量守恒观点出发，讨论了副面为椭圆的环焦天线的口径场分布，并导出了计算其方向图的简单表达式。

The aperture field distribution of the ring focus antenna is reviewed in view of the energy conservation law, and the simple formula for calculating its radiation pattern is deduced.

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