结果表明，在保持增益不变的情况下合理选择主反射面的焦距是能够达到降低雷达散射截面的需要的。

The conclusion shows that reasonable selections of the focal distances of the main reflector may be able to obtain low RCS, keeping the high-gain under the antenna unchanged.

youdao

之后，通过合理控制前固定组球差及后固定组焦距，使变焦过程中的像面保持稳定。

Then, image surface position was kept steady during a zooming process by controlling the spherical aberration of front fixed group and the focal length of back fixed group.

youdao

之后，通过合理控制前固定组球差及后固定组焦距，使变焦过程中的像面保持稳定。

Then, image surface position was kept steady during a zooming process by controlling the spherical aberration of front fixed group and the focal length of back fixed group.

youdao