设x[n]是长度为N的序列<img src="http://jgxm-question.oss-cn-beijing.aliyuncs.com/psst/files/44dbfbb9250d4a6897032ef5a7330098.png?x-oss-process=image/sharpen,200"/>，其N点DFT为<img src="http://jgxm-question.oss-cn-beijing.aliyuncs.com/psst/files/b053b8140f2f43678bf709d5ec5d6721.png?x-oss-process=image/sharpen,200"/>，用X[k]表示以下序列的DFT<img src="http://jgxm-question.oss-cn-beijing.aliyuncs.com/psst/files/127134df9b8e4d46bcd7ba1425d9f244.png?x-oss-process=image/sharpen,200"/>