按频率的高低来划分时，中频（MF，Medium Frequency）是指，频段由300KHz 到3000KHz的频率，多数作AM电台。按其在电路中的位置与作用来划分时：IF中频(Intermediate Frequency)是指高频信号经过变频而获得的一种信号。
The digital IF signal is converted to zero IF by digital down converter, then taken FFT spectrum analysis with Hann window in advance.
数字中频信号首先通过数字混频下变频至零中频，然后作加海窗的复FFT谱分析。
参考来源 - VXI总线宽带数字化监测接收机方案研究To overcome this problem, we think to digitized the signal at medium frequency, even RF, and then demodulate it in digital domain.
为克服这一问题，人们考虑在中频，甚至射频就对信号数字化，再在数字域内进行解调。
参考来源 - 高速数据采集系统的研制According to the block classification, it embedded the watermark into the larger coefficients of the mid-frequency of selected blocks.
水印为二值图像,根据块分类以不同的嵌入强度嵌入到所选择块的中频系数中。
参考来源 - 一种基于DCT的模糊聚类自适应水印算法It should be pointed that the sp~3 content in the DLC films prepared by middle frequency reactive magnetron sputtering technology is not high, hence, their resistance against sand blowing is not enough even though their resistance to corrosion seems good.
中频非平衡磁控反应溅射制备的含氢的类金刚石薄膜的sp~3含量不够高，不能很好的抗击砂尘冲刷；耐腐蚀性测试性能良好。
参考来源 - 中频非平衡磁控溅射制备DLC膜的工艺研究·2,447,543篇论文数据，部分数据来源于NoteExpress
他在过去的几年中频频来这里治疗小儿麻痹。
He had been there frequently in past years for treatment for infantile paralysis.
性话题往往在电视和其他媒体中频频被提到。
It's a topic that comes up on television and in other media.
浏览求职板块，对简历中频繁出现的库有一个大概了解。
Check out the job boards to get a sense of which libraries are showing up frequently on resumes.
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