波长为1～10 mm(对应的频率为300～30 GHz)的电磁波称之为毫米波。在此波长范围的电磁波有一系列突出特点,如可用的频带宽、传输的信息量大、方向性强、抗干扰能力强以及传播损耗小等,因而在雷达、通信等领域具有广泛的应用前景。迄今,对毫米波的应用研究已有40多年的历史。早在第二次大战期间,美国就研制出可供实用的毫米波速调管。50年代,毫米波器件得到相当大的发展, Wavelength of 1 ~ 10 mm (corresponding to the frequency of 300 ~ 30 GHz) of electromagnetic waves called millimeter wave. The electromagnetic wave in this wavelength range has a series of salient features, such as available frequency bandwidth, large amount of information to be transmitted, strong directivity, strong anti-interference ability and small propagation loss, and thus has broad application prospects in the fields of radar and communications. So far, the application of millimeter wave has been more than 40 years of history. As early as the Second World War, the United States developed a useful millimeter-wave klystron. In the 1950s, millimeter-wave devices were considerably advanced,