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一、概述在无线电计量中,截止衰减器是衰减计量的一种主要的标准器。我院于1980年建成的30MHz一级标准截止衰减器,是一段工作在截止频率以下的圆波导,波导中一端装有激励线圈,由30MHz信号源激发起以H_(11)波型为主模的电磁波,波导的另一端为接收线圈。波导内的场强按指数规律变化。在线性工作段,衰减改变量A是接收线圈与激励线圈之间距离改变量△l的线性函数:A=a·△l(1)式中,a是该波导的衰减常数,单位是dB/mm;△l是长度量,单位是mm。a主要由长度和频率两个基本物理量决定的。由于截止衰减器与长度计量关系密切,所以温度将直接影
I. Overview In radio metering, cut off attenuator is a measure of attenuation of the main standard. Our hospital built in 1980, 30MHz first-class standard cut-off attenuator, is a part of work in the cut-off frequency below the circular waveguide, the waveguide is equipped with an excitation coil at one end, excited by the 30MHz source H_ (11) wave-based model Of the electromagnetic wave, the other end of the waveguide for the receiving coil. The field strength inside the waveguide changes exponentially. In the linear work section, the attenuation change amount A is a linear function of the distance change Δl between the receiving coil and the exciting coil: A = a · Δ l (1) where a is the attenuation constant of the waveguide in dB / mm; △ l is the length of the amount, the unit is mm. a is mainly determined by the two basic physical quantities of length and frequency. Due to the close-end attenuator and length measurement closely, so the temperature will be directly affected