| 摘要 |
PURPOSE:To avoid the frequency change against temperature change, by selecting the linear expansion coefficient due to temperature so that the expansion and compression of a metallic rod fitted in parallel with a supporting rod through clipping the supporting rod of an inner conductor between outer conductors can be cancelled with that of the supporting rod. CONSTITUTION:A temperature compensating device 6 consisting of metallic rods of left and right pair which clip a supporting rod 4 and lead in parallel with the supporting rod, is provided to the lower outside of an outer condutor 1 of a coaxial type filter consisting of the outer conductor, inner conductor 2, inner conductor expansion and contracting metallic fixture 3, inner conductor supporting rod 4 and a fixing metallic fixture for the supporting rod 4. Taking the length of the supporting rod 4 at a temperature T as la, the length of the device 6 as lb, the change in the supporting rod 4 and the device 6 as + or -DELTAla, + or -DELTAlb,when the temperature changes by + or -DELTAT, then the length of the inner conductor 2 is as expressed in equation. By selecting the linear expansion coefficient of the metallic rod 4 and the device 6 so that + or -DELTAla - or + DELTAlb=0 can be obtained, the length of the inner conductor 2 is not changed against the temperature change, resulting that the tuning frequency of a coaxial filter is not changed, allowing to make stable the characteristics of the filter. |
