output side feed through section 14 b as shown in fig2 a and 2b the output side feed through section 14 b is formed by a through conductor that operates as the signal line 18 the upper dielectric 17 a and the lower dielectric 17 b the upper dielectric 17 a and the lower dielectric 17 b being typically made of ceramic output side micro strip lines 37 39 are formed on the lower dielectric 17 b the characteristic impedances of each of them as viewed from the input side or the output side are determined by the electrostatic capacity it produces with the grounded metal plate 13 and the inductance component of its own the input side feed through section 14 a has a configuration substantially same as the output side feed through section 14 b more specifically the signal line 18 is sandwiched between the upper dielectric 17 a and the lower dielectric 17 b that are typically made of ceramic and surrounded by the conductors of the metal frame 12 and the grounded metal plate 13 the width wif of the input side feed through line 31 is reduced if compared with the width wim of the micro strip lines 30 31 at the part thereof that is surrounded by the metal frame 12 in order to make that part show an impedance substantially same as the preceding and succeeding parts thereof see fig2 b fig3 a shows the input side feed through section 14 a when the characteristic impedance is 50 u03c9 taking the thickness of the lower dielectric 17 b the line width wif of the input side feed through line 31 is about 0 4 mm and the line width wim of the micro.