PURPOSE: To obtain a fixed resistance attenuator having comparatively satisfactory frequency characteristics by inserting the resistors of ≤1/8 wavelength in series between transmission lines with a distance of a 1/4 wavelength compared with the using frequency.

CONSTITUTION: The 3rd transmission line 32 is put between the 1st and 2nd transmission lines 30 and 31. These lines 30∼32 have the same line impedance and are connected with each other by the 1st and 2nd resistors 33 and 34 having ≤1/8 using frequency. In this case, the electrical length of the 3rd transmission line 32 is selected at 1/4 using frequency so that its impedance is equal to the pure resistance in terms of both resistors 33 and 34. For instance, the impedances of lines 30∼32 are set at 50Ω with the resistance values of resistors 33 and 34 set at 20Ω respectively. Thus a 4∼6GHz using frequency band is secured together with 3.5dB insertion loss and 20dB reflection loss 20dB respectively.