| 摘要 |
1. A bandstop filter for very high frequency transmission lines having distributed constants and being implemented in a planar structure and more particularly in accordance with the microstrip technique, comprising at least a first filtering element (10) and a second filtering element (20), said first element being intented to prevent the transmission of a first frequency band to whose central frequency a wavelength lambda1 is associated and formed by a set of two transmission paths (21, 22) arranged in parallel which separate at the input point (E) of the bandstop filter and are recombined at the output point (S) of this bandstop filter in such manner that the electrical length of these two parts are equal to one quarter and three quarters of the wavelength lambda1 , respectively, and the second filter element (20) being constituted by a quarter-wave filter having an electrical length equal to lambda2/4, connected to the input point (E) of the bandstop filter and defining at this point a short-circuiting plane, the value of lambda2 different from the value of lambda1 being the value of the wavelength associated with the central frequency of a second frequency band which constitutes the band cut by the second filtering element, characterized in that the second filtering element (20) is located within the first filtering element (10) and in that the second frequency band cut by the second filtering element (20) is adjacent to the band cut by the first filtering element (10), such that the different between the central frequencies is small compared with said central frequencies. |
