INDUCTANCES, CAPACITANCES AND RESISTANCES 



m-derived T sections, which is then divided up to form pi's, in the same 

 manner as classical pi sections may be found from classical T sections. 



Real component 

 of terminal 

 impedance 



m derived section i 

 m =0-6\ 



classical 

 section 



Wc 



w • 

 Figure 5.30 



The band-pass filter — In order to pass a band of frequencies between 

 coj^ — the lower cut-off frequency — and co^ — the upper cut-off frequency — 

 we could of course connect in cascade a high-pass filter section cutting off 

 at cDj^, and a low-pass section cutting off at a>2, the sections both being designed 

 for the appropriate characteristic resistance R. 



1/2 Ci 



Figure 5.31 



Figure 5.32 



There is, however, a special band-pass section, which is shown in Figure 

 5.31 in the T form, and in Figure 5.32 in the pi form. The design equations 

 are 





2R 



COa 



COi 



(ft>2 — COj)R 



L,= 



C,= 



(cog — a)i)R 



20i^CO2 



CO2 — ft)j 



Vz/Lz 



1/2 /.J 



^ 2ft>ia>2^ 



nmnnnnn 





Figure 5.33 



Figure 5.34 



The band-stop filter — This is a section having the inverse property to the 

 above, in that it passes all frequencies except those lying between a lower, 

 coj, and an upper, co^- In the T form it is as in Figure 5.33, and in the pi 

 form as in Figure 5.34. 



92 



