
Filters and Attenuators 649
13.8.7 Limitations of Constant K-type Filters
The constant K-type filters have mainly the following two limitations:
1. The characteristic impedance of the filter circuit does not remain constant over the pass
band and it is a function of frequency, that is, it varies with frequency.
We know filter gives ideal performance only if it is terminated by a resistance equal to
the characteristic impedance.
Since in constant K-type filters, characteristic impedance is different at different fre-
quencies, a mismatch occurs.
2. Its attenuation does not rise abruptly beyond the cut-off frequency as shown in Figure ...