29.08.2013 Views

DESIGN AND ANALYSIS OF ANALOG FILTERS A Signal ...

DESIGN AND ANALYSIS OF ANALOG FILTERS A Signal ...

DESIGN AND ANALYSIS OF ANALOG FILTERS A Signal ...

SHOW MORE
SHOW LESS

You also want an ePaper? Increase the reach of your titles

YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.

A <strong>Signal</strong> Processing Perspective 305<br />

where the zeros, and the poles, may be, and in general are, complex,<br />

then consider the results of the lowpass-to-bandstop transformation.<br />

Case I<br />

Consider the case where is real. To determine the corresponding bandstop<br />

filter poles, let<br />

It follows that<br />

or the two poles corresponding to the one lowpass prototype pole, are<br />

Theoretically, could be real however such will not be the<br />

case for practical bandstop filters. Therefore, consider<br />

Also, note that since the numerator as well as the denominator of the transfer<br />

function is multiplied by in order to form the above quadratic equation, it<br />

follows that two transfer function zeros are introduced at<br />

Therefore, each real pole in will yield a pair of complex conjugate<br />

poles in . as developed above, and two zeros at Note that if<br />

> > then the imaginary part of those complex conjugate poles will be<br />

approximately<br />

Example 9.17<br />

Suppose and It follows that<br />

will be the resultant poles, and there will two zeros at<br />

Section 9.4 Lowpass-to-Bandstop Transformation<br />

.

Hooray! Your file is uploaded and ready to be published.

Saved successfully!

Ooh no, something went wrong!