Hi,
I need to design a 4th order bandpass filter which has 10kHz cut-off frequency and 5kHz bandwidth with Chebyshev.
I am using "Practical Analog and Digital Filter Design, Les Thede, 2004" for working on the priniciple of filter design, but i stucked in a place.
I attached a photo about determining the order of the filter, but i don't know what is the meaning of alfa-pass and alfa-stop values. Can you help me about the meaning of these values, what do these values correspond?
Thanks for your help!

 

hi MU,
This link may help to define those parameters.
https://en.wikipedia.org/wiki/Chebyshev_filter



E

 

Alfa-pass? How about omega-pass and omega-stop - both of which are given in the problem.

 

Alfa-pass? How about omega-pass and omega-stop - both of which are given in the problem.

As far as i know, omega-pass and omega-stop determine the rising and falling speed, and it is defined as rad/sec.

 

As far as i know, omega-pass and omega-stop determine the rising and falling speed, and it is defined as rad/sec.

No, that is not correct. If it makes it any easier for you, try omega-passband/bandwidth and omega-stop/cutoff frequency.

 

... It appears that there are two different types of Chebychev filters ... The above diagram is for the type two version. ...no passband ripple, but some in the stopband.

 

Alpha is for attenuation. As in maximum attenuation in the passband, which limits the ripple. It's how filter specs are written.

 

Thanks for your answers,

This helped me about designing my circuit but there is one thing still i can't understand,

If i make cascade connection of two Sallen-Key or four Multiple Feedback topology, then i have a 4th order filter but what is the thing which determines the difference between Butterworth and Chebyshev?
I mean i know difference between Butterworth and Chebyshev at graphics or usage areas, but what is the mathematical definition of this difference, because at the end, Response function of Sallen-Key is stable, which value does create a ripple at Chebyshev?

 

The derivation of the Butterworth characteristic starts with the requirement for maximal flatness. The requirement for maximal flatness leads to a condition on most of the derivatives of the transfer function that they disappear. The Chebychev chracteristic allows some of those derivatives to be non zero which leads to ripple in the passband.

Here is the wiki on Butterworth:
https://en.wikipedia.org/wiki/Butterworth_filter

For a more in depth treatment I suggest:
Van Valkenburg,M.E., Analog Filter Design
https://www.amazon.com/Analog-Filter-Design-M-E-Valkenburg/dp/0030592461/ref=sr_1_fkmr0_1?ie=UTF8&qid=1482106249&sr=8-1-fkmr0&keywords=Van+Valkenberg,+M.E.,+Analog+Filter+Design