chebyshev filter -3db point

[franticEB]

hello I would like to create a bandpass filter in the range 7-15 kHz in which the points at 5 and 18 kHz are attenuated of 3dB, with 0.1dB ripple.
Now as for the butterworth answer i can easily carry out the calculation, but I can not figure out how to find the -3db points in the case of the Chebyshev response.
Could you give me some help?

 

[kripacharya]

sure.... there are several tools available which can make this easy for you.
I have a few on which I could run your specs, but first I need to know your input/ output impedances ?
And also what Q of inductors you can use ... the value range is likely to be in the range of 100uH - 5mH

 

[LvW]

hello I would like to create a bandpass filter in the range 7-15 kHz in which the points at 5 and 18 kHz are attenuated of 3dB, with 0.1dB ripple.
Now as for the butterworth answer i can easily carry out the calculation, but I can not figure out how to find the -3db points in the case of the Chebyshev response.
Could you give me some help?

If you use some tools which are available for designing filters you should be aware of the following:
In particular, for filters with Chebyshev response it is common practice to define the bandwidth according to the allowed ripple.
That means: In you case, the bandwidth is specified between the first and the last frequency that is 0.1 dB below the maximum possible magnitude.
More than that, you have to decide if you like to create a passive RLC or an active RC filter.

 

[franticEB]

i'm using matlab to obtain the transfer function...
so i understand that the points @ 0.1db will be 7 and 15Khz...
@ -3db there is 8 and 19khz.
is it possible to define the -3db points in this kind of filter? thanks

 

[LvW]

i'm using matlab to obtain the transfer function...
so i understand that the points @ 0.1db will be 7 and 15Khz...
@ -3db there is 8 and 19khz.
is it possible to define the -3db points in this kind of filter? thanks

To define or to find?
I don`t know the meaning of "in the range 7-15 kHz". This should be specified in the text for your work.
In case, you are required that at 7 and 15 kHz, respectively, the magnitude is 0.1 dB down - and at the same time at 8 and 15 kHz, respectively, 3 dB down, you have to find a filter order that is able to fulfill these requirements. But I don`t know the exact wording for your homework.