Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

What happens with phase characteristic of an Ideal filter after converting to causal?

Status
Not open for further replies.

doggone

Newbie level 3
Joined
Feb 7, 2006
Messages
3
Helped
0
Reputation
0
Reaction score
0
Trophy points
1,281
Activity points
1,302
Hey what's happening with phase characteristic of an Ideal filter when we convert it to causal filter...
 

mami_hacky

Full Member level 6
Joined
Mar 28, 2002
Messages
337
Helped
18
Reputation
36
Reaction score
11
Trophy points
1,298
Location
Some where
Activity points
3,428
Phase Characteristic

Do you mean that filter phase will not remain linear?
As far as I know in real implementation it is important for the filter's phase to be linear.
As you know the conversion between ideal filter and the casual one is nothing special in real practice. Just some delay elements.
Real filters have also linear phase.
 

Kral

Advanced Member level 4
Joined
Mar 28, 2005
Messages
1,326
Helped
280
Reputation
558
Reaction score
85
Trophy points
1,328
Location
USA
Activity points
13,400
Re: Phase Characteristic

doggone,
Real filters are approximations to the ideal "brickwall" filter. It is possible to obtain exact phase linearity (but not "brickwall" amplitude response) with an FIR digital filter. All you need to do is make sure that the filter coefficients (multipliers) are symmetrical with respect to the middle coefficient. The well-know "moving- average" filter is one example.
~
You can obtain neither exact phase linearity nor brickwall amplitude response with an analog filter. There are several filter types that provide various degrees of phase linearity. The Bessel filter provides reasonable phase linearity over a wide frequency range, but its amplitude response is lousy. Another approximation to an analog linear phase filter is the "equi-ripple" phase response filter. Filter coefficients for these filters are available in the published literature.
Regards,
Kral
 

Status
Not open for further replies.

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Top