Continue to Site

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.

Register Log in

Total harmonic distortion in filter?

Status
Not open for further replies.
S

spbhu

Member level 2
Joined
Dec 5, 2005
Messages
42
Helped
0
Reputation
0
Reaction score
0
Trophy points
1,286
Activity points
1,601
For a high order filter(e.g. 4th order), if a specified THD <-60dB is required, how do we design each stage to meet this requirement? i.e. how large THD the first stage required, and how large THD the second stage required? Is there any paper make analysis on this topic? thanks for help...
 

It depends on how you design the filter. If you are going for an active-RC implementation, the most important thing is your amplifier. Try to make that as linear as possible. The stages are usually ordered by amount of gain (bigger gain stage first) and Q (lower Q stage first) so it might be better to leave it like that.
 

You must understand the factor affecting THD. Any nonlinearity can contribute to THD. For example, The amplifier need enough gain and bandwidth to get good linearity. You can use matlab model to estimate the performance of filter before design.
 

Some more points,
If the filters transfer function is not flat, it will change the THD at the output.
Mind the noise of the filter, it may decrease your SNR and effectively decrease your THD
 

Higher Q has sharp edge which can suppress the higher harmonic. But the higher Qalso introduces the higher group delay. so is there any trade off between Q and THD.
 

Status
Not open for further replies.

Similar threads

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Back
Top