Re: Wave filter question (mainly for Joerg)

Hello Joel,


Simple question on wave filters, that I've heard about but never used: Rumor has it that wave filters are just the digital simulation of a classical L-C (ladder-type) filter structure. True?


Yes. You'll have to first design the analog structure and then transfer it. I don't know of any other design methodology.


I skimmed the TI application note on DTMF detection using wave filters, and there's an awful lot of unfamiliar (to me) material there. Somewhere I have a print out of some IEEE tutorial on the subject, but I can't place my hands on it at the moment.


Most of the stuff I have is in German so I guess that wouldn't help you. Professor Fettweis published his famous 1986 paper "Wave Digital Filters: Theory and Practice" which is still considered "the WDF paper". I don't have it but if you have access to IEEE-Explore you should find it.

I could send you some info about WDF. If interested let me know your real email address but it needs to be one where you can receive a huge file. Might be until tomorrow to get to the stuff though.

The design program I am using is the one from Professor Mildenberger:
http://www.ite.fh-wiesbaden.de/~mildeno/
Download links are at the page bottom but you'll need at least some elementary knowledge of German and a dictionary next to the keyboard. Also, if it's still the old stuff it'll be DOS-based. Mine is an old licensed copy that I bought but now it's free AFAIK.

There is also WDF design SW at Texas Instruments, from the group around Dr.Ulrich Kaiser. I only got it under the condition not to distribute but they told me that others can ask TI support for it. I like the Mildenberger SW better (but I understand German...)

Just don't expect any exhaustively documented software or fancy user interface. It's more like bare-bones race cars assuming you know how the fire extinguishing and all that works :-)


What I'm really after is trying to find efficient (in terms of, e.g., multiply/accumulate cycles) tone detectors...


WDFs are pretty good at that if you have to do it on budget hardware, IOW when there are no leather seats and hardware multipliers. They are also very stable in the presence of disruptions, something that needs extra tricks on classical digital filters (but can also be done there).

Goertzel is another option as Tim mentioned. However, they will quickly clog your processor when you need to detect more than a handful of frequencies simultaneously. You'd have to "price out" whether a full FFT might be better in terms of economy.

Regards, Joerg

http://www.analogconsultants.com
.

Relevant Pages

  • Re: Modelling Interference Filter Performance Using Zemax and Encrypted Coatings Files
    ... light incident on the filters can have varying amounts of non-random ...  This variation in incident polarization will have an effect ... I'm using Zemax as a design tool and trying to estimate/calculate the ...
    (sci.optics)
  • Re: PWM in a switching power supply
    ... to switching power supply design. ... filters, feedback systems, principles of power systems, EMC, ... If consumer pushed bean counters to reduce costs, ... some sell power supplies only using cost ...
    (sci.electronics.basics)
  • Re: filter design
    ... > Suppose I want to design a digital filter for some application. ... is relatively simple but does not necessarily provide "good" filters. ... I am not sure how good the matlab implementation ... a nonlinear conjugate gradient optimization method. ...
    (comp.dsp)
  • Re: Arbitrary frequence response
    ... Do you know how to design FIR filters by ... The OP probably meant "implementation efficiency" - it ... matlab function FIR2 is a filter *design* function. ...
    (comp.dsp)
  • Re: FH Wiesbaden: Prof.Mildenberger?
    ... schnellebigen Branche Ewigkeiten. ... Die Leute in Asien hatten es tatsaechlich fertiggebracht, die ganze Steuerung da drin in einen 8051er Kern zu zwaengen. ... Die Unbekanntheit von WDF und das Nichtvorhandensein gescheiter Design Software dafuer ist einer der Gruende, ...
    (de.sci.electronics)
Quantcast