An Astounding Digital Filter Design Application

Rick LyonsJuly 7, 201613 comments

I've recently encountered a digital filter design application that astonished me with its design flexibility, capability, and ease of use. The software is called the "ASN Filter Designer." After experimenting with a demo version of this filter design software I was so impressed that I simply had publicize it to the subscribers here on dsprelated.com.

What I Liked About the ASN Filter Designer

With typical filter design software packages the user enters numerical values for the desired filter's parameters such as cutoff frequency, stopband attenuation, etc., hits a "design" button, and is presented with a frequency magnitude response curve and a list of filter coefficient values. If you want to change the filter's frequency-domain performance you have to start over and re-enter new desired numerical parametric values. Not so with the ASN Filter Designer software! Here's why.

With the ASN software, when you first specify your desired parameters you'll see the following main window:

This article is available in PDF format for easy printing

To change the filter's frequency-domain performance you merely use your computer's mouse to click on the little red squares ("Markers") and move them around in the frequency response plot. That will automatically change the frequency response curve and the z-plane pole/zero locations, as well as update the filter's coefficients. No new numerical data entry is needed!

Once a high-order IIR filter is designed it can be converted to a cascade of 2nd-order biquad IIR sections to enable a stable filter implementation using fixed-point arithmetic.

Designing Specialized Filters

The Filter Designer allows you to design specialized filters by way of manipulating the pole/zero locations using your computer's mouse. For example, you can design a lowpass IIR filter and then manually position a pair of conjugate zeros so that they reside at 60 Hz (or 50 Hz) to provide a deep frequency response notch in order to highly attenuate AC power-line spectral noise.

Signal Analyzer Capability

As if the easy filter design capability weren't enough, the software designers also provide a way for the user to specify test signals that are applied to the input of the designed filter. This means you can monitor the output of a designed filter (in both the time and frequency domains) in real-time as you manually manipulate the filter's frequency response 'markers' or z-plane poles or zeros. I know of no other filter design software with that powerful capability.

Filter Scripting Language

Remarkably, the Filter Designer also allows the user to write mathematical scripts that compute the numerator and denominator coefficients of a desired filter's z-domain transfer function. Similar to MATLAB and Octave, this capability enables the user to easily design filters defined by mathematical equations such as the filters described in: https://www.dsprelated.com/showarticle/972.php

Better than I can do here with my words, you can see a videos describing the ASN Filter Designer software at:



The ASN Filter Designer appears to be the Swiss Army Knife of filter design software packages. The software's designers seem to have thought of everything! If you're interested in digital filters, check out this software—you'll be glad you did.


I realize this blog makes me look like a salesman for the ASN Filter Designer software. I'm no salesman, I've written this blog out of pure enthusiasm.

Appendix A: Downloading a Demo Version of the Filter Design Software

At the 


web address, scroll down until you see the following:

To download a demo version of the ASN Filter Designer software, click on the blue down-pointing arrow. The available 'User's Guide' shows how to install the demo version of the software on your computer.

Appendix B: Downloading the User's Guides (Manuals)

At the


web address, scroll down until you see the following:

Click on the '[+] Documents' line item to see the following:

Click on the two PDF symbols to download the two User's Guides.

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Comment by dcomer_backupJuly 26, 2016
I wanted to post a follow-up to my purchase of ASN filter designer. I typically do not like to post "reviews" of purchase transactions as typically everyone is too busy no one cares about specific problems. In this case I think Sanjeev deserves a HUGE amount of credit for responding to my issue and resolving it so quickly. I now have a license (within hours of the PayPal payment) and all is good. Not to take the spotlight from any of Rick's comments about the product (How could I Rick is "the man!") but I find this software to be some of the best I've seen. It is intuitive, has features I have not seen in software at this price and, although MATLAB is the standard, allows entry lever and experienced level DSP engineers the ability to design filters and perform what-if mathematical (and graphical) analysis very easily. I compare this product to another I purchased a few years ago that required a hardware key, that was > $1000. That software did have a code generator, but the cost to performance was dismal in comparison. So, I just wanted say that I am one very happy customer.
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Comment by dcomer_backupJuly 18, 2016
I agree with Sanjeev and did not intend on discouraging ordering the product, quite the contrary; Sanjeev has been very helpful and responsive in attempting to resolve the issue I am having. I do not know why the banks in my area discourage SWIFT transfers. I would really like to see ASN filter designer do well. From a personal order point of view, the ordering process is a bit challenging and I simply wanted to provide feedback as I feel, as Rick originally pointed out it is, "An Astounding Digital Filter Design Application".

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Comment by biomedical_engineerOctober 11, 2017

hi Dave i just need an arm cmsis ıır example . can you just send me the code?

i am an student and cant afford the software. dont know what to do. any examle is okey for me . İ can adjust it


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Comment by dcomer_backupOctober 13, 2017

Don't we all? There are plenty of references for designing filters (Google IIR Filter CMSIS), or, spend some time with CMSIS DSP documentation, I think you will find it's easier than you think. What is not so easy are the coefficients for the filter and that depends on the filter specification you are targeting. So, instead of asking me to your homework, do a bit of research on CMSIS, If you cannot afford AFNFilter Designer, download a free copy of Octave or SCILAB and Google a bit. 

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Comment by JesswadeNovember 17, 2021
Don Lancaster's Active Filter Cookbook is a classic for op amp filters. Specific op amp types will become obsolete, but this is a decent cookbook approach to designing and using active filters using PayPal payment methods. It's still available, and multiple pdf copies showed up when I googled it just today.
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Comment by asnJuly 26, 2016
Just to give you all an update as to the ordering status with credit cards. We have now created a PayPal account (Dave was our first client), and can now accept all major credits, Paypal and of course Wire transfers. We look forward to hearing from you!!

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Comment by dcomer_backupOctober 13, 2017

And a very satified customer indeed. Especially with the CMSIS update. Pole/Zero display is one aspect, being able to dynamically drag the poles and zeros to custom tailer a filter is very nice, scripting, and the other features of this software, I value. I throught about writting my own program do some of what ASN has accomplished, but realized that my time is better spent on deveoping embedded software and focusing on the algolrithms. The price of ASNfilter designer is a fraction of what MATLAB costs (if you are paying for the commercial version of MATLAB), and the time spent writing, debugging, and enhancing a program that does what ASN Filter Designer does exceeds to cost of the product. To those that want to roll their own, go for it. I find high value in that ASN Filter Designer does. My Opinion of course.

Oh, and Sanjeev listened to my issues on the payment process and promptly resolved them, I have just upgraded to version 4.x and moved from the educational version to professional version after deciding I loved the software.

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Comment by dcomer_backupJuly 7, 2016
Hi Rick. I am going to order a copy of this software. I agree, it is very user friendly and the fact that you can script, See the updates real-time wow. Let me know if you receive your commission check :) All kidding aside, thanks for taking the time out to point this product out.

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Comment by kazJuly 8, 2016
It is nice tool for beginners play but there are some free zero/pole editors around anyway.
I wouldn't buy it for serious work as I can use Matlab etc to same effect. It is not useful for advanced filter designers of say equalisers, multirate systems and techniques of reducing resource at implementation.
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Comment by asnJuly 8, 2016
Kaz: many users have told us that the tool's interactivity cuts down development time compared to Matlab, and the tool's matlab output means that a designed filter can be quickly integrated into a matlab algorithm . Regarding advanced filter design: I would kindly ask that you have a closer look at the scripting language. Thanks.
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Comment by napiermJuly 10, 2016
Kaz: I have a program I wrote in 1989 in Pascal to do some of what is in this program. Specifically, the ability to add arbitrary zeros in the stop band while have the pass band be equ-ripple. Very handy in instrumentation with harmonics of power line and VLF/ELF trying to get in. If there is a Matlab script that will do the same thing I don't know about it.


Mark Napier
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Comment by dcomer_backupJuly 15, 2016
Rick, I attempted to purchase this software, and the person (I assume the author) I was dealing with was very polite and responsive, but they required a SWIFT transfer of funds to the Netherlands which many banks either discourage or charge a hefty fee. I then tried Western Union and that was a but impossible in my experience. I did use the free version and really like the educational aspect of the software and the intuitive design. I have to believe this software is going to be expanded with more advanced features. I agree MATLAB is better for more advanced designing.That said, I am not sure why the author does not offer a simple way to purchase the software as others do around the world. I think this software was well written and would be much more accepted especially in the educational to beginning market segment purchasing were made easy. Later, an advanced design upgrade would be a no brainer.


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Comment by asnJuly 18, 2016
Without focusing too much on finances rather than the product itself, I thought that it may help if I provided some more details about the difference between the US and the European banking concept.

My understanding is that in the US credit cards are the preferred way of purchasing products/services, but it’s too bad that (although SWIFT is supported) wire transfers are discouraged by US banks. This is quite different to Europe where wire transfers are the norm, and all personal/business bank account packages offer international wire transfers in all major currencies as standard. Funnily enough, credit card payments are discouraged due to the extra costs involved.
For the moment we hope that ‘discouraged’ is not interpreted as ‘impossible’, since we have successfully sold licenses to a few US corporations. In addition, please bear in mind that all clients outside the EU are VAT (value added tax) exempt, which is in essence a 21% discount. This discount should cover a majority of the bank service costs.

We’ll look closely over the next month or so for an alternative solution that is closer to the US/Canada market concept.

Regards, Sanjeev.

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