Is there a complex coefficient IIR filter VI?

IIR filter VI will take a complex signal in, but it doesn't look (or act) like it takes complex coefficients.
Is there an IIR filter VI that does use complex coefficients?
--Mark

The FIR and IIR filter VIs only accept real-valued inputs. When you wire an array of complex numbers into either of these VIs, or any other VI that accepts only double-precision numeric inputs for that matter, the complex values are simply coerced to doubles by taking the real component.
LabVIEW doesn't have any FIR or IIR filters capable of handling complex values directly.
Jarrod S.
National Instruments

Similar Messages

Reset an IIR Filter with new data

hello one and all, i am creating waveforms and pumping them into an IIR filter. at times the parameters of the experiment change and i want to reset the data that the IIR filter is drawing off of so that it is calculating from scratch. i know about the reset input of the IIR filter, however, it is for redesigning the filter coefficients, etc., as stated in the labview help file. so how do you tell the IIR filter that the waveforms coming in are now a new set of waveforms?
thank you in advance.
lucas

Hi Lucas,
I assume you are using the Digital IIR Filter.vi. The logic is not immediately obvious on the diagram of the instances of this VI, but there are two sorts of reset that can happen, namely a coefficient redesign, and a filter state reset. The coefficient redesign happens when either:
1. It is the first time the VI has been called
2. The reset control (on Digital IIR Filter.vi) is true
3. The dt value of the waveform changes from the previous iteration
4. The design specifications change from the previous iteration.
The filter state reset (which is what you want I think) will happen:
1. If there has been a coefficient redesign
2. If the timestamp of the last point of the previous waveform does not match the timestamp of the first point of the current waveform + dt. This is basically an assumption of continuity of the waveforms over consecutive calls to the VI.
I think you have two choices to get the behavior you want. First, you can use the continuity of the waveforms as a way of controlling the reset of the filter state. When you want a reset, then make the current waveform discontinuous. The second option would be to use the lower level VIs on the signal processing->filters->IIR palette. This allows you to explicitly separate the design and implementation of the filter on your diagram, with explicit reset control on the filter states.

O/p of butterworth filter and o/p of butterworthcoeff- cascade coeff- IIR filter is different?

Hello All,
I am designing a system wherein i need to make use of a IIR butterworth Low pass filter .
I tried implementing the same in Labview using 2 methods:
1st method:
Selected Signal processing-->Filters-->ButterworthFilter.vi
Got the o/p.... attached image 1--> Waveform
2nd method:
Selected Signal processing-->Filters--> Advanced IIR filter-->ButterworthCoefficients.vi-->CascadetoDirectCoefficients.vi -->IIRfilter.vi
Got the o/p...attached image 1--> Waveform Cascade Coefii
Both the o/ps differ from in each other if you apply for order 5, LPF, cut off: 35...samples : 250000....
Could you please let me know what difference is there in selecting either of the filter designing way.....
Please reply back asap as im stuck here and am confused....also im new to signal processing....so not sure abt the error im making...
Thanks in advance...
PSADSP
Attachments:
output difference.JPG ‏46 KB

Afternoon PSADSP,
I would dare to say it is possibly your implementation of these VI's that is giving you a difference in your results. The "Butterworth Filter.VI" uses the "Butterworth Coefficients.VI" and the "IIR Cascade Filter.VI" as sub vi's to do its thing.
Have another look at there VI's and post back if you still having issues.
regards
Richard
Richard S
Applications Engineer
Certified LabVIEW Associate Developer
National Instruments UK&Ireland

IIR filter, not contiguous, signal processing

Hello!
I am acquiring data countinuously from several voltage output sensors. I am sending the waveforms through an express vi filter (bandpass) and I am using the default setting for IIR filtering. The program is setup such that data acquisition is done with a while loop. The DAQ wile loop is inside of a bigger while loop which is related to program start and stop.
Every time I am doing data acqusition through the filter I get a warning that tell me the waveforms are not contiguous. Again, this is not flagged as an error but rather as a warning. The attached example might clarification.
The question is: is the IIR filter uses previous waveform information to judge the current waveform? If this is true, then I do not like the solution; if this is not true, the I should probably just ignore the warning...
Does the express vi has some type of reset that would activate when the whole program stops because I do not see the warning message first time I start the vi?
Thanks
Attachments:
FIlterCase.zip ‏58 KB

Thank you for your answer.
From your answer I deducted that whenever I restart the data acquisition while the main program is still running I'd better make sure I reset the filter such that it will now "know" that it is new data coming in. I did not have a chance to check inside the express vi yet but from what you are saying it must be some sort of reset button in there that I could 'pull out' in the connector block of the subvi..
The band widths I am using are anywhere between 100 Hz to 40000 Hz so the transient duration will be short to very short and the system, the way it is setup now, will allow enough time to the IIR filter to handle correctly new data.
Finally there is always the option to acquire just the raw data. later I could read it back and filter it if necessary. However, there are situations when I want to filter out noise and possible alising frequencies; moreover, I acquire vibrations and forces in the same time on the same board - if I need the 40kHz sampling rate for vibrations, automatically I will have it too for the "low end" signals as well (0 to 10V from power and force sensors). I believe doing some filtering and maybe some decimation after filtering will help me keep the amount of data low on the 'low end' signals side. Am I correct in my assumptions?
Thanks again.

IIR Filter without using a loopm t

I'm trying to apply an IIR filter equation to a large array and for this reason I don't want to use a FOR loop - because it takes forever to get through the array. Is is possible to do this using array functions? I have done similar things for FIR filters but it's the use of previous output values that has me stumped.
Can anybody help?
Thanks,
Ken

Ken,
There are two VIs that should be available to help with this. Look for IIR Cascade Filter.vi and IIR Filter.vi. Both implement the filter with the coefficients being inputs. The difference is in the layout of the coefficients. IIR Filter.vi uses direct form, IIR Cascade Filter.vi uses cascaded 2nd or 4th order stages. The layout for both structures can be found in the online help.
-Jim

Passband IIR filter does not have correct cutoff

I am trying to implement a bandpass filter using the digital IIR filter vi. The input comes from a signal generator and the output is displayed as a waveform on the screen of my PC. When I test it out by varying the frequency of my input, the cutoff is always not where I programmed. Does anyone know what could be wrong? Is there some limitations of the software filter which could explain this phenomenon?
Thanks
hlseck

What is the amplitude of the desired signal (the 1 kHz signal)? Can it change frequency? If so, how much?
The amplitude of the desired signal is around 0.5V.The frequency can change by around 20Hz.
What is the nature of the undesired signal(s)? Single tone interference? Multiple interfering tones? Broad band noise?
The noise is broadband noise from electronics circuit.
What are the amplitude(s) and frequency(ies) of the interferring signal(s)?
I am not aware of the amplitude of the interfering signal but the frequency would be broadband.
How much attenuation of the desired signal is
acceptable? Can you amplify it after the filter? Is the phase of the
signal important? If so, how much phase shift can be tolerated?
The attenuation of the signal is not so crucial as it can be amplified but the phase is important. As the filter signal will eventually be used to drive an external circuit, any phase shift would reduce the accuracy. My computer is acting as the feedback since I am not using any hardware, my pc is actually filter the input signal and feeding it back to the system. So any delay or phase shift would not be undesireable.
How much of the interfering signal can the system
tolerate after the filter? Or, How large must the output signal to
interference or noise ratio be?
My estimate is that the interfering signal be -10dB below the desired signal.

Is there an easy way to filter a 2-d array based on the values of two of the fields?

Is there an easy way to filter a 2-d array based on the values of one of the fields. In my attached VI the output array has the following format:
TimeStamp        Ident                Frame Type        Bytes    Data
10:57:07.621   3AD00016   CAN Data Frame   8          0000000000000000
10:57:07.622   3AD00017   CAN Data Frame   8          000005E000000000
10:57:07.624   3AD00018   CAN Data Frame   8          0000000003300000
10:57:07.625   2DC00000   CAN Data Frame   8          0000000000000000
10:57:07.626   3AD00019   CAN Data Frame    4         0000030000000000
I would like to delete any rows that do not have an "Ident" between the values of 3AD00000 and 3AD0001E. So for the above data the fourth row would be deleted. The only way I can see to do it is to form a 1-d array. Is there a better approach?
Thank you.
Solved!
Go to Solution.
Attachments:
CMM_SN_MULTI.vi ‏20 KB

Hi chuck72352,
after you have sorted your data, you can use the InRange Function. Combined with a "search 1D Array" you'll get the range you really want.
Mike
Attachments:
ArraySubset.PNG ‏25 KB

Product Delivered Status Date should be there in Standard Search and Result screen of Service Order. Product Delivered Time should be Available in Result screen and In Result screen there should be facility to filter on basis of Time

Hi team,
Product Delivered Status Date should be there in Standard Search and Result screen of Service Order. Product Delivered Time should be Available in Result screen and In Result screen there should be facility to filter on basis of Time.
How to add this in search result screen.configuration is it possible? or any changes in development.
Compnent - BT116S_SRVO
Thanks
Kalpana

Hi Kalpana
Please reread my comment. I said to try and populate "Requested End" Date.
Make sure the date profile assigned to the transaction includes this Date Type.
If you can populate this either manually or programmatically the solution should be quite forward.
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IIR filter for multiple ATD data

I have 3 ATDs simultaneously sampling. The digital IIR filter works on the first board data of 16 waveforms. The second and the third ATD data do not get filtered at all. They just output zero for all the channels. I tried different instances of the IIR filter to be used with different ATD data and the result is the same. If I turn off the digital filter, then the data shows up correctly.
Please help.
Thanks,
Narayana

Hello Nadim,
Thank you for replying. In fact I just came from the lab after solving the problem. Yes, it is an analog-to-digital board - with 16 inputs. All these boards are tied together with respect to sampling-using a synchronization cable. the ATD board is what NI used to call PCI-MI0-16E-4. During my troubleshooting, I realized that the data coming from the first board has a t0 and dt value in the waveform attributes. The other two boards did not have these two attributes - they were zero. Once I gave the waveforms the proper dt and t0 value, the IIR filter could operate on the waveforms. So the problem was solved.
But thank you for replying. If I did not make myself clear above, I can post an image of the code.
Thank you,
naroowal

How to design a stable IIR-Filter for FPGA?

Hi, I´m new to Labview for FPGA and currently trying to design a lowpass-filter (for a digital mixer, more or less). It should work with a sample-frequency of 200kHz, a passband edge frequency of 3Hz and a stopband edge frequency of 8Hz. An FIR-filter would have a too large order to be implemented, an IIR one seems more practicable. For the design of the filter I'm using the digital filter design toolkit, refering to its manual and the casestudy with analyzing, modeling, simulating and generating a fixed-point filter. Now, I have problems to get a stable filter. While the manual states to adjust the coefficents by trial and error, the designed filter never matches the floating-point reference. Does anyone have experience in creating such filters? Or a hint, how to optimize the coefficient finding process?
Thanks in advance!
thilo

LabVIEW FPGA 8.20 does include a Butterworth filter function (1st, 2nd and 4th order) in the FPGA palette. You can configure it directly using a dialog on your FPGA diagram. The cutoff may not be quite as sharp as you want but it could be an option for you to consider. Once you have configured the filter VI, you have the option of opening up the subVI with the code that is generated based on your filter parameters, which would allow you to further configure the code directly.
I have attached the configuration dialog with the settings you specified.
Message Edited by Christian L on 11-16-2006 09:27 AM
Christian Loew, CLA
Principal Systems Engineer, National Instruments
Please tip your answer providers with kudos.
Any attached Code is provided As Is. It has not been tested or validated as a product, for use in a deployed application or system,
or for use in hazardous environments. You assume all risks for use of the Code and use of the Code is subject
to the Sample Code License Terms which can be found at: http://ni.com/samplecodelicense
Attachments:
filterdialog.JPG ‏44 KB

Is there a bug in Automator filter finder items?

I'm trying to do a batch processing script and there seems to be a bug with items created earlier in the script. For example, the 2brokegirls.jpg file was created earlier in the script and added to the main folder whose contents can be seen in the get folder contents action at the top. however, the filter finder items misses that item when filtering by the extension ".jpg" which as you can see obviously appears at the top. Is this a bug in Automator? My guess is that the filter is using some spotlight indexing and that index hasn't been updated since the file was just added. Does anyone know of a workaround?
Thanks.

I also have this problem. I am getting literally hundreds of emails each day althoug i have clicked all the radio buttons to not receive any emails in "my preferences... email notifications. THis is gumming up my Ipad, Iphone and email in box Help!!

Is there a way to sort/filter hinting?

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Ottonomy, here's what to do.
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Is there a alternative for the filter oil paint?

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Design of direct form IIR Filter

while designing IIR filters(dirtect form coeff) using advanced IIR filtering VIs, i hv found that for a given filter spec,the coeff generated by LV and matlab are different in some cases specially higher order filters. The direct coeff. of a 6th order butterworth bandstop filter, fL=65 Hz and fH= 222Hz, when used in matlab showed a considerably different respose than LV, and the step response when evaluated in matlab turned out to be unstable. can someone explain the discrepancy. Thanks.

It sounds like they are just using different algorithms. I would suggest e-mailing into the NI support, with the Matlab script and the LabVIEW VI you are using. They may be able to find out where or how the two algorithms differ.

Is there an alternative to Column Filter?

Hello,
Is there any function that can do a similar job as the "Filter function" of a column does, say, a search function that search the list, because for some reason I don't want to use the filter function.
Thanks a lot!

Hello,
You can use query string parameters to perform wildcard filtering against columns that you ordinarily could not filter on. This is similar to a search.
Try doing something like this in your address bar:
[page url]?FilterName=[internal name of field to filter on]&FilterMultiValue=*[text you want to search for]*
With a little bit of JavaScript/HTML in a content editor web part, you can add a "search box" to your page which really just filters against a specified field using that query string manipulation.
<input type="text" style="width:50%;" id="search_input" onkeydown="javascript:if(event.keycode==13){ApplyFilter()}" />
<a style="font-weight:bold; display:inline-block; text-decoration:none; background-color:#9b9b9b; color:white; padding:4px; margin:1px;" href="javascript:ApplyFilter();">Search</a>
<script>
/* This regex part puts whatever you just searched for into the text box after every search */
var filtervalue = new RegExp("[\\?&]FilterMultiValue=([^&#]*)").exec(window.location.href);
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var value = filtervalue[1].substring(1,value.length-1);
document.getElementById("search_input").value = unescape(value);
function ApplyFilter(){
var term = encodeURI(document.getElementById("search_input").value).replace('&','%26');
window.location.replace('http://yoururl.goes.here/yourpage.aspx?FilterName=FieldYouWantToSearch&FilterMultiValue=*'+term+'*');
/* in the preceding line, replace the URL with your actual page URL, and replace FieldYouWantToSearch with the internal name of the field you want to search on */
</script>

Is there a complex coefficient IIR filter VI?

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