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- Different coefficients calculation methods for CIC filters using in orbit subblocks

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02-27-2019 05:52 AM

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In orbit and time base plot (simulated) sub blocks such as "OAT convert to even angle signal" , "OAT order magnitude and phase", etc it is needed to design CIC (cascaded integrator comb filter) and to calculate the coefficients of these filters various methods are implemented such as window method (using kaiser window), using park- Mccllelan method , or simply using convolution theorem to design a proper filter regards to their application (interpolation or decimation). But how the designers decide to choose one of these methods for calculating the CIC filter coefficients? Is it related to interpolation or decimation factors or does it have another principles?

I will appreciate if any one help me in this case.

Regards

02-28-2019 09:58 AM

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Hi mahsayazdanian, and welcome to the forums!

I've attached some documentation regarding the functions you mentioned, as well as for a cascaded integrator comb filter. It may help to clarify what you're looking for here--are you wondering how to implement these functions?

OAT Convert to Even Angle Signal VI Help

OAT Order Magnitude and Phase VI Help

Cascaded Integrator Comb Filters (Digital Filter Design Toolkit) Help

Claire M.

Applications Engineering

National Instruments

Certified LabVIEW Developer

Applications Engineering

National Instruments

Certified LabVIEW Developer

02-28-2019 10:15 AM

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Hi

Thanks for the reply. Actually I ve read these help documents before . In fact I want to know which parameters are taken into account to decide which methods of calculating the CIC filter coefficients( such as park McClellanmethod , window method like using Kaiser window etc) are appropriate use ?

Regards

03-01-2019 12:51 PM

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Hi mahsayazdanian,

Since this is internal information about the development of NI's software, I'm wondering what design considerations on your end require this information? If there's a requirement you're trying to build around, then we can see what information we can provide to get you pointed in the correct direction.

Nick Smith

Product Support Engineer

C Series Controllers

National Instruments

Product Support Engineer

C Series Controllers

National Instruments

03-01-2019 11:26 PM

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Hi

thank you for the reply. I'm trying to learn digital filters such as CIC filters based on what National Instrument decided to design these kinds of filters by implementing various coefficient calculation methods. For example I want to understand the demodulation technique ( order magnitude and phase block in LABVIEW) in case of how to select the appropriate CIC filters and how to select the best way for calculating their coefficients. As another example,It is confusing for me how I can decide to use various kinds of filters such as CIC compensation filter in "OAT demodulation with decimation " block. Specially a block named "OA_Get CIC decimation filter coefficients" which calculates the coefficients of CIC compensation filter by Park-Mccllelan method whereas the Kaiser window method is implemented to calculate the CIC LP truncation filter coefficients.

Actually I understand that my question may be somehow complex and it is related to the details of LABVIEW software information but since I choose NI as a reliable reference to understand the practical implementation of using digital filters so I will appreciate if you help me in this case.

Kind regards

Mahsa