Questions tagged [digital-filter]

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3
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2answers
2k views

Relationship between order of filter and impulse response?

I see that the slope of the frequency response of a filter (such as the Elliptic, Butterworth...) becomes steeper as its order increases; for instance, a low pass Elliptic filter with an order of N=3 ...
2
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3answers
705 views

Linear Phase Response

In many cases it is demanded that the filter has a linear phase response. (like in case of FIR ). Why linear is so important? Why not constant or anything else(any other shape)?
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3answers
508 views

Physical significance of group delay

What is the physical significance of the group delay of a system/filter?. Why is the slope of the phase response critical in a communication system.
1
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1answer
222 views

Group delay when using a matched filter

Supposing I have a discrete time signal x(n). when I pass this through an FIR filter h(n), and again pass this result through h(n) again (essentially this is a second order filtering), the group delay ...
0
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2answers
576 views

Usage of complex filters in communication

In the last stage of a communication transmitter, at the front end a filter is used to eliminate unwanted signals from other frequencies. As far as I read in literature, are these filters "real" ...
3
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2answers
1k views

Magnetometer tilt compensation without accelerometer

I need to use the magnetometer in a device to accurately determine how many degrees the user twists (rotates in x-y plane) it. I don't care about absolute orientation, just the angular delta. Of ...
1
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1answer
800 views

Using a Kalman filter requires a truth value?

I have some accelerometer data that I need to filter and clean. However, based on the online examples that I see, the filter requires what's called a "Truth value". The code is based on this: http://...
0
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2answers
317 views

FIR filter output result Interpretation While input is taken from ADC161S626: 16 bit

I have implemented a 20 order FIR Low pass filter, 1000 HZ cutoff frequency on Sparten - 6 FPGA. First I calculate the coefficients in Matlab, Then I directly put them in vhdl code. Here are my ...
15
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3answers
9k views

Why should I use digital filters for bandpassing rather than simply manipulate signals in frequency domain and then recover them into time domain?

I'm quite a novice for signal processing and I know this question may be too broad. But I would still like to hear hints from experts. I was taught to use butter (...
3
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3answers
9k views

Why is Direct Form 2 (Digital Filters) equivalent to Direct Form 1

According to Wikipedia : The alternate Direct Form II only needs N delay units, where N is the order of the filter – potentially half as much as Direct Form I. This structure is obtained by reversing ...
1
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3answers
9k views

Time delay: digital low pass filter VS analog low pass filter

I am new on digital filter, hopefully I can get some intuitive insights here. So, here is the question: A low pass filter with 5Hz cut-off frequency is to be designed. The signals presented have ...
2
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3answers
923 views

SNR improvement from placing analog filter ahead of digital filter

We have designed a PCB containing a data collection circuit for a customer, and their external expert presents this "helpful suggestion": Question about signal averaging vs. longer integration ...
12
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3answers
8k views

Why too many capacitors in parallel for Vdd supply net? Can't we just add all to replace with one big capacitor?

Here is a schematic of a Basys-2 board's power regulator IC and filters. It is just an example but this is fairly similar to many designs I've seen. Why are there so many capacitors added in parallel ...
0
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1answer
1k views

Finite state machine FSM model of FIR filter in VHDL for FPGA

I want to make a FSM model of FIR, for that I need to write FIR calculation code line in FSM implementation. Here is the actual and correct code for FIR ...
0
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1answer
380 views

Poor man's equalizer with a few digital bandpass filters - how to overlap band edges

I am trying to implement an equalizer in an FPGA. It's not hifi or anything so 3 or 4 bands should cut it. So I have a low, band, and high pass filter covering the entire voice spectrum (0-4kHz in ...
1
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1answer
407 views

What is digital Termination and when is it used?

I have heard transmission line termination but today I came across this "Digital termination" but couldn't find out why is it used and what effect does it have on digital signals?
4
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1answer
159 views

Bireciprocal lattice wave digital filter

I am trying to model a bireciprocal Cauer filter in LTspice but I don't get the expected results. More precisely, using \$\gamma = \frac{re(p_i)-1}{re(p_i)+1} \$ where \$re(p_i)\$ is the realpart of ...
0
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1answer
156 views

How to decide to cuttoff frequecies of filter in case of using ADC( Flow: Analog-signal to ADC to bits to fir_filter to filtered_output) [closed]

FIR filter has to be used for removing the noise. I don't know the frequencies of the noise that might be adding up into the analog feedback signal I am taking. The ADC has takes just a voltage value ...
3
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4answers
2k views

Do digital Anti Aliasing filters exist for traditional ADCs?

I'm currently learning about Analogue to Digital Converters. From what I understand, aliasing occurs if the input signal being sampled has power above the "Nyquist frequency" of the ADC(Sampling ...
-2
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2answers
270 views

Band-pass filter confusion

I'm having trouble understanding the concept of a Band-pass filter. Not, that I have the following signal (in the frequency domain): What I essentially need to do is remove the noise and only keep ...
3
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2answers
274 views

Dedicated digital filter

I have built a DDS (0-80MHz) with an FPGA (XC3S400) that I can program it for making almost any wave form (limited frequency by the wave form complexity). After weeks of struggling with making a ...
2
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1answer
521 views

Low pass Filter on an Analog Signal

I havent had much experience with low pass filters but,I do understand what they do. I was implementing one on an AC signal above. This is a sampled input, and I dont see how would you call the ...
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2answers
112 views

predicting the charcteristics of Filters

I would like to know one thing that say if you know Processor word length(TMS320VC5510 DSP) it accumulator and guard bits can you make a guess about filter characteristics to be used for this ...
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2answers
2k views

How to implement FIR filter for Altera DE2?

I understand that a DSP is preferred rather than FPGA for an FIR filter, but my task is to implement both fixed-point and floating-point software filters (in C) for the Altera DE2. I barely know what ...
5
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3answers
2k views

What are the origins of the window functions in DSP? Why not just use a rectangular window?

As far as I know, in DSP we wish to remove or reduce the effect of some undesired signals by separating its frequency spectrum from the spectrum of the whole signal (our main signal and the noise). ...
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1answer
576 views

Passive and active filter design [closed]

I'm very interested in filter design and would like to learn more about them; however, I don't want to waste my time learning about them if there is no point. I already know the basics of filters and ...
1
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1answer
1k views

Is it possible to compute delay with an IIR filter between peaks?

I am developing a project which receives accelerometer signals as input, which must then be analysed via peak-detection algorithms (among other techniques). In order to do so more effectively, I ...
3
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1answer
454 views

How is noise reduced using a sigma-delta converter?

Perhaps I'm sleepy but I can't quite get my head around how a sigma delta converter takes the noise that is in a bandwidth of (X) Hz and by over sampling spread, that same amount of noise over 2(X)Hz. ...
2
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2answers
1k views

Is Kalman filter suitable for smoothing sound spectrum?

I'm implementing a software similar to a real-time spectrograph with a modified FFT. The output vector summarizes the intensities of various musical tones present in the input signal. Its size is a ...
5
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3answers
7k views

Fastest moving averaging techniques with minimum footprint

I have tried few running averaging techs for smoothing the change in ADC data in AtMega48 for controlling lights(PWM) when rotating a pot(ADC). The filters (pseudo codes): Moving average: ...
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1answer
327 views

Microchip circuit [closed]

I am planning to start designing circuit on microchip but do not know where to start. I will be programming some band pass filter using c++. Any advise on which microchip is better. Hope this question ...