Questions tagged [digital-filter]

A digital filter is a system that performs mathematical operations on a sampled, discrete-time signal

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Digital Signal Processing vs. Analog Signal Processing for 100kHz DAQ project

I have a dumb question to ask (for a lot of you) but it has been bugging me for a while and I need someone who can give me a clear answer... (I'm a second-year in electrical engineering) So, I am ...
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2 votes
1 answer
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Filter signal on oscilloscope using math functions

Is there a way to do a time domain low pass filter, in software, on a Siglent SDS2000X Plus series oscilloscope using these math functions? The ones that stand out the most are ...
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Adaptive Particle Filter: unknown process Equation

In my design and implementation of a SIR particle Filter, I don't have the state process equation of the actual system, which would have given a very good estimation of the real signal. I was ...
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decimator circuit using dflipflops

I am studying about DPLL. There are questions among CDR papers written by the same researchers. Is the symbol likes step symbol after Adder a quantizer? The output of Decimator by factor 2 is -1,0,+1 ...
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Laplace of third-order lead-lag filter

For Butterworth low-pass filters, the Laplace function of the third-order filter is $$ H(s)= \frac {1}{\left(1+\frac{s}{\omega_c}\right)\left(1+\frac{s}{\omega_c}+\frac{s^2}{\omega_c^2}\right)} $$ ...
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How to implement digital filter that will attenuate the voltage over certain ranges in my voltage-temperature plot

I have a temperature sensing circuit that has a "somehow linear" output voltage over the range 20-80 °C. I plan to use an 8-bit ADC to have a digital representation of the voltages. However,...
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Is there a way to convert a time delay into a sample delay?

I have been given a time delay of a signal and the sampling frequency, however, I am trying to calculate the delay in samples. My logic is: delay frequency divided by sampling frequency, however, this ...
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Digital filters that can be applied to both static and dynamic measurements

Is there a digital filter that can be applied to both static and dynamic measurements WITHOUT changing the parameters of the digital filter? For example I made a temperature measuring device that can ...
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3 answers
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Creating a digital PLL

I want to drive a quartz crystal resonator at its resonant frequency so I need to stay locked on to its resonant frequency as its resonant frequency changes. I'm using an FPGA to do this. I want to ...
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IIR digital filter: samples not matching the frequency response

I am working on a small project in Mathematica involving a Chebyshev 4th order highpass filter, trying to obtain its digital IIR filter with the bilinear transformation. I implemented the differential ...
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1 answer
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Apply S-Domain Notch to Time Signal

I have a signal in time domain which shows an 8Hz oscillation. I've designed a notch (band-stop) filter in frequency domain (S domain) to filter this 8Hz oscillation. Notch design parameters are Width,...
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Software filter for load cell readings

I looked through lots of questions, but I didn't find a suitable answer for the project I'm working on. The project can be thought of as a simple control box, water valve, and scale. The mcu control ...
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How to identify low pass, high pass, band pass, and band stop filters?

I'm taking a course dealing with signal processing which includes filters. In a certain task I got these two filters h and g: These parameters are given: A1=159 A2=138 theta C = 0.26pi N=337 Both ...
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1 vote
1 answer
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How to properly implement an IIR High-Pass filter with a cut off frequency ~20Hz

I am trying to implement a digital High-Pass filter (IIR) with a cut off frequency around ~20Hz on a STM32H753ZI with the CMSIS DSP API. Every time I try to go test it, the output is no longer ...
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Why using a pi filter when the applied voltage is DC?

We had to simulate this circuit for an assignment but I still don’t understand why c1, c2, c3 are used in this converter. Are they used as a filter?
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2 votes
1 answer
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MATLAB filter designer giving out filters with huge DC gains

hope y'all beings safe out here and doing well. I am trying to create a single stage biquad (2nd Order) butter worth filter using MATLAB's filter designer tool. Just to see, I tried plugging back the ...
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5 votes
3 answers
312 views

Simple low pass digital filter implementation for non-uniform sampling?

I have a system sampling an analog input and I want to filter that value using a simple, first order filter. EG something of the form: Yn = A*Xn + B*Yn-1 However I have no control over the ...
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DC filtering for digital audio amplifiers

I am working with digital amplifiers and from what I can see there is a DC blocking filter that is placed at the start of the signal chain. Why is this DC filter placed at the start of the signal ...
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1 answer
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Filter for rotary encoder

I'm attempting to use PID for DC motor control. The motor is geared, with a magnet on the motor shaft coupled with a single hall effect sensor to help measure speed. This is all wired up to a capture ...
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How to draw SPL curve for a parametric equalizer?

I want to show (graphically) the Gain/Attenuation vs frequency of a parametric equalizer. This is my circuit: https://sound-au.com/project28.htm The same schematicas as a screenshot: I want to show ...
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1 answer
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Low Pass filter using Parrallel components

I have a PCB design that I need to add a low pass filter. However I can only add components in parallel. It is going to be very difficult to cut the tracks or add components in series. Is there any ...
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Are there advantageous situations when we cascade filters by descending Q-factor instead of ascending?

We usually cascade filters in ascending Q-factor to avoid saturation in each individual stage. But are there advantageous situations when we cascade filters by descending Q-factor?
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Exercise relating to FIR filter [closed]

I was trying to resolve a problem from "Understanding Digital Signal Processing". I have some questions about it. Why do we need to redesign the filter if we find out that the sample rate is ...
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Laplace transform to Z-transform for filter design

I was given an answer to the following question I can't understand, that how is the Impulse Invariance transformation of $$\frac{(s+a)}{(s+a+jb)(s+a-jb)}$$ is $$\frac{(1-e^{-aT} cos(bT) z^{-1})}{(1-e^{...
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1 vote
1 answer
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RC filter impulse response is exponential decaying but inverse Fourier is Sinc function

As we all know that the inverse Fourier transform of a frequency domain unit pulse/rectangular function (which looks like low pass filter) is Sinc function. So, I was under the impression that any low ...
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2 answers
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Relationship between latency and sampling rate of a digital PID controller

I am trying to set up a fast digital PID controller. The error signal is read by an ADC and sent to an FPGA. The FPGA uses a PID equation to compute the integer sent to the DAC. At the moment I am ...
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Bilinear transformation: why does it cause a deformation on my filter

So I'm designing a Butterworth 4th order highpass digital filter. I developed all my equations (I can put them here if it is relevant) and arrived to this graphs for the frequency response. In red ...
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4 answers
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Is an MPU capable of equal quality digital synthesis as a dedicated DSP chip? [closed]

Is there any factor which would cause a modern microprocessor ( such as an ARM Cortex A/M ) to be inferior at performing digital synthesis compared with a dedicated DSP chip of comparable speed? At a ...
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why should I use NYQ(Nyquist Frequency) to get the propoer value of the cutting frequency in high or low pass filter? [closed]

I am working on signal processing using filters (basic,IIR,FIR) but I didn't quite got the intuition behind the next operation when I am performing a high pass filter with the cut frequency defined as ...
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Matlab Digital filter not working, how come?

Before reading any further, to give you on some insight on the output level of the oscilloscope picture's the ~340mV green signal is normal. If you know me I posted a question as to why its 340mV but ...
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1 vote
1 answer
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Output signal is being attenuated after the Biquad filter direct Form 1, why?

Thought this would deserve a separate post on its own. What's going on is that I finally got my low pass digital filter working on the STM32H753ZI using the PMODI2S2 peripheral and I noticed the ...
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4 votes
1 answer
152 views

DSP low pass filter (IIR) no longer works when changed to a new MCU

I am having troubles understanding why a DSP low pass filter was that working on the M4 is no longer working on an M7. I recently switched over to a STM32H753ZI from a STM32L432KC. In addition to ...
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0 votes
1 answer
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Sampling and Filtering

In my system I measure signals with interesting bandwith from DC to 2 kHz. I have an analog low-pass filter with 200 kHz cutoff frequency in order to filter noise. The ADC samples the signal with 500 ...
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1 answer
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What are the challenges of designing high Q digital filters?

I am not familiar with digital filters and digital signal processing. I do know that implementing an analog filter with a high quality factor is not practical, because (please correct me if I'm wrong) ...
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Why is the prewarping not working as it should?

Just playing around with the 'c2d' command from matlab and trying to convert a continuous 2nd - order lowpass Butterworth function to a digital one which has the specs of Fc = 20e3Hz and Fs = 44....
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0 votes
3 answers
453 views

Digital filtering after analog to digital conversion (ADC)

I am making a PCB that receives a signal with a frequency band of 3-50 Hz and peaks of up to 10's of uV. I have implemented proper analog LP and HP (band-pass) filters and am using a 16-bit isolated ...
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1 answer
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Digital control stability for more than impulse response stability?

I have a digital control system which is described by the transfer function $$ Y(z) = \frac{-\beta}{z - 1 + k \beta} X(z) $$ where \$\beta\$ is a real parameter I can adjust to modify the ...
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1 answer
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Software oscilloscope

I have been developing a C language software for software oscilloscope which is part of a control software. From timing point of view the software consists of two execution loops. The first execution ...
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1 answer
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Why does this part of an OLED filter light only when orientated correctly?

Note: The screen is an OLED screen. I had assumed it was LCD, therefore the post mentions it as such. I was disassembling a Samsung phone (GT-I9305) and was able to seperate the LCD into two sections....
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2 votes
0 answers
145 views

How to amplify the output of a digital low pass filter?

I have used the transfer function of a RC low pass filter to design a IIR Digital low pass filter. \begin{equation} H(s)= \frac{1}{sRC+1} ;First \space order \end{equation} \begin{equation} H(s)= \...
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3 votes
4 answers
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How to pick correct filter for a given signal processing task?

I did a study on digital signal processing and I found many theories. But I don't know how to figure out which filter to use when I get a practical signal processing task. Is there a procedure for ...
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1 vote
5 answers
822 views

Calculate cutoff frequency of a digital IIR filter

I have an ADC with 1 kS/s and would like to append a digital anti-aliasing filter to it as I have to downsample the data to 10 Hz. As it's on an FPGA and I don't have any multipliers, I thought ...
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4 votes
1 answer
117 views

How to make my difference equation make the deadline constraint?

Back at it again. STM32L43KC Datasheet: The question this time is I am finally starting to implement my digital filter which can been see as: Z - Transform: $$LPF_D=\frac{Y}{U}=\frac{0.3957z^2+0....
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0 votes
2 answers
77 views

Truncation noise in digital circuits

I was reading a chapter of my book (I am not putting it as reference since it is not in english) about the quantization noise problem in digital filters. Specifically, it writes about a filter that ...
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1 vote
2 answers
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"Order" of a digital filter (FIR and IIR)

I have some doubts about the meaning of order for digital filters. All I'll put here is taken from these slides. 1) Let's start from the definition of FIR filters: From this definition we see that ...
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3 votes
2 answers
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Physical operations of discrete - time circuits

I have a basic doubt about discrete time circuits. A discrete - time signal is a sequence of values which are taken at specific time instants (let's call them sampling instants), as we can see from ...
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2 votes
2 answers
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Doubts about IIR filters definition and transfer function

I have some basic doubts about IIR digital filters. My first question is about its definition. IIR means Infinite impulse response, so my question is: is it physically possible to realize such ...
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1 vote
0 answers
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Converting an analog Butterworth filter into a discrete filter

Here again to ask about another question. This time asking how to convert an analog transfer function to a discrete transfer function using standard continuous to discrete methods. The application ...
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5 votes
2 answers
4k views

How can I design a low pass filter using Z transform in Microcontroller?

I have generated a signal which is a mixture of 50 Hz and 250 Hz sine waves using a microcontroller and DAC. Check the screenshot of the excel file: The values of row 4 (i.e. f1+f2) are feed to an 8-...
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When to choose ZoH method over Tustin in Discrete design?

Hey guys I am kinda confused as to which method to pick from, in terms for a digital filter. Which method is appropriate for this application and how did you come to pick it? I want to convert a ...
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