Questions tagged [digital-filter]

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

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2answers
69 views

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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1answer
60 views

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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1answer
64 views

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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1answer
56 views

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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3answers
266 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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1answer
45 views

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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1answer
60 views

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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0answers
39 views

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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1answer
57 views

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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1answer
46 views

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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1answer
46 views

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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29 views

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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1answer
123 views

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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2answers
77 views

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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34 views

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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4answers
110 views

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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1answer
61 views

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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2answers
103 views

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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1answer
66 views

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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1answer
132 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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1answer
58 views

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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1answer
72 views

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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0answers
103 views

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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3answers
206 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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1answer
57 views

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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1answer
105 views

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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1answer
174 views

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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0answers
102 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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4answers
730 views

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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5answers
602 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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1answer
113 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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2answers
49 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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2answers
55 views

“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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2answers
46 views

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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2answers
141 views

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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30 views

How do I write a requirement of an asynchronous input signal, when the sampling clock has a certain resolution?

Let's say I have an asynchronous input (let's call it enable_h). This signal is supposed to be active high for 100us. My 2mhz clock is double-registering this async input. So once it is in my clock ...
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76 views

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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2answers
2k 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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56 views

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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2answers
931 views

How to implement a discrete transfer function into an arduino?

I am here asking how does one transfer a difference equation into a MCU? I have never done it personally and looking into this topic I was never able to find a good answer. Its usually used with ...
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1answer
148 views

What is the difference between a 1st and 2nd Order Digital Filter

I was just curious as to the differences between the two order filters? How I created these discrete filters for references Designed in Continuous first then converted into Discrete Using Tustin's ...
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2answers
294 views

Why use convolution for pulse compression in radar instead of correlation?

I have not understood the way to process pulse compression in radar signal processing. I think it's correct to use correlation for pulse compression, but I saw many materials about pulse compression. ...
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0answers
88 views

Accelerometer to detect when product has been picked up by user

I have a 3-axis accelerometer on my board and i was hoping to use it to detect when a user lifts the device up. I would like to avoid false triggers when the table shakes or when the user nudges the ...
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3answers
975 views

The term Feed-forward and its meaning?

I am trying to understand the technical meaning of the term 'feed-forward', when and where it can be used and where it cannot be used? I have seen this term in various different areas. For example: ...
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1answer
118 views

LM567 or Custom bandpass filter

I'm using a array of hydrophones to localize an underwater pinger (37.5 kHz and 45 kHz) and I'm thinking of using LM567 tone decoder as a frequency filter. The other option is to design a custom ...
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0answers
44 views

Filtering analog audio signal using TLV320AIC3111-EVM

I'm working on a project to filter analog microphone data using the audio codec from TI, the TLV320AIC3111. We are using the EVM However, I'm facing problems with implementing the filters on the ...
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1answer
67 views

Xilinx FIR filter behavior

We're currently simulating some Xilinx AXI Stream Finite Impulse Response (FIR) IP cores. https://www.xilinx.com/support/documentation/ip_documentation/fir_compiler/v7_2/pg149-fir-compiler.pdf The ...
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141 views

Time delay using IIR filters

I am trying to implement a cardioid pattern with two microphones. I was reading this paper titled "Digital Filter Array Optimization for Directivity Pattern". The link to download the paper is this. ...
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6answers
3k views

Extremely low frequency filters

I have a data acquisition board(A/D+Digital Signal Processor) and I want to check if a digital high-pass filter(implemented in DSP) at an extremely low cut-off frequency(0.05Hz) is actually working. ...
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1answer
58 views

Inverse Z-transform Problem [closed]

I'm rather stuck trying to compute the inverse Z-transform y[n] of the function below. I'm having trouble selecting the correct formulas from the table to achieve the right solution. Any help with ...