Questions tagged [digital-filter]

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

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1answer
46 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
40 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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1answer
446 views

Anti-Aliasing Filter example

I need help in solving the below question. Bandwidth of the signal is 1KHz. Use a 12-bit ADC with SNR of 78dB for sampling. the sampling frequency is 12KHz. Choose suitable filter order and cut-off ...
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3answers
72 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
53 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
118 views

Same z transformed function, but different answers of inverse z transform?

Given z transformed function is E(z)=1/(z+4) I know there are several ways to get the inverse z transform of this function. use partial fraction E(z)=1/(z+4) E(z)/z=1/z(z+4) apply partial fraction ...
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1answer
1k views

Is this alternator W RPM input circuit ok and how can I improve it?

I need a robust and reliable way of taking a RPM signal from the W terminal of a standard automotive alternator. Most of the time the signal will come from a 12V alternator but there is a requirement ...
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2answers
175 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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1answer
104 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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3answers
10k views

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

I'm quite a novice in 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 (...
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3answers
731 views

Linear Phase Response

In many cases, it is demanded that filters have a linear phase response (like in the case of FIR). Why is linearity so important? Why not a constant phase response, or anything else (any other shape)...
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4answers
465 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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3answers
189 views

Predicting decay time of a resonant bandpass filter?

In a typical resonant bandpass filter, resonance is set as none at 0 and full at 1, such that the filter rings infinitely at 1 and not at all at 0. If there is a two-pole resonant bandpass filter, ...
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2answers
193 views

Efficiency of FIR filter in verilog language

Implementing a 4-tap FIR unity coefficients, is this code efficient in power and area ? ...
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1answer
157 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
92 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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5answers
526 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
111 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
39 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
26 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
40 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
137 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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0answers
27 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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2answers
335 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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0answers
66 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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28 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
303 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
100 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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0answers
78 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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1answer
187 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 ...
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3answers
937 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
84 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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41 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
61 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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2answers
866 views

How to improve my digital filter to extract DC from noises?

Digital filter description: The filter's input are sensor data and output will be provided to a PID controller. Sampling rate: 64kHz Noises spectrum: from DC to 10kHz Filter target: to get DC ...
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117 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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3answers
11k 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 ...
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6answers
2k 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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3answers
192 views

Sharp and Simple Analog Filter suggestions

I'm looking for schematics of some simple opamp-based analog filter, which has a sharp band-pass functionality. I want it to control small robot with sounds of different pitch. The matter is like ...
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1answer
57 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 ...
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2answers
127 views

Error implementing IIR filter on FPGA

I want to implement several IIR filters on an FPGA, using VHDL. The filters is for audio. I start out by implementing a single filter with the following transfer function: $$H_1(z)=\frac{304 -304z^{-...
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1answer
380 views

DSP Library not working in MPLAB X

I have to make a digital filter with a dsPIC30F4011 (I'm completely new to microcontrollers). I was reading the documentation about the DSP Library to figure out how to use it. I created a simple C ...
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0answers
606 views

FIR filter in dsPIC with DSP Library

I have to make a digital filter with a dsPIC30F, but I don't know much about it. I've read part of the documentation about the dsPIC30F and the DSP Library, and I found a page on Microchip website ...
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1answer
148 views

Filtering Audio Signals in MATLAB

I'm trying to apply a filter to an audio signal in MATLAB and having some trouble processing it. So far, I have a transfer function that describes a K-weighted filter, and I am able to create a bode ...
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0answers
75 views

Why do we need an (adaptive) equalizer when we have a matched filter at the receiver?

When both can perform the same task of reducing the effects of ISI, why use both and not just one at the receiver end?
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1answer
118 views

Understanding digital filters, specifically their effects on time domain information, how to preserve the waveform of a signal being filtered?

According to Steven W. Smith, in his book: The Scientist and Engineer's Guide to Digital Signal Processing, when designing a digital filter, "Good performance in the time domain results in poor ...
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2answers
107 views

Digital vs Analogue Filters From an Non-Audio Perspective

Recently I have been reading about the use of digital filters. By deriving the transfer function of the desired filter (in the s-domain) and multiplying holds (ZOH or FOH). What is the general ...
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1answer
51 views

Filter gyroscope's error from linear acceleration?

I need to use 3-axis angular velocity data for my application, but the gyroscope outputs angular velocity when under linear acceleration (not rotating). Is there a way to filter this error?
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1answer
67 views

How does an IIR filter change depending on the approximation used? [closed]

What are the main differences between the filters when using Butterworth, Chebyshev type I, Chebyshev type II or Elliptic aproximations.
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1answer
352 views

FPGA filter - sinusoidal wave at clock frequency observed in filtered signal

I am using an FPGA to implement FIR filters, specifically for this question I have implemented a 12 point moving average filter. At the moment I am just using a signal generator as an input to the ...