Questions tagged [digital-filter]
A digital filter is a system that performs mathematical operations on a sampled, discrete-time signal
125
questions
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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 ...
1
vote
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 ...
-1
votes
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?
2
votes
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 ...
5
votes
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 ...
0
votes
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 ...
0
votes
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 ...
0
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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 ...
0
votes
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 ...
0
votes
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?
0
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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 ...
0
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0answers
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^{...
0
votes
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 ...
1
vote
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 ...
0
votes
0answers
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 ...
1
vote
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 ...
-1
votes
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 ...
1
vote
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 ...
1
vote
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 ...
4
votes
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 ...
0
votes
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 ...
2
votes
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) ...
2
votes
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....
0
votes
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 ...
1
vote
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)
$$
where \$\beta\$ is a real parameter I can adjust to modify the ...
0
votes
1answer
105 views
Software oscilloscope
I have been developing a C language software for software oscilloscope
which is part of a control software. From timing point of view the
software consists of two execution loops.
The first execution ...
2
votes
1answer
174 views
Why does this part of an OLED filter light only when orientated correctly?
Note: The screen is an OLED screen. I had assumed it was LCD, therefore the post mentions it as such.
I was disassembling a Samsung phone (GT-I9305) and was able to seperate the LCD into two sections....
2
votes
0answers
102 views
How to amplify the output of a digital low pass filter?
I have used the transfer function of a RC low pass filter to design a IIR Digital low pass filter.
\begin{equation}
H(s)=
\frac{1}{sRC+1}
;First
\space
order
\end{equation}
\begin{equation}
H(s)=
\...
3
votes
4answers
730 views
How to pick correct filter for a given signal processing task?
I did a study on digital signal processing and I found many theories.
But I don't know how to figure out which filter to use when I get a practical signal processing task.
Is there a procedure for ...
1
vote
5answers
602 views
Calculate cutoff frequency of a digital IIR filter
I have an ADC with 1 kS/s and would like to append a digital anti-aliasing filter to it as I have to downsample the data to 10 Hz.
As it's on an FPGA and I don't have any multipliers, I thought ...
4
votes
1answer
113 views
How to make my difference equation make the deadline constraint?
Back at it again.
STM32L43KC Datasheet:
The question this time is I am finally starting to implement my digital filter which can been see as:
Z - Transform:
$$LPF_D=\frac{Y}{U}=\frac{0.3957z^2+0....
0
votes
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 ...
1
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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 ...
2
votes
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 ...
2
votes
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 ...
0
votes
0answers
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 ...
1
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0answers
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 ...
4
votes
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-...
0
votes
0answers
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 ...
2
votes
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 ...
1
vote
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 ...
3
votes
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. ...
2
votes
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 ...
7
votes
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:
...
2
votes
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 ...
0
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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 ...
1
vote
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 ...
0
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0answers
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. ...
13
votes
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.
...
0
votes
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 ...
