Questions tagged [aliasing]

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ADC and RC filter importance

TI and ADI suggest using an RC filter, ADI noted that SAR ADC have switching kickback and say it's really important but STmicroelectronic says the components of the RC filter discussed in the TI and ...
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2 answers
127 views

What is happening when a signal is acquired at exactly Nyquist frequency?

So I am doing some some simulations with 1V sinusoidal signals, and a 1 second acquisition at sampling frequency of 100 kHz. Now I am slowly increasing the frequency of the sinusoidal signal. Trying 1 ...
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2 answers
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Best practice for anti-aliasing very low sample rates?

I'm looking to sample a signal using an ADC at very low rates - perhaps once every minute. What's the best practice for anti-aliasing filtering in this situation? Obviously, trying to construct a ...
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0 answers
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Analog low pass filter noise versus anti-aliasing effect

I am designing a nano-volt-sensitive, 32-bit ADC system for research. The signal of interest is 10~100 uV and DC to 100Hz the goal is 10nV sensitive system. The signal will be amplified by a pre-...
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1 answer
69 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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2 votes
3 answers
232 views

Adding anti-aliasing filter to op-amp before ADC, clock frequency or sampling frequency?

I am designing an anti-aliasing filter for an MCP3202 ADC. I'm kind of confused by defining my corner frequency Fc, I'm working with a 60 Hz input signal with harmonics until around 3 kHz that comes ...
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1 answer
132 views

How to plot the alias frequency?

I've been getting into sampling recently, and seem to have a problem with how to actually "plot" an alias frequency, and was hoping some of you might be able to help. I have a sin-wave with ...
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0 answers
78 views

ADC input filter design for a low sample rate data logger

I am looking to get advice on anti aliasing filter design for a data logger I am developing, which has a sample rate configurable from 100 ms (10Hz) up to 24 hours (i.e. wake up, take a sample, write ...
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0 answers
342 views

DAC "aliasing" of harmonics

While reading articles and application notes regarding DACs and their output spectrum, I stumbled across aliasing of higher harmonics to the first Nyquist band. For example, when generating a single ...
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1 answer
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Alias frequency

I have plotted the graph above that has an Amplitude of 1, and a Frequency of 1 Hz. Sampling rate used is 3/4 of a cycle. The book wants me to find out what the alias frequency that the green dots ...
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0 votes
2 answers
66 views

What is meant by the signal energy to alias ratio and how is it quantified?

Below solid black curve is the bandwidth of a signal(a 4kHz RC low pass filter). And when we sample the signal at 8kHz rate due to folding the blue dashed line shows the aliasing: 1-) It looks very ...
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1 vote
5 answers
269 views

Sampling theorem clarifications

whenever the sampling theorem was explained to me, a situation of this kind was proposed to me. If we look at the previous image we will see that the condition to avoid spectral aliasing is that we ...
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2 votes
1 answer
189 views

Is using passive anti-aliasing filter with its transfer function instead of an active filter common or reliable?

I need to ask this general question with an example for clarity. Imagine I have to measure a signal with BW of 5kHz and I need to make a unity gain active anti-aliasing filter with a steep roll off ...
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13 votes
6 answers
3k views

Why does increasing the sampling rate make implementing an anti-aliasing filter easier?

From an answer to a question regarding sampling rate and anti-aliasing filter I read the following: The closer you get to the theoretical minimum sample rate, the more difficult the analog filter ...
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0 votes
1 answer
236 views

Calculating sampling frequency off of estimated stop band attenuation

I'm trying to calculate what I will have to set my microcontroller's ADC sampling rate at in order to sample a band of 500kHz to 1.6065MHz without aliasing. Some constraints here are that I have to ...
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1 answer
137 views

Can an amplifier slew rate be used as a low pass anti-aliasing filter?

A slew rate calculator says that for an arbitrary 100MHz signal a minimum slew rate of 1884V/μS is required. If I used an amplifier with that exact slew rate is it also a low pass filter? It seems ...
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3 votes
2 answers
3k views

what is memory aliasing?

I was reading about ARM M series and somewhere it was written that: "the flash memory area is aliased from address 0x0000 0000". what does it mean?
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1 answer
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How do you find the resulting frequency of sampling a tone at too slow of a rate?

For example, I have a 1500 Hz tone that I am going to be sampling at 1200 samples/second. How would I figure out the tone resulting from this sampling?
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1 vote
3 answers
360 views

Anti-aliasing filter with a higher corner-frequency (>10 MHz)

I'm currently working on a design with an adc3424 ADC with 125 MHz sampling frequency. This is my first design with an ADC and I assumed picking an anti-aliasing filter (AAF) would be a trivial task. ...
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1 answer
497 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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1 vote
1 answer
134 views

Decimate ADAR7251 Sigma-Delta ADC Output

I'm working with a Analog Devices ADAR7251 Sigma-Delta ADC. It has multiple sample rates to choose from (1800 kSPS, 1200 kSPS, 900 kSPS, 600 kSPS, 450 kSPS, and 300 kSPS) but my application requires ...
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1 vote
1 answer
815 views

A question on aliasing and sampling in a measurement system

Before asking my question here is the scenario how the voltage signals are used: Where I work some are performing data acquisition of four DC signals through four channels by a daq device at a ...
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1 vote
1 answer
127 views

Specific noise while using arduino ADC in free running mode

To make an oscilloscope in matlab environment, for data acquisition on arduino side, when inbuilt analogRead() is used, it's working fine, but with very low ...
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2 votes
3 answers
1k views

ADC anti-aliasing filter

I bought a 16bit, 250kSPS AD7689 ADC. The circuit I am designing will amplify voltage (from 300uV up to 300mV) across a current-sense resistor (by 13x) to match 4.096V reference and feed this into an ...
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0 votes
1 answer
196 views

Sampling and Aliasing Problem

I have this problem where I was able to solve for both a and b but I am stuck on c and d. For part a I came up with 0 Hz, 4.77 Hz...
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0 votes
2 answers
278 views

How to determine the frequency of input signal from Sensor to ADC?

I am using a Pressure Sensor that gives out an Analog Output of 0V to 10V depending upon the sensed pressure. I am trying to design a filter (or at least determine some starting RC values) for the ...
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6 votes
3 answers
10k views

Divider and lowpass combined

I am using the following circuit for two purposes: As a voltage divider, to reduce DC sensor output to a range suitable for my ADC. As a lowpass filter, to remove high frequency noise from the signal....
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5 votes
2 answers
2k views

Anti-Aliasing filter design

I appreciate that different applications have different criteria, but could someone give a ball park figure of how much attenuation is needed for an anti aliasing filter at the Nyquist frequency to ...
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3 votes
2 answers
7k views

Aliasing vs Imaging. What is imaging?

In DSP for audio, I understand what Aliasing is (fixed with an anti-aliasing filter), but there is also something called Imaging (fixed with a reconstruction filter). Aliasing is when a higher ...
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1 vote
1 answer
1k views

Guitar signal preamplifier - ADC input to STM32F4

This is for a DSP project. I am trying to prepare my guitar signal for as best as possible ADC response in order to detect harmonics to the 5th of the highest note of the guitar (1175 Hz for 22 frets),...
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0 votes
1 answer
642 views

Sampling Anti-Aliasing Filter Bandwidth

if i'm using Sampling frequency less than Nyquist Sampling frequency, Aliasing will occur which will scramble the whole signal, so one solution is to use anti-aliasing filter How can i calculate it'...
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0 votes
2 answers
187 views

Anti-aliasing filter as notch and lowpass

In order to reach a steep attenuation for an analog antialiasing filter, there are issues if a high Q notch filter is followed by a low order lowpass filter (or vice versa)? The notch resonance could ...
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-1 votes
2 answers
225 views

Sampling alias phase when undersampling

I have to measure the sum of the magnitude of two sinusoidal signals and I think I can exploit the undersampling method in order to superimpose the alias of the sinusoid at the higher frequency over ...
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  • 93
2 votes
1 answer
2k views

Nyquist frequency mirroring

I need someone to check my understanding of Nyquist frequency. I understand it in the following manner. $$F_{nyquist} = ( F_{sampling}/2 ) * n$$ where n is an integer (negative and positive). For ...
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1 vote
1 answer
793 views

Cyclical output counts from a D Flip Flop, what is this effect called?

While working on a frequency divider/counter (in this case a frequency subtractor) using flip-flops, I discovered a strange effect in a D flip-flop when I left the clock at a constant frequency, but ...
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0 votes
1 answer
90 views

Sampling frequency range of an discrete signal

Is it possible to detect each and every frequency above the nyquist frequency? Or this can be also discrete Thank you.
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2 votes
1 answer
163 views

How to measure energy distribution

I want to evaluate the energy flow in a battery powered system. So when the system runs a specific task the energy distribution between the different loads can be obtained ( similar to a Sankey ...
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1 vote
0 answers
145 views

why my DAQ signal is a noisy signal?

background: My goal is to use an Arduino with two proximity probe (sensors) to achieve some output. It is worth mentioning that the output of the proximity probe has two components: DC output that ...
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7 votes
3 answers
414 views

Measuring low-duty-cycle supply current

I am trying to measure average current draw of low-duty cycle, low current devices. For example, a Bluetooth Low-Energy device might draw 16 mA during the radio transmissions (for a millisecond or so)...
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