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-1
votes
1answer
18 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 ...
0
votes
0answers
67 views

Understanding the Sharp IR output measured by arduino

Sharp IR output was varying a lot about some value dependent on the distance at which it has an obstacle before it. So, I wanted to observe the variation. Hooked up to oscilloscope and observed a very ...
0
votes
1answer
43 views

Sampling frequency and FFT

I have tried this example code for sampling and FFT in MATLAB, but I have noticed that when the signal frequency becomes closer to nyquist frequency , some errors ( small frequency components near the ...
1
vote
1answer
44 views

the voltage resolution for an analog signal with an amplitude

say,i have 16-bit DAQ that can read at a rate of 250kSamples/second. What is the voltage resolution for an analog signal with a 2V amplitude? For what value of signal frequency can I safely digitize ...
11
votes
3answers
454 views

Exactly what is the role of the zero-order hold in a hybrid analog/digital sampled-data system?

I'll admit, I am asking this question rhetorically. I am curious what answers will come back out of this. If you choose to answer this, make sure you understand the Shannon-Nyquist sampling theorem ...
1
vote
1answer
44 views

Non-unique Sample Rate

Given $$x[n] = \cos\left(\frac{\pi}{3} n\right)$$ That was obtained by sampling $$x_c(t) = \cos(4000\pi t)$$ At \$T\$ samples per second, find \$T\$. Is \$T\$ unique? Why or why not? $$x[n] = ...
0
votes
1answer
47 views

Getting a consistent and precise voltage for sampling

I have a 9V battery connected to an LM317T voltage regulator and it's regulating the voltage almost perfectly but I intend to use it for sampling and it fluctuates over a few mV. Generally between ...
0
votes
1answer
35 views

Using an mbed and piezo disc to determine frequency

I am attempting to determine the frequency of an instrument from its vibration using a piezo disc and an mbed LCP1768. I attempted this with a raspberry pi but couldn't get the sample frequency high ...
1
vote
2answers
72 views

Power supply Harmonics calculation using FFT

I am trying to calculate harmonics of power supply with using a FFT. My sampling rate is 400 samples/sec. This means 8 samples per cycle. I am not getting sensible answers and think that I am making a ...
2
votes
3answers
56 views

Sampling rate for PID control to balance an inverted pendulum using 8051 - AT89c51rc2

I want to control a dc motor(to balance an inverted ;endulum) I want to sample the input from sensors(e.g.: ADXL345) and convert it to digital using a DAC. The maximum output data rate(ODR) for ...
0
votes
1answer
39 views

Sampling rate in dacs

I am using a DAC form analogous devices viz - AD565A. Now, according to Nyquist theorem the minimal sampling rate for a decent reconstruction of a signal twice the rate of its highest frequency ...
4
votes
1answer
88 views

256-point FFT, but only need 5-6 frequencies, is there a better way?

Due to the constraints of my system, I have a 256pt FFT. However, I only care about the energy at 5 or 6 of the 256 bins. 256pt FFT is still faster than 5 or 6 specific DFTs, but it seems wasteful ...
0
votes
1answer
75 views

can we achieve signal compression by reducing the sampling rate?

Does the reduction in sampling rate causes compression of the signal? If yes, can you please provide me some specific example?
0
votes
1answer
50 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.
1
vote
0answers
33 views

About coherent sampling

In Coherent sampling, it states the condition for coherent sampling is given by $$ \frac{f_{in}}{f_{s}}=\frac{M_{cycles}}{N_{samples}} $$ Where \$N_{samples}\$ value must be a power of 2 and ...
1
vote
2answers
150 views

Sampling rate analog to digital converter

I am a novice in microcontroller subject and have just learned that ADC converts analogue voltage on a pin of, for example, an Arduino, to a binary number. Since the ADC on the Arduino is a 10 bit ...
0
votes
1answer
43 views

Received waveform frequency is way too low than it was sent

I am using Quartus 12.1 sp1, vhdl and Altera Nios II programmed in C code for DE0-Nano Development. Basically, what I have is, data is sent from fpga vhdl block to NIos II system, Nios II system sends ...
-2
votes
2answers
63 views

I need to sample 8 audio sources at audio quality, what MCU can I use? [closed]

I need to sample 8 audio sources at the same time, at a decent frequency (say, 40Khz). Being only familiar with Arduino, I searched online for tutorials and articles about using interfacing it with ...
1
vote
1answer
59 views

ADC samples half frequency

I'm using a dsPIC33F (Microchip) to sample a 555-timer signal. I've tried square, triangular, and "sinusoidal" signal shapes, but always have the same problem: the ADC samples the waveform correctly, ...
0
votes
2answers
115 views

Preparing Signal for Sampling

I want to sample a voltage signal from mains. I found the following circuit but im not sure how it works. The circuit consists of precision amplifier and a buffer which I can't make sense of, the rest ...
0
votes
3answers
124 views

Appropriate Method of Counting counts from a Quadrature Encoder

I'm using an Mbed to drive a DC motor which will follow a trapezoidal trajectory. What is the most appropriate way to determine position from the quadrature encoder? Should I use interrupts, or is ...
1
vote
1answer
91 views

Am I getting DC bandwidth correctly?

I am computing Johnson and shot noise in a DC circuit, where I have an Arduino Due sampling with "delay(100);", i.e. at 10Hz. Sampling rate and bandwidth follow Nyquist sampling theorem. According ...
1
vote
3answers
387 views

DSP Cutoff vs Sampling frequency question on low pass filter

Is it unrealistic to have a 125 MHz sampling rate with a cutoff frequency of 5 Hz? I downloaded a few filter programs and used their methods and it seems that even with thousands of taps it still ...
0
votes
2answers
118 views

Choice between Pseudo-Differential Unipolar and Pseudo-Differential Bipolar ADC Input

While reading about Pseudo-Differential Inputs for ADCs, I came across the document below from LT. Link : http://cds.linear.com/docs/en/product-selector-card/2PB_sarinputtypesfb.pdf Below are copied ...
0
votes
2answers
58 views

Sampling Signal using microcontroller

I would like to decode a signal from a radio clock source, using an off the shelf receiver, and a microprocessor. The output of the receiver is a digital level which encodes either carrier on or ...
0
votes
1answer
75 views

ADC output level query

This query is related to my old post: ADC outputs random values to constant input I made further tests, and still struggling. The reason I made a new post is, the query is different. I am using FPGA ...
3
votes
6answers
688 views

16-bit or 24-bit converters?

I wanna build some DSP effects on, for example STM32F4 processor, with frequency 96 or 192 KHz. Are 16-bit converters (ADC and DAC) enough for that kind of operation? Can I hear a diffrence when ...
1
vote
1answer
102 views

ADC outputs random values to constant input

I am using ADC (ADS7822) from TI and I have some strange behaviour with it. Below diagram explains the voltage inputs and connections. I was reading strange values with this setup. I removed ...
0
votes
1answer
58 views

why it is hard to generate an impulse train ?

I have understood the concept of Ideal impulse sampling ,but i have struck upon the fact that practically generation of impulse train is not possible.
1
vote
1answer
39 views

Source/Drain terminals in a MOSFET Sampling circuit

In a simple sampling circuit consisting of a MOS as the switch and a capacitor, how does one decide which of the terminals are source/drain? Thanks.
0
votes
1answer
135 views

Why does my bandpass RF filter complain about Ts in Simulink?

I am doing a basic amplitude modulator, and I'm using as input signal for now a Gaussian noise generator, then I modulate it with a carrier fc=2e9Hz. When using Simulink along with a RF bandpass ...
2
votes
1answer
214 views

Simultaneous sampling of several channels with single ADC?

I am looking at this 8-channel, 18-bit and 200 ks/s ADC. The datasheet claims the sampling is done simultaneously for all the channels, but the diagram shows that there is only one ADC, so how is ...
0
votes
3answers
246 views

Sampling Rate Passband Signal

What is the maximum/minimum possible sampling rate for the signal to be full recovered for a passband signal?
12
votes
2answers
440 views

Why doesn't aliasing of broad band noise 'pile up' in the sample band?

I recently built a simulation to study sampling, the effects of aliasing and the effects of anti-aliasing filters on the sampled signal. For fundamental frequencies above the sample band it's obvious ...
3
votes
1answer
1k views

Relationship of FFT Size, Sampling Rate and Buffer Size

I am asking this question because I want to make sure I understand the relationship of FFT length, the sampling rate and the buffer size. This question is with respect to the CMSIS DSP library, ...
0
votes
1answer
101 views

Signal sampling question here please?

We have the signal \$y(t)=7\cos(wt) \$.We have \$f(s)=100~Hz\$.I need to find \$f(T)\$ and reconstruct the signal so that we wont have loss of signal. I think that we need to take \$f(T)>2f(s)\$ ...
0
votes
2answers
1k views

What is Subsampling in image processing?

I was going through some image processing document. And I came cross this term "sub sampling". What does it mean? Is it sampling again already sampled data .. ?
0
votes
1answer
213 views

Maximum signal data rate

I have a frequency signal range from 25 Khz to 35 Khz. I know that the the minimum signal sampling to assure reconstruction of the signal from the samples is 70 Khz. Would it be correct to assume ...
1
vote
2answers
222 views

Suggestions to interface a photodiode in the MHz range

The task at hand is to read the variations of incoming light at speeds up to 1 MHz, with some dynamic range capability (10-1000lx with 1% accuracy would suffice). This is to be used in a device which ...
1
vote
1answer
364 views

Choosing sampling rate according to the bandwith reponse in accelerometer datasheet

In an accelerometer's datasheet, the bandwidth response in the x and y axis is 350 Hz. There is another information related to the internal sampling rate (shown below). I don't know how these two ...
0
votes
1answer
71 views

Sampling: how to determine a “good” sampling rate based on a given filter

I assume that the sampling rate is w_s = 2w_max if we have an ideal low-pass filter that nulls frequencies whose absolute value is higher than that of w_max. Therefore, that the only reason for ...
-1
votes
2answers
128 views

IF signal amplify without delay

I have a RF Frontend that has an 4 IF signal output (2 I channel and 2 Q channel from 2 receiving anettans). Each channel of the IF has a signal rangining from 1.5V to 3.5V with a DC offset of 2.5V. ...
0
votes
3answers
239 views

What's the relationship between samples and bits?

I was talking to a friend today that I have a transmitter which is capable of sending 128 samples/second. Note that each sample is a voltage level represented by a floating point decimal. He then ...
0
votes
1answer
124 views

Choosing the right sampling frequency for WLAN 802.11ac signal (BW : 80 MHz)?

I’ve got a WLAN 802.11ac signal & it’s bandwidth is 80MHz, now I would like to know the ideal sampling frequency for this signal. As per the nyquist theorem , the sampling frequency could be 160 ...
1
vote
0answers
445 views

STM32 ADC: Multiple channels with different sampling rates

I am trying to figure out how the STM32 multiple channels ADC conversion works (regular group). Lets say I want to convert on two channels, channel 1 and channel 2, on ADC1 and the sampling rates are ...
1
vote
2answers
109 views

Sampling frequency from audio jack

I want to start a project where i'll sample directly from the audio jack. Now i don't know what the sampling frequency should be. I don't know what is the maximum frequency of sound, i don't know it ...
1
vote
1answer
83 views

Nyquist Sampling rate

We have \$z(t)=\cos(100πt)\cos^2(500πt)\$ . Find Nyquist sampling rate. Well, I know that \$f_s=2f_{max}\$. My main problem is that I am not entirely sure if I could re-write the above signal as: ...
1
vote
3answers
85 views

what is the difference in u-controller processor sampling frequency and the z-domain conversion sampling frequency?

I have observed a bit confusing behavior of my system response (or may be i am missing something). I have a transfer function in S domain converted to Z domain with a 1kHz sampling frequency at the ...
1
vote
1answer
277 views

Weird samples from SAR ADC

I am playing around with some SAR (Successive Approximation) A/D-converters. I have made a test circuit where I have a 16-bit DAC from Texas Instruments (R2R-based) and an 16-bit SAR ADC from Analog ...
1
vote
1answer
386 views

Connect VLF antenna to raspberryPi

I want to connect two VLF antenna (given below) to a RaspberryPi using it's GPIO ports with a MPC3008 ADC. Desired frequency range is between 3kHz to 30kHz, and MPC3008 supports 200,000 samples/sec ...