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# All Questions

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38 views

### I/Q plane plot understanding?

I am experimenting with some signals. I ma generating a 2.47 Ghz signal from signal generator and receiving it by an SDR (LMS7002m Rf chip) with Rx frequency tuned to 2.47 GHz. Upon plotting the ...
58 views

### How to determine sampling frequency for an x(t) signal avoiding aliasing?

The antitransform of the function is given: $\hat{x}(f) = \frac{123 + i246\pi f}{246 - 24600 \pi^2 f^2 + i4920\pi f}$ I'm asked to determine which frequency can I sample using the function x(t) ...
62 views

### with given Sampling rate, what max frequency human voice can be captured?

I'm new to signal processing and sampling rate, I was asked interview question related to this. This is the exact question asked: With 8Khz of sampling rate, whats the max frequency that human ...
62 views

### Why does my sinusoid look “AM” in shape?

My code is : Fs=200e6; Ts=1/Fs; NFFT=2^14; Runtime=(NFFT-1)*Ts; t=0:Ts:Runtime; f_in=90*1e6; y_in=sin(2*pi *f_in *t); plot(t,y_in) ylim([-1.5 1.5]) Then why does ...
2k views

### Why doesn't sampling a periodic continuous-time signal yield a periodic discrete-time signal?

I have been studying signals and systems lately and I have came across the following claim: The uniform sampling of a periodic continuous-time signal may not be periodic! Can someone please ...
29 views

### barker sequence in signal processing

In our class test we were given a signal with barker sequence and a 10101010... sequence ahead of that and were asked it's importance. So what is the significance of that 10101... sequence?
115 views

### Alignment of 2 Set of Samples from Different Sensors

If we measure the heart rate of a subject with two different devices, which have big different sampling rates then how we can compare their outcomes. For instance, one of the devices has the sampling ...
262 views

### Periodicity of sum of discrete signals

In my lecture slides for school and from this website here "The sum $z[n] = x[n] + y[n]$ of periodic signals $x[n]$ with fundamental period $N1$, and $y[n]$ with fundamental period $N2$ is periodic ...
55 views

### histogram bin size vs. data sampling rate

I have a set of numerical signals that give me a set of zeros calculated based on some numerical procedure. I make a histogram of those zeros. Here, a following problem arises: If the histogram ...
30 views

### What is wrong with my PSD computation?

I'm trying to calibrate the RX of my SDR Board to become a measuring receiver. I.e, by connecting it to a known source of power (in my case, a frequency generator), at a fixed frequency, I'm trying to ...
307 views

### Are resolution increase and noise reduction from oversampling mutually exclusive?

Oversampling a signal means sampling it with a significantly higher sampling frequency than the Nyquist rate. As far as I know, there are three advantages: Easier design of anti alias filter Increase ...
191 views

### Uncertainty Relation between time and frequency

Typically, humans can hear sound waves in the frequency range 20 Hz to 20 kHz. If one wants to make digital record of sound such that no audible information is lost, what is the longest time interval ...
316 views

### RF signals database

I'm trying to learn more about RF signal modulation/demodulation. I wanted to experiment with some real signals, but I don't have any data to work on. Is there any open database of RF signals? Like ...
833 views

### Use of the Dirac delta as a sampling operator

As we are all taught in signal processing classes, the Dirac delta is not a normal function but a generalized function. It is sometimes defined as either the limit of some normal function whose ...
436 views

### Compensation for Irregular Time Step for DFT (FFT)

I want to run a clustering algorithm (svm, knn) on the ferquency spectrum data of a temperature sensor that published at irregular times. Here is the temperature data to take the FFT: I got the ...
167 views

### Does the Nyquist Sampling Theorem hold for a triangular wave?

Does the Nyquist Sampling theorem hold for a triangular wave produced by a function generator? For example, a triangular wave with a frequency of 15 Hz sampled at 60 Hz, 180 Hz and 15000 Hz.
109 views

### How to find DC bias of periodic signal from samples that include a non-integer number of periods?

I'm using an ADC to sample a periodic signal and I want to calculate the DC bias of the signal from the samples. The obvious solution is to take the average of the samples. This works fine if there ...
174 views

### Signal Processing for Discrete Events

This is less a specific question, and more... "what is this called" and "where can I read more about it"? Several times in my career, I've had to work with datasets with "discrete events". Lets say ...
67 views

79 views

### Sampling orthogonal signals

Suppose I have two signals $f,g$ which are orthogonal in the sense of the usual inner product on $\mathbb R^d$. Then if I'm not mistaken these signals have disjoint spectral support, i.e their fourier ...
44 views

### What happens to the fourier transform of sample result of $30kHz$ sinusoidal signal when sampled with sample frequency $44.1KHz$?

As the title says,w hat happens to the fourier transform of the sample output of $30KHz$ when sampled with sample frequency $44.1KHz$? I do not get how alias can appear, because fourier transform of ...
587 views

### FFT on Hamming Window Function [duplicate]

I want to apply Hamming window function the Audio sample then find out its fft.. ...
400 views

### Extending a waveform

Apologies if this makes no sense or seems rather simple, I'm a Matlab newbie. Basically, I've got a .wav audio waveform which I am resampling to various different frequencies and then trimming the ...
2k views

### Can the order of filtering and downsampling be exchanged?

Say for example, I have a signal with maximum frequency at 600Hz, and I originally oversampled it at 2000Hz. Afterwards I was only interested in frequency less than 500Hz. I guess I could first filter ...
1k views

### Using Goertzel Algorithm in under-sampling

I plan to calculate a signal's phase using Goertzel Algorithm. I have 2 signals coming to microcontroller's ADC. Need to measure the phase difference between them. Signals are 15MHz sinusoids. Sample ...
81 views

### What does it mean for audio to be 'sped up'? How can I undo it?

I very simply have a .wav audio file, but there is a note with it that says "This audio has been sped up by 10x". I am wondering, what does it mean exactly from a signal processing perspective for an ...
2k views

### FFT of Square Wave and Sin Wave

When we have FFT of Square wave of a pure real signal with high frequency(close to f(max), less than half of sampling frequency) we see only 2 symmetric high peaks but when we decrease the frequency ...
37 views

### Matlab:Sampling Curve into Frames and Plotting

I have a Output Curve of following characteristics http://i.imgur.com/hABfsiC.jpg Following is the data which represents the output curve cited above ...
107 views

### Using under-sampled data, what determinations can be made about the Nyquist rate (correct sampling rate)?

Using under-sampled data, what determinations can be made about the Nyquist rate (correct sampling rate)? If my instrumentation limits me to sampling data at a fixed but insufficient rate what, if ...
501 views

### Calculating an incoherence property from sub-optimal sampling patterns

EDIT (after comments and subject matter review) CS is based on a choice of a sensing basis $\Phi$ relative to a representation basis $\Psi$. Using an "Incoherence Property" $\mu$ that measures the ...
976 views

### Why do we read that Hilbert transform can be used for envelope detection?

We can often read that Hilbert transform is useful for envelope detection (e.g. Hilbert transform to compute signal envelope?) I have done some tests with various soundfiles, and ...
1k views

### Envelope follower not smooth enough

With the following code, I get the "envelope" of a sound signal. However in the "envelope" there are small oscillations (high frequency) : it is not smooth enough... I imagine that it's possible to ...
203 views

### Map the Amplitude Envelope from [dbmin,dbmax] to [-inf,dbmax]

I would like to map the envelope of a sound (which has max dB level = dbmax, and min dB level = dbmin) from [dbmin,dbmax] to ...
161 views

### understanding discrete wavelets

I was reading section 4.3.3 from chapter 4 of "A Wavelet Tour of Signal Processing", "...Let $\bar{f}(t)$ be a continuous time signal defined over $[0,1]$. Let $f[n]$ be the discrete signal obtained ...