All Questions

3
votes
1answer
83 views

Example of non-equivalence of the two PSD definitions

According to the book Introduction to Spectral Analysis by P. Stoica and R. Moses, the power spectral density (PSD) $P(\omega)$ can either be defined as the discrete-time Fourier transform (DTFT) of ...
0
votes
0answers
8 views

OFDM modulator: Transmission time calculation

I have a problem with a certain task. The frequency of the signal sampling at the OFDM modulator output is 20 MHz. The length of the protection period is 2 microseconds and it is 20% of the ...
0
votes
0answers
4 views

How to detect the spreading code in MATLAB

Suppose we have the modulated signal $x = 10$ which is spread using one of the hadamard matrix codes (each column of matrix represents a code) as below: $$H = \begin{pmatrix} 1 & 1 & 1 & ...
0
votes
1answer
26 views

How to find a variance of sample sequence

I have a sequence such as $$r[n] = y[n]v[n]$$ I need to find a variance of $r[n]$ and show that is equal to $\sigma ^2_y\sigma^2_v$. I know that $y[n]$ has variance of $\sigma ^2_y$ and I also ...
1
vote
1answer
139 views

What is an “innovation filter”?

I'm a math postgrad student working through a paper on eigenvalue decompositions of matrices of FIR filters (used for stuff like total decorrelation, convolutive mixing, MIMO). Towards the beginning, ...
0
votes
0answers
20 views

When we compute doppler FFT, how can we find values corresponding to negative frequency?

I have a question. In case of FMCW radar processing, we compute 2stage FFT. The first FFT(range FFT) is used to find a distance between a radar and a target, The second FFT(doppler FFT) is used to ...
1
vote
1answer
32 views

What does the phase discriminator portion of the Costas Receiver do mathematically?

What does the phase discriminator portion of the Costas Receiver do mathematically? The output of the I-channel is $ \frac{1}{2}A_C \cos \phi \, m(t) $. Which means for small deviation of phase $ \...
29
votes
5answers
2k views

Detecting Trail in Forest Images

Is anyone aware of any research/papers/software for identifying a trail (as a line or point-to-point curve) in an image of a forest scene (from the perspective of the camera standing somewhere along ...
2
votes
3answers
549 views

Convolution that results in an all-zero sequence

I am asked to find a pair of sequences, each one of which contains three distinct values and where the convolution is an all-zero sequence. I've came to the conclusion that one of the sequences must ...
0
votes
0answers
30 views

Time-frequency and time-amplitude audio analysis - Python

I've been wondering for quite a while about how to get a 2d array in which the key indicates the time and the value indicates the frequency (or sum of all frequencies) of the audio at that time in an ...
0
votes
0answers
11 views

problem in selecting correct algorithm for project (RCNN)

I am doing a deep learning project in which i have to identify different models of car. i am a bit confuse for the following reason: first is what algorithm should I use, i have studied that RCNN is ...
0
votes
2answers
54 views

About using Walsh matrix as spreading sequence

I'm asking about some details about using the Walsh matrix as spreading sequence code. For example, suppose I'm using a $4\times 4$ Walsh matrix given by $$H = \begin{pmatrix} 1 & 1 & 1 & ...
-1
votes
0answers
9 views

HMM Model HTK TOOL KIT [on hold]

I have trained the hmm model on audio files. I followed the following tutorial for training. Link So the problem is that I am getting the negative accuracy. ...
0
votes
0answers
37 views

How should I modify my filter coefficients for the filter to be unaltered, when I change my sample rate

I am guessing this is a commonly encountered problem, but I am lost on how to really solve it. I have FIR filter coefficients that are used to match the frequency response of data sampled at 3 kHz. I ...
0
votes
1answer
37 views

Calculating filter coefficients of a Moving average with error correction

I have an oversampling ADC where I need to correct Gain/offset errors 'during' each conversion. This also links to my previous question - Moving average and linearization of two piecewise linear ...
0
votes
0answers
24 views

QPSK demodulation problem due to apparent transmitter clock frequency drift

I am using FPGA to generate 10Mbaud QPSK signal in two channels corresponding to two quadratures. Upsampling to 1GSample/s (using raised cos filter for interpolation) and complex upconversion (f_up=...
0
votes
0answers
26 views

Separating Ultrasonic signal from echo at the receiver

A transducer is acting as a transmitter and a receiver. It keeps on sending pulses which can hit an object placed at 5cm. Echo comes back and hits the transducer while it is continuously sending ...
0
votes
0answers
15 views

How to implement hermitian symmetry before ifft in matlab?

If I use hermitian symmetry after IFFT and clip negative part to make it only positive signal for VLC system. I am getting an only straight line in BER curve. Can anyone help me with this problem? I ...
1
vote
2answers
49 views

Spatial Audio (Ambisonic) and calculating sound source position

I have 4ch Spatial Audio (Ambisonic) WAV file and I want to calculate sound source position and put it on 2D plane. What I know so far is the following: WAV file consists of signals that support of ...
0
votes
2answers
43 views

Why Coherence is not a valid metric when performing impact excitation?

INTRODUCTION I have understood that Coherence is a function that explains the linear relationship between an excitation signal and a response signal. I know how it is calculated and why it is bounded ...
0
votes
1answer
46 views

Spectrum Inversion Problem

For a signal with $f_c$ (Centre Frequency) $=1200MHz \,\,$ and $BW= 100MHz$ ,which of the following Sampling Frequency ($f_s$) will cause spectrum inversion: A)$\, 287.5MHz \quad$ B)$\,575MHz \quad$...
0
votes
2answers
69 views

why is my FFT magnitude of real time recording so volatile?

My goal is to do spectrum analysis of a gear motor. I used Python with the Pyaudio package and made a crude spectrum analyzer that displays the FFT as the sound is being recorded. I recorded 10 ...
1
vote
0answers
29 views

Moving average and linearization of two piecewise linear systems

I have 2 oversampling ADC's running parallelly, each to process data in a specific range of the input as shown below: Each ADC can process only half cycle range of a sine wave. Each ADC adds its own ...
0
votes
1answer
1k views

Generate the Matrix Form of 2D Convolution Kernel

We know that a convolution can be replaced by a multiplication with a toeplitz circulant matrix. Meaning, assume I have convolution kernel $h$ and matrix $I$ (of size $m \times m$ for example), then ...
1
vote
0answers
22 views

Recovering signal statistics from non-uniform sampled signal

I'm interested in estimating the mean and standard deviation of a signal that was sampled non-uniformly. Assuming I have an estimate of the signal bandwidth, what algorithms would provide estimates of ...
0
votes
3answers
33 views

split radix ifft/fft algorithm

I want to implement A Split radix 128 point fft/ifft algorithm in matlab. I have read a few books and papers but I'm not really good at programming. So, Any advice on how to write a code would be ...
-1
votes
0answers
20 views

Physical meaning of cross spectral matrix in a microphone array

Currently I am processing data from a 64 microphone array to identify noise source locations on an airfoil. I am using the simple sum and delay beamforming algorithm. I get good results, however in ...
0
votes
0answers
31 views

How do I play and record audio at the same time?

So this question is more related to Matlab itself. Some background info: I'm trying out the Exponential Sine Sweep method to obtain the Room Impulse Response with my laptop speakers and microphone ...
1
vote
4answers
98 views

Detecting moved and dirty areas between two snapshots/images

I'm new to image processing and trying to figure out best way to identify 'moved' and 'dirty' rectangles between two desktop screenshots.Basically, lets say there is a round circle moving on a screen, ...
0
votes
1answer
21 views

GCC-PHAT (Generalized cross correlation) always peak at delay=0 on real audio signal

I have studied the GCC-PHAT algorithm to estimate TDOA on audio signals at 2 mics. Here is my MATLAB implementation: ...
0
votes
0answers
8 views

Trellis-converging offset and the min-sum algorithm

I am going through a paper on the design of interleavers for Turbo codes and I am a little bit confused about how to calculate what they call Trellis-Converging offset. They define such parameter of a ...
0
votes
0answers
12 views

Calculating the Mean Square Error (MSE) in Wavelet Denoising

I´m currently reading the paper (to be more precise: it´s a chapter from the book "Shearlets, Multiscale Analysis of Multivariate Data" by Kutyniok and Labate) "Image Processing Using Shearlets" by G....
0
votes
1answer
14 views

Confusion regarding lacunarity of koch curves with same fractal dimension but different orders

I'm trying to use the concept of lacunarity to classify images, as per how a few research papers have done it. To verify whether my equations and implementation are correct, I'm trying to verify the ...
1
vote
0answers
13 views

Interpolating inertial sensors data to correct for packet loss

I am using inertial sensors to calculate orientation using a accelerometer, gyroscope and magnetometer. There is Bluetooth connectivity and writing samples to SD card involved in the data collection ...
0
votes
1answer
31 views

Error reading a .PCM file

I want to convert a .wav file with a sampling frequency of 44100 Hz to a 16 depth .pcm. I don't why I'm getting those peaks at the beginning of .pcm plot (second figure below 2). If you could ...
0
votes
1answer
22 views

How do I find the frequency of a particular bin in a cosine transform, and two other questions

I have a discrete series of values and I have applied a Discrete Cosine Transform to it, obtaining values like: ...
1
vote
1answer
26 views

Checking Parseval's Theorm for Gaussian signal by using Scipy

I'm trying to check Parseval's theorm for Gaussian signal. It's well known that fourier transform of $\exp(-t^2)$ is $\sqrt{\pi}\exp(-\pi^2 k^2)$. So I implement it by using quad and simps. I think ...
2
votes
0answers
20 views

What is a correct way to find or “guess” a kernel which transforms an image into another image using Fourier Transformations?

Assuming I have two images, apple and orange; also assuming a filter kernel that transforms an apple image into an orange image possibly exists, how would some series of Fourier Transformations (and ...
0
votes
0answers
22 views

Is there a way to find a picture inside another picture, using only 2D Fourier Transforms of both images?

Can Fourier Transforms of both images tell anything about "likeliness" of two pictures? If yes, how precise? Can it still work if only several pixels are different or can it tell they are same if one ...
0
votes
0answers
12 views

Problem with Spectral Correlation Function for cyclical signal analisis

I am using the autofam() function in Matlab for the Spectral Correlation Function (link: https://github.com/sayguh/MastersProject/blob/master/matlab/sandbox/autofam.m) for a BPSK modultated chirp ...
0
votes
0answers
62 views

Recover Audio from Spectrogram Image

I have applied transformation(Constant Q Transformation) to my audio time domain signal, this gives me Frequency vs Time representation. Now, the CQT values consists of complex values(84*260), but ...
0
votes
0answers
31 views

Some difficult-to-approximate signals to test an signal extracting algorithm

I am searching for some strange signals in order to test an algorithm that I am developing. I've found an article by Donoho and Johnstone where they propose to test the algorithms using Blocks, Bumps, ...
1
vote
1answer
28 views

Best way to resample an OFDM signal without interpolating + filtering?

I am working on a custom transceiver with a sampling rate of 3.84 MHz (256 OFDM subcarriers at 15 kHz, although 56 subcarriers are null). I would like to resample the signal to 5 MHz, in order to use ...
0
votes
1answer
30 views

Computing the gains of a piecewise affine system

I have a piecewise affine (and memoryless) system, e.g., a response like the following one. I could manually find the gain in each region by applying a ramp signal. However, the system's input must ...
0
votes
2answers
19 views

Camera Calibration - why do you have to move the calibration board?

I understand the mathematical derivation of Zhang's Method for camera calibration but what I don't understand is why we need to move and rotate the calibration board for several frames in order to get ...
12
votes
4answers
18k views

How do I get the most accurate camera calibration?

First off, I hope this is the correct Stack Exchange board. My apologies if it is not. I am working on something that requires me to calibrate the camera. I have successfully implemented the code to ...
0
votes
0answers
21 views

Multipath propagation: pass loss [on hold]

1) I read that the path loss exponent depends on an height of antenna, frequency, polarization, climate. And also the post Question about path loss exponent estimation from measurment Ms MBaz wrote ...
8
votes
2answers
1k views

IIR Filter for Smoothing (Low Pass Filter)

I am using IIR filter for smoothing $$y[n] = ax[n]+(1-a)y[n-1]$$ My question is, if I add another IIR filter, will it be the second order of IIR filter? If not, what it can be called? My second ...
0
votes
1answer
24 views

What is fft input size for ofdm?

From the Transmitter comes a block of size N+L (where N is the number of subcarriers and L is the cyclic prefix length). Then the block goes through a Channel which adds delay and AWGN, so this ...
4
votes
1answer
138 views

Teager's Energy Operator

Does anyone know how to find information on the derivation (rather than the definition and application) of Teager's Energy Operator, both for the continuous and sampled case. I have Kaiser's early ...

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