# Questions tagged [discrete-signals]

A discrete signal or discrete-time signal is a time series consisting of a sequence of quantities.

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### Need help with DTFT problem

Prepping for exam and this is one of the practice problems: I just want some clarification on some of the steps my professor took. This is the answer in the answer sheet Only thing I dont understand ...
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### Phase Unwrapping Issue of IQ data sample in Radar Signal Processing

I am doing radar Sensor signal processing. The radar sensor gives iq data corresponding to the range(sweeps) I want to detect micro motion so that phas analysis is used. Sweep is the distance ...
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### Fourier transform why can I convert one of the axes into an imaginary number?

Contextualizing This question is inspired by the following video: https://www.youtube.com/watch?v=-qgreAUpPwM&t=60s&ab_channel=3Blue1Brown I own a sign, a drawing of a square with 200 points ...
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### Periodicity of a discrete time complex exponential signal?

I'm new to DSP and I'm struggling to solve a basic problem. I think I've solved it but I feel that something's off in my reasoning. The problem involves investigating a signal of the form $e^{jk\pi n}$...
1 vote
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### When is perfect analytic filtering (discrete) suboptimal?

Defined as "negative DFT bins zero", when are such filters suboptimal for AM/FM extraction or related filtering? This answer reads, [nulling] also has the worst performance compared to ...
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### Odd artifacts after sinc interpolation

I am trying to upsample a signal using sinc interpolation. I have written a way to do this in python. ...
1 vote
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### Why is Envelope noisy even after filtering and achievement of SNR gain (-6dB SNR to 14dB snr)?

A noisy signal with 500 MHz bandwidth, with negative SNR, when filtered to 6 MHz bandwidth, should attain a theoretical SNR gain of 20 dB. So if the original signal has -6 dB SNR, after filtering we ...
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### Different PI controller implementations and their respective discrete transfer functions

So I need to implement a PI-controller and I found an Implementation of an PID-controller with some background explanation. I adapted the implementation to an PI-controller, implemented it and got the ...
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1 vote
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### Why use sinc function to downsample an image in fourier domain?

I'm very confused about downsampling in image processing and the use of sinc function to do it. I read this post : 2D Fourier downsampling some time ago that talked about my own doubt, that is to ...
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### I just computed an DFT and FFT of a sinc function, but when I visualise them the results are strangely different? what am I missing

The idea here is to improve a Sinc function by manipulating its Fourier transform. As you can see, the tophat has ripples in the bands of interest and I want to eliminate them by smoothing them with a ...
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### GNU Radio Volk phase rotation function does not work properly

I am implementing a CFO recovery algorithm in GNU Radio. The CFO is set in the GNU Radio and the correction section in the C++ OOT module is given below, which works fine :) ...
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1 vote
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### Sampling Precision, Jitter, and PID

I am having difficulty understanding the effect of quantization noise and ADC resolution in a digital PID controller. I am also trying to understand the effects of sampling jitter on a PID controller. ...
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### Compact books for reviewing signal processing

I am about to start a new engineering job in the fields of signal processing and machine learning. I have a bachelor's degree in electrical engineering, but for the last two years I have been doing a ...
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### Understand carrier power, output power and dBC?

I have a question regarding the concept of carrier power, output power and power relative to carrier (dBc). Suppose I have a carrier frequency of 4Hz and signal bandwidth = 4 Hz. The signal span is ...
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### Basis Pursuit Denoising (BPDN) algorithm for Direction of Arrival Estimation

I am working on Compressive sensing algorithms for DOA estimation. Can i get any references for writing BPDN code in MATLAB.
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### What are the criteria for a change-of-basis transform to be doable in $O(n \log(n))$?

The Fourier basis is a common choice for transformations, but a lot of times, it's not the best for a specific application. For instance, wavelet bases give us better spatial / temporal locality than ...
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### Scilab - possible to get transfer function, H[z], with negative powers of z?

I use Scilab. Is is possible using Scilab primatives like poly(), horner(), etc., to generate and display a discrete time transfer function with only negative powers of z? I have tried a number of ...
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1 vote
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### What is the best way to decide whether a periodic signal is present in a noisy environment with a limited number of samples?

Suppose I have few samples (e.g. 20) of a decaying sinusoidal function and I am heavily noise-dominated (SNR ~1, noise is Gaussian or Poissonian). Let's think of e.g. \begin{equation} y(t) = A \, \sin(...
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### A problem on FIR filter design given a difference equation

Given the following difference equation: \begin{equation} y(n)=2x(n-2)+3x(n-5) \end{equation} describing the structure of an FIR filter, design the direct form of one. What is the order of the filter? ...
192 views

### Constructing an input signal whose response is determined by the impulse response

I'm self-studying Signals and Systems by Alan Oppenheim, and I have some trouble understanding the solution to a homework problem. P5.13 tries to find the sufficient and necessary condition on the ...
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### Problem with the existence of inverse DTFT

I am having trouble on the following exercise and I can't figure out where I am doing something wrong: Given an LTI system described by the following difference equation: $$y(n)=x(n)+2x(n-2)+y(n-1)$$ ...
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### How to calculate roll and pitch from an accelerometer in whatever orientation?

I’m trying to use a tri-axial accelerometer as an inclinometer, measuring the so called roll and pitch angles. The underlined principle is that in stationary conditions an accelerometer senses only ...
1 vote
104 views

### Axes of Discrete Fourier Transform

Problem Given $X[k] = \sum_{n=0}^{N-1} x[n]e^{-j2\pi kn/N}, k = 0, ..., N-1$ What are the units on the x-axis and y-axis? Note that for the x-axis there are two answers. Attempted solution My first ...
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1 vote
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### A problem on $\mathcal{Z}-$transforms and signal stability

I am doing the following problem for my DSP exam and I am doubting my answers while being stuck on the last part: Given a causal LTI system and difference equations $y(n)=x(n)+20y(n-1)-100y(n-2),$ ...
1 vote
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### Get shape of a recurring pulse event in my plant video signal

I'm studying plants - specifically how the color of their leaves change throughout a day. I have a camera pointing at a leaf which takes a picture every 47 minutes and calculates the average green ...
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### How to maintain DFT symmetry for zero padding in frequency domain? [duplicate]

I am looking for a mathematically correct way of zero-padding in the frequency domain when we have an even number of points. (i) If we zero pad in the center of the DFT, after the Nyquist value, the ...
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### Sampling rate for a 200 kHz signal

I'm using a rsp1 to sample the output of an underwater acoustic transducer which has a resonant frequency of 200 kHz (with a 500 Hz bandwidth) . The transmitted signal is a CW pulse which can vary ...
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### Which type of noise can we see from the given image signal and its abs of 2D FFT?

1. Background: I get an 128*128 2D one-channel noisy image as follows: I get the shifted absolute values of 2D FFT result by the following Python code: ...
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