Questions tagged [modulation]

Modulation is the process of varying one or more properties of a high-frequency periodic waveform, called the carrier signal, with the amplitude of low-frequence modulating signal which typically contains information to be transmitted.

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How to find the noise power in my simulation

I am currently working a tricky communication chain that I want to simulate into Matlab. The chain is like a classic BPSK modulator/demodulator chain, but where the BPSK modulated signal has been ...
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2answers
165 views

Up-converting a sinusoidal signal

I want to up-convert a baseband sinusoidal signal of frequency $4000 \, \rm{Hz}$ using a carrier frequency of $20\, \rm{KHz}$. I read that one can up-convert a baseband signal to a passband signal ...
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93 views

Multiply signal $x[k]$ with $\cos(2\pi\nu_0k)$, then given $X(\nu)$ draw resulting function in frequency domain?

Let $$y[k]=x[k]\cdot \cos(2\pi\nu_0k) .\tag{1}$$ Then, given a signal $x[k]$ with the DTFT $X(\nu)$ according to the following figure what will the frequency domain for $Y(\nu)$ look like for a ...
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242 views

How to calculate the accurate BER expression of circular 8-QAM constellation modulation?

It is easy to understand the BER derivation of square QAM, but the circular 8-QAM? I'm quite confused. The decision region is not in a rectangular shape anymore, meaning regular way does not work here....
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95 views

Does anyone recognize this modulation?

I'm trying to extract the code of my garage remote, but i have some difficulty to find witch modulation has been used. At first I thought it was a simple digital modulation, but there is some strange ...
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794 views

Information in GFSK signal

I was measuring a Bluetooth LE Signal, particullary a Channel with center frequency 2402 MHz and Bandwidth of 2 MHz, 2401 - 2403 MHz. Those measurement points are just the highest peaks. In the ...
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448 views

Demodulation distortion in single-sideband and double-sideband

I am trying to compare the demodulation for single sideband (SSB) and dual sideband modulation formats (DSB) when the reconstructed carrier is not perfect (i.e. shifted in both frequency and phase). I ...
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220 views

What is dynamic pulse-width modulation?

I'm working through exercises in a book called The Audio Programming Book and have been doing okay for nearly 300 pages, but have just got stuck. (I'm a musician, not programmer or audio specialist ...
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137 views

TDE, OFDE and FDE equalizer simplest exmple in matlab

I want to implement the equalizer in matlab. I am just learning this. I want a good kick start code that can help me to learn it further. I searched a lot on Google but do not find a good reference ...
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1k views

How to implement GMSK demodulation

I am currently trying to implement a GMSK demodulator, using Java. I am actualy trying to use the model of this block diagram. However, I really do not know what goes on within the mode selector and ...
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5k views

Adaptive Delta Modulation For Speech Signals

I need to implement an adaptive delta modulation encoder and decoder using matlab for my term project. How can I code a good adaptive delta modulation? How can I change ...
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9k views

Maximum Frequency deviation in Frequency Modulation

I am writing a script to frequency modulate the stereo audio signal, and later calculating the modulation index wrt time. As we have to modulate the stereo audio signal, I have to first synthesize ...
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1answer
34 views

Bandwidth of a modulated signal in analog domain

If i am using QPSK modulation with data rate 4 Mbps with rolloff factor $0.5$, then the bandwidth will be symbol $\rm rate\times (1 + rolloff\ factor)$. So here it will be $\rm 2\ MHz\times 1.5 = 3\ ...
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36 views

What is difference between Phase shift keying (PSK) and Quadrature Amplitude Modulation (QAM) mathematical equation

I went through a literature and found the following expression for PSK signal. On this basis, what will be the equation for **QAM signal **. Also from where i would be able to read about this equation ...
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8 views

Model of modulator and demodulator in Simulink. Why is MER so lowest?

I created a simple model in Simulink of a quadrature modulator, amplifier and quadrature demodulator. On the oscilloscope(scope in Simulink) and spectrum analyzer the displayed results look normal (at ...
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42 views

What is DAB modulation in signal generators?

I am using R&S signal generator and for generating a DAB signal there is an option for mentioning the modulation level in %. For example, we can generate DAB modulation 50% . I can understand that ...
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160 views

What's wrong with my M-ary ASK modulation demodulation MATLAB code?

My MATLAB code linked below implements ASK modulation of an M-ary signal, impresses it on a carrier, adds AWG noise of various SNRs. Then, for each SNR, demodulates the signal and calculates the ...
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138 views

GNU Radio - Bandwidth and Band Reject Filter

I am currently trying to generate a psk modulated carrier with gnu radio. Attach is an image of my flow graph. As can be seen I am generating a bit stream using the Random Source module and ...
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63 views

Pulse shape estimation

Given a captured noisy BPSK signal, how do I formulate the maximum-likelihood problem so as to estimate the matched filter? The model of interest would be baseband BPSK with AWGN: $$c(t) = \sum_{\ell=...
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1answer
651 views

How to generate IQ component for transmitting 2FSK

I am trying to generate IQ components for 2FSK modulation. I have started off from this thread FSK and IQ modulation , but I don't quite understand the IQ TX components plotted in the example there by ...
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124 views

low-frequency amplitude with phase modulation of low Hz carrier

I am writing an FM/PM synthesizer, using Java. For the most part it works pretty well. What I am curious about is an attempt to use a low frequency tone as a carrier. By low frequency, I mean in the ...
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65 views

Is an extra symbol at the origin of a QAM constellation ok?

This question is specifically directed at Maximilian Matthé (as you work with 5G systems), and to anyone who can shed some light. I am trying to implement a GFDM system with a total of N = K*M ...
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67 views

Mathematics in selection of RC time constant for an envelope detector for AM

Let the capacitor be charged to voltage $ V(t_0) $ at $ t=t_0 $ and then start discharging. At time $ t \, (>t_0)$, the delayed capacitor voltage is $$ v(t)=V(t_0)\operatorname{exp}(- \frac{t-t_0}{...
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115 views

How to find and fix the delay of a modulation

I am creating a model in MATLAB to simulate power line communication, but I found a problem. I'm very new to the DSP area, I get my code below from a MATLAB example. ...
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69 views

ssbmod single sideband modulation artifacts

clc; clear all; close all; [c,fs]=audioread('60hz.wav') r=ssbmod(c,160, fs) r=r/max(max(abs(r))) audiowrite('artifacts.wav',r,fs,'BitsPerSample',24) I am trying ...
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344 views

FSK demodulator by integration if the samples per symbols is 2

Say I have a binary FSK with +f and -f frequencies and I have two samples per symbol. Let's consider the "1) multiply with <...
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628 views

Determining frequency deviation FM

I am trying to understand the concept of frequency modulation. As written in Wikipedia, if I have a signal containing information $x_m(t)$ and I want to transmit it using frequency modulation, I need ...
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555 views

How do I decode(demodulation) and get original data from audio sample data

Here I'm talking about the less-than-ideal situations, in other words, the audio sample data may have burrs or error bits in it. Encode and decode theory: I am using FSK to encode my original binary ...
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941 views

BER of OQPSK Modulation

I am unable to find out a formula for the BER for the OQPSK Modulation. Currently, I am using the berawgn function from Matlab to calculate the BER for OQPSK but I am looking for an expression for ...
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292 views

Minimum Shift Keying (In-phase, Quadrature Components derivation)

In the derivation of the minimum shift keying in-phase and quadrature components in Simon-Haykin Communication Systems 4th ed (p.387-390) we start off with the definition of the signal to be $\ s(t) $...
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96 views

transmitting data using phase modulation of two sine waves passed through distortion

I have two sine signals with frequencies f1 and f2, and phase p1 and p2. I modulate the phase of these signals to transmit two symbols simultaneously, chosen from the set [0,1,2,3]. For example, I ...
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125 views

Calculate a Kind of Equivalent Baseband Signal by Examining the Zero Crossing

I have a device (whose behaviour I can't change) which does the following signal processing: The incomming signal contains two frequencies $f_1$ and $f_2$. One has a huge amplitude, the other a ...
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205 views

PPM Variant - Analytic symbol error probability

I'm trying to calculate symbol error probability of variant of pulse position modulation considering only AWGN channel. The decoder is maximum likelihood so the implementation of the detector is by ...
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115 views

The transmitted signal of DPSK

I am very confused about how to get the transmit sequence of the DPSK signal. In my lecture notes, teacher give as the following example. ...
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2answers
52 views

Coding an LFO in C

I want to know how I could implement a Low Frequency Oscilator on a simple synth I've coded in C. First in order to understand how to make this happen I would like just to modulate a sine wave by a ...
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22 views

modulation depth

When a value for the power dissipated by an AM signal is given, and the depth of modulation is also given. Then you are told to find the modulation depth required to increase the power to a higher ...
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44 views

Why does the frequency in fft plot of the baseband modulated signal isn't changing at the receiver

I have designed a transceiver system for cellular frequencies(800MHz). On the receiver side, I have converted the band signal to baseband signal through digital mixing. I have added the Inphase and Q ...
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33 views

Non coherent detection BFSK demodulation?

I am simulating BER performance of BFSK under AWGN and Rayleigh fading, BFSK has two symbols one entirely on the real plane while other on the complex plane for representing let's say zero and one, ...
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16 views

Representing the signal $ u(t)=A_c \cos (2 \pi f_c t + \beta \cos 2 \pi f_m t) $ in terms of Bessel function

I want to represent the signal $ u(t)=A_c \cos (2 \pi f_c t + \beta \cos 2 \pi f_m t) $ in terms of Bessel function. I have done the exercise. I want someone to check whether what I have done is ...
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1answer
44 views

Why does my digital upconversion result in two tones?

I am using Xilinx's RFSoC in I/Q mode. The important point is that in the digital space I have real and complex samples. I take the incoming data and multiply it by a complex sinusoid. In my test ...
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21 views

How do you determine the power required for a phase shift keying modulation scheme?

This wiki article has a diagram : which shows how the message "11000110" is conveyed as a waveform. I'm trying to understand how the power to transmit this message can be determined. Do I need ...
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Is this PSK or FSK

I am analysing a captured 433.92MHz signal sampled at 2MHz: If we zoom in: I am thinking this is PSK? Am I wrong? Thanks
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Can you help me to understand Multi-tone FSK, and how I can implement it?

Any paper, book, Matlab file... that you would recommend. Thanks.
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24 views

What is the range for a demodulated AM signal?

Lets say I perform amplitude modulation (modulation index = 1) of a signal that has a range of [0, 1]. If I demodulate by taking the absolute value of this signal and then low-pass filter it, what ...
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45 views

Length of CDMA code and message length vs. number of participants

What is the minimum code size for CDMA codes for synchronuous CDMA (not asynchronous CDMA!) with N number of participants? Furthermore, suppose N parties want to uniquely transmit a message of length ...
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33 views

Learning PSK Modulation and Demodulation - Good Text to Read?

Title sums it up. I am curious to see what you all suggest. I'm a newbie and just need some beginner/intermediate material. Thanks!
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OQPSK - GNU Radio Companion

I was wondering if anyone has had any success in implementing OQPSK in gnuradio. I have a working theory of expanding on the Constellation Modulator to include a custom OQPSK function. I have ...
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32 views

How to make SL to RF inport in simulink work real time?

I am using qam in the simulink and need to upconvert the complex baseband data and obtain the time domain passband signal. I pass the complex baseband data to SL to RF inport and then do the ...
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68 views

Generating a phase modulation frequency spectrum with jitter

I would like to produce a frequency spectrum plot like this: (from All About Circuits) I know that one can take the modulation frequency and multiply it by a given order and scale by the modulation ...
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25 views

How to compare two 802.15.4 O-QPSK modulated digitals signals?

I am working on wireless sensors project and I am trying to simulate a transmission between two nodes. So let's say I have two nodes which transmit the message to each other, i.e. node 1 transmits ...