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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Gettiing a rectangular waveform from OOK in Python

I have a wave (wav) sound file with on-off keying. I can read the signal value at any point in time (granularity of the sample rate) from an array. I want to create another array, the same size as ...
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2answers
57 views

C/C++ library for digital modulation [on hold]

Is there a library written in C/C++ that offers functions like QPSK modulation?
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1answer
12 views

How to model the dispersion which introduces a modulation driver of EML?

I need to model the dispersion which introduces a modulation driver of EML, in matlab simulations. The parameters are: Lambda: 1310nm PAM4 power: Pmax = 1.09 mW Pmin = 0.13 mW Bandwidth = 56Gbps
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2answers
61 views

Tuning a radio to a certain frequency

I've a fundamental problem with understanding terminology used in DSP. What does it mean to tune a radio (for example, a software defined radio) to a certain carrier frequency $f$? The received signal ...
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0answers
51 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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2answers
41 views

Reason of circular conv in OFDM

In OFDM system, after IFFT a CP is added at the beginning of the OFDM symbol by copying it from the end of the symbol.My question is that with CP why we use cyclic convolution instead of linear ...
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1answer
44 views

How to transmit the real+imaginary output of an IFFT over a transmission channel?

I'm working on a modem system using a 16-QAM scheme. The transmitter runs an IFFT to modulate the signal, and has a 12-bit DAC. The receiver runs an FFT to demodulate the signal, and has a 12-bit ADC. ...
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1answer
146 views

Modulation and it's application [closed]

Why do we need different modulation techniques? Is it because we need to convert from analogue to digital data sometimes? Also what are typical applications where modulation schemes are used apart ...
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1answer
68 views

Normalizing 32QAM constellation points [closed]

By which value can the constellation of a 32QAM be normalized? for example 16QAM is normalized by squareroot of 10.
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17 views

BER and SER of QAM [duplicate]

I want to find the SER and BER of the 4QAM,16QAM,32QAM. I know that the formulas for SER and BER are different but I cant find them in any text book. The formulas for the BER that I found: 4QAM = ...
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0answers
44 views

OFDM Rayleigh Channel 16-QAM

Is there a difference in the BER of a 16-QAM modulated signal that is sent through a rayleigh channel using OFDM versus not using OFDM? I know for BPSK, there is barely any difference in the BER.
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1answer
143 views

How is the symbol error rate for M-QAM, 4QAM,16QAM and 32QAM derived?

How do you derive the theoretical symbol error rate as a function of $E_\mathrm{b}/N_0$ for 4QAM? I know that the result should be $Q\left(\sqrt{2E_\mathrm{b}/N_0}\right)$ but I am ĺooking for the ...
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1answer
54 views

Really basic question about OFDM

I am new to signal processing and am currently doing research into the subject. I am learning about Orthogonal Frequency Division Multiplexing and have a question. Most definitions of OFDM mention its ...
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2answers
40 views

How do you perform OFDM modulation?

I'm new to OFDM modulation. During OFDM modulation in the frequency domain, are the negative frequencies modulated with a conjugate version of the data of the positive frequencies, or do the negative ...
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0answers
28 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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1answer
57 views

MSK spectral efficiency explanation

Why is MSK (minimum shift keying or FSK with a modulation index of 0.5) said to be a spectrally efficient form of FSK?
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1answer
35 views

what are the applications of fourier transform in modulation

what are the applications of Fourier transform in modulation ? What are modulation schemes that use Fourier transform? I guess, FSK & PSK are related to Fourier transform since it both have ...
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1answer
110 views

Simulink for Amplitude Modulation

I am using Matlab Simulink to analyse Amplitude Modulation in Noise. I attached my system below. My problems: 1)In the mixer I am using a bandpass filter and another one after the envelope ...
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3answers
2k views

Can we break the Shannon capacity?

I have a friend working in wireless communications research. He told me that we can transmit more than one symbol in a given slot using one frequency (of course we can decode them at the receiver). ...
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1answer
95 views

Implementing QPSK Demodulation

I conducted a research on how to implement a QPSK demodulator. I found out the Quadrature QPSK demodulation technique which seems very straight forward. Here is what i understood from the explanation ...
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0answers
38 views

TDOA using demodulated signal

Is it possible to find time delay of arrival using demodulated signals (of bandwidth ~200hz)? I have a setup in which I receive (multiple receivers, of course) modulated signal from a source. I want ...
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0answers
78 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 ...
2
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1answer
86 views

How do I implement the delay of the Q-Phase Input in GMSK?

I am on a project to write a function in Java to perform GMSK modulation. I have a good understanding of the GMSK modulation block diagram to an extent, but I have a challenge on what it means to ...
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1answer
81 views

QAM for analog and digital waves [closed]

I tried the following code for modulation of two analog waves. Can anyone point to how to modulate and demodulate for an analog and a digital wave? I tried by replacing the second signal (x2) with a ...
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41 views

MTF for laplacian of a gaussian

am trying to plot a modulation transfer function of a gaussian from -40 to 40 mm in conjunction with a laplacian of gaussian filter, width = 4 mm and sigma = 1. i have a trouble scaling the MTF for ...
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2answers
200 views

QPSK and OQPSK Modulation

In QPSK, after splitting the odd and even bits into the I and Q channels, and then multiplying them with the sine and cosine function, what next am I suppose to do? Do I rearrange them back into ...
2
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1answer
68 views

Software-based sound card OFDM

I'm trying to implement an sound card-based OFDM modem. A paper says: ...A serial to parallel converter is applied and the IFFT operation is performed on the parallel complex data. Say I have ...
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42 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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0answers
530 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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1answer
2k views

QPSK Modulation/Demodulation in C++

I'm trying to implement a QPSK Mod/DeMod system in C++. So far i have a bit generator that generates N bits and stores it into an array: ...
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1answer
167 views

How to compute the free distance in TCM (Trellis-Coded Modulation)?

I would like to be able to compute the so-called "free distance" for a TCM with a rate 2/3 convolutional code (two inputs, three outputs) inside that I plan to use for 8PSK. My previous assumption was ...
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1answer
59 views

2-PAM or 4-PAM if I want to send data as fast as possible?

I would like to ask if I should use 2-PAM modulation or 4-PAM modulationif I want to send data as fast as possible given that in each case I have the same frequency spectrum available.
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56 views

Line coding for a modulation order that is not power of 2

In case a symbol encodes a non-integer number of bits, how is done the bit-symbol pairing? For example, we have a 3-levels FSK with bit rate of 1Mbps and a sequence 01011001. What is the symbol ...
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1answer
74 views

Modeling Load Modulation

I'm trying to create a simple NFC/RFID software simulator and am having a hard time understanding the math fully. I know that NFC tags respond by load modulating the 13.56 MHz wave that the reader is ...
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60 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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2answers
167 views

16 psk demodulation

I have to implement a complete receiver in digital communications. The transmitter gives me an output vector which has real and imaginary values. It uses 16psk for modulation. How would I ...
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1answer
224 views

How would sigma-delta modulation work in software?

I've recently come across this YouTube video that shows a PCM stream being played back via the 1-bit internal "PC Speaker", and after hours of googling I've come to think this is done via Sigma-Delta ...
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0answers
92 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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1answer
41 views

Algorithm to change an already sampled guitarstring to sound like it was a bit damped by the hand [closed]

I'm trying to simulate the damping of the hand on a guitarstring on an already recorded/sampled open guitarstring sound. I've been trying to use low pass filter and had a moving frequency range but ...
0
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1answer
86 views

I can't figure out why spectral features are “displaced” on a spectrogram

I'm trying to create a spectrogram of a complex signal 'y', but I'm running into a problem where the spectrogram that I create appears to have its spectral features "displaced" in frequency space, and ...
2
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1answer
258 views

QPSK, from Square Root Raised Cosine to Rectangular Impulse Shaping

I have implemented a QPSK modulator and demodulator using classic text-book examples: Square Root Raised Cosine Impulse shaping and Matched Filtering. The problem is that I've been told that I could ...
0
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1answer
978 views

Power Relation in DSB-FC AM [closed]

So, in my class I have to learn how to derive the power relation in a Double Side Band, Full Carrier Amplitude Modulated Wave However, I have hit a wall somewhere. ...
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1answer
68 views

Complex Exponential Narrow Band Channel

We can describe a BPSK signal, x, as: $$x=cos(2\pi f_c t+n\pi),\;n\in \{ 0,1 \}$$ The BPSK signal is then transmitted through a narrow band frequency flat Rayleigh channel, described by a single ...
0
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1answer
648 views

SINR calculation

I would like to calculate the total SINR of a IQ modulation system in time domain. $$ SINR = \frac{P}{N+I}$$ The blocks of the system are. Bit generation QAM modulation pulse shaper (sq root ...
3
votes
1answer
229 views

Improving the communication speed on a 10km cable (with high capacitance)

I'm working on improving the modem communication speed that can be achieved over a 10km cable. The current modem achieves a speed of 9600 bps via hardware (phase locked loop) and I'm looking for ways ...
0
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1answer
149 views

Barker Sequence for QPSK

I'm trying to implement a QPSK burst modulation and demodulation through a channel and I'm now considering the synchronization part. I've read that Barker sequence were excellent option for this as ...
2
votes
2answers
415 views

Is there a way to calculate modulation depth after the modulation process?

Suppose I have some amplitude modulated carrier wave $x$. If I have no access to the original message wave nor the unmodulated carrier, is it some how possible to calculate what is the modulation ...
0
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1answer
68 views

FM synthesis fuzzy sound

I'm trying to reproduce this !!!WARNING LOUDNESS!!! sound in C. In the website, it says to use Carrier: 500 Hz, modulator frequency: 1 Hz, modulator index: 500, however I'm getting lots of clicks and ...
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2answers
191 views

Why the carrier frequency does not appear after AM modulation?

Okay, this might be a very basic question, but I'm completely new to the field. I have a $40$ Hz sine wave ($1000$ samples, $fs = 1$ kHz), which I have amplitude modulated to a $4$ Hz sine wave ...
2
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1answer
350 views

Frequency detection

What I have: A digital signal sampled at Fs composed of a QPSK modulation at Fmod plus some additive white gaussian noise. ...