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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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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14 views

Image to Binary stream for OFDM with qpsk/qam modulation matlab

Im looking to covert a .png or .jpeg image into bitstream so that I can further use it as input bit stream for OFDM with QPSK/QAM modulation in Matlab. I would really appreciate the help on that. ...
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1answer
31 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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29 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
45 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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2answers
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
50 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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30 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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32 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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1answer
73 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
58 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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20 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
131 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 ...
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1answer
45 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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0answers
40 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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374 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
960 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
128 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
49 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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48 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
54 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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55 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
158 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
166 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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81 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
36 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 ...
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1answer
71 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 ...
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1answer
225 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 ...
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1answer
755 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
63 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 ...
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1answer
498 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 ...
2
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1answer
218 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 ...
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1answer
135 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 ...
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2answers
278 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 ...
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1answer
67 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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142 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 ...
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1answer
290 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. ...
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1answer
49 views

Double sideband AM

In A3E transmission, I wonder how a single antenna is used to transmit a carrier wave, upper sideband and lower sideband altogether at the same time?
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1answer
215 views

FM Modulation Index and Frequency trippler

Suppose I have an FM signal with modulation index mf which is passed through a frequency tripler, then what will be the modulation index of output waveform ?. Thanks in advance....
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3answers
107 views

What is the most computationally efficient way to generate 100 sine waves layered on top of each other?

Right now I simply do this (pseudocode) for freq in freqs: for i in len(samples): samples[i] += sin(...) Is there a better way? This is for ...
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1answer
226 views

How to implement IDFT using the positive frequencies of DFT, modulation and resampling on MATLAB?

This question is a continuation of the discussion at How can a linear operator on DFT vector produce the same vector using only half of the DFT vector?, where the higher level motivation is better ...
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214 views

Bandpass filter BPSK

I have a question concerning BPSK and the bandpass filter that seems to be sometimes placed before the receiver circuit (the receiver is a mixer and lowpass filter). Basically, from what I've ...
3
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1answer
82 views

What are the options for turning a bit stream into a byte stream?

I am creating a system (modulator and demodulator) for broadcasting binary data through an analog signal. I'm using BPSK with great success – at least, I'm generating great graphs. Green is input ...
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1answer
225 views

OFDM training symbol format

For OFDM synchronisation, we are using two training symbols according to the Schmidl and Cox method of frequency synchronization and timing synchronization. The paper says: The first OFDM training ...
2
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1answer
195 views

obtaining “4 Hz modulation energy”

Could anybody tell me a method to calculate the "4 Hz modulation energy" for a speech signal? Thanks. EDIT I get some details : 4 Hz modulation energy: Speech has a characteristic energy modulation ...
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1answer
113 views

How should I modulate a $16$ bit input using FSK?

I need to graph a $16$ bits binary sequence, assuming that it'll be a FM analog signal I need to apply FSK to it. So, I think I should use the formula $A \cos(2\pi f_1 t)$ for binary $1$'s $A ...
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1answer
195 views

Why is a precoder necessary for DQPSK and what does it accomplish?

I've implemented a soft-decoder for DQPSK using the wonderful answers I received here: How to soft decode DQPSK? To get the soft-decoder working properly I needed to precode the data I was sending ...
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2answers
567 views

How to soft decode DQPSK?

I'm successfully soft-decoding D-BPSK by taking the dot-product of the constellation-position of the symbol and of the previous symbol. If the result is >= 1, then the symbol phase hasn't changed and ...
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1answer
225 views

Non-coherent receiver for DBPSK: Implementation details

I am implementing a non-coherent receiver for DBPSK. I have a computer science background with little knowledge of DSP so my questions here may seem obvious. The design of the receiver I am trying to ...
2
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1k 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 ...