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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BPSK modulation with Eb/N0 computation

Good Morning to everyone. My goal is to create a BPSK modulated signal starting from Eb/N0. The signal is composed by I-Q components both modulated using BPSK and pulse shaped with squared-root raised ...
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What is the correct interpretation of the capacity formula with modulation?

Someone sent me the image below, and I think I'm confused as well. Is the second formula (modulation) correct? What does it mean? From the symbol, I think it represents capacity, but it doesn't make ...
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problems changing SSB Modulation frequency on Octave

i'm trying to implement SSB Modulation on Octave. i based my code on this: https://www.mathworks.com/help/signal/ug/single-sideband-modulation-via-the-hilbert-transform.html it works ok, until i ...
52 views

16-QAM with RRC filter shows a point in the middle (bad EVM)

I build a PCB with the DAC3174 from TI and I'm using it initially to test it as a channel, like shown in the diagram from the datasheet: The analog signal is mixed with the PLL carrier frequency (at ...
27 views

Modulating with 64-QAM modulation

I'm new to this community. I'm trying to make a sender receiver device with using 64-QAM modulation. But I don't know how to code it or making the waveform. I am trying to make it on Altera Cyclone IV ...
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What's wrong with 180 degree phase shift in QPSK?

I red that 180 degree phase shift causes spurious high frequency components which As a result methods such as OQPSK are invented, but I can't understand how it can happens? In fact, I can't find any ...
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Are there modulation schemes that use more bandwith than they need to, but don't require a spread-spectrum code to decode? (besides AM)

In this answer to Have deep-space spacecraft always used some form of spread-spectrum for data downlink? space scientist Mark Adler explains that while spread-spectrum proper (using specific codes in ...
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Wireless Communication: detecting if a bit 0 changed to 1

I am new in wireless communication, and now I have a 0/1 string like 0010000 (only one bit 1) and wanna send it to the receiver wirelessly. Am I able to detect if the receiver get this string ...
1 vote
44 views

BER of coherently detected DBPSK?

I understand that differential PSK is generally used when coherent detection is not possible, and so is usually detected non-coherently. However, for sake of theoretical analysis/understanding, what ...
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Bpsk implementation python

I found this code in a book to generate polar RZ for a bpsk modulation, if someone can explain to me how the upfirdn function is used here to generate it: Function to modulate an incoming binary ...
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General question on where to learn modulation and radio theory

Does anyone have any good books/videos or courses to learn about radio waves,frequencys,phase spread spectrum and modulation? I need a something that goes through the basics until advanced. Thank you ...
120 views

5G BER vs SNR for QPSK, 16QAM, 64QAM

Recently been running simulations where I run through simulating passing random data bits through LDPC Encoding, Modulation (4, 16 or 64) and then AWGN. The code itself is 90% developed by myself with ...
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What is the most used signal for basic pulse?

My professor said that: in order to avoid interferences/harmonics caused by the nature of the square wave g(t) (sinc will have these secondary lobes), it's better to change the basic pulse g(t) to ...
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Why don't two multiplication of the same cosine wave let me come back to the original baseband signal but instead shifts it further?

I'm trying to do a simple modulation and demodulation of a digital/binary source. I'm multiplying it by a 1khz cosine to center it at 1khz instead of 0. Then, to demodulate, I multiply again with the ...
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1 vote
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Implementing signal processing techniques for consistent RSSI signal reception

I've tried to optimize the LoRa setup using Arduino IDE libraries to ensure accurate or acceptable RSSI measurements and for distance estimation between multiple nodes and a master in an outdoor ...
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1 vote
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How to understand haw many matched filters to use?

I have a question that i can not find a concrete answer. Haw many matched filters should be used for 8-PAM/16-QAM/64-QAM/BPSK? Can somebody shortly explain the logic we should follow? Thank you.
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Frequency Modulation - Demodulation - Distorted frequency shape

I am interested in the effect frequency modulation has on the signal. I am using an acousto-optic deflector to steer a laser beam. The deflector receives a Radio-frequency (RF) signal (~100 MHz, sine-...
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How to derive the error probability for pulse position modulation in digital communication?

I am trying to build a simulation on MATLAB for PPM transmission through AWGN channel. I have a function wrapping the transmitter, channel and receiver that takes a SNR value as input. My simulation ...
87 views

delta modulation

I need to implement some sort of simple delta modulation for my homework. The test signal is $x(t)=10\sin(20\pi t)+\cos(100\pi t)$, sampled at $f_s=40f_{\tt{max}}$ Block scheme of delta modulator is ...
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Why do I find a low frequency oscillation when I add a carrier frequency to my baseband signal ? And Why is my demodulation step not working?

I am trying to build a simulation for a 2PPM signal, modulate it at high frequency and then retrieve my baseband signal. Here is my full code (minus the plots) before explaining more. ...
371 views

How should I decode Pulse Density Modulation signal?

I'm trying to learn the concept of Pulse-density Modulation. The wiki page gives a good overview and pseudocode of encoding procedure, but it lacks the decoding part: The process of decoding a PDM ...
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Choosing a suitable modulation format

I'm trying to deal with this question about multiplexing and choosing an appropriate modulation format. It's in two parts. (i) You need to design a system for the transmission of surround audio ...
1 vote
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Sending and receiving an image

After studying digital communication courses, I wanted to implement these theories and create an application for sending and receiving a gray image via WiFi between two Raspberry Pi devices. The ...
82 views

Convolution with an impulse train in time, what happens in frequency domain

Following figure is drawn as the block diagram of the digital modulator: The output of the filter block (with the impulse response p(t)) is the convolution of the weighted impulse train with the ...
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Does MSK modulation maintain continous phase after spectrum spread?

I need to check if MSK modulation keeps the phase continuous after DS spectrum spread. My thinking is that since we're expanding the bandwidth, it likely involves abrupt frequency changes so it won't ...
1 vote
50 views

Continuous Phase Modulation - Phase trajectory expansion

For continuous phase modulation (CPM), the circular phase trajectory is expressed as follows: $$\phi(t) = 2\pi h\int_0^t\sum_k \xi_k g(\tau - kT_s)d\tau + \Phi_0\tag{1.1}$$ Where: $h$ is the ...
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1 vote
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spectral density of Modulated ofdm signal

I have formed my OFDM symbol his length is 88 (Nsubcarrier=72,Ncp=16) with Fs=1080000 Hz we call this symbol as Signal_from_baseband I want to modulate the OFDM symbol with Fc carrier=2.1 GHz and plot ...
1k views

Help me understand the concept of IQ signals

I am a computer science student working on a school project involving RTL-SDR receivers, and I have a hard time grasping the concept of IQ data. Basically what I think I have learned from all of the ...
1 vote
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What is the relationship between Symbol Duration and Sampling Frequency in a 256 MPSK radio link

I'm struggling to work out the relationship between Symbol Duration and Sampling Frequency in an MPSK link. For instance, if the Sampling Frequency is 10MHz this means that a sample is taken every ...
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