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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 ...
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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 ...
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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 ...
yao zhao's user avatar
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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 ...
Mouh Kramo's user avatar
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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 ...
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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 ...
Dudley008's user avatar
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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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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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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 ...
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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. ...
Aloys Reant's user avatar
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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 ...
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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 ...
Mouh Kramo's user avatar
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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 ...
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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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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 ...
ahmed bennani's user avatar
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4 answers
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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 ...
Kuba Lhotský's user avatar
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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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How is the normalized power required for unipolar NRZ twice that of polar NRZ?

So, the normalized power for unipolar NRZ scheme is $\frac{1}{2}V^2$. According to my book, the normalized power required for polar NRZ is half that of unipolar NRZ. So, the power should be $\frac{V^2}...
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Oqpsk pll delay axis ambiguity

I don’t understand how this phenomenon appear in OQPSK carrier recovery loop. I found nothing on google. Is it a normal phenomenon in OQPSK loop or specific? Why does it get reversed I and Q? In the ...
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What are different encoding schemes used in gigabit ethernet?

I was reading about digital transmission, there are many steps namely Analog to Digital conversion Source coding Channel coding Line coding Pulse shaping Modulation Multiple access techniques Out of ...
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Is there an open source "Data over Voice" library?

I need to transfer data from A to B using audio as the medium, with a speaker at one end and a microphone at the other. Sometimes simply through the air, but it must also work through legacy phone ...
Björn Morén's user avatar
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Pulse amplitude modulation

I am reading from the internet and my professor's course on PAM. This course is not well-organized, and I would like to ask for book recommendations. I know that this modulation is divided into two ...
Mouh Kramo's user avatar
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1 answer
114 views

Is BPSK relevant, or does it even exist, in wireless data transmission?

I ask this question because it seems to me that if pulse shaping has been applied in the transmitter, the signal that is actually transmitted is not phase modulated at all, rather, it is amplitude ...
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How does PAM-4 encoding of a digital signal relate to theoretical *pulse* amplitude modulation?

Pulse amplitude modulation in general is often explained using plots like this one from wikipedia: There is a sinusoid analog signal (red) to be "imprinted" on a train of pulses. The result ...
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Exactly when is pulse shaping applied in the radio transmitter, before or after modulation, and is it applied differently in BPSK, QPSK and 16QAM? [duplicate]

I previously asked at which stage pulse shaping is applied in a WiFI transmitter and my question was closed due to duplication. The answers I was directed to have only served to confuse the issue for ...
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What is the phase of $Y(\omega)$ in relation to the phase of $X(\omega)$ where $x(t)$ modulated with an exponential carrier that has no phase shift?

A homework problem of a free online course I am taking, asked to draw the magnitude and phase of $Y(\omega)$ where $y(t) = x(t) c(t)$ where $c(t)$ is $e^{j 3 \omega_{c} t}$ and where $X(\omega)$ is: ...
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Preparing data for modulation classification based on RML2016

I would like to validate a trained model based on RML2016.10a. My idea is to capture a certain amount of data (20 Msps) for approximately 0.3 seconds. Then, I identify all the signals in this ...
Ivan's user avatar
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Comparing communication systems with different modulation orders and code rates

I propose an end-to-end communication method in my research. The key part of the method is not the channel coding and modulation but we use them anyway. I am using 1/3 rate Turbo codes with QPSK and ...
tuna's user avatar
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Raised cosine filter and root raised cosine filter IQ for modulated signal QAM/QPSK

If I am passing a QAM signal through Root raised cosine Tx filter and measure the constellation at output, it seems very bad. If this bad output again pass with other another root raised cosine Rx ...
kecbackbencher's user avatar
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2 answers
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Demodulation + LPF gives derivative of modulated signal

I'm new in this community and I hope it is the right place to post my question. Unfortunately, signal processing and electronics in general are not my fields, so I'm sorry if the question is trivial. ...
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Does phase shift introduce high frequencies?

In PSK phase modulation scheme, the signal phase is shifted, hence it looks something like this: I cannot understand why this doesn't introduce a set of unwanted high-frequencies, as the steep ...
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Why does NB-IoT use standard QPSK in multi-tone transmission, when pi/4 QPSK is implemented for single-tone?

I've been studying the modulation schemes used in NB-IoT communication, with a particular focus on energy efficiency. I've noticed that QPSK (Quadrature Phase Shift Keying) is used in multi-tone ...
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Clarification on video about frequency deviation in phase modulation bandwidth

I am watching this video and at 7:12 he calculates the frequency deviation $\Delta f = f_{c}f_{m}A_{m} $ where the $c$ underscript is for "carrier" and the $m$ underscript is for "...
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modulation transfer function and ground resolved distance

I am trying to understand something in remote sensing but lack a background in science and technology so it is difficult. Hopefully this is a reasonable question to ask. In sensing there are different ...
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Why for bandpass signals complex envelope and pre-envelope signal representations are used in digital communications/analog communications (FM)?

When we need to analyse band pass signals we use complex envelope and preenvelope representations, wherein a signal is given an equivalent low pass representation. My issue is why it is done, though I ...
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Meaning of roll-off factor 0.5 and bandwidth

We currently have a radio that is transmitting at the following RF params: Modulation: OQPSK Data rate: 500Kbps Uplink coding: BCH I am interested in understanding what is the associated uplink ...
ITried's user avatar
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I don't understand which signal I should use as a carrier in my excersise

$\DeclareMathOperator{\sinc}{sinc}$ Given 3 signals $x_1(t) = \sinc(t) , x_2(t) = 10\cos(2\pi f_2t)$ and $x_3(t) = 5\cos(2\pi f_1t)$, where $f_2 = 100\text{ kHz}$ and $f_1 = 1\text{ kHz}$. I must ...
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DS-CDMA Spreading Code Length Selection

I'm trying to wrap my head around the process of selecting DS-CDMA spreading codes, and I'm having trouble understanding the tradeoffs of longer codes. For all scenarios described below, I'm using a ...
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