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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27 views

Why Bluetooth 2 use pi/4-DQPSK instead of OQPSK?

From the peak to average power ratio point of view OQPSK is better than pi/4-DQPSK. What is the advantage of pi/4-DQPSK compare to OQPSK? Why Bluetooth 2 use pi/4-DQPSK instead of OQPSK?
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Find the total amount of frequency multiplication needed for an Armstrong indirect FM modulator, when frequency deviation is adjustable in a range

I am currently practicing for my college exams and in this question, they are asking us to find the total multiplication needed in the system. But I am stuck because I have no idea of how to make use ...
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AM and FM frequency range

I don't know what I misunderstood or what but I thought in FM and AM you can transfer your frequency characteristics of modulating signal anywhere you want but I find out that there is a range for ...
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23 views

Transmitting an approximate CW with an FM modulator

Imagine we had an FM modulator with carrier frecuency $f_c$. My doubt is about the optimal approach to use it for transmitting a tone (CW) of a frequency $f_c+\Delta f$. Let $x(t)$ a and $y(t)$ be the ...
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I/Q Imbalance Correction using S.W. Ellingson Algorithm

Correcting I/Q phase and amplitude imbalance using S.W. Ellingson method. https://www.faculty.ece.vt.edu/swe/argus/iqbal.pdf -- S.W. Ellingson Algorithm When I try to use the set of equations to ...
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2FSK implementation with VCO GNURadio

I am fairly new to GNURadio. I am trying to generate a 2FSK with minimum frequency shift. Instead of multiplying with a 8MHz complex carrier, I directly use VCO to generate two frequencies. One at 7....
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97 views

Audio signal arrival timing, impulse response, and reverberation

I'm building an application that requires determining the arrival time of an audio signal with a very high degree of accuracy (within 1ms would be ideal) using commodity smartphone hardware. I found ...
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1answer
52 views

Why symbols have to be upsampling, if the symbol rate and sample rate is same what happen?

In digital modulation process, after constellation mapping and before pulse shaping, the symbols are upsampled with the number L(samples per symbol). At this moment, why symbol have to be upsampled, ...
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Clock recovery using Mueller and Muller adds noise affecting EVM or SNR (Two cases - GNU Radio & Python code)

The implementation of the Mueller and Muller clock recovery that I am seeing adds a large amount of 'noise' or degradation to the Error Vector Magnitude (EVM) to the symbols on the constellation. This ...
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32 views

SDR and amplitude modulated signals

Can I view every signal that has been transmitted using software defined radio as a amplitude modulated signal? For example I could make a frequency modulated baseband signal in GNU Radio and connect ...
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Calculate moving RMS with exponential averaging

This is moving RMS, now how to add exponential averaging in this df['signal'].rolling(21*24*60).apply(lambda x: np.sqrt(x.mean()))
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63 views

Adding phase noise to a signal results in amplitude variation on a constellation - whats the mistake? *plots inside*

I am attempting to add phase noise to a modulated signal. I am doing this by taking a phase noise mask (single sided 0 Hz to 1 MHz), which shows dBc values away from central value or reference value. ...
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85 views

Error probability for orthogonal signaling with unequal symbol probabilities

I'm trying to derive the equation of error probability in orthogonal signaling. Here what I've tried: Let $\vec{s_1} = (\sqrt{E_b} , 0)$ and $\vec{s_2} = (0, \sqrt{E_b} )$ be vector representation of $...
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How to solve this question on communication lines?

The Question asked is as follows: A communication link operates at a bitrate of 20 Mbps. The receiver is expected to perform at a $BER$ of $10^{-6}$ or better using $QPSK$ modulation scheme. [Note: $...
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Why we only can transmit a real signal? [duplicate]

i just wondering, why we always transmit a real signal but when we deal with a baseband signal we use a complex signal ? are this is related to up and down conversion of the signal (Because complex ...
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Is the modulation on my WiFi different to the modulation on cellular?

Is the modulation method, or nature of modulation otherwise, between my phone and my WiFi modem, versus my phone and a cellular mast, different?
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Adaptive Delta Modulation: Logic for step size control at receiver

I read that in adaptive delta modulation, we have a block for step size control (diagram below) which takes into account the one bit quantizer output in a feedback loop and modulates it, the intent ...
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is there a single process/term to describe dissipation and amplification of a signal?

I am writing a paper, and the topic is about a signal that could be either amplified or dissipated while traveling through a medium. Since I don't wanna write everywhere "amplified or dissipated &...
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Clarification Regarding Changing the Variable

Assume I have that : $$ X(j\omega)=\begin{cases}e^{-2\omega}&\text{if $|\omega|<2\pi$}\\0&\text{if otherwise}\end{cases} $$ Say, I want to make this change substitution $X(j(\omega-\Omega))$...
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Spectral efficiency of with OFDM vs without OFDM?

OFDM has advantage over frequency selective channel with addition of cyclic prefix after IFFT of MPSK or MQAM symbol. but I wonder that the spectral efficiency of with OFDM vs without OFDM.
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Direct downconversion (IQ downconverter) with ASK modulation— what kind of Balun do you need?

I have a simple but confused question. I am trying demodulate a 915MHz ASK modulated signal with direct downconversion. So what I am building up is: Antenna --> SAW bandpass filter @915MHz --> ...
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Does direct-digital RF signal generation have a “baseband?”

Semiconductor technology has advanced to the point that the digital representation of a modulated RF signal can be applied directly to a DAC for transmission. Is there, then, any distinction between a ...
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Energy per symbol calculation

I am having trouble calculating my Energy per symbol and Es/No. Using these parameters and equation $N_s = $Number Symbols $R_s = $Symbol Rate $T_s = $Symbol Time $sps = $samples per symbol x = signal ...
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Using DFT Rotation for Frequency Down-Mixing

Is it possible to perform Frequency Down-Mixing (sometimes referred to as Down-Conversion) by simply rotating the DFT sequence? If so what are the Advantages and Disadvantages of this method?
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Why do I see a frequency shift from center when transmitting a QPSK via USRP with GNU Radio?

I am transmitting a QPSK signal via GRC and when I look at it on the spectrum analyzer, the signal is shifted away from my center frequency. This shift increases the higher the center frequency (i.e. ...
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Time domain representation of a modulated signal when symbol rate >> carrier frequency?

I need to understand the relationship between carrier vs. bits with PSK modulation, and what the signal in the time domain would look like if my symbol rate is far greater than my carrier frequency. ...
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69 views

Why Does ASK Modulation Create Fourier Sidebands?

I know why analog amplitude modulation has side bands, it is related to (fc+fd) and (fc-fd). But what about DAM? ASK(DAM) is a type of digital modulation, and there are only two state: carrier signal ...
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Do we assume modulating and carrier signal uncorrelated in AM modulation?

I am new to communication and studying amplitude modulation. Let us assume an amplitude modulated wave given by $$\big(m(t)+ A\big) \cos(2\pi f_c t)$$ Now we have formula for efficiency as $$ \eta=\...
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What modulation is done when I connect a signal source to a USRP block in GNURadio?

When I connect a sinusoidal signal source to a USRP sink and upconvert the frequency, what modulation is done to convert the baseband signal to a passband signal?
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105 views

Error probability for 8-PSK

How can I calculate bit error rate for 8-PSK modulation when I have $E_b/N_0$ given? I know that for QPSK/BPSK the matter is quite simple, but I cannot cope with 8-PSK. Let's say that my $E_b/N_0$ = ...
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SPL dB to voltage conversion misunderstanding

base on these links: https://electronics.stackexchange.com/questions/96205/how-to-convert-volts-to-db-spl https://electronics.stackexchange.com/questions/302833/convert-digital-and-analog-values-to-...
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how to find frequency response of microphone

hello I want to find the frequency response of a microphone. I give the input signal to my speaker and it produces a specific SPL with specific frequency. on the other side, I read the microphone ...
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70 views

Demodulating unknown signals - unmatched frequency sampling

My goal is to make an approach to recognize modulation type of unknown signals. I have energy detector which monitors spectrum and it provides information about center frequency and bandwidth of ...
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295 views

Block diagram of M-PSK modulation and demodulation

I have come across this quadrature modulator block diagram in many books and websites: I've read that the quadrature modulator allows to realize many different digital modulations, including ...
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Why in FSK the phase shift is allowed?

FSK modulation encodes information into the frequency of the signals. But when I checked the reference books, the formal expression for a frequency modulated signal is: $x_i(t) = \alpha cos(2\pi f_it +...
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Finding the maximum phase and the maximum frequency deviation of an angle-modulated signal

I have an angle-modulated signal: $$ s(t)=10\left[\cos\left(10^8\pi · t + 5\sin\left(2\pi\cdot10^3·t\right)\right)\right] $$ How would I go about finding the maximum phase and the maximum frequency ...
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115 views

Bandwidth of PSK modulated signal

What does it mean that the bandwidth of PSK modulated signal without applying any filtering or shaping of the pulse, is equal to the sampling rate with "1st lobe" equal to two times of ...
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Is there a way to describe the pattern of a signal as a numeric value?

I've been digging a little into signal processing and I just started a networks and telecommunications class at college. We saw there are different encode techniques Amplitude, Frequency and Phase ...
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Filtering a QPSK signal

Envelope variation due to filtering of a QPSK signal becomes more pronounced at greater phase steps. Why is that? Why do greater phase steps (180 vs 90 degrees for example) lead to more pronounced ...
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Issue with demonstrating amplitude modulation of sinusoid using MatLab

I am trying to demonstrate Conventional and DSB-SC modulation of a signal $ \sin(2\pi1000t) $ using MatLab. My carrier signal is $ \sin(2\pi f_ct)$ where $f_c = 100\text{ MHz}$. Now according to ...
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Does baseband signal has negative frequency?

Does baseband signal has negative frequency? In wiki baseband signal means that can include frequencies that are very near zero. I wonder whether baseband signal has negative frequency. Thank your ...
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What is the correct block diagram of CDMA communication system?

I was reading someone's thesis and now i am more confused about CDMA system. From what i understood is CDMA is multiplexing which allows multiple signals to transmit over single channel. so general ...
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FM modulation - recovering bits

I'm trying to complete one task: Download some FM modulated signals from page http://www.w1hkj.com/modes/index.htm. Calculate their spectrograms, i.e. short-time Fourier transform. Observe different ...
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Questionable Eb/N0 results for different modulations - measurements for 8-PSK do not match the theory

I would like to warn you that this post will be long, so thank you in advance to everyone who reads it and is able to help. I am running a certain simulation. I created a measurement environment (...
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156 views

Why 8-PSK modulation has higher Eb/N0 than QPSK or BPSK?

I run a transmitter/receiver simulation using QPSK, BPSK, and 8-PSK modulations. As far as I have noticed, the best SNR per bit results are obtained when simulating with 8-PSK modulation (and also at ...
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Simulating Rayleigh channel - Problem with adding channel coefficents

I am currently trying to simulate a Rayleigh channel using python (numpy). Full Jupyter Notebook on GitHub: Jupyter Notebook I assume that the channel changes with each new symbol. So I create myself ...
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Which modulation technique is better for long distance transmission, if I'm using the CC1101?

I'm using the Texas Instrument transceiver cc1101 at 430-440 [MHz] and I'm wondering what the best modulation technique is for long distance transmission. This transceiver offers several modulation ...
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What is conceptually happening in this modulation function?

I know this is a programming question but i am trying to understand the logic of this. I have come across below function which is basically written in the groovy, ...
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1answer
40 views

Find which signal was transferred in 32QAM

I've been assigned to solve a problem for 32QAM signals. The thing is, there are little to none sources in my native language to get any decent information on the topic. The problem is (in its ...
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If a function has slowly varying amplitude and phase what is the bandwidth of the amplitude and phase individually?

I am dealing with time histories that are narrow band with slowly varying amplitude and phase. I wish to extract the amplitude and phase but there is noise on the time history. An example of the type ...

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