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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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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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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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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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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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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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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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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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
$$ \eta=\...
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Error probability for 8-PSK
How can I calculate bit error rate for 8-PSK modulation when I have $E_b/N_0$ given? I know that for QPSK/BPSK the matter is quite simple, but I cannot cope with 8-PSK.
Let's say that my $E_b/N_0$ = ...
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how to find frequency response of microphone
hello I want to find the frequency response of a microphone. I give the input signal to my speaker and it produces a specific SPL with specific frequency. on the other side, I read the microphone ...
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Demodulating unknown signals - unmatched frequency sampling
My goal is to make an approach to recognize modulation type of unknown signals.
I have energy detector which monitors spectrum and it provides information about center frequency and bandwidth of ...
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Block diagram of M-PSK modulation and demodulation
I have come across this quadrature modulator block diagram in many books and websites:
I've read that the quadrature modulator allows to realize many different digital modulations, including ...
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Why in FSK the phase shift is allowed?
FSK modulation encodes information into the frequency of the signals. But when I checked the reference books, the formal expression for a frequency modulated signal is:
$x_i(t) = \alpha cos(2\pi f_it +...
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Finding the maximum phase and the maximum frequency deviation of an angle-modulated signal
I have an angle-modulated signal:
$$
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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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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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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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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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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SNR measurement
I am using QPSK modulation for a BER of $10^{-6}$ at $\text{SNR}=E_b/N_0=10 \ \rm dB$.
If my data rate is $5 \ \rm kbps$ then
$$S/N_0 = 10\log_{10}(5000)+10 = 47\ \rm dB$$
And if my RF section has a ...
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Difference between delta modulation and differential PCM
Delta modulation encodes the difference between a sample and the previous sample in only one bit.
Differential PCM encodes the difference between a sample and its predicted value. Is this difference ...
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Wideband FM bandwidth estimation
In the book Modern Digital and Analog Communication Systems by B. P Lathi, there is a section for the estimation of WBFM bandwidth. First, the staircase approximation of $m(t)$ is constructed by the ...
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Power of an angle-modulated wave
Let $$\phi(t) = A\cos(\omega_c t + km(t)) \tag{1}$$ be an angle-modulated wave(FM or PM). What's the power of $\phi(t)$? Intuitively, it seems that the answer is $$P = \frac{A^2}{2} \tag{2}$$ since ...
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How composite signal in CDMA is normalise in general?
I had CDMA composite signal with 3 users. I assume that the signals are linearly sum together so for my maximum and minimum amplitude of composite signal are +3 and -3 respectively.
Reference:
...
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How to remove the modulation before doing frequency offset estimation?
To use DFT/FFT (or maximum likelihood) method to estimate the frequency offset introduced by the channel, we need to remove the modulation on the received data samples in the front. If the unknown ...
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Mathematical relationship between phase modulated (PM) signal and the complex phase/magnitude of the frequency component at the carrier frequency?
What is the mathematical relationship between phase modulated (PM) signal and the complex phase/magnitude of the frequency component at the carrier frequency used?
This is partially related to the ...
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Digital Phase Modulation baseband or passband?
Say I want to transmit messages using PSK:
I send the message
$$s_m(t) = \text{Re} \left [g(t) e^{\frac{j 2 \pi (m-1)}{M}}e^{j 2 \pi f_c t} \right]$$
where $f_c$ is the carrier frequency. Now my ...
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How to separate Even and odd part (in-phase bit streams I and quadrature-bit streams Q) of the signal?
I am working on communication system in simulink and wondering, how can i separate the Even and odd part of the signal.
In my Transmitter block, I have :
$$
\boxed{\text{Binary Data signal}}{\...
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Non-coherent FSK and Orthogonality and square-law detectors
This is a basic figure that explains how Non-Coherent FSK actually works. The incoming signal
$ r (t)=\sqrt{2 P}{Cos}(2 \pi t (\text{fc}+\text{fi})+\text{n(t)}$
where P denotes the signal power in ...
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