Questions tagged [amplitude-modulation]
The amplitude-modulation tag has no usage guidance.
58
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Why Hilbert Transform is terrible choice for amplitude demodulation of broadband signals?
A reference answer empirically demonstrates that Hilbert envelope does not work well for the (amplitude) demodulation of a broadband signal. I am looking for the math which explains why...
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Deriving SER & BER for 4QAM, 16QAM and 32QAM
Required to find symbol error rate vs $E_b/N_0$ for 4QAM, 16QAM & 32QAM. Thought that SER & BER are the same but did my research to find that BER is $1/\log_2(M)$ of SER. Could you please ...
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Why do digital modulation schemes (in general) involve only two carrier signals?
In my digital communication, class we have covered the various modulation schemes, namely QAM and its derivatives (B(A/P)SK, PAM and (Q/M)PSK) as well as BFSK. These two schemes have one or at most ...
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Why is the carrier suppressed by AM-DSB-SC modulation?
Lets say I have a message that is a sine wave at 1KHz. As I understand it, I can perform amplitude modulation by multiplying this signal with a carrier, lets say 10KHz, and this process is essentially ...
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FFT of a AM modulated signal
I am generating an AM modulated sinusoidal wave. The carrier frequency is set at $1000 \ \rm Hz$; the modulation frequency is set to $40 \ \rm Hz$ and $100 \%$ of the amplitude is modulated.
I ...
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Amplitude modulation vs sampling rate?
As a sampled tone's frequency nears $f_s / 2$, amplitude modulation grows apparent:
("Actual" curve in grey; blue is what we get if taking samples (dots) "at face value"). This is ...
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Absolute value based AM envelope detection viewed in the frequency domain
In my understanding when a passband AM signal is demodulated with an envelope detector taking the absolute value restores the original baseband version of the signal and the low-pass filter removes ...
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Why complex signal doesn't remove "beatings" while sampling?
My motivation to this post has arisen from the accepted answer to Amplitude modulation vs sampling rate?
Sampling the signal with the frequency close to $f_s/2$ can lead to some kind of "beatings&...
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Fractional Bandwidth of a Gaussian Amplitude Modulated Signal
a gaussian modulated sinusoidal signal may be expressed as
$$x(t)=A\cdot e^{(j2\pi ft)}\cdot e^{\left[-\frac{1}{2\sigma^{2}}\cdot(t-t_{0})^{2}\right]}$$
Let's consider the case in which the gaussian ...
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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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Why don't I hear the carrier wave or higher-pitched audio when tuning slightly away from the center of an AM station?
Let's say I'm listening to an AM radio station in the United States at 680 kHz. From my understanding that means there's a carrier wave at 680 kHz and the bandwidth for the station goes from 675 kHz ...
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Is there any relation between QAM and streaming?
I am trying to determine whether there is any relation between QAM and streaming (e.g., video streaming).
I know that QAM can be used for broadcast TV. I'm not sure if QAM is used for WiFi bit ...
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2
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Mixing with Deformed Local Oscillator Signal
I've decided to build up an AM receiver which is intended to capture sound signals from a nearby broadcasting station that is operating at 954 kHz. I've completed the system design and started to test ...
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How do I determine the carrier frequency of a given AM signal?
I am trying to figure out what the carrier frequency of a signal is given only its discrete-time domain information and the fact that it is a signal on the AM radio frequency band(550 - 1700kHz). Is ...
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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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Question about Hilbert transform of a cosine signal
In the paper entitled "On instantaneous frequency", it is claimed that the Hilbert transform of a signal in the form of $A(t)cos(\phi(t))$ would result in $A(t)sin(\phi(t))$, where $A(t)$ is ...
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Creating uneven sidebands with AM + PM modulation?
I am trying to modulate an optical signal such that I create a pair of sidebands with arbitrary phase and amplitude with respect to each other. For example I would be like to be able to modulate my ...
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1
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What's the maximum allowable amplitude modulation frequency for a given carrier frequency?
I'm currently studying wavelets and had an interesting thought experiment: If you were to calculate the wavelet transform of a signal using a wavelet of a fixed frequency, you would get time varying ...
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Omission of 8-PSK and 32-QAM in LTE/5GNR
In 4G LTE/5G NR, the modulation schemes 8-PSK (which is an intermediate scheme between QPSK and 16 QAM) ,32-QAM (which is in between 16 and 64 QAM) are omitted. If the channel is bad , or the distance ...
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Why a demodulated signal can appear at a double frequency?
Why during demodulation, the demodulated signal might double its frequency?
A minimal example:
...
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How to eliminate a cyclic spectrum estimation window artifact?
I am using an implementation of the averaged cyclic periodogram (section 3.2.4 in Antoni, Jérôme. "Cyclic spectral analysis in practice." Mechanical Systems and Signal Processing 21.2 (2007):...
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Power of signal in specific frequency in FM and AM modulation
My professor gave us the following problem:
Given a sinusoidal signal with $f_m = 1KHz$ which is put into an AM
and FM modulation find the modulation index of FM and AM if you know
that (amongst ...
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How to analyze multiple amplitude modulated signals?
What I'm doing is that I send an audio signal consisting of a single frequency into a resonator. To check whether and how the signal has changed I perform a QAM demodulation.
I do not need intend to ...
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RF Downconversion using Heterodyne Principle
after a RF down-conversion using heterodyning principle, will there be an information loss?
If we translate to a fixed IF frequency, is there is an intuitive way of explain that the information can be ...
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Anomaly in Magnitude Spectrum plot of an ASK Signal
Following is a SciLab code and Plots for Modulation of ASK Signal:
My question is :
For these particular values of fm and t, I get two weird small spikes on either side of main lobe, which doesn't ...
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Amplitude modulation in SDR [closed]
I understand the theory of amplitude modulation. However, I couldn't understand it's implementation in SDR, which use IQ data, and I would like to learn
end to end amplitude modulation system in ...
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Do amplitude shift keying modulation occupies a large portion of the spectrum?
In the PySDR online course, to the question "Why can’t we directly transmit the ethernet signal [directly in the antenna]", one answer is the following :
Square waves take an excessive ...
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How to Get Started On Demodulating Signals Such As Amplitude Modulation and Pulse Width Modulation
I'm looking to understand how signal modulation/demodulation works.
My goal is to be able to demodulate a 315 MHz key fob and be able to tell what buttons are being pressed so I can have a Python ...
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What is the difference between sending pulses and modulating waves?
If you look for amplitude, frequency, phase modulation, you typically get some picture saying you have a wave and you modulate the corresponding parameter (amplitude, frequency, phase). On the other ...
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Problem related to phase spectrum of DSB-SC signal
I have tried to solve this question (4.2.3). I got the magnitude spectrum right but the phase spectrum wrong. I am getting the phase spectrum at $ \frac{\pi}{4} $ and $ - \frac{\pi}{4} $. However, in ...
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How harmonics happens when you mix two signals?
Doing a search in quora about Why does Amplitude Modulation have sideband frequencies? i found an answer and within it, a user answered with the following statement:
"When you try mixing two ...
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Amplitude modulation and FFT query
I am generating a 0.5Hz sine wave, to which I'm adding a ramp envelope, to get a signal that ramps its amplitude from 0 - 10 - 0 Vpp. I then did an FFT (DFT? sorry not that up on the exact terminology ...
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Why don't we need frequency and phase correction in AM and FM?
As far as I understand, double sideband AM with carrier and FM can be demodulated via SDR (Software Defined Radio) without frequency or phase correction. For AM, received signal is
$$r(t) = A(t)\cos(\...
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Eb/N0 on a VLC simulation using OOK modulation
I have been doing a matlab simulation of a VLC (visible light communication) system that uses OOK for the modulator.
I have to explain the basic knowledge behing the simulation and I´m having lots of ...
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Why does the Superheterodyne AM Receiver use an envelope detector?
I'm currently learning about the Superheterodyne AM Receiver and I don't understand why does it use an envelope detector (as suggested here) rather than taking the signal back to its baseband ...
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Frequency modulation in MATLAB
I am trying to frequency modulate a cosine signal(for assignment). I have written the following code but not getting the required output.
...
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Diode demodulation for AM
What is the capacitor and resistance at output of LPF meant for in the document it was mentioned that it is DC blocker I don't get it can't message contain DC value.
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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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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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Bandwidth of amplitude-modulated wave with triangular envelope
I have the following wave:
I know that it is demodulated by an envelope detector whose source resistance is 0Ohm and its load resistance is 250Ohm. Now, I need to calculate a C capacitor in order ...
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Need for rectification in cochlear implants
In cochlear implants, the input signal is fed to a set of bandpass filters and is then half-wave rectified and low pass filtered to estimate the envelope signal.
What is the need for doing ...
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How Can I correct amplitude and smoothness of FFT?
I am trying to create 10 individual signals with on-off keying modulation format, add them up to have a final signal, and then take a Fourier transform of that signal. I tried to zero padd the final ...
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Phasor diagram of Phase modulated signal
While studying the phasor diagrams of Amplitude modulation and Frequency modulation, I am stuck at a problem involving the phasor diagram of an angle modulated signal whose equation is given by $$s(t) ...
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How to compute a complex modulated signal from an audio file?
I have a 30-seconds wav audio file with a sample rate of 44100Hz, obviously this array of samples is a 1D array, and so when I modulate it in AM (Amplitude Modulation) I get back a 1D array, but I ...
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How to choose frequency of local oscillator for heterodyne principal
I am trying to implement the heterodyne principle in order to make an AM signal demodulator that can demodulate signals on a set bandwidth(550 - 1720kHz). Is there a formula or some other method of ...
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ZOH non ideal sampling loss formula
Hello i am trying to calculate the amplitude loss of non ideal sampling.
My signals amplitude is 10 at 70 frequency.
When we sample it at Fs=400 we have al 0.511 loss as shown in plot bellow.
How can ...
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CDMA scheme that preserves constant envelope (NRZ/ASK shape)
(This is a followup question to Is this a "valid" CDMA modulation?)
Is it possible to find a CDMA scheme in which the receiver can only have a simple slicer?
In other words, for the ...
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Please, help me interpret my Simulink simulation of AM. Why does carrier not appear in the spectogram?
Carrier is 2 * pi * 25, modulating signal is 2 * pi, all the amplitudes are 1s and zero phase.
I realized that I could add a sine wave right at the end. I get a carrier in frequency domain, but my ...
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What is the name for amplitude variation over time with angle measurement called?
I am trying to create a method in my real-time algorithm to measure the variation in time based on a simple technique to avoid a huge overhead in the processing on the hardware.
The first method I am ...
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FFT of frequency bands and limited amplitude modulation
In this paper they preprocess a cent spectrum of an audio file.
For comparison of audio files they create the Logarithmic Fluctuation Pattern(LFP)(p.3).
For this I have to use a FFT on each frequency ...
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