Questions tagged [amplitude-modulation]

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Information signal sketching [closed]

We are given this function $m(t) = \sin(2\pi t)/t$ This signal amplitude modulates a carrier of 20-Hz frequency. a) Sketch the ...
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1answer
31 views

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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1answer
33 views

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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1answer
74 views

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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1answer
45 views

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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1answer
76 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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1answer
33 views

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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1answer
36 views

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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1answer
203 views

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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3answers
81 views

Creating a PAM function with Matlab

So I need to make a function that will be called as function [t, pulse] = PAM (array). My function should have a result like this when I use ...
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2answers
145 views

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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1answer
174 views

Transferring data over sound with QAM / QPSK

Been working on a FSK Modem in the last few weeks and have gotten it to work with 400bps, very reliable, atleast over a virtual audio cable, but it also works when playing a sound directly into a ...
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3answers
967 views

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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2answers
677 views

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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1answer
115 views

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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1answer
218 views

Why the bandwidth in frequency spectrum of AM wave is 2fm and not 2fc?

We know, the instantaneous voltage of AM wave is: ...
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0answers
26 views

modulation depth

When a value for the power dissipated by an AM signal is given, and the depth of modulation is also given. Then you are told to find the modulation depth required to increase the power to a higher ...
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2answers
283 views

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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1answer
49 views

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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2answers
135 views

Minimum value of G (Amplitude) that guarantees an error probability of at least $10^{-2}$ in a 32-PAM transmission system

pretty much new here. This question comes from an Online course quiz which i have already completed but cant seem to get a good sleep over, just because i cant figure it out. Below is the question ...
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2answers
60 views

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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1answer
40 views

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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1answer
62 views

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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0answers
54 views

What kind of Modulation causes "drops" in FFT Power Spectrum

I am analyzing a signal with FFT and I found an effect, that I do not understand. I am expecting to have an amplitude modulated signal. As far as I know, if you compute the power of the FFT of an ...
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2answers
236 views

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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1answer
199 views

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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3answers
281 views

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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3answers
263 views

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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0answers
97 views

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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1answer
113 views

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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1answer
62 views

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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161 views

Which equipment to use for testing performance of AM, FM, and DAB

I want to test the performance of AM, FM and DAB radio in RTL-SDR. I want to measure sensitivity, adjacent channel selectivity, cross-modulation/blocking, and third-order intermodulation to be some of ...
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1answer
96 views

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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1answer
21k views

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 ...