Skip to main content

Questions tagged [amplitude-modulation]

The tag has no usage guidance.

Filter by
Sorted by
Tagged with
1 vote
1 answer
31 views

Amplitude Modulation in Scipy Documentation on Hilbert transform

I was reading the documentation on the scipy.signal.hilbert and an example was given there to illustrate the principle. To make it easier to understand, I copied ...
pi_6Squre's user avatar
0 votes
1 answer
49 views

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 ...
uhoh's user avatar
  • 231
2 votes
2 answers
68 views

Recovering a quasi-periodic signal subject to amplitude modulation and additive noise

Consider an unknown, quasi-periodic signal $x(t)$ with approximate slowly varying unknown period $T_x(t)$. A noisy, amplitude modulated version of this signal is observed: $$r(t) = a(t) x(t) + n(t)$$ ...
rhz's user avatar
  • 457
0 votes
1 answer
70 views

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 ...
JMC's user avatar
  • 101
1 vote
1 answer
52 views

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 ...
Vibhav shivadeker's user avatar
0 votes
1 answer
75 views

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 ...
Thanos's user avatar
  • 1
0 votes
0 answers
26 views

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 ...
GGChe's user avatar
  • 153
0 votes
1 answer
136 views

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 ...
neil_huygens's user avatar
4 votes
1 answer
1k views

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 ...
LuckyPants's user avatar
0 votes
1 answer
183 views

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(\...
unique's user avatar
  • 123
1 vote
0 answers
190 views

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 ...
unique's user avatar
  • 123
1 vote
1 answer
148 views

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 ...
Rêve's user avatar
  • 35
1 vote
1 answer
200 views

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 ...
phanitej's user avatar
  • 450
2 votes
2 answers
256 views

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&...
Curious's user avatar
  • 355
1 vote
3 answers
162 views

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 ...
Chris Akridge's user avatar
1 vote
1 answer
115 views

Why a demodulated signal can appear at a double frequency?

Why during demodulation, the demodulated signal might double its frequency? A minimal example: ...
Gideon Genadi Kogan's user avatar
5 votes
3 answers
2k views

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...
Gideon Genadi Kogan's user avatar
1 vote
1 answer
54 views

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):...
Gideon Genadi Kogan's user avatar
0 votes
1 answer
188 views

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 ...
Elias4l's user avatar
  • 25
1 vote
1 answer
264 views

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 ...
average_discrete_math_enjoyer's user avatar
0 votes
1 answer
211 views

Message signal and the Envelope of AM wave

Amplitude modulated signal is represented by $$ x(t) = (E_c + E_m \cdot \cos(2\pi f_m t)) \cdot \cos(2\pi f_c t). $$ At t=0, we have max. amplitude i.e, Ec + Em. Since the envelope is periodic, I ...
Anantha Krishnan's user avatar
0 votes
1 answer
200 views

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 ...
Aami's user avatar
  • 325
1 vote
2 answers
1k views

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 ...
Alexis Evelyn's user avatar
1 vote
0 answers
71 views

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 ...
user674907's user avatar
1 vote
2 answers
121 views

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 ...
Karakoncolos's user avatar
0 votes
1 answer
178 views

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 ...
Amy 's user avatar
  • 53
0 votes
1 answer
155 views

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 ...
Essam's user avatar
  • 267
0 votes
1 answer
455 views

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) ...
Mathpdegeek497's user avatar
0 votes
1 answer
172 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 ...
DrBwts's user avatar
  • 103
0 votes
1 answer
221 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 ...
yarin Cohen's user avatar
1 vote
1 answer
2k 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 ...
user58046's user avatar
0 votes
1 answer
131 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 ...
user58046's user avatar
1 vote
1 answer
394 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 ...
Faruk UNAL's user avatar
1 vote
1 answer
63 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=\...
Userhanu's user avatar
  • 181
1 vote
1 answer
69 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 ...
Stanissse's user avatar
-1 votes
1 answer
2k 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 ...
B. T.'s user avatar
  • 1
2 votes
2 answers
1k 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 ...
Kinka-Byo's user avatar
  • 334
0 votes
1 answer
897 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 ...
Jax Teller's user avatar
4 votes
3 answers
6k 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 ...
Mathieu's user avatar
  • 213
2 votes
2 answers
2k 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 ...
OverLordGoldDragon's user avatar
0 votes
1 answer
416 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 ...
FourZeroFive's user avatar
0 votes
1 answer
716 views

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

We know, the instantaneous voltage of AM wave is: ...
hafiz031's user avatar
  • 143
0 votes
0 answers
47 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 ...
Jasky Obi 's user avatar
1 vote
2 answers
897 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 ...
Pirooz's user avatar
  • 69
1 vote
1 answer
158 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 ...
radar101's user avatar
-1 votes
2 answers
394 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 ...
Dhavids's user avatar
0 votes
2 answers
129 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 ...
rocko445's user avatar
  • 171
0 votes
1 answer
106 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 ...
divB's user avatar
  • 473
0 votes
1 answer
291 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 ...
Alex's user avatar
  • 13
0 votes
0 answers
108 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 ...
PeterO's user avatar
  • 123