Electrical Engineering Stack Exchange
Electrical Engineering Stack Exchange

Questions tagged [amplitude-modulation]

71 questions
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10 answers

How exactly does AM/FM carry both pitch and loudness of voice?

Almost every tutorial on AM/FM modulation shows the modulating signal as something like a simple tone or continuous sine wave. Now that's easy, and for AM you just superimpose the modulating signal over the carrier wave as an envelope, and voila,…
aAaa aAaa
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7 answers

Why is superheterodyning better than direct conversion?

What is the advantage of having the extra stage of IF, extra local oscillator and extra filtering stage and amplification. It just seems like more work and circuitry. Surely the direct conversion to baseband and the intermediate conversion to…
Lewis Kelsey
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3 answers

Can Bandwidth be Traded Off with SNR in Analog Modulation?

With typical linear digital modulation schemes, we can, for a given bit rate, make a trade-off between modulation bandwidth and modulation order (effectively, how close the constellation points are). For example, let's say I require a bit rate of 1…
LetterSized
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5 answers

Does an AM radio wave make use of a lower side band?

I believe my problem is I am having some confusion on the meaning of "side bands". I read the wiki but I am wondering that since an AM signal is rectified doesn't that eliminate the lower part of the wave? On the other hand what would the difference…
Sedumjoy
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6
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2 answers

How is volume not affected by signal strength in AM radio?

I was wondering how the range of the volume is transmitted in AM radio. With amplitude modulation, the volume is directly linked to the amplitude of the radio signal. But this would mean that the overall volume of the radio receiver would decrease…
Rémi Baudoux
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2 answers

Why do AM radio stations have secondary frequencies?

First thing I'm sorry if this question sounds too much beginner-ish. I don't major in electrical engineering so I may lack the basic knowledge. I have been noticing that, while tuning my AM radio, nearly all stations have a "secondary frequency"…
MattCat15
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1 answer

Where and how are the carrier and message signal multiplied in this circuit?

I have this circuit diagram of an AM modulator and I am trying to understand what is going on. I know that the c(t) is taken from the collector of transistor Q1 and the multiplication of signals : m(t)c(t) is taken from the collector of transistor…
Ashwin Singh
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1 answer

Controlling gain and modulation depth of long-tail pair as AM modulator?

I'm investigating use of a differential pair as an AM modulator. The schematic below illustrates the general plan, but the values aren't really specific (not least because this isn't working yet!) Here's the thing, as I understand it, the…
Toby Eggitt
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3
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2 answers

Advice for an AM detector using a BJT

I'm designing an AM detector that uses a 2N3904 transistor in common collector configuration. Pardon me if my design's silly because I'm still quite a novice with using BJT transistors as amplifiers, but after a bit of calculations and a lot more…
kene02
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3
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2 answers

How does this modulation cause sidebands?

The following figure is an excerpt from this paper: Input Differential-Mode EMI of CRM BoostPFC Converter by Fei Yang. Q#1 (first highlighted sentence): How does the modulation line frequency cause sideband harmonics? As far as I know, modulating a…
WeTech
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1 answer

Noise of a precision/active rectifier

I am trying to build a precision rectifier circuit to implement AM demodulation in a sensor signal chain. For now I have calculated the sum RMS noise of the total signal chain except that of the precision rectifier. I was ready to use a zero…
Stanley
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3 answers

How to design an amplitude modulator with common-emitter amplifier circuit?

I am facing a problem on how to design an amplitude modulator using a common-emitter amplifier circuit. I am asked to use a carrier frequency of 50MHz and an input signal of 1kHz to 14kHz. In order to solve this problem, I designed a common-emitter…
Eddy Miner
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1 answer

Why does the frequency deviation of a FM wave have different definitions?

Source 1 defines the modulation index in the expression for FM as follows: As per the expression for frequency modulated wave, isn't the frequency deviation same as Modulation index 'M'? "The max value for the quantity inside bracket…
Divya K.S
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2 answers

Ring modulator not working (LTspice simulation)

I found this ring modulator circuit on the internet I tried to simulate this circuit on LTspice, but it doesn't work. Here is the LTspice circuit: And these are the simulation results: (Green: message signal, Blue: carrier, Red: DSB-SC output) I…
Prathik Prashanth
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2 answers

Is there an advantage of reducing the single sideband carrier in amplitude modulation over supressing the carrier completely?

In amplitude modulation, one of the single sideband techniques is to reduce the carrier power instead of supressing it altogether. Is there an advantage to doing this and having some of the carrier signal or power still be present, as compared to…
AndroidV11
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