Questions tagged [amplitude-modulation]
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63 questions
1 vote
1 answer
98 views
IQ Demodulation: Does AM demodulation require phase sync?
I'm reading up on how SDR works and trying to develop an intuitive understanding of how IQ detection works. For a normal AM signal, if there was phase sync between the receiver and transmitted signal, ...
1 vote
2 answers
85 views
Handling Summation in Autocorrelation Function for PAM Signals with Random Shifts
I am working on the autocorrelation function of a Pulse Amplitude Modulated (PAM) signal, which is given by: $$ X(t)=\sum_{n=-\infty}^{\infty} A_n p(t-n T-\phi) $$ where: $A_n$ are i.i.d. random ...
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0 votes
1 answer
98 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 ...
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0 votes
1 answer
202 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 ...
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0 votes
1 answer
87 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 ...
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0 votes
1 answer
234 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 ...
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0 votes
1 answer
338 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(\...
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1 vote
1 answer
283 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 ...
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