Signal Processing Stack Exchange
Signal Processing Stack Exchange

Questions tagged [demodulation]

Demodulation is the act of extracting the original information-bearing signal from a modulated carrier wave.

A demodulator is an electronic circuit (or computer program in a software defined radio) that is used to recover the information content from the modulated carrier wave.

Source: Wikipedia.

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Improving SNR using DSP techniques

I am building an optical OOK (On off Key Ring) system without a carrier frequency. [However I have a guard time in between symbols, so a consecutive "1" messages will result in a pulse train as opposed to DC, see image]. Essentially, the presence…
Frank
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Is IQ demodulation through sampling offset posible

These topics are full of words I don't fully understand. So it's very possible I missed the point somewhere but I saw a feature on a microcontroller and wondered if it was applicable. I have an ADC with several channels and they can be command to…
foreverska
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Implementing a basic demodulator

I'm trying to implement a simple demodulator as an evening project (to understand how this works - my background is in physics not engineering) and was wondering if anyone has any advice. To make a working demodulator I think I need to implement…
Tom Kealy
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DC to phase relationship with Low pass filtered sine and square wave multiplication and it's pitfalls. IQ Demodulation

From what I have read about signal (de)modulation I understand that multiplying two sine waves, both with the same frequency, gives a two frequency component sine wave. One at DC and one at $2\omega$. Using a low pass filter will let us remove the…
uniquenamehere
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I/Q Sample demodulation to input data

I am trying to convert some raw unscaled I/Q sample data back to the original input data. I've been reading a lot of different posts and articles in I/Q demodulation and the focus is almost solely on the process of combining the two separate I and Q…
Danny Flack
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ASK demodulation using DSP

I need to implement an ASK (ampliltude shift keying) demodulation using a DSP ( a dsPIC ) and programming in C. Especifically talking, I need to demodulate a signal from a car's key transponder. I already have a circuit of antenna that receive the…
Daniel
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OFDM Phase compensation

I need to compensate a OFDM-16_qam constelation rotation but I could not find out how to implement it with MATLAB I have a Matrix [48 x 25] where each colum is a OFDMsymbol without CP , pad and pilots, this matrix was passed through a Multipath…
Luiz
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Discontinuous jumps in phases from complex demodulation

I am using complex demodulation to estimate slow amplitude and phase changes over time of a single sinusoid. The time series consists of continuous blocks with large gaps (~30% of block lengths) between them. The amplitude results are fine, but…
Chris
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16-QAM demodulation

I wonder how higher order QAM modulations (like 16-QAM) are demodulated in practice. Let us assume hard detection for simplicity. For 4-QAM, checking sign of real and imaginary parts is enough, but in my opinion this approach does not scale and…
Pawel
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Demodulating signal by passing incoming carrier wave through low pass filter as opposed to multiplying by carrier wave?

Demodulation through many resources found online says that the incoming signal is multiplied by the carrier wave and then passed through a low pass filter that removes the carrier wave from the modulated signal. I understand this. However, we know…
kepsek
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Term for signal waveform correction or demodulation

Let say a periodic signal waveform $v(t)$ can be modeled as: $v(t) = f(\phi) A \sin(2\pi ft + \psi)$ where $A$ is a constant amplitude, $f$ is signal frequency, $t$ is time and $\psi$ is a constant phase. While $f(\phi)$ is $f = k \cos(\phi)$, where…
Karsun
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Recover signal from sum of AM and FM

I have samples of a signal that contains an AM signal added to an FM signal with the same carrier frequency $f_c$. The AM signal is a sinusoid with frequency $f_{AM}$ and the FM signal is a sinusoid with frequency $f_{FM}$. I know how to recover…
Greg Owen
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Does this technique have a name?

It is possible to do IQ demodulation by using a zero crossing detector and a timer to take 4 samples of a sine wave if a reference signal is present. When there is no phase difference between the signals the 4 samples are taken at exactly 0, 90, 180…
uniquenamehere
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What is the BER for multilevel modulated signal

Assume I want to transmit a low or high symbol which can be BPSK modulated. For ordinary BPSK, bit 0 can be mapped to 1+i0 and bit 1 mapped to -1+i0. In my question, each two bits are BPSK modulated and a level dependent so bit 01 is mapped to 2+0i…
Riva11
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Downconversion / Demodulation of RF signal to DC

My question is around down conversion of a signal (e.g. RF) to DC and the affect of negative frequencies. If I have a signal whos spectral content is say between 2-4kHz and I mix this with an intermediate frequency of 3kHz, ignoring the upper…
CatsLoveJazz
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