# Questions tagged [demodulation]

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

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115 views

### Detecting I/Q imbalance

Are there any methods of detecting, measuring, and/or estimating I/Q imbalance (from, say, an upstream quadrature mixer and/or ADC), without using or having a controlled test signal (other than ...
51 views

### BPSK demodulation [duplicate]

For experimental reasons i created a function that helps me to modulate a signal using BPSK, the input signal is {1,1,0,1,0} and it works fine ...
337 views

### Removing I/Q phase rotation

What is the most reliable and agnostic way to correct for a phase rotation of I/Q downconversion - without time alignment of the signal and support different lengths of transmitted and received data? ...
89 views

### Does anyone recognize this modulation?

I'm trying to extract the code of my garage remote, but i have some difficulty to find witch modulation has been used. At first I thought it was a simple digital modulation, but there is some strange ...
533 views

### Square law demodulator. How can we eliminate the term containing $m^2(t)$?

We are trying to extract the message signal from the AM signal using square law demodulator. In the final expression, $V_2(t)$, the term encircled in blue has to be retained, and the others have to ...
304 views

### AM demodulation from a real RF signal

I'm capturing an RF signal transmitted at 433.8MHz, with a bandwidth of about 50KHz. My goal is to be able to save it as a .wav file. I'm using an RTL-SDR dongle and a software named HDSDR, where I ...
4k views

### AM Modulator Demodulator in Python

I am trying to make a AM modem using Python Numpy and Matplotlib. I am successful in generating the AM Signal but I cannot demodulate it using a lowpass filter function that I made. The demodulation ...
352 views

### Mystery signal - FSK, BPSK?

I have a mystery audio signal that I need to decode, it's from a discontinued product. Inspecting the object code shows a module called decodeFSK so that suggests ...
510 views

### Prepare IQ Data for Goertzel Algorithm

I have a quadrature (IQ - 0..255) data byte stream that I receive from an rtl-sdr dongle as IQIQIQIQ..... That means that negative values are < 128 and positive values >= 128 I am attempting to ...
682 views

### Extracting the carrier signal from AM

I am new to DSP and leaning about amplitude modulation. I am trying to demodulate a 5 Hz signal that is modulated by a 50 Hz carrier. I am trying to extract the carrier, not the the 5 Hz signal. A ...
32 views

### How to model airborne sound channel

I'm making a soft demodulation/decoding to communicate a microphone and a speaker in short range. I have to calculate the LLR using my constellation and the airborne sound channel probability density ...
320 views

### FM demodulation

I have a frequency modulated signal. My problem is the following: The sidebands are asymmetric. Meaning that the amplitudes of the sidebands left and right are not equal. Does anyone know what this ...
199 views

### How to calculate baudrate?

I'm going through this article https://www.elttam.com.au/blog/intro-sdr-and-rf-analysis/ and I find it hard to understand the following part: However, in our case we might want to transmit this ...
144 views

### mpsk demodulation using digital sample

I am trying to receive and demodulate a 8PSK modulated sinusoidal waveform (real not complex) which is constant envelop and changing only in phase of the continuous sinusoid carrier every Symbol ...
249 views

### Recovering DSSS signal from below noise Floor

I want to understand what actually happens in the direct sequence spread spectrum demodulator ? Why is it said that the signal is recovered from below the noise floor ? Can someone please explain the ...
564 views

### Demodulating AM signal from carrier signal on Matlab

I'm trying to demodulate a voice signal (bandwidth approximately 5 kHz) from a carrier signal (100kHz). [y,Fs]=audioread('Signal1.wav'); h=10*sinc(10*(-10:10)); y1=filter(h,1,y); But ...
151 views

### How is a signal with SNR less than unity demodulated?

The title pretty much says it all. What technique can be used to demodulate a signal with SNR less than 1?
709 views

### Demodulation on noise

I'm new in DSP, and I'm working on dsp application involving machinery (Diagnostics based on noise), and to do this I need to make DEMON processing. I want to process the signal like in the picture (...
2k views

### Downconverting real signal to IQ baseband

Despite reading various answers on this site and on other sites I am still confused about how to convert a real-valued signal back down to its original IQ baseband values. Note I am still a beginner ...
47 views

4k views

### How to correct the phase offset for QPSK I-Q data

I have an I-Q data of QPSK modulation, the data is is smeared and I have to correct the phase offset that causes the smearing problem, how can I apply the Phased-locked loop or the Costas loop on this ...
551 views

### FSK analysis: only ever find one frequency

I've trying to write this software as part of my amateur radio and SDR hobby for analyzing various two-level FSK signals. I'm very new to DSP but have been having a lot of fun so far learning more ...
245 views

### How to find a know signal in another signal which contains other signals along with the signal i need in python

I am working on BPSK with sound waves a carrier waves. Actually I am modulating my data with some known sync bits along with the information I need to send. So the things I will be having at ...
A modulating signal $m(t)= \sin(2 \pi \nu_m t)$ is transmitted via a carrier of frequency $\nu_c$ using upper sideband (USB) modulation. Show that the USB modulated signal can be demodulated using a ...