Signal Processing

Questions tagged [demodulation]

Ask Question

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

266 questions
Newest
Active
Bountied
Unanswered
Filter by
Sorted by
Tagged with
1
vote
1answer
78 views

What is the maximum rate of a coherent demodulator implemented in a PC?

I would like to implement my own xPSK coherent demodulator on a traditional PC connected to an acquisition board. I am wondering what kind of bitrate it is possible to reach processing only with the ...
0
votes
0answers
32 views

Digital Selective Calling (DSC) Decoder in GNU Radio

I’m attempting to develop a GNU Radio FSK decoder for Digital Selective Calling on marine VHF but I seem to be stuck. I got my hands on a Standard Horizon handheld marine VHF unit with DSC capability ...
0
votes
1answer
61 views

weird Demodulated BPSK waveform

I am using an acoustic wave of 3khz(audio BPSK) as my carrier frequency with a sampling rate of 10k samples per bit. at the receiver end, I play the audio from my phone to my computer, record it ...
0
votes
2answers
35 views

synthesizing a signal from inphase and quad components

I have a newbie question: Let's say I have a signal (fc = 308 kHz, B= 30 kHz) as plotted below I demodulate the signal to derive I and Q components at evenly-distributed time steps as (only the first ...
0
votes
0answers
16 views

Best choice to digitally rotate reference for an IQ filter?

I have analog GHz signal modulated with 60KHz signal and I analog mix it with reference GHz and low pass filter so now I have a 60KHz signal $a$ which I enthusiastically sample (at 1MHz). Meanwhile I ...
0
votes
2answers
30 views

Real-time FM demod results in clicking and strangely-shaped output

hardware engineer here dipping his toes into software DSP and running into some issues. I'm attempting to demodulate in realtime a simple narrowband FM signal with samples from an RTL-SDR, and play ...
4
votes
2answers
85 views

How to demodulate PM with signal faster than carrier?

I have a signal that is a periodic concatenation of truncated Lorentzians ($\frac{1}{1+x^2}$), like so: The exact shape of the signal is unimportant I guess. I can approximate it with its first few ...
1
vote
1answer
75 views

FM demodulation using complex differentiation

I'm trying to implement the complex differentiation discriminator which is taken from Software-Defined Radio Using MATLAB, Simulink, and the RTL-SDR. The final result is $$s(t) = \frac{s_q'(t) s_i(t) -...
1
vote
1answer
70 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 ...
0
votes
1answer
45 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 ...
0
votes
1answer
34 views

Cut-off frequency for Low-pass filters in Arctangent Demodulation

According to literature, the arctan-demodulation method commonly used in Radio-frequency radar systems is the one shown below: Is there a rule of thumb regarding the cut-off frequency of these Low-...
1
vote
1answer
121 views

Clock Recovery with FSK Demodulation in GNU radio

I'm working on demodulating an fsk signal sent from a cubesat on the ground to an antenna station. I'm trying to do it in GNU radio but I am not quite getting the original signal back. The cubesat ...
0
votes
1answer
69 views

Soft bits in large constellations

I am working on a soft iterative receiver for an M-ary modulation. Since my constellations, M=2⁷ — M=2¹², are rather big, the log likelihood ratios also become large. Is there a way to compress these ...
1
vote
0answers
53 views

Software implementation of Gardner Loop

My objective is to create a Gardner loop to remove the timing offset present in my signal. To achieve best timing SNR, I downsample my signal to 2 samples per symbol. It is depicted below: where blue ...
0
votes
0answers
30 views

RRC filter in receiver side well applied?

I would like to ask question bout the rrc filter that I applied as an matched filter for receiver side in communication. My aim after RRC filter is to draw the eye diagram, and so far the eye opening ...
0
votes
0answers
45 views

The timing offset remains after Gardner loop

I would like to use Gardner loop to remove the timing offset in order to demodulate the signal. My signal contains the frequency offset, however I know that the Gardner loop can handle substantial ...
1
vote
1answer
161 views

Symbol timing recovery in Python

My objective is to demodulate QPSK signal. At the receiver I apply RRC filter and interpolate the signal to get the values of the signal (approximately) at the sampling instances. Then I am concerned ...
0
votes
1answer
59 views

How to perform a phase recovery for higher order modulation schemes

My objective is to demodulate the signals with different modulation orders and schemes. In particular, I want to recover the phase first. Let us say, my signal looks like in the constellation below . ...
0
votes
0answers
22 views

Sampling and Demodulation question

if I have an analog modulated signal with a DSBSC modulation (modulation index 100%) as an input in my receiver and I want to convert it to a sampled signal, do I need to demodulate the signal (with ...
0
votes
0answers
52 views

bpsk demodulation only with STM32

for an internship I have to create a communication between 2 devices at 30Khz. we choose a BPSK modulation. I create du Tx with a stm32 and a DDS (AD9834). Now I trying to code the demodulation with a ...
0
votes
0answers
135 views

SDR : IQ GMSK signal demodulation

I'm trying to develop an application for the demodulation of some GMSK signals transmitted over the air. I'm using a RTL-SDR which outputs 8 bits IQ samples of the baseband signal. Here is what I've ...
1
vote
1answer
111 views

LPF in the stage of IQ demodulator is it a analgor filter or digital filter?

I recently designed the LPF of the IQ demodulator using the Butterworth LPF refering to https://dspillustrations.com/pages/posts/misc/baseband-up-and-downconversion-and-iq-modulation.html. But I have ...
0
votes
2answers
155 views

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 ...
0
votes
1answer
84 views

QPSK sync sequence detection problem

I have IQ data collected This is the beginning of the packet that includes preamble and sync sequence. Red is real part, blue is imaginary. Also constellation diagram for this data I don't have ...
1
vote
1answer
256 views

QPSK demodulator on GNURadio continuously loses phase lock

I am designing a QPSK demodulator to be used for receiving Meteor M2 (LEO satellite) signals (QPSK at 72Kbaud). However, I am finding a lot of problems in my way. First of all, this is the flowchart I ...
1
vote
1answer
85 views

Demodulating unknown signals - unmatched frequency sampling

My goal is to make an approach to recognize modulation type of unknown signals. I have energy detector which monitors spectrum and it provides information about center frequency and bandwidth of ...
2
votes
1answer
393 views

Block diagram of M-PSK modulation and demodulation

I have come across this quadrature modulator block diagram in many books and websites: I've read that the quadrature modulator allows to realize many different digital modulations, including ...
0
votes
2answers
188 views

Most efficient way to find single dominant frequency (without amplitude) in analog signal

I want to construct a reference locked sine oscillator. The multibit sine wave is calculated using DDS. The multibit reference signal is typically not sinusoidal, can have offset and substantial noise,...
0
votes
2answers
88 views

Why in FSK the phase shift is allowed?

FSK modulation encodes information into the frequency of the signals. But when I checked the reference books, the formal expression for a frequency modulated signal is: $x_i(t) = \alpha cos(2\pi f_it +...
0
votes
0answers
47 views

FM modulation - recovering bits

I'm trying to complete one task: Download some FM modulated signals from page http://www.w1hkj.com/modes/index.htm. Calculate their spectrograms, i.e. short-time Fourier transform. Observe different ...
0
votes
0answers
29 views

Bit error rate transient

I see often people here posting about GNU Radio, I hope mine is not in the wrong place. I try to implement a demodulation chain and would like to measure its performance. I added a BER block and it ...
0
votes
0answers
83 views

Decoding images from NOAA satellite APT signals

I've been working on a decoder for these APT images for a while now. I started years ago, in Python, and was able to implement a working decoder quickly. A few months ago, I came back to the project ...
1
vote
0answers
67 views

Trade-off in sample-rate & FFT-size & Doppler

I've got a stream of digital IQ samples let's say at $F_s = 1 MSPS$ that consist of a narrowband signal, in awgn. Let's say the signal BW is ~ 100Hz. The narrowband signal's center (or base) frequency ...
2
votes
1answer
92 views

Dealing with bias in an FFT for frequency correction

I'm working on using an FFT for frequency correction of a generic modulation signal. My algorithm basically attempts to balance the energy in the positive and negative frequencies of the FFT to be ...
0
votes
0answers
15 views

How to make 2 finger rake receiver to counter intersymbol inferference?

I have to transmit Walsh sequence (spreading codes) modulated with 8 psk with a channel impaired by intersymbol interferences, fast fading . Suppose i have a stream of data for instance 1 0 1 1, 0 0 0 ...
0
votes
1answer
49 views

Digital Phase Modulation baseband or passband?

Say I want to transmit messages using PSK: I send the message $$s_m(t) = \text{Re} \left [g(t) e^{\frac{j 2 \pi (m-1)}{M}}e^{j 2 \pi f_c t} \right]$$ where $f_c$ is the carrier frequency. Now my ...
1
vote
0answers
61 views

Non-coherent FSK and Orthogonality and square-law detectors

This is a basic figure that explains how Non-Coherent FSK actually works. The incoming signal $ r (t)=\sqrt{2 P}{Cos}(2 \pi t (\text{fc}+\text{fi})+\text{n(t)}$ where P denotes the signal power in ...
6
votes
3answers
213 views

How a diode-detector affects to Frequency Response?

I have a question related to crystal radio. I can't understand how a crystal detector (diode) shifts the spectrum from the carrier frequency to zero. The antenna receives bunch of signals and the LC ...
1
vote
3answers
91 views

QAM Amplitude Levels

I'm working on a project to stream video between 2fpgas by using QAM. While mapping symbols with different amplitude pulses(PAM) a question popped up in my mind. In real life how does communicating ...
2
votes
0answers
49 views

Determining the right order of time-domain low pass filter for desired cutoff frequency

I've been stuck on a problem regarding complex demodulation of a signal for a while and wondered if anyone could help. Suppose I have a signal $X(t)$ such that \begin{align} X(t) &= A(t)\cos(\...
0
votes
2answers
82 views

BPSK and QPSK demodulation computational complexity

I wanted to ask about the real operations of BPSK and QPSK demodulation. How can we calculate it? I mean for example if I have a received symbol +0.6, then I need to demodulate it to be 0 or 1. what's ...
0
votes
1answer
47 views

Non Coherent BPSK with no Channel State Information at the receiver

Where or what is the proof for the failure of BPSK in fading channel when we have no knowledge of the fading coefficient $h$ at the receiver in the equation $y=hx+w$, where $x$ is BPSK symbol equally ...
2
votes
1answer
163 views

What is the functional difference between DSB and 2SB mixers, and why exactly would 2SB be better for radio astronomy?

The Astronomy SE question 2SB mixer in radio astronomy? asked in 2014 in its entirety: In literature about the instrumentation of radio astronomy, I frequently come across a type of mixer described ...
0
votes
1answer
91 views

Does the FFT size matter in OFDM demodulation?

The DFT size in OFDM demodulation is usually matched to the DFT size in the modulation process. This makes modulation/demodulation simple where each FFT bin (i.e., sample) represents one symbol. What ...
2
votes
1answer
145 views

Demodulating a LoRa data symbol

LoRa integrate data into symbols by selecting the starting frequency of an up chirp. The resulting up chirp traverses across BW and arrives at the same place it started. At the demodulator, this chirp ...
1
vote
1answer
39 views

A communication system

I am solving the following problem as an exercise. I have a signal $$z(t) = x(t)\cos(wt) + y(t)\cos(ut)$$ and we assume $x,y$ to be band-limited continuous time signals. In the frequency domain we ...
2
votes
0answers
82 views

How to demodulate DominoEx-like signal with liquid dsp?

I found a proprietary protocol that is used on ham radio bands. The author have published details,claiming that it's a version of DominoEX with slightly different baud rate and FEC. I want to try to ...
0
votes
1answer
60 views

Cross-correlation with SDPSK modulation

I'm trying to detect a sync word in a signal using Symmetrical Differential PSK (bit 0 = +90° phase, bit 1 = -90° phase). Given the signal is encoded in the phase difference between two symbols, the ...
2
votes
0answers
63 views

symbol synchronization

PLL is typically used in carrier synchronization and its diagram is well known, consisting of a multiplier, a low pass filter, and a VCO. In "Phase-locked Loop" at wiki (https://en.wikipedia.org/wiki/...
0
votes
0answers
78 views

Non coherent detection BFSK demodulation?

I am simulating BER performance of BFSK under AWGN and Rayleigh fading, BFSK has two symbols one entirely on the real plane while other on the complex plane for representing let's say zero and one, ...

1
2 3 4 5 6

Your privacy

By clicking “Accept all cookies”, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy.