Questions tagged [qpsk]
Quadrature Phase Shift Keying
127
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20 views
Why do I see a frequency shift from center when transmitting a QPSK via USRP with GNU Radio?
I am transmitting a QPSK signal via GRC and when I look at it on the spectrum analyzer, the signal is shifted away from my center frequency. This shift increases the higher the center frequency (i.e. ...
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36 views
understanding FIR SRRC filter with memory implementation in C
I translated the Matlab QPSK receiver/transmitter into real-time C code that I have running on a PlutoSDR platform. QPSK receiver/transmitter
I wrote the square root raised cosine filter for the TX ...
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1answer
60 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 ...
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1answer
47 views
Error probability for 8-PSK
How can I calculate bit error rate for 8-PSK modulation when I have $E_b/N_0$ given? I know that for QPSK/BPSK the matter is quite simple, but I cannot cope with 8-PSK.
Let's say that my $E_b/N_0$ = ...
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1answer
90 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 ...
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31 views
Correcting large frequency offsets at very low data rates
Consider a typical BPSK system running at a baud rate of 1 kbaud/sec - the receiver needs to deal with severe frequency offsets, let's say up to +/- 1 MHz offset and that the frequency offset can ...
2
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1answer
173 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 ...
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1answer
20 views
Spectral properties of QPSK modulation
From what I've read, the spectral properties of the modulation largely depend on the rate of change of the signal phase - "a signal in which the phase changes stepwise has a broad spectrum, well ...
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43 views
What does this mean? The elliptical constellation in the QPSK constellation diagram?
Can you explain what kind of signal is this or what can you characterize when you see QPSK constellation like this? to get a better signal it needs to be near 1 and be a round circular constellation. ...
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30 views
Questionable Eb/N0 results for different modulations - measurements for 8-PSK do not match the theory
I would like to warn you that this post will be long, so thank you in advance to everyone who reads it and is able to help.
I am running a certain simulation. I created a measurement environment (...
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2answers
74 views
Why is the bandwidth for this QPSK system larger than expected?
Below is my gnuradio-companion graph.
As you can see the sample rate is 100k, I am modulating with QPSK, and am filtering the waveform (RRC) with the "Excess BW" parameter, at 0.35. The ...
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1answer
86 views
Why 8-PSK modulation has higher Eb/N0 than QPSK or BPSK?
I run a transmitter/receiver simulation using QPSK, BPSK, and 8-PSK modulations. As far as I have noticed, the best SNR per bit results are obtained when simulating with 8-PSK modulation (and also at ...
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0answers
10 views
Simulating Rayleigh channel - Problem with adding channel coefficents
I am currently trying to simulate a Rayleigh channel using python (numpy).
Full Jupyter Notebook on GitHub: Jupyter Notebook
I assume that the channel changes with each new symbol. So I create myself ...
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0answers
78 views
Offset QPSK Demodulation using GnuRadio
I am currently trying to demodulate an Offset QPSK signal coming from a satellite using GNURadio.
If I understood correctly, an OQPSK is a QPSK with one of the two bits per symbol delayed by half a ...
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0answers
47 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 ...
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1answer
73 views
Transferring data over sound with QAM / QPSK
Been working on a FSK Modem in the last few weeks and have gotten it to work with 400bps, very reliable, atleast over a virtual audio cable, but it also works when playing a sound directly into a ...
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61 views
QPSK transmission simulation
I am trying to simulate a QPSK transmission using GNU Radio following mpsk_stage6.grc example in Gnuradio tutorials.
Currently I have no idea where is the problem and everytime I execute the flow ...
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43 views
Packet Encoder GNU QPSK Transmission
Hello everyone!.
This is a template to QPSK transmission but Packet Encoder block is no longer available in new GNURadio versions, what do I need to replace this block in order to do a QPSK ...
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1answer
78 views
How to separate Even and odd part (in-phase bit streams I and quadrature-bit streams Q) of the signal?
I am working on communication system in simulink and wondering, how can i separate the Even and odd part of the signal.
In my Transmitter block, I have :
$$
\boxed{\text{Binary Data signal}}{\...
2
votes
3answers
364 views
Use of pulse shaping in digital modulation
Sorry, I am a little bit confused here cause I thought when we say QPSK, the signal looks like the following.
I thought the bits to send/receive depends on the phase shift of the carrier, or is the ...
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1answer
88 views
When I double bit rate I do not see a difference in I_spectrum and Q_spectrum, but why?
I wanted to compare two different I-Q spectrum plots of a basic transmitter, one in which I doubled the bit rate. I expected a different result, that of possibly a higher/faster graph. It looks sort ...
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1answer
65 views
Modulation upsampling method
I try to implement a qpsk modulator in Octave.
The chain is the state of the art I guess:
$$\text{Symbol mapper} \rightarrow \text{Upsample 4} \rightarrow \text{Root raised cosine filter} $$
My main ...
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1answer
135 views
Differential Encoding for M-PSK
Confused about a few topics w.r.t. differential encoding/decoding. First, consider the below BER curve taken from wikipedia ( https://en.wikipedia.org/wiki/Phase-shift_keying ) comparing BPSK/QPSK and ...
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1answer
33 views
How to deal with modulator jitter?
I have a question regarding an implementation of a modulator.
I guess some people here have an FPGA background.
I would like to implement a QPSK modulator of 31 Mbit bitrate using a 125 MHz clock.
I ...
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3answers
144 views
What causes this type of distortion in a constellation I/Q plot?
I'm transmitting QPSK through a digital pulse shaping filter (RRC, 35% excess BW, 2 samples per symbol, 64 taps) at a rate of 56Msym/sec.
Receiving it on standard lab equipment (Vector signal ...
3
votes
1answer
341 views
Sample rates, Samples per Symbol, and Digital Pulse Shaping
Having some confusion about digital pulse shaping for complex baseband (passband) signals. The complex baseband linear modulation equation is
$$s(t)=\sum_{m=-\infty}^{\infty}\text{Re}\{a_m\}h(t-mT)+j\...
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1answer
47 views
How to Tx CDMA signal physically using an existing point-to-point modem? [closed]
I am working in acoustic communication, I want to test CDMA network capabilities in acoustic environment. I had an acoustic modem that has serial interface, a WHOI micromodem.
How can i serialized ...
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1answer
1k views
Python code for QPSK modulator [closed]
Have any of you done anything like QPSK Modulation in python? I am in the middle of it and having problems in setting up bits? like odd and even bits.
Have you got any idea?
Regards,
Sam
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2answers
43 views
How are pulse trains generated in a radio transmitter?
When simulating a PSK signal in MATLAB or Python, I often create an impulse train where each impulse is modulated with a symbol. This modulated impulse train then passes through a pulse shape filter ...
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1answer
66 views
How to plot BER Vs SNR of a received signal
I am using USRP to transmit and received MIMO frames similar to Wi-Fi standard that I created on my own. After receiving the signal, it is processed as described in the standard.
While I plot the ...
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2answers
144 views
MATLAB: Issue with passing data through AWGN Channel [closed]
I am trying to send QAM data through AWGN channel and I have 256 samples/symbol, I have the following code:
...
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1answer
55 views
Phase Noise in Constellation Plot
I have the following phase noise plot (-100dBc/Hz @ 1MHz offset and -130dBc/Hz noise floor):
The integrated phase jitter for this phase noise is around $4.6^\circ$. According to my understanding the ...
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2answers
187 views
IQ Mismatch and Image
I was reading the following paper about direct conversion receivers from TI: link.
In this paper they compare the performance of direct conversion and heterodyne receiver with IQ mismatch.
The ...
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1answer
144 views
Carrier Tracking Loop: Tracking noise vs Phase Noise Trade-off
I would like to compare two different implementations of carrier tracking loop which differ in the way phase detection happens in the PLL. I am using PSK modulation for the data.
In the first ...
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1answer
105 views
Signal Timing Recovery, Loop Bandwidth and SNR
As explained in the answer here, for the symbol timing recovery loop we need to keep loop bandwidth sufficiently below the modulation bandwidth of the signal so as to avoid the filtering of the signal ...
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1answer
91 views
MATLAB: Generating a random bit stream in a frequency Band for PSK Modulation
I want to generate a pseudo-random bit stream in MATLAB in a given frequency band for PSK Modulation. I am using the idinput function to generate the bit stream:
<...
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1answer
74 views
Loop Bandwidth for Carrier Demodulation loop
I am trying to implement a simple MATLAB model for the demodulators for phase modulated signals (PSK) used in communication systems.
For the detection of the phase modulated output (PM out in the ...
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1answer
29 views
Modulation classification via demodulation confidence?
I'm not sure if this is the right place to post this question, but will try anyway :-)
I recently started reading up on the field of automated modulation classification (AMC) where an algorithm ...
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1answer
72 views
Digital Tanlock carrier recovery loop
I’m currently trying to understand a digital tanlock carrier recovery loop for QPSK (for example)
I cannot understand how it works.
For example we an ideal QPSK constellation.
phi = atan2(Q/I) = pi/...
0
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1answer
106 views
ADC sampling rate implications Matlab/Simulink M-PSK modulation
I am trying to find a way to evaluate what would be the minimum sampling rate used in a modulated waveform using matlab / Simulink.
The real scenario would be let say a M-PSK waveform of Y bandwidth ...
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1answer
96 views
Burst QPSK demodulator
I am working in burst QPSK demodulator. I just want to double check if what I am doing is right.
Large frequency feedforward recovery by FFT
Carrier recovery Costas with 4 samples/symbol
Timing ...
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0answers
83 views
Nyquist sampling theorem / Nyquist - Shannon theorem evaluation over M-PSK
I am trying to simulate an M-PSK Tx-Rx System on Simulink and analyse what the effect of sampling rate reduction would have on it. More, particular I am trying to prove what Nyquist sampling theorem ...
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2answers
229 views
Understanding Matlab's Automatic Gain Control function
I am trying to understand the automatic gain control block provided by the communications toolbox. The documentation is here: Documentation
My questions are in regards to two of the configurable ...
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0answers
35 views
Learning PSK Modulation and Demodulation - Good Text to Read?
Title sums it up. I am curious to see what you all suggest. I'm a newbie and just need some beginner/intermediate material.
Thanks!
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0answers
276 views
GNU Radio - Bandwidth and Band Reject Filter
I am currently trying to generate a psk modulated carrier with gnu radio.
Attach is an image of my flow graph.
As can be seen I am generating a bit stream using the Random Source module and ...
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1answer
59 views
Mapping soft symbols in DQPSK
I'm trying to soft decode DQPSK. According to this paper the bits are:
$b_1 = \mathrm{Re}\{s_n s^*_{n-1}\}, b_2 = \mathrm{Im}\{s_n s^*_{n-1}\}$
If I put 0.707 as a 100% probability of 0:
$\begin{...
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0answers
38 views
lte matlab baseband IQ recovery
I am a beginner again to signal processing, I did my degree over ten years ago, and I am relearning all my signal processing stuff.
I am a software developer by trade but now I am looking at some LTE ...
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1answer
133 views
Phase shifts of QPSK
I'm honestly lost on creating timing diagrams for bit sequences. I understand for QPSK there are symbols 00, 01, 10, 11 with phase shifts of 45,135,225 and 315.
I'm just not understanding how you ...
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1answer
533 views
What is the minimum sampling rate for QPSK or what is the bandwidth of QPSK signal?
Consider we have created a QPSK signal with a carrier frequency 100kHz. Before applying matched filter or demodulation we need to take samples from the received signal. So what is the minimum ...
0
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1answer
30 views
BER performance of a space-time code over Rayleigh channel model
For a given space-time code, and in general terms, how would one proceed in the evaluation of the BER performance of this code ?
In order to be more clear, say i have 16 code matrices(who's elements ...
