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Questions tagged [constellation-diagram]

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What determines the maximum/minimum values in I/Q constellation diagram?

I need to do some data analysis on I/Q samples and was trying to know what are the parameters that determine the maximum/minimum values of these samples. In other words, what determines the maximum/...
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1answer
385 views

Average Energy of modified QAM Constellation

How to compute the average energy for the modified 16-QAM constellation below? I know that for regular/rectangular 16-QAM we can utilize the 4-PAM along each axes but I'm not sure how can we find $E_{...
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1answer
116 views

QPSK constellation from baseband signal

My IQ sampler is measuring a QPSK carrier at a set frequency/bandwidth (40MSamp/s), but shifts the signal spectrum to baseband. My signal is 1.5Msym/s, but sampling at 1.5Msym/s gives me a ...
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2answers
178 views

Carrier Frequency Offset, Rotating Constellation and Correlator

I have been further reading up on carrier recovery methods and something is not clear to me: It's written that a carrier frequency offset results in a rotating constellation diagram but if you are ...
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1answer
60 views

Phase versus time graph of QPSK

In wikipedia, there was an example on QPSK modulation where the main signal was 11000110 and I contained 1001 and Q contained <...
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1answer
135 views

Why is Error Vector Magnitude (EVM) measured as an RMS value?

I do understand Voltage/Current measurement of a Sine Wave is in RMS, as average yields a zero, and RMS gives a true 'DC equivalent' value. But I do not understand why an EVM measurement could be in ...
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1answer
323 views

What techniques are available for correcting constellation rotation due to phase ambiguity?

In order for a receiver to recover a baseband signal, it needs a carrier signal equivalent to that used by the transmitter for upconverting the original baseband signal. Unless pilot tones are used, a ...
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1answer
58 views

Understanding unexpected i/q calculation on a downsampled signal

I am reading samples with an RTL-SDR, centered on an FM broadcast station: ...
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0answers
42 views

Constructing Contour for Star QAM Equalization

I am trying to equalize the 16 Star QAM using known blind channel algorithms such as CMA,MMA,SCA,RCA,IRCA,CXA,SCXA.I now need to contruct a new contour for equalizing the 16 Star QAM.As it is in ...
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471 views

How to generate amplitude and Phase values (I,Q) for 8 QAM?

I am trying to simulate 8QAM with (4,4) amplitude levels. I want to get a constellation like this: What are the amplitude levels should I select for I and Q?
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1answer
332 views

Aliasing in digital communication system

In a digital communication system, is it possible to counteract the aliasing problem by properly tuning the constellation order $M$ and/or the carrier frequency? Here is my train of thought, please ...
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3answers
176 views

Zeros inserted in QAM Constellation

I need to ask about insertion of Zero Symbols after QAM modulation in a OFDM system. Such that the 4 QAM has a constellation with 4 corner and 1 center symbol indicating zero. What advantages or ...
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2answers
546 views

How to scale measured QPSK points to determine magnitude error?

I am trying to determine the magnitude error between demodulated I,Q values and reference values on a constellation plot for a QPSK signal. The reference points are at (1,0),(0,1),(0,-1), and (-1,0). ...
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1answer
2k views

Matlab : How to plot the constellation diagram for this method?

I am trying to generate symbols +1,-1 using a function by partitioning the interval of the function into two levels. The function is the Tent Map. This in a way achieves bpsk modulation. I want to ...
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1answer
169 views

P2 symbol constellation in DVB-T2

DVB-T2, 32K SISO, not extended. I've acquired P2 symbol, PRBS bits have matched with bits recovered from pilots. Then equalization was applied to all subcarriers. The constellation I've got looks ...
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1answer
746 views

Generating QPSK Constellation Diagram

I was wondering how a diagram like this is generated. I am generating a QPSK signal using MATLAB by taking a cos and sin wave, multiplying each one by either 1 or -1 and adding them together to form ...
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2answers
2k views

OFDM symbol acquisition block in GNU Radio gives rotating constellation even if there is no carrier offset. How is this possible?

Why does the constellation rotate when using OFDM Symbol Acquisition block in this flow graph below ? The only explanation I could think of would be carrier frequency offset but in this flowgraph ...
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1answer
929 views

How does carrier frequency offset effect the constellation diagram in OFDM?

In the case of OFDM modulation, if the carrier frequency is slightly off then how does that effect the constellation diagram ? Is there some general rule how it will change (such as rotate) ? Or ...
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0answers
400 views

Problem in constellation diagram

In a waveform designing i am getting this type of constellation(image_attached). Can anyone please tell me why i am getting this type of constellation? this constellation is after frequency correction....
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1answer
3k views

GNU Radio - PSK Mod block - unexpected constellation diagram

I am simulating a QPSK modulation in GNU radio. Here is the flowgraph: . The source is a binary stream coming from the Random Source block. There are 4 PSK Mod blocks configured identically (4 ...