All Questions
Tagged with quadrature digital-communications
16 questions
0
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1
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360
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Performing IQ imbalance correction on sampled quadrature signals
What are the techniques which can be used to perform digital IQ amplitude and phase correction in a wideband receiver system when input signals can be of unknown different frequencies and occupy ...
- 500
2
votes
1
answer
293
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Efficient Implementation of Digital Upconversion
I have an application where I have a pulse shaped QAM signal, at 2 samples per symbol. I need to take the I/Q samples and perform quadrature upconversion so that they can be output on a DAC that's ...
- 733
2
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1
answer
355
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Maximum NCO frequency and filter design for down-conversion of complex input signal
I am trying to perform digital down conversion by using the DDC from Matlab dsp toolbox. My question is that the bandwidth property is limited to Fs/2 and the filters created are real filters. If the ...
- 500
0
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2
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4k
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Understanding FFT size in OFDM modulation
I know that the FFT size is the the number of subcarriers OFDM system have. But I also know that the FFT has to be $ 2^N $ big (in order to process N samples from time domain to frequency domain).
...
- 19
0
votes
1
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89
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QAM constellation coder - transmitting a file
The file with size 6 MB is transmitted in 100 seconds using a constellation coder QAM with a constellation of 6 bit/symbol
$ { M = 10^6, B = 8} $
Tasks:
1. What is the signal bandwidth if the band ...
- 19
4
votes
1
answer
2k
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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 ...
- 143
0
votes
1
answer
191
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Modeling channel response as complex vs splitting I and Q
If I have a communications channel where a digital QAM signal is transmitted, I can either model the channel's impulse response as a complex $h(t)$, or as 2 separate impulse responses $p(t)$ and $q(t)$...
- 107
1
vote
1
answer
2k
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In-Phase and Quadrature components of low-pass equivalent of a band-pass signal?
I was wondering what is the physical meaning of IN-PHASE and QUADRATURE components?
In the context of low-pass equivalent of band-pass signals.
Any help is appreciated!
- 41
3
votes
4
answers
3k
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How can the I and Q components of a quatrature signal be different from each other (apart from the 90º phase shift)
I've spent many hours reading and doing research about this. I don't attend any university classes or any type of classes that may approach such a topic. I am trying to learn this by my own without ...
- 31
4
votes
3
answers
2k
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Sending complex signal over a single wire
The G.hn protocol uses OFDM to transmit data. And it sounds like they are doing it on a single wire. OFDM symbols are a complex number with I and Q components. How are they able to send two separate ...
- 233
1
vote
1
answer
317
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Why is no phase information lost when a received signal goes through a mixer?
I'm sorry if the question is too philosophical or makes no sense, but I need to be able to explain why it doesn't make sense.
When we take the in-phase and quadrature-phase base-band components of an ...
- 13
2
votes
1
answer
4k
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How to "draw" the function/wave to send symbols using QAM?
Say you have the following 8QAM constellation diagram:
Say, you want to send the sequence:
001 110 101 000 001
How would you draw the function/wave containing the symbols?
My problem in ...
- 121
1
vote
2
answers
110
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How do you compute for fc and t in modulating an I and Q component
I know that in a $2^b$-ary QAM system you need to modulate the $I$ and $Q$ components through the mixer and are separated by 90° through a local oscillator (by applying a $\cos$ and $\sin$).
By ...
- 69
3
votes
2
answers
20k
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How to reconstruct RF signal using IQ data
I have a complex IQ signal: $s = X + Yi$. I know my original $f_0$ was $5\textrm{ MHz}$.
I can calculate the magnitude/amplitude of $s$: $A = \sqrt{X^2 + Y^2}$
and phase, $\phi = \arctan\left(\frac ...
- 133
5
votes
2
answers
658
views
Quadrature modulation
I have a question:
What is the difference between
$ I \cos(t) - Q \sin(t) $ and $ I \cos(t) + Q \sin(t) $
except that they are phase shifted 90 degrees ?
On the internet I can find both ...
5
votes
2
answers
3k
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Difference between these two digital down conversion methods
I can think of two possible methods of digital down conversion. One seems superior to the the other for most cases, but I'd like to get some DSP experts' comments on the practical differences between ...
- 251