12
votes
Accepted
Can humans hear Hilbert transform in audio?
Can humans hear Hilbert transform in audio?
Generally no.
The human auditory system is fairly insensitive to monaural phase shifts. "Monaural" means "same phase shift for both ears&...
- 42.6k
10
votes
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Phase synchronization in BPSK
Phase (or carrier) Recovery for BPSK can be done over the entire sequence using the information from every sample. Here are common approaches to doing Carrier Recovery:
Frequency Doubling (squaring):...
- 48.9k
10
votes
Accepted
FSK Demodulation, Bit Timing Recovery
I am currently implementing acoustic FSK modulation and demodulation. I am not a signal processing guy…
Since you say you have matched filters, and you mention non-coherent detection, I think you're ...
- 29.6k
9
votes
Accepted
QAM constellation slicer with unknown carrier phase
What you need is carrier phase synchronization. This is a complicated topic with many different approaches. The approach that you'll choose could depend on things like:
Data-aided versus blind: Does ...
- 24.5k
8
votes
I'm missing something when it comes to understanding FM
In addition to the perspective offered in @Ash's answer, Claude Shannon touches on FM in his paper "Communications in the Presence of Noise" (Proceedings of the IRE, January 1949). He ...
- 11.8k
7
votes
FSK and IQ modulation
What is the advantage of performing the FSK using IQ modulation?
You only need one RF oscillator operating at a single frequency, instead of having 2 (or more in the case of M-ary FSK) oscillators ...
- 121
6
votes
Accepted
Beginner BPSK demodulation question
An "integrate and dump" filter is a common approach for this application, which is essentially an averaging filter averaged optimally over your symbol period. To implement this, you simply ...
- 48.9k
5
votes
I'm missing something when it comes to understanding FM
Large modulation indexes are preferred because the signal-to-noise ratio has a cubic dependence on modulation index ($\beta$).
$$SNR_{FM}=3\beta^2(\beta+1) CNR$$
Where CNR is the carrier-to-noise ...
- 880
4
votes
Given a real signal, increase modulation frequency
You can simply multiply by another cosine: $x(t)\cos(2\pi f_ct)\cos(2\pi 0.001f_ct)=x(t)\cos(2\pi0.999f_ct)+x(t)\cos(2\pi1.001f_ct)$ (ignoring scale factors). If $x(t)$ is very narrow in frequency, so ...
- 14.9k
4
votes
Accepted
Matlab: What should be the BER performance for BPSK using Constant Modulus Algorithm equalizer
Well, I took a look at your code, and spent a lot of time on it, and I have discovered some mistakes, some practicals and some theoretics. Here are my answers:
(1) You can use the function filter. ...
- 677
4
votes
why does the decision boundary change in BPSK? is it true?
Zero-mean noise by itself can't modify the decision boundary. However, the number of things that can go wrong in your system is large.
Is your channel flat or frequency-selective?
You can think of ...
- 14.9k
4
votes
FSK and IQ modulation
There are many ways of demodulating the FSK signal
Indeed!
What is the advantage of performing the FSK using IQ modulation?
Depends. Generally, IQ is the only shape you have your signal in, so ...
- 29.6k
4
votes
Accepted
Mystery signal - FSK, BPSK?
After playing around in GNURadio, this waveform looks like 2 level ASK bursts (OOK bursts plus some residual carrier).
The carrier appears to be at 12.4 kHz.
At the 44.1 ksps sample rate, there ...
- 2,700
4
votes
Detecting I/Q imbalance
As long as the assumption of equiprobable data with independent I and Q reasonably holds (and over the long duration with whitened transmissions this is typically a good assumption), then IQ imbalance ...
- 48.9k
4
votes
Quadrature demodulation, homodyne detection, lock-in detection - what's the difference?
They are essentially the same but may have key differences varying across implementation. The process is identical in terms of multiplying a signal by a sine wave at the center frequency of the signal ...
- 48.9k
4
votes
Why would we simulate baseband rather than passband
One very obvious advantage of baseband simulation of communication systems is the low sampling rate it requires.
Considering a narrowband communication system having a few MHz of bandwidth to a few ...
- 28k
4
votes
Accepted
In case of using a Doppler radar, do we have to use IQ demodulation to find the direction of a target?
Radar designer here: It sounds like you’re talking about pulse-Doppler (PD) radar systems. For PD radars, the process is essentially as you described:
Generate a waveform (typically at IF) and then ...
- 853
4
votes
Accepted
Positive slope of BER with a greater frequency deviation?
This could happen as discriminator gain is increased with a filter discriminator approach since in many of those approaches the gain would be maximum and linear for small signals only and then the ...
- 48.9k
4
votes
Accepted
Block diagram of M-PSK modulation and demodulation
So this seems to be a general block diagram for these types of modulations.
No, this is a block diagram of a IQ upconverter with some unspecified digital data modulator on the input.
You need to ...
- 29.6k
4
votes
Can humans hear Hilbert transform in audio?
Here's my GNU Octave code I used to create Hilbert transform of the music:
...
- 233
4
votes
Accepted
Understanding homework solution - why are $\{X_t\}$ and $\{Y_t\}$ joint WSS, and finding Wiener filter + error
Now that the OP has responded with his textbook's definition of jointly wide-sense-stationary (WSS) processes as those that are individually WSS and whose cross-correlation function $R_{X,Y}(t_1,t_2)$ ...
- 20.2k
4
votes
Help me understand the concept of IQ signals
The important takeaway is: using a radio, you can transmit two signals "at the same time" (technically: over the same bandwidth). One of the signals is known as I (in-phase), the other as Q (...
- 14.9k
3
votes
Accepted
How to correct the phase offset for QPSK I-Q data
Assuming we have timing recovery resolved (meaning our system knows the correct time locations for our symbol decisions), then we can use the decided symbols along with our pre-decision values in a ...
- 48.9k
3
votes
Accepted
Demodulating upper sideband (USB) signals
Apart from scale factors, your USB signal is
$$f(t)=m(t)\cos(2\pi\nu_ct)-\hat{m}(t)\sin(2\pi\nu_ct)\tag{1}$$
(as you've correctly stated in your question). Now if you multiply with a (coherent) ...
- 88.9k
3
votes
Accepted
OFDM demodulation, how to set the sampling rate?
Your receiver will consist of, apart from synchronization blocks, an FFT. You want that FFT to generate one output bin for each of the subcarriers. Therefore, you should make use of the relationship ...
- 24.5k
3
votes
Accepted
OFDM symbol acquisition block in GNU Radio gives rotating constellation even if there is no carrier offset. How is this possible?
Got me at that one! The "OFDM symbol acquisition" block is in fact not from gr-digital (where your other OFDM blocks come frome), but from gr-dtv, where it is used ...
- 29.6k
3
votes
Given a real signal, increase modulation frequency
$$\cos(A\pm B) = \cos(A)\cos(B) \mp \sin(A)\sin(B)$$
and so $$2\cos(A)\cos(B) = \cos(A + B)+\cos(A - B).$$
It follows that multiplying the received signal $x(t)\cos(\omega_c t)$
by $2\cos(1.001\...
- 20.2k
3
votes
IQ sampling vs 2X f0 sampling for SDR
I can envision advantages (or convenience) in doing this for lower IF signals certainly, as long as the sampling rate is significantly higher than the signal bandwidth to contain the phase dispersion ...
- 48.9k
3
votes
Accepted
Amplitude Modulation with large carrier and suppressed carrier
In short: you can use envelope detection on a suppressed-carrier signal, but you'll recover $|m(t)|$, not $m(t)$.
One easy way to see it is by drawing the signals. Draw an arbitrary signal $m(t)$, ...
- 14.9k
3
votes
I/Q Sample demodulation to input data
In addition to hotpaw2's answer:
Presumably, the signal originated from a binary output on the transmitter end.
I'd say that is most probably wrong.
The typical digital transceiver based on ...
- 29.6k
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