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12 votes
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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&...
Hilmar's user avatar
  • 45.4k
10 votes
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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 ...
Marcus Müller's user avatar
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):...
Dan Boschen's user avatar
  • 52.1k
9 votes
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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 ...
Jason R's user avatar
  • 24.6k
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 ...
TimWescott's user avatar
  • 12.8k
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 ...
GordonFreeman's user avatar
7 votes
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Matched filter reference signal

What you have ia not a matched filter at all but instead a correlation receiver which correlates the received $r(t)$ with the possible transmitted signals $s_1(t)$ and $s_2(t)$ (note no time-reversal) ...
Dilip Sarwate's user avatar
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 ...
Dan Boschen's user avatar
  • 52.1k
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 ...
Ash's user avatar
  • 915
5 votes

Are there modulation schemes that use more bandwith than they need to, but don't require a spread-spectrum code to decode? (besides AM)

Yes, analog wideband FM is another example where the occupied bandwidth is wider than the bandwidth of the modulation signal, and provides a similar processing gain to digital spread spectrum ...
Dan Boschen's user avatar
  • 52.1k
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 ...
MBaz's user avatar
  • 15.3k
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 ...
Marcus Müller's user avatar
4 votes
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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 ...
Andy Walls's user avatar
  • 2,710
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 ...
Dan Boschen's user avatar
  • 52.1k
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 ...
Dan Boschen's user avatar
  • 52.1k
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 ...
Fat32's user avatar
  • 28.3k
4 votes
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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 ...
vintagevogue's user avatar
4 votes

Getting the bitstream of an unknown RF signal

The IQ data looks like a sinusoidal modulated pulse train with binary phase shift keying (BPSK) superimposed. The BPSK symbol rate appears to be at the same rate as the pulse repetition frequency (PRF)...
rjan87's user avatar
  • 166
4 votes
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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 ...
Dan Boschen's user avatar
  • 52.1k
4 votes
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Demodulating a LoRa data symbol

The resulting up chirp traverses across BW and arrives at the same place it started. not quite exactly right, but very close: it ends up in the DFT bin before the bin it started from. This makes the ...
Marcus Müller's user avatar
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 ...
Marcus Müller's user avatar
4 votes

Can humans hear Hilbert transform in audio?

Here's my GNU Octave code I used to create Hilbert transform of the music: ...
juhist's user avatar
  • 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 $R_{X,Y}(t_1,t_2)$ ...
Dilip Sarwate's user avatar
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 (...
MBaz's user avatar
  • 15.3k
4 votes

Matched filter reference signal

This system is designed to identify whether $r(t) = s_1(t) + n(t)$ or $r(t) = s_2(t) + n(t)$. Assuming the transmitted signal is $s_i(t)$ for $i = 1$ or $i = 2$, then the received signal is $r(t) = ...
MBaz's user avatar
  • 15.3k
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 $m(t)$, ...
MBaz's user avatar
  • 15.3k
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 ...
Dan Boschen's user avatar
  • 52.1k
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 ...
Dan Boschen's user avatar
  • 52.1k
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) ...
Matt L.'s user avatar
  • 90.4k
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 ...
Marcus Müller's user avatar

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