# Questions tagged [baseband]

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### Downconversion and CFO estimation after package detection

I'm currently working on generating a function to simulate a passband transmission. In my simulation, I assume that the received signal is twice of my transmitted signal (without adding any noise and ...
12 views

### Calculating PSNR using STFT of sampled signal

I have a baseband IQ sampled signal from a Pluto SDR with a bandwidth B and also fs = B, how can I calculate its PSNR using the STFT of the signal in Matlab. Do I need to take into account the RBW of ...
60 views

### Why do I find a low frequency oscillation when I add a carrier frequency to my baseband signal ? And Why is my demodulation step not working?

I am trying to build a simulation for a 2PPM signal, modulate it at high frequency and then retrieve my baseband signal. Here is my full code (minus the plots) before explaining more. ...
107 views

### PSD of real and imaginary parts of complex envelope of a bandpass signal

I know that we can write a real bandpass signal x(t) as: $x(t)=x_c(t)\cos\omega_ct + x_s(t)\sin\omega_ct$ $x_c(t) = 2x(t)\cos\omega_ct$ for $|f|<W$ $x_s(t) = 2x(t)\sin\omega_ct$ for ...
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### Adding Narrowband Interference to Spread Spectrum Signal in MATLAB (Baseband Model)

I am interested in adding a narrowband interfering signal to my spread spectrum signal. In the waveform model, it's straightforward to generate a narrowband signal within the frequency range of the ...
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1 vote
320 views

### Why are all baseband signals low-pass?

A baseband signal is just a signal that has not been used to modify a carrier signal. Now, I have noticed that all baseband signals are low-pass too. Why is that? I can understand why digital baseband ...
128 views

### Is BPSK relevant, or does it even exist, in wireless data transmission?

I ask this question because it seems to me that if pulse shaping has been applied in the transmitter, the signal that is actually transmitted is not phase modulated at all, rather, it is amplitude ...
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691 views

### How can I generate a OFDM baseband signal with the output of the ifft?

I have some understanding problems with OFDM. I think I have understood most of the theoretical concept. At the moment, I am trying to write some Python code to simulate the transmitter part. This is ...
1 vote
105 views

### The baseband sampling frequency when the negative spectrum is considered

Suppose I have a signal $x(t)$ of bandpass bandwidth of $2W$ Hz. The sampling frequency must be at least $2W$ in baseband, because the largest frequency component is $W$ Hz. I understand that, when we ...
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### Practical problems in down-converting via Hilbert filter

While teaching communication system to my students, I showed different ways to define the diagram block of the system responsible for transforming a bandpass signal, $x(t) \in \mathbb{R}$, into its ...
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### Binary Polar vs 4-PAM Signalling

Why is binary polar signalling not feasible for a data rate of 2.0Mbps within a bandwidth not exceeding 1MHz? Is it due to the fact that binary signalling can only transfer 1 bit of data per symbol ...
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5k views

### QPSK Data Rate vs Bandwidth at Passband: Why can it only transmit 1 bit per Hz and not 2 bits per Hz?

1) This is a follow up question to the most up-voted answer to this question. 2) The accepted answer is that "QPSK transmits 1 bit per Hz at passband". 3) The theory found in books seems to agree ...
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1k views

### Converting complex baseband signal to passband signal

I have to convert baseband signal (BW-20MHz) to passband signal centred at 20MHz. I am implementing this in matlab. so, this is how I tried it. I have already generated LTE Waveform BW- 20MHz , fs =30....
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### Why would we simulate baseband rather than passband

My question is, Why do we usually use baseband in simulation rather than passband? however, if we want to test our simulated idea in real environment, it must be sometimes in passband !! So, should ...
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1 vote
1k views

### IQ modulation: baseband to bandpass transformation

Given is a baseband signal representation. A : Complex Signal R : Real Signal If I multiply baseband signal with FT(cos) then the signal will look like first plot ...
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### IQ modulation principle

I am new in the signal processing. I hope I can get help. I want to ask a question regarding IQ modulation work . Why can’t I simply multiply a complex base-band signal with a cosine to modulate it?
1 vote
26 views

### Can you use the theory of Signal Space to study Band Base digital systems?

Introduction: There is one way to study different modulations in band pass digital systems and is working with "signal space" and the Constellation Diagram. My questions about this are: 1) Is it ...
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