# Tag Info

### What's the difference between frequency shift, frequency offset, phase offset, and phase noise?

To complement Dan's answer, this is the way I usually use these terms. Frequency shift: a change in the frequency of a bandpass signal. It can be intentional, as when downconverting a signal in the ...

### What's the difference between frequency shift, frequency offset, phase offset, and phase noise?

Frequency shift and frequency offset could reasonably refer to the same thing, but a shift suggests something that has moved (from one frequency to the next as would occur in a changing Doppler) while ...

### Why do we ever use low-order modulation schemes?

As we go for higher modulation order, detection complexity increases by exponentially , Hypothesis grows and detection becomes computationally intensive task. Also in use cases where channel condition ...

### 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 (...
Accepted

Accepted

### How is the normalized power required for unipolar NRZ twice that of polar NRZ?

If the levels of the polar signal were $\pm V$ you would be right, but then it wouldn't be a fair comparison with the unipolar signal with levels $+V$ and zero. A fair comparison would be to have the ...

### Help me understand the concept of IQ signals

It might be best to compare an IQ signal with complex numbers, or circle on an XY plane, or phasors. As the IQ signal is a sum of sine wave with some amplitude and cosine wave with some amplitude, the ...
1 vote

### What is use of Quadrature Converter in OFDM?

"Mixing" has a different meaning for RF than it does for audio. In audio mixing is a linear combination of the two (or more) signals. In RF, it's the modulation that bumps a baseband signal ...
1 vote

### Time of arrival

$t_e$ is the absolute time when the signal was transmitted from the transmitter. $\frac{d}{c}$ is the Time of Flight (TOF). The Time of Arrival (TOA) is the absolute time when the signal reaches the ...
1 vote

### How Reducing Dynamic Range by Boosting Signal Improves Burst Detection?

1) How boosting the signal reduces the dynamic range? I don't think the comment is correctly describing what is happening. Just scaling the entire data set by a constant value, in this case ...
1 vote
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### How correctly choose a channel model?

Different links can have different channel characteristics. If your (A) is very close to (B) and any scatterers are far away then the LOS component dominates which could be modeled using a Rician ...
1 vote

### Why can interleaving make the channel "memoryless"?

[Posted as an answer because it is too long to be left as a comment] It is not the case that a channel with memory can always be treated as a memoryless channel with sufficiently long interleaving. If ...
1 vote
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### What is discrete in value/amplitude/magnitude?

A specific example, and common application where this occurs is with an "Analog to Digital Converter" (A/D), which is the boundary between the analog and digital world. Computers store ...

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