# Tag Info

## Hot answers tagged software-defined-radio

6 votes
Accepted

### Why do we need to increase sampling frequency at the transmitter?

Three reasons to increasing the sampling rate further are 1) To relax the requirements of the post D/A conversion filtering for image rejection. 2) Increase signal SNR by spreading quantization ...
• 37.1k
5 votes
Accepted

### Recommendation for good ressources on digital processing and D-QPSK

Wow, I'm honored by Matt L. doing what I'm often doing: Referring people to GNU Radio. The project actually has a list of recommended literature, but I don't know how well that'd fit you. It's ...
• 26.3k
5 votes

### Why is phase range between $-\pi$ and $+\pi$ (instead of $0$ and $2\pi$)?

First, when you're talking angles, in DSP pretty much all angles are $\mod 2\pi$. So $2\pi \equiv 0$. Usually it's more convenient to keep angles on the interval $\left [-\pi, \pi \right )$, because ...
• 8,285
5 votes

### Why is phase range between $-\pi$ and $+\pi$ (instead of $0$ and $2\pi$)?

It is just a convention, but it is useful in some cases. For example, the phase of the DFT of a real discrete-time signal is odd only if the angles are expressed in the range $[-\pi, \pi)$. Sometimes ...
• 13.8k
4 votes
Accepted

### I/Q sampling with just one ADC

Is this an entirely stupid idea? No, but you've just came to the conclusion that instead of sampling complex, with Nyquist rate being the bandwidth, you should do twice as many samples. That simply ...
• 26.3k
4 votes
Accepted

### Time Alignment of 2 Sensors Sampling the Same Signal with Different Hardware Delays

If the above is a good representation you should just try to infer when there is energy in the signal to align them. As it seems they start with nothing (Zero value). Then all needed is just to find ...
• 40.7k
4 votes
Accepted

### Compare the quality of IQ data from different Software Defined Radios (SDRs)

First and foremost, I would recommend against over the air testing for this given the significant challenge in really being able to provide the same signal to each radio (since you have both temporal ...
• 37.1k
3 votes
Accepted

### Use of I/Q representation for unmodulated Rx Signal

If you are "observing" the source, this implies there is some sort of information you are looking to get out of it, whether it be the total background noise, interference levels etc. Do you ...
• 37.1k
2 votes
Accepted

### Trouble with time-syncing two radio signals using cross-correlation

It will work when you take the 2nd gradient of the signals: ...
• 36
2 votes

### why transmitting a long pulse its spectrum gets spread?

this is John BG 1.- GFSK is not same as single tone According to the CC1101 specs you refer to, the C1101 uses GFSK. GFSK varies the varrier frequency, therefore the spectrum cannot be a delta. ...
2 votes

• 29.9k
1 vote

### Technical Term for the Sum I + Q

There's no specific term, as far as I know, but it's a very common operation with quadrature mixing. It's the result of taking the real part of an analytic signal. You have a complex baseband signal \$...
• 80.2k
1 vote

### How can the I and Q components of a quatrature signal be different from each other (apart from the 90º phase shift)

In terms of visualization, I think you may be confusing phase shift and delay. In the case of a single-frequency complex exponential , a plot of the imaginary part appears to be delayed from the real ...
• 486
1 vote

### How can the I and Q components of a quatrature signal be different from each other (apart from the 90º phase shift)

Let's start from the beginning. Given a real signal to a quadrature circuit, two components are generated, I, the real component, and Q, the imaginary component, which is the same as I, only it has a ...
• 466
1 vote

### How can the I and Q components of a quatrature signal be different from each other (apart from the 90º phase shift)

You are mistaken in your 2nd paragraph. The I and Q components are not always identical with a 90 degree phase offset. Instead, they are usually generated by multiplying some real or complex signal ...
• 34k

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