Questions tagged [spread-spectrum]
Anything related to spread spectrum techniques, i.e. methods used in telecommunication engineering that make the spectrum of the transmitted signal to be spread across a much wider bandwidth than in normal modulation schemes. Spread spectrum techniques are used to improve the reliability and robustness of communications.
23 questions
-1 votes
1 answer
63 views
spreading factor in LoRa PHY (CSS)
I wonder how the spreading factor (SF) is defined in LoRa PHY. Specifically, in other spread spectrum techniques (e.g DS, FH), we have: W = R * SF W is the (spread) bandwidth, and R is the symbol rate....
- 69
1 vote
2 answers
98 views
External spread spectrum phase-shifted clocks versus unsynchronised spread spectrum in multiple buck converters
I'm working on a design where I have a need to generate about 10A at 5V across a long bar-shaped board. This is generated from an incoming 12V DC rail. For a number of reasons (physical constraints, ...
- 11.5k
1 vote
1 answer
356 views
Why the increase of the Spreading Factor (SF) by one, in the LoRa modulation, results in doubling of the transmission time of a symbol (T_symbol)?
Recently, I have been reading about the LoRa modulation and I am curious, why the symbol transmission time (T_symbol) doubles, if the Spreading Factor (SF) is increased by one. The SF is equal to the ...
- 45
0 votes
1 answer
694 views
Dithering Modulation Frequency and Dithering Rate
I have a question regarding dithering. I was reading this Application note and under section 4.1 page 5,they have given below, I understand that we perform dithering in the DC-DC Switching converters ...
user220456
0 votes
2 answers
110 views
What is the irregular signal at the bottom of this "spectrogram"?
I am reading research papers about LoRa, and I have come across the below figure in this one. The horizontal axis is clearly labeled frequency, but the vertical one isn't. I recognize the chirps in ...
- 3
1 vote
2 answers
198 views
How do we separate source signals in spread spectrum?
In a point-to-point mode, that is, one transmitter and one receiver, I understand how a spread spectrum receiver can read the transmitted signal from a spread spectrum transmitter by knowing the code. ...
- 463
2 votes
1 answer
445 views
Calculate power of an LTE Signal
I am looking for the formula to convert the power level of an OFDM RF signal to an absolute power level. For example if I have my typical rectangular RF spectrum and the bandwidth of the signal is ...
- 101
0 votes
1 answer
278 views
CDMA and correlation function
In layman terms, what does it mean that correlation function is being high between received signal and the code? Does this mean that the received signal is compared against spreading codes and the ...
- 297
4 votes
2 answers
2k views
Why different SFs in LoRa are said to be orthogonal?
As orthogonality is an important characteristic in LoRaWAN but most public references just make a conclusion that different SFs are orthogonal. This confused me a lot and hope to make a clear ...
- 41
-1 votes
1 answer
65 views
(W)CDMA, any repeating information?
I am looking to characterize a WCDMA channel to study the effects of multi-path. In order to do this I need to be able to find some repeating information (bit sequence) being transmitted by a station. ...
- 71
0 votes
2 answers
351 views
Demodulation of direct sequence spread spectrum technique [closed]
I can't intuitively believe that a signal could be demodulated whose voltage is below the noise floor. Can some one explain me how this demodulation of direct sequence spread spectrum happens without ...
- 111
2 votes
2 answers
134 views
Why is noise power not multiplied by spread gain?
In my intuitive consideration, noise power should be enlarged as spreading gain times. The reason why I think this is: Let us consider that the information signal is of bandwidth W Hz. Then, the ...
- 145
1 vote
1 answer
278 views
FPGA CDMA tracking
Consider a CDMA transmitter using DSSS that is in motion with respect to the receiver (satellite). Suppose the PN code is synchronized to within one chip, i.e. acquisition has been completed. How is ...
- 6,287
0 votes
2 answers
153 views
Spread spectrum bandwidth
Can someone explain how it derived the bandwidth for spread spectrum on following link http://www.ausairpower.net/OSR-0597.html (paragraph 9)?
- 297
2 votes
1 answer
437 views
Is CDMA more secure than LTE or GSM?
I know that this question is very direct, but I was curious to know why is it that in defense applications, CDMA is preferred over LTE? Is CDMA more secure than LTE and hence more difficult to ...
