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.

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### 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 ...
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314 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 ...
58 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 ...
1 vote
137 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. ...
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261 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 ...
122 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 ...
• 287
1k 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 ...
57 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. ...
300 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 ...
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91 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 ...
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1 vote
229 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 ...
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97 views

Can someone explain how it derived the bandwidth for spread spectrum on following link http://www.ausairpower.net/OSR-0597.html (paragraph 9)?
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388 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 ...
374 views

### Can SSC be a problem if operating PCIe interface asynchronously through a re-driver?

I am operating PCIe over copper cables via re-drivers asynchronously. i.e. I only send over the RX/TX data. The clock is sourced locally at the end point. For the host root port, I am designing a ...
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341 views

### ISM band rules for spread-spectrum: how much do I need to spread?

I'm doing a preliminary study for a 5.8 GHz ISM band data downlink for a cube satellite. I know that spread-spectrum is mandatory for ISM, but the FCC rules seem pretty opaque on how much I need to ...
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1 vote
208 views

Are Frequency Hopping Spread Spectrum (FHSS) and Direct Sequence Spread Sequence (DSSS) modulations? I am confused because I have read that these are also used e.g. with Gaussian Frequency-Shift ...
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131 views

### Spreading of a pulse in time domain

I have a small doubt. Suppose I transmit just 2 square pulse with frequency of 100 MHz over a wireless channel, will it spread in the time domain when received by a wireless receiver. In other words, ...
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443 views

### How does spread spectrum VCXO (voltage controlled oscillator improve EMI on your board?

I have seen people adding spread spectrum voltage controlled oscillator to EMI on the board, How is EMI affected by single spectrum crystal and with spread spectrum crystal.
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### Worldwide usage of 902-928 MHz band

I don't know if this is the most indicated stackexchange site to ask this, but I'll give it a try: I know 902-928 MHz is part of ISM band, and I know for sure it is a free band to use in Region 2 (...
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1 vote