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.

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1answer
245 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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3answers
2k views

How to build a simple DSSS (direct sequence spread spectrum) transceiver?

I have a modern microprocessor (Cortex-M3) with a decent ADC (10-bit 400kSPS or 12-bit 200kSPS). How to design and build a simple DSSS system for learning purposes? What is the simplest RF front-end ...
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2answers
57 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 ...
2
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2answers
368 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.
2
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2answers
2k views

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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2answers
185 views

Why CDMA is able to use whole band, when Wimax is subchanneled?

Original wording of question: What is fractional network access? I'm having trouble figuring out what this term actually means, though I can find a ton of whitepapers about how some-standard-or-...
1
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1answer
152 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 ...
1
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1answer
172 views

Spread spectrum

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 ...
0
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2answers
157 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 ...
0
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2answers
222 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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3answers
93 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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2answers
70 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)?
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1answer
310 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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1answer
36 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 ...
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1answer
43 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. ...