Electrical Engineering Stack Exchange
Electrical Engineering Stack Exchange

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.

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 against interference (either casual or intentional, e.g. jamming) and eavesdropping.

See also Wikipedia on spread spectrum.

21 questions
8
votes
1 answer

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 spread (for DSSS). The only references I could find…
Synchrondyne
  • 3,764
  • 21
  • 31
4
votes
2 answers

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 understanding. As @Chris Stratton show me in the link…
Armstrong
  • 41
  • 3
4
votes
3 answers

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 that would be needed for this? The bandwidth is…
jpc
  • 5,302
  • 1
  • 24
  • 45
2
votes
1 answer

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 10MHz, if my signal power needs to be 23dBm, what…
Eoin O Connell
  • 91
  • 6
2
votes
2 answers

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 (USA, Canada...). I am in Region 1, Europe. I have…
Roman Rdgz
  • 123
  • 5
2
votes
2 answers

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 receiver suffers from the noise of bandwidth W Hz as…
Danny_Kim
  • 145
  • 7
2
votes
1 answer

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 intercept?
Tarandeep Kalra
  • 61
  • 5
2
votes
2 answers

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.
dr3patel
  • 1,620
  • 3
  • 22
  • 31
1
vote
1 answer

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 number of bits transmitted in a symbol, i.e. the…
pstr
  • 35
  • 4
1
vote
2 answers

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. But I cannot understand how different codes can…
Noob_Guy
  • 395
  • 2
  • 11
1
vote
1 answer

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 code tracking implemented currently on FPGAs? What…
user110971
  • 6,067
  • 1
  • 15
  • 23
1
vote
1 answer

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 Keying (GFSK) modulation? Can modulated signal be…
Quirik
  • 277
  • 1
  • 2
  • 6
1
vote
2 answers

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-another means to support it. I know it's related to…
ExpedientSmith
  • 21
  • 4
0
votes
1 answer

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 to reduce the emission magnitude at the…
user220456
0
votes
2 answers

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 the middle, so I understand that the vertical axis…
Boba0514
  • 3
  • 2
1
2