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Pure sinusoids

  1. Jun 5, 2012 #1
    Hi,
    if we transmit 3 different pure sinusoids with different frequencies using 3 transmitters at the same time in the air (wireless), is this possible for a single receiver to receive all the 3 signals at the same time, so we many know frequency components of the signals using FFT?
    If yes how?
    If no why?
     
  2. jcsd
  3. Jun 5, 2012 #2

    sophiecentaur

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    If you bear in mind that a 'receiver' is no more than a filter (usually with amplification), followed by a detector / demodulator of some sort, then why not? In the case of your proposed system, the ADC and processing constitutes a demodulator. The actual answer to your question really depends upon the details of your setup but if your bandpass (low-pass) filter admits the three sinusoids then you sample fast enough (Nyquist limit plus some in- hand) the signal that your ADC looks at can be analysed in blocks using FFT and will produce three peaks in the frequency domain, corresponding to the three carrier frequencies.
     
  4. Jun 6, 2012 #3
    Thanks sophiecentaur for your reply, actually I am using ISM band (2.4GHz ), frequencies from 2.4 to 2.6 GHz,my procedure is as follow (please correct me if I m wrong)
    1. I will have to use an analogue bandpass filter to collect only this band of frequencies.
    2. Will use ADC or simply a sampler at nyquist rate.
    3. Will pass it through FFT
    so In simulink a single FFT block and single ADC works for all the 3 or more signals to be analysed.
    Is this possible practically to use a single ADC for all signals or I have to use 3 ADCs for 3 signals?
     
  5. Jun 6, 2012 #4

    sophiecentaur

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    You will, presumably be doing down-conversion and analysing at a more reasonable IF frequency. What is the frequency spread of the three signals? A single ADC will need to be able to deal with this bandwidth. Your sampling rate doesn't actually need to be at the IF rate - if your signal is suitably filtered, the sub-sampling shouldn't be a problem.
    I should have thought that there is no advantage in using three separate ADCs - just extra aggro.
    You'd need to be more specific about the details and then we'd need someone with more knowledge than me about specific device performance - not trivial, I'm afraid.
     
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