Frequency Translator for Wifi

Discussion in 'Wireless & RF Design' started by Kea, Mar 29, 2012.

  1. Kea

    Thread Starter New Member

    Mar 29, 2012
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    I need to translate 2.4 GHz to a VHF band. Do you know of any frequency translators I can buy?
     
  2. evilclem

    Member

    Dec 20, 2011
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    What exactly are you trying to do?
     
  3. Kea

    Thread Starter New Member

    Mar 29, 2012
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    I'm trying to implement the "super wi-fi" concept by transmitting a baseband signal over a further range using wifi technology. Therefore I have to take the wi-fi signal (2.4 GHz) and down convert to a white space in the VHF band from the transmitter side and up convert the white space to the wi-fi signal.
     
  4. evilclem

    Member

    Dec 20, 2011
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    I think you've slightly misinterpreted the Super Wi-fi concept. The idea is to modulate the data directly onto the VHF frequency rather than convert it from an existing 2.4GHz signal.
     
  5. Kea

    Thread Starter New Member

    Mar 29, 2012
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    Ok! so how do you reckon I implement it.
     
  6. Papabravo

    Expert

    Feb 24, 2006
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    I recommend that you start by identifying how much bandwidth your signal will require and where you will locate that signal. Just because there is no occupant in a frequency band doesn't mean it is a wild west type free for all. Next I would investigate what power levels you will be using, which will determine your RF footprint. That is, what area do you intend to cover e.g. a 10-mile radius from a central hub. Now you need to study modulation techniques to cram as much data as possible into your intended bandwidth.

    The tradeoff for using a lower frequency to achieve greater distance is that the data signals will be slower. A 10 Mhz. Ethernet channel will consume at least 2 former VHF television channels. A 100 HMz. Ethernet channel will consume 17 former VHF television channels. Whoops, there never were 17 VHF channels. A 1 GHz. Ethernet channel would consume more spectrum than was ever allocated to television broadcasting since the dawn of time.

    IMHO this is a fruitless quest.
     
  7. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    What will be the distance to be covered?
    If it is in one straight line, you might think of using light for the communication.
    In the Ronja Project there is a full description how this can be done:
    http://ronja.twibright.com/

    Bertus
     
  8. Kea

    Thread Starter New Member

    Mar 29, 2012
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    The distance is approximately 500m
     
  9. Kea

    Thread Starter New Member

    Mar 29, 2012
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    BTW non-line-of-sight is a requirement for the project
     
  10. Papabravo

    Expert

    Feb 24, 2006
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    Bandwidth and data rate??
     
  11. Kea

    Thread Starter New Member

    Mar 29, 2012
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    data rate of 1 Mbps and bandwidth of 5MHz
     
  12. Papabravo

    Expert

    Feb 24, 2006
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    So you're looking at maybe 4 channels of 1 Mbps in a 5 MHz slice of bandwidth. Now you need to decide on a multiplexing and modulation scheme. Once you have that nailed down you need a network topology.
     
  13. Kea

    Thread Starter New Member

    Mar 29, 2012
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    If I use an 802.11b transreceiver and want to transmit a baseband DSSS signal over longer ranges. Am I right when are say the following:
    Is the baseband DSSS signal modulated onto a frequency from the VHF band or is it translated to a frequency from the VHF band?
     
  14. Papabravo

    Expert

    Feb 24, 2006
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    It is normal to say that a baseband signal, especially a data signal, is modulated onto a signal in the VHF range. Frequency translation by itself supposes that you have an RF signal which is suitable for propagation. Baseband signals do not usually have this property, and thus are unsuitable for frequency translation.
     
  15. Kea

    Thread Starter New Member

    Mar 29, 2012
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    Thanks for the clarification
     
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