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Coaxial to Normal Wires

  1. Sep 28, 2009 #1
    Hi Guys,

    For my design project, I am dealing with a horn antenna that has coaxial wire for the input and output. The problem is, I need to take the signal recived from the antenna by the coaxil and feed it to another circuit, since I need to us a circuit to down convert the freqeuncy or convert it to DC, and then power an LED.

    Are there converters avalible in the market to do so?

    If there is any information you could add please do so, about coaxial etc.

    Thanks

    p.s. Normal Wires may not be the appropriate term to use, so bear with me.
     
  2. jcsd
  3. Sep 28, 2009 #2

    vk6kro

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    You haven't given frequencies, but a horn antenna is only used for microwave frequencies.
    Possibly in the range 3 GHz to 12 Ghz or higher.

    You may be asking about splitters. Yes, these are available. You would have to ask at specialized microwave / satellite TV stores.

    Depending on the frequency, you can get down-converters to convert to lower frequencies, often to provide TV from satellites. These have some gain and make the setup more sensitive. Being at a lower frequency, it is easier to process the signal too. Very good layout and components are required to do anything directly at 12 GHz.

    You could look at the Analog Devices chip, the AD8307 which is a logarithmic amplifier that works up to 500 MHz. This will give you a sensitivity down to about 30 uV but cope with signals up to 100 mV or more. Much more sensitive than using diodes to rectify the signal.

    Being a design project, the rest of it is up to you.
     
    Last edited: Sep 28, 2009
  4. Sep 29, 2009 #3
    thanks vk6kro,

    You are correct, we will be using a microwave frequencey of 2.45 GHz, and I will ask about those "splitters" once I have the chance. Thanks for your feedback it was quite informative.
     
  5. Sep 29, 2009 #4

    vk6kro

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    At 2.45, you could probably just use a coaxial T-junction.

    If it is a F type system ( small screw connection about 5.3 mm diameter) , these T-pieces should be available.

    This would be a bit crude if you were receiving small signals, but if you are rectifying with a diode, you must have plenty of signal.
     
  6. Sep 29, 2009 #5
    Unfrotunatley, the signal will be small, we are trying to transmit power through air. No fancy stuff, only a small model with emphasis on saftey. Most of our work will be on simulation, but we have to build a small model, to add some practial design work to the process, instead of all of it being simulation and theory.
    We will abide by the 5-8mW/cm^2 for the power density saftey standard, and so you can see that our hands are tied regarding transmitting alot of power to compensate for the many losses invloved, the largest of which as I believe is the 1/r^2 attenuation factor.

    So yes the signal we must get will be sufficent for only powering a small LED (150mW) and losses that can be minimzed, must be.

    So what do you say?
     
  7. Sep 29, 2009 #6

    vk6kro

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    That is still a big signal. See if a T joiner is acceptable.

    Can the LED be switched by a transistor or does it have to switch with the rectified RF?
     
  8. Sep 29, 2009 #7
    For now it will be switched on with the rectified RF.
     
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