2.4ghz Amplifier WLAN applications

Discussion in 'Wireless & RF Design' started by Ostenn, Sep 26, 2009.

  1. Ostenn

    Thread Starter New Member

    Sep 26, 2009
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    Hi,
    I'm new to these forums and require some assistance in sourcing circuit diagrams and building a 2.4ghz amplifier - TX and RX.
    This is a project for university and I have alot of equipment at my disposal - CRO's and function generators ect.

    The final product is for WLAN applications, and will sit inbetween the antenna and the network card. I'm looking to find a gain of 15-25. Whilst using capacitors to filter noise.

    Although im fairly new to electronics (im first year), i've been playing around with the LM741 Op-amp and im quite proficient with it.

    Is anyone familiar with 2.4ghz amplification?

    Anyhelp would be appreciated.

    Thanking you,
    Ostenn.
     
  2. bertus

    Administrator

    Apr 5, 2008
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  3. Ostenn

    Thread Starter New Member

    Sep 26, 2009
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    Thank you for those links, they are very useful!

    Within those links I found a datasheet and circuit diagram of a Amplifying LNA

    http://www.nxp.com/acrobat_download/applicationnotes/AI_BFG480W_2400M_1.pdf

    The circuit diagram looks within my capabilities of constructing. What do you think? Also would you know where to find the transistor required?
    Any e-stores which are reliable and sell electronic components.. (Sorry i'm really new to all this)

    I would've thought a dedicated IC would be more effective than the "BFG480W transistor"?
     
  4. bertus

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  5. t_n_k

    AAC Fanatic!

    Mar 6, 2009
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    It's quite a jump from the LM741 - which is a relatively low frequency (audio) amplifier - to the 2.4GHz band? The circuit boards incorporate microstrip lines and the components are surface mount. Are you planning to make the board from scratch??

    Have you done any surface mount construction work previously? It requires a good deal of skill and care to perform the soldering - after all this is a microwave amplifier. Probably you would want to buy the board and components as a kit.

    I know it will be great experience doing the construction work but have you thought about just buying something off the shelf - even if that's just the amplifier board pre-assembled. Then build the total Tx/Rx system from these sub-units. It's a fair challenge for a first year undergrad!

    One clue would be to search the web and see if amateur radio or WiFi lovers are attempting this sort of thing from the "ground up" or are they using pre-fabricated sub-units such as your low noise amplifier.
     
  6. Ostenn

    Thread Starter New Member

    Sep 26, 2009
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    I wasnt planning on building anything on the micro scale of things.

    I was more planning on using bigger resistors ect, so that soldering is easier. I also found a high power linear amplifier:
    the RF2126 thats aval. on ebay to buy. (i had trouble finding the NXP transistor BWG480).

    As far as the PCB board goes, doing it on a grander scale so i could solder everything properly was my idea. I dont mind if the amplifier sits in a bigger plastic box with 2 SMA connectors and an LED blinking away.
    I was just going to buy a PCB board that already perhaps has holes in it, and solder away.

    Are there any issues i may run into if the components are larger?
    As far as the inductive and resistive microstrips go, could i simply replace them with inductors and/or resistors? Or is this in itself an issue.

    Honestly guys its more of an experiment for me, everyone is sticking to much lower frequency stuff.. but i could use this and it interests me much more.

    Just realised how hard it is going to be, so i found this !
    http://www.minikits.com.au/kits2.html

    An australian site that provides an entire kit for building the amp. I need to research into it more, but looks promising. Hopefully i can be used for WLAN applications.

    Ill post an update soon. Thanks.
     
    Last edited: Sep 27, 2009
  7. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    Wich kit are you looking for?
    A lot of these kits do not work with WLAN, as they are not capable of recieving signals.
    As stated some need a licence.

    Greetings,
    Bertus
     
    Last edited: Sep 27, 2009
  8. t_n_k

    AAC Fanatic!

    Mar 6, 2009
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    Hi bertus & Ostenn,

    I guess Ostenn is looking for something along the lines of Tx / Rx devices such as those on this site

    http://www.rflinx.com/products/amplifiers/2400/ca/

    Indeed conditions will no doubt apply to the allowable antenna input power and nature of signal (spread spectrum, frequency hopping etc) in each country for devices operating on this particular band.

    Rgds,

    t_n_k
     
  9. Ostenn

    Thread Starter New Member

    Sep 26, 2009
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    Hi,

    Yes, the circuit needs to be bidirectional. The actual circuitry, amplifier is compatible with wireless lan applications:

    http://www.minikits.com.au/kits2.html#gali84
    http://www.minicircuits.com/pdfs/GALI-84+.pdf

    Therefore, if i was to purchase two of these kits, and put some kind of RX-TX switching devices before and after the two linear amplifiers, it would become bi-directional?


    RX/TX SWITCHER<--->GALI RX<-->RX/TX SWITCHER
    .......................<--->GALI TX<-->.......................

    So when recieving, switches to the GALI RX, when sending switch to the GALI TX.

    What you guys think? building an RX/TX switching device? Anyone have experience with this sort of thing?

    Or i could even use some sort of bypass, ignoring the TX amplification process. Doesnt bother me.
     
    Last edited: Sep 29, 2009
  10. blueroomelectronics

    AAC Fanatic!

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    Why not just build a decent antenna? What range are you hoping to get?
     
  11. Ostenn

    Thread Starter New Member

    Sep 26, 2009
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    Its for the sake of an experimental project for school. I need to build an amplifier of sorts and study it.

    Linear amplifiers only amplify one way. Could I put a RF switch on it and bypass the TX amplifier stage?

    I think ill purchase that kit from minikits, the 2.4ghz linear amp and see what i can come up with.
     
  12. Ostenn

    Thread Starter New Member

    Sep 26, 2009
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    I've nearly finished the prototype.
    Basically I'm using 2x directional 2.4ghz kits from minikits and using two microwave diodes to restrict the TX and RX paths so that it acts like an automatic switching device.

    I'll upload multisim diagrams tonight for anyone who is interested.

    Unfortunately I cannot test the bi-directional compatibility with WLAN until the prototype is completed 100%.
     
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