Tuesday, July 6, 2010

Doble-Dual Biquad 16-17 dBi

This is cheap and easy biquad wlan antenna whit great gain of 16 to 17 dBi
The main thing of this antenna is small pcb in the center of the antenna.

This wifi antenna is from www.digdice.com

Biquads are with standard size 31mm outer size.
Will be interesting to find more pictures of this wifi antenna.
Seems easy to be build and tested.


  1. dual-whatever is a phased array of antennas. Dual doublebiquad is a phased array of 2 doublebiquads.
    It's gain is different for TX and RX, and is even different for RX and RXsnr.
    When RX, PA doubles it's aperture and doubles RX power compared to single antenna in this array. So, it has +3 dB gain over single antenna.
    Sadly, big aperture doubles noise/interfence also +3 dB.
    Though total signal is +3 dB (if measured instrumentally), its SNR/CINR is the same as single antenna has.
    Modern electronics is not amplify-limited, RX sensitivity nowadays is limited only by SNR/CINR. So this aperture gain is not helpful and is not equialent to the gain of single antenna with the same gain.

    When TX, each antenna receive 1/2 power from feeder and aperture rise doesn't influence to radiated power.

    TX and RXsnr gain is defined by PA radiation pattern / beamwidth.
    Additional antenna does sharpen beamwidth, at best +3 dB (for simple antennas like dipole, but qouble-biquad is already complicated antenna with quite complex current flows and radiation pattern. cross section of this complex pattern won't give +3 dB beamwidth sharpening)

    More realistic gain of this antenna is 13-14 dB (TX & RXsnr) and 16-17 dB for RX. For this size and weight it's not big deal.

    Other thing is SWR. Double-biquad itself is complicated design. SWR 1.3 is best you can get, if you make reflector at least 2x1 lambda size (123x246mm for 2.4 Ghz) with side lips 30 mm long.
    Without lips and with small reflector SWR goes well abobe 1.6.

    For phased array, SWR issues are too complicated. SWR 2.0 would be a good achievment. With long coax line and with TX which has constant output resistance / voltage, SWR 2.0 mean more than 6 dB loss.

    In real world, this dual double-biquad can work worse than single double-biquad

    1. i am a wisp. can i use this antenna for my network for 2.4ghz 5.8ghz. if able then what will be the power requrement....?

    2. Wow ... seems that you did a very detailed study of this antenna. It is true that the antenna is an array of elements and that impedance matching is an important issue. However I do not really understand the RX / TX part of your explanation, neither the SNR/CINR. Would you please explain more in details how is it possible for a passive element (antenna) to have different performance for RX and TX? I assume the antenna does not really know whether it is receiving or transmitting :)
      Now let's get serious - does anyone have measured the antenna impedance, gain and direction?

  2. Kindly mention wire thickness in mm or swg

  3. Hello I would like to publish the latest development on the antenna bicuad!
    How can you put photos in the bolg?