Thursday, July 10, 2014

Double BiQuad sector antenna for 2.4 GHz / WiFi / WLAN

Introduction

This is basic instructions on building a handmade Double BiQuad antenna for WiFi/WLAN 2.4 GHz with ~14 dBi Gain. (~13.6 dBi if antenna without lips)

Note: The dBi scale is logarithmic in base 10, where +3 dBi is a doubling in gain! An increase in gain of +1 dBi is equivalent to an increase of 26% and +2 dBi is equivalent to an increase of 60%. This means that the increase in +1dBi is a big deal.

On the internets you can find quite a lot guides how to make handmade BiQuad antenna for WiFi 2.4GHz but this guide is slightly different as I used computer software 4nec2 (antenna modeler and optimizer) version 5.8.11 to model theoretically the perfect antenna. This makes this guide more accurate than others, because others are using approximate parameters while mine measurements based on very careful analysis with computer software which results many times has been proven to be quite accurate and reliable in physical world.

Description


Target - frequency 2450 MHz. (8th and 9th WiFi/WLAN channels) 
Simulation NEC Input files:
Configuration symbols in NEC Input files:
  • ED  - Element square diagonal length / 2
  • WR - Wire radius
  • S - Spacing between element and reflector
  • RH - Reflector height / 2
  • RL - Reflector  length / 2
  • LH - Height of reflector "lips"

All dimensions in .NEC data files and graphs are in wave-length ratio.

Main 4nec2 windows with parameters (antenna with lips on the left, without on the right)




Gain (antenna with lips on the left, without on the right)




3D Radiation pattern


  

Overview




Scheme for double biquad without "lips"



Wave length (lambda)  =  \lambda = \frac{299800(SpInVacuum)}{2450MHz} = 122.367 mm \approx 12.237 cm


Calculated measurements for antenna with "lips"
Calculated measurements for antenna without "lips"
Section length - 2/√2×ratio×lamba = 30.89 mm ≈ 3.1 cm
Wire diamter - wire.radius.ratio×lambda×2 = 1.517 mm   (Wire area A = πd2/4 ≈ 1.8 mm2)
Element spacing -  element.spacing.ratio×lambda = 11.099 mm ≈ 1.1 cm
Reflector height - ver.length.ratio×lambda×2 = 131.2 mm ≈ 13.1 cm
Reflector length - hor.length.ratio×lambda×2 = 281.79 mm ≈ 28.2 cm
Height of reflector "lips" - lips.length.ratio×lambda =  28.5 mm ≈ 2.9 cm

Section length - 2/√2×ratio×lamba = 30.7 mm ≈ 3.1 cm
Wire diamter - wire.radius.ratio×lambda×2 = 1.517 mm   (Wire area A = πd2/4 ≈ 1.8 mm2)
Element spacing -  element.spacing.ratio×lambda = 10.07 mm ≈ 1 cm
Reflector height - ver.length.ratio×lambda×2 = 126.16 mm ≈ 12.6 cm
Reflector length - hor.length.ratio×lambda×2 = 279.66 mm ≈ 28 cm
  


 

Parts Required

  • N-Type (female) panel mount connector
  • Reflector - Any metallic sheet like copper or Copper Plated Blank Circuit Board 1.6mm thickness
  • Cable - read this guide before doing anything else: Guide to Antenna Cables & Connectors
    (Very important to choose proper cable! the longer the cable length, the more signal loss you'll have through the cable. Long cable will defeat the purpose of the antenna. Read the guide for more info.)
  • ~60 cm length of copper wire for the element. 1.2-1.5 mm in diameter. Wider is not recommended.
  • Spacers in each end of the element to hold its position and spacing correct height between the radiator and the reflector. Spacers must be from any non-metallic material. Plastic will do alright.

N-Type (female) connector

Single Sided Copper Clad Board

Building the antenna

I will not show you picture after the picture how to drill the hole in center of reflector. How to use ruler. How to do proper soldering. What kits to use and etc. There are plenty of tutorials for these steps: http://www.ziva-vatra.com/index.php?aid=16&id=SGFyZHdhcmU=, http://martybugs.net/wireless/biquad/ or http://martybugs.net/wireless/biquad/double.cgi
(Note: You really want to use mine calculated data and measurements for 2.4 GHz antenna.)

(Note: Pictures below not to scale)

Element bending

 

Use this PDF file for bending wire contour. Print without changing scale and contour will be correct size on paper.

Before you start to bend the wire, make it straight as you can. 
Ensure each side of the element is as straight and symmetrical as possible.
The element sides are rectangular and widths are 3.1 cm, measured from wire center to wire center. 
The more accurate you do the better as the analysis shows a huge impact in element dimensions.



Mine wire bending technique in the crossing sections.
Note: You must leave a ~1.5 mm gap between the element wires cross overs and solders.


Guidance and recommendations



N-connector in the center of reflector. Maintain correct reflector’s dimensions.


Maintain correct spacing between the element and the reflector! 1.1 cm (1 cm if without lips)


You must leave approx. 1.5 mm gap between the element wires cross overs and soldered contacts.
Use spacers in each end of the element to strengthen its position and spacing proper height between the radiator and the reflector.
Spacers must be from any non-metallic material.


Finished. Lying on the belly.



Usage

 

This antenna should get the best performance at horizontal polarization.
Note: The antenna is horizontally polarized then reflector is held vertically.


Outdoor usage


If you intend to use this antenna outdoor, you will need to make it weather-proof to prevent corrosion.
Some people have used small tupperware containers, but it looks ugly at the top of the roof. I rather choose the corrosion… Or the good painting with some silicone on soldered contacts.




After you build your own antenna, you need proper cable with connectors to connect antenna with your modem.

Click here: Guide to Antenna Cables & Connectors


References

3.5 GHz antenna 4nec2 analysis and testing: http://wimaxvedlys.blogspot.com/2013/02/double-biquad-35-ghz-wimax-antenna.html
MIMO technology tests, two antennas gives better performance (Use two only if you have weak signal with one): http://www.danlampie.com/?p=708
How-To: Build a WiFi biquad dish antenna: http://www.engadget.com/2005/11/15/how-to-build-a-wifi-biquad-dish-antenna



Last updated on 10 Jul 2014

12 comments:

  1. Nice tutorial, I have a couple of questions
    What is the range of this antenna?
    Do I need these antennas at both ends for long distance WiFi.?
    What if we use a similar biquad as the transmitter and a laptop or smartphone as the receiver.

    ReplyDelete
  2. this antenna tutorial is intended for receiver side only, still I think there is nothing to stop using it as sender.
    The range ? all depends on sight obstacles and AP.
    As i said, its just one side guide. For long distances its best to use very directional antennas (<20º), this one is more like moderate directional antenna (>30º) which fits better as client side.

    ReplyDelete
  3. I have one question about constant value named element.spacing.ratio and other "ratio's" How to calculate this value? Please help me.

    ReplyDelete
  4. i do it. thank you so much. i got about 13 db

    ReplyDelete
  5. Hello Friend
    in which it is based to get these values?
    Section length - 2/√2×ratio×lamba = 30.89 mm ≈ 3.1 cm
    Wire diamter - wire.radius.ratio×lambda×2 = 1.517 mm (Wire area A = πd2/4 ≈ 1.8 mm2)
    Element spacing - element.spacing.ratio×lambda = 11.099 mm ≈ 1.1 cm
    Reflector height - ver.length.ratio×lambda×2 = 131.2 mm ≈ 13.1 cm
    Reflector length - hor.length.ratio×lambda×2 = 281.79 mm ≈ 28.2 cm
    Height of reflector "lips" - lips.length.ratio×lambda = 28.5 mm ≈ 2.9 cm

    I want to know how to get
    wire.radius.ratio lips.length.

    Thank you

    ReplyDelete
  6. This comment has been removed by the author.

    ReplyDelete
  7. This comment has been removed by the author.

    ReplyDelete
  8. This comment has been removed by the author.

    ReplyDelete
  9. This comment has been removed by the author.

    ReplyDelete
  10. if that's the best antenna you can make?
    i love it's pattern . and i will use it on my 10 microsecond pulsed microwave over magnetron radar, if i ever build one.
    why do the boat radar antennas look so different?
    i wana make a 100 element ~9.4ghz version. do you think it will have gain over the oem mobile hardened version?(with an appropriate dome enclosure of course


    make it 3d with multiple passive directors

    solder the a 2450 magnetron directly to the antenna and pulse it with a car coil threw a 25kv .1nf for 100 nanoseconds .. powered threw a vcr head ferrite or maybe a coaxial dc motor driven by a dc motor with a long shaft threw a 1" id sealed for life Timken pall baring welded to a pedestal plate with a nitrile timing belt pulley etc....

    don't forget to remove the heatsink since it will only be using 1 watt with 20 watts for the filament

    better just use a front wheel drive hub bearing

    ReplyDelete
  11. Thanks for a well written instruction, I understand the dual biquad, but in the bottom photograph painted/unpainted. you have 4 separate biquads all connected together, does it have a wider beam than a dual biquad and a gain? I am only planning to use it on the receiver and I need a wider horizontal coverage rather than a narrow point to point link. Is there any mathematics involved in the the separation of the 4 separate biquads

    ReplyDelete
  12. this four separate biquads array doesn't work better than single one. period. I build it and tested it. same with double biquad doesn't perform better than single. Reflector is 1.2 Ghz resonance freq. doesn't make sense. waste of time and materials.

    ReplyDelete