• Bas van Ooijen

Create your own antenna in Ekahau


This is the second in a two-part tutorial on the collection of antenna data and how to create customized antenna patterns using Ekahau. The first tutorial focused on methods for adding an antenna to an access point (AP).

The focus of this article is to customize a new antenna for WiFi and Bluetooth. In some cases, you might be able to find a vendor to supply you with the antenna data you need. However, if that is not the case, these instructions are a workaround for that.



Let's say we want to add this 5Ghz antenna pattern, and the antenna has a maximum gain of 5dBi. The antenna scale starts at 0dBi, and this also reflects the maximum gain of 5dBI. It is important to know that Ekahau does not start at 0, but at maximum gain.


For example, a measurement of:

· 0dbi is in fact 5dBi,

· -1dBi is in fact 4dBi

· -2dBi is in fact 3dBi

· -3dBi is in fact 2dBi

· -4dBi is in fact 1dBi

and so on.


In this case, we are going to start with 0 degrees on top, and go clockwise in increments of 5 degrees. This means that each step in is -5dBi. Take note that this vertical pattern is rotated 90 degrees relative to the horizontal pattern.


We can use Ekahau to add reasonably accurate data through the antenna pattern as a map. This map is scaled at 50 meters for an inward step for easy calculation. Assuming this, we can say that every 50 meters equals 5dBi. For example, a measurement of 84.1 meters equals -8.41dBi.


We can now measure from the outer 0dBi ring inwards to the center of the red stripe, you do this for every 5 degrees.


In this case, we measure:

0 degrees 84.1 meters equal to -8.41dBi + 5dBi (maximum antenna gain) = -3.41dBi

5 degrees 77.3 meters equal to -7.73dBi + 5dBi = -2.73dBi

10 degrees 6.26 meters equal to -6.26dBi + 5dBi = --1.26dBi

The accuracy of your measurement points depends on you. This might not be the fastest or the best way to do it, but it works. I found an error in an existing antenna that reads -18dBi different from the datasheet using this method. Ekahau confirmed this and solved it in an update.



let's talk code


To add or modify antenna patterns in Ekahau, navigate to the configuration folder (e.g. C:\Program Files\Ekahau\ Ekahau Pro\conf\). Look for and open antennas.zip.

Here you will find all the antennas in Ekahua. Add the new antenna in this zip file.

The code in these files will look something like this:


{ 
 "directional": true,  
 "horizontalPlane": {  
 "alignment": {  
 "degrees": 0.0 
    },  
 "gains": [  
      { 
 "angleInDegrees": 0.0,  
 "dBi":  -3.41
      },  
      { 
 "angleInDegrees": 5.0,  
 "dBi":  -2.73
      },  
      { 
ect.
 } 
    ],  
"type": "Azimuth",  
 "scaleMin": -25.0,  
 "scaleMax": 5.0 
  },  
 
 "elevationPlane": { 
 "alignment": {  
 "degrees": 90.0 
    },  
 "gains": [  
      { 
 "angleInDegrees": 0.0,  
 "dBi":  -2.78
      },  
      { 
 "angleInDegrees": 5.0,  
 "dBi":  -2.60
      },  
      { 
ect.
   } 
    ],  
 "type":   "Elevation",
 "scaleMin": -25.0,
 "scaleMax": 5.0
  },
 "frequencyBand": "FIVE",
 "accessPointVendorModel": {
 "vendor": {
 "vendor": "Custum"
    },
 "model": {
 "model": "Antenna 001"
    }
  },
 "wcsMapping": {},
 "defaultTiltAngle": {
 "degrees": 0.0
  },
 "manufacturerMaximumGain": 5.0,
 "antennaTechnology": "WIFI",
 "defaultMounting": "WALL",
 "apCoupling": "EXTERNAL_ANTENNA"
} 

Definitions of some code terms

 "directional":

True for directrional antennas, False for Omni antennas.


 "alignment": {
 "degrees": 0.0
    },

Alignment offset in degrees from 0 to 360.

You can also exclude some alignment offset in degrees in this manner "alignment": {}









 "angleInDegrees": 

Increments in degrees of difference from 0 to 360, for example, 0. 5, 10, 15, and so on.


"dBi": 3.41

Describes the dBi value at a certain degree of the antenna pattern.


 "scaleMin":-25.0,
 "scaleMax": 5.0

Describes the minimum and maximum scale of the antenna pattern, which can also be entered as NaN.


frequencyBand": 

TWO for 2,4GHz, FIVE for 5GHz in double quotes and continued with a comma.


 "accessPointVendorModel": {
 "vendor": {
 "vendor": "Costum Antenna"
    },
 "model": {
 "model": "Custom Antenna 001"

Name the vendor and model in double quotes


 "defaultTiltAngle": {
 "degrees":
  },

Tilt angle in degrees from 0 to 360.










"manufacturerMaximumGain": 

Maximum gain described in the antenna datasheet, or NaN continued with a comma.


"antennaTechnology": 

"BLUETOOTH", "WIFI" in double quotes and continued with a comma.


 "defaultMounting": 

"WALL" or "CEILING" in double quotes and continued with a comma.


"apCoupling": 

"INTERNAL_ANTENNA" or"EXTERNAL_ANTENNA"



After you have modified or created the code, you can save it in the zip file under the name of the antenna with a .json extension.You can now use this antenna in Ekahau.


If you have created an internal antenna, you need to take an extra step:

Navigate to the configuration folder (e.g. C:\Program Files\Ekahau\ Ekahau Pro\conf\). Look for and open accessPointsTypes.xml with admin rights (right-click on the file and choose “Run as administrator”).

Add this piece of script and change the red highlighted data using the datasheet of your selected AP, then add your antenna in the script, like so:


  </accessPointType>
  <accessPointType vendor="Custum" model="Custum Antenna 001">
    <radioType technology="n" frequencyBand="2.4" mimo="2x2" spatialStreams="2" defaultAntenna24="Custum Antenna 001 2.4GHz" defaultAntenna5="Custum Antenna 001 5GHz"/>
    <radioType technology="ac" frequencyBand="5" mimo="3x3" spatialStreams="3" maxSupportedBandwidth="160MHz" defaultAntenna24="Custum Antenna 001 2.4GHz" defaultAntenna5="Custum Antenna 001 5GHz"/>

more about custom AP and antenna combinations at https://www.wireless-blog.com/post/custom-ap-antenna-combination-in-ekahau



Note

with an incorrect code it can happen that ekahau no longer starts up or that the edit Access Point no longer works, this can usually be solved by removing your antenna from the zip file.

Also backup the files as well,this will be rewritten with the next update.


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