# Need help with antenna design

Question asked by khan.omair on May 14, 2014
Hi, I am designing a device with the M24LR. I am new to etched antenna design and need some help using the Antenna.exe

I was trying to run an example using the ANT7 15mmx15mm reference board just to see how the software works but have some questions on how to count the segments and turns.

At first glance it appears the antenna has 9 turns and 36 segment. However, it is replicated on both sides of the board. So in the calculator, should I enter 9 turns and 36 segments or 18 turns and 72 segments, or 9 turns and 72 segments?

Also, with either of these values I am not getting the 5000nH that the antenna should be according to the equation in AN2972 and the 27.5pF internal capacitance of the M24LR.

The other values I used in the calculator were:
w = 0.2mm
s = 0.2mm
thickness = 35.56 microns
L coil = 15mm
W coil = 15mm

The results I get are:
Turns = 9
Segments = 36

L ant = 1396.38nH

and if...
Turns = 18
Segments = 72

L ant = 2019.31nH

and if...
Turns = 9
Segments = 72

L ant = 1994.63nH

Any help you can provide in how to correctly count the segments is appreciated, and also I'm not sure why these values are so far off the 5uH mark.