User's Guide

BL28RW-001 OEM Manual and User Guide
Using an online impedance calculator, the line width under the NAD for a 50 ohm line is 16.9mils
(433micron) shown below:
BL
Figure 6-4
The calculation for the microstrip line width outside the NAD is 37.7mils (967micron) shown below:
Figure 6-5
Due to the nature of the weave chosen for each PCB, the dielectric constant of the NAD board is 4.1 while
the main board is 4.3. A dielectric constant of 4.2 was chosen in the stripline calculation, while 4.3 was
used for the microstrip calculation.
Main board stack up may vary so these line widths may need to be recalculated. IT IS HIGHLY
RECOMMENDED TO USE A SIMILAR STACKUP AS SHOWN IN FIGURE 39 WITH MICROSTRIP
ROUTING AND GND CUTS ON LAYER 2 WITH GND REFERENCE ON LAYER 3. THERE
SHOULD BE NO ROUTING ON L2 AND SOLID GND ON L3 UNDERNEATH THESE ANTENNA
LINE MICROSTRIP TRACES.