I am routing the RF trace for a Microchip RN2903 LoRa module. The datasheet states the following:
I wanted to use Altium to calculate the width of the trace automatically, so that it had a 50 Ohm impedance. In my layer stack manager, I have the following:
Note that Altium calculates that the trace should be ~100 mil wide, which is significantly higher than what the datasheet suggests (0.75 mm=30 mil). The datasheet is using an FR4, 1 oz copper, 2-layer PCB, with a thickness of 1.55 mm. I am using these same values, except the width of my PCB is 62.992mil=1.6 mm (not significantly thicker).
Any ideas as to why this discrepancy? The only thing that could vary would be the Dielectric Constant of the FR4. I am using Altium's default: 4.8. Maybe this is another value, any ideas as to what it should be?
EDIT: Modified first figure to point to 6mil=0.15mm gap between RF trace and ground plane.