I'm designing a PCB (I have very little previous experience). Among other components, I am using the microcontroller MSP430G2553 and the RF module Sigfox TD1208R (868 MHz). I have doubts to design the trace from the RF pin of the TD1208 to an U.FL connector. As I understand it, this trace has to be a 50 ohm microstrip-line (same impedance as the RF pin of the TD1208) but, how do I do it with Proteus ARES?
The PCB properties can be seen in this image:
Using this data, I have calculated the trace width in this Microstrip Impedance Online Calculator and the trace width should be 100 mils:
These are the doubts I have:
1. Have I made any mistakes in the previous steps?
2. Both the PAD of the RF pin of the TD1208 and the PAD of the U.FL connector are have a width much less than 100 mils. How should I decrease the width of the track to connect it to the PADs? Should I reduce the track width slowly or quickly?
3. What length should the microstrip line have? How much shorter is better?
4. If the U.FL connector is placed as close as possible to the RF PAD, is the trace width less important?
Finally, searching in google, I found in this blog (ioter.io) the files in EAGLE of a TD1208 development board for the RF module TD1208 but the width of the RF track (70 mils) is lower than it should be according to the online calculators of microstrip-line and the properties of the PCB. For this reason I have decided to ask, because I do not know if that design is correct because it does not agree with the theory (or so I think).