Length Of coaxial fed line of Microstrip antenna
Anyone, help me...
If you are using 50 ohm coax, and the 50 ohm input impedance point for the antenna element, then moderate length of 50 ohm transmission line (microstrip) at your frequency of interest will be fine (a few wavelengths, otherwise you could start to see the insertion loss creep up).
The bigger question would be "how much ground plane should I have surrounding the edge of my antenna element"? This is somewhat dependent upon your antenna type, but generally, for a quarterwave microstrip patch, you'd want at least 1-2 times the longest dimension from each edge of the patch, to the edge of the PCB.
Can I directly solder the BMA Connector with Microstrip Line?
Whether the conducting line that connecting the BMA Connector and Microstrip should be in a same line?
Assuming the metals are both solderable, then yes.
I'm not sure I understand what you are asking, can you plz clarify?