I'm working on designing a board with the RFM22B-S2 SMD Wireless Transceiver - 915MHz. The board module requires a 50 ohm feed line to the antenna. I've been looking at trace impedance calculators and I'm confused. So far every calculator I've found has a micro strip, a single trance on top with a ground plane on the bottom.
Why is there not a ground plane on top as well?
Is there a calculator that accounts for the top ground plane or is there some minimum amount I have to pull the top plane back from the feed line?