In my application, the device is going to be placed on top of a metal disc, less than a centimeter away from the pcb!
Now I have prototyped up the device using a nRF24L01+ breakout board with only a chip antenna, and I can communicate with the device from a few meters away (obviously from a receiver with line of sight to the PCB, not from underneath the disc). However, if I want to enhance my design and enhance the reliability of the wireless link what kind of antenna should I use?
Should I switch to a lower RF frequency band?
From what I have read around the internet, a patch antenna with a ground plane underneath might be a good antenna to use, because the effects of the metal disc underneath the whole pcb will be reduced since our design involves a ground plane underneath the antenna anyway. This seems to take up a lot of space as opposed to a IFA antenna etched directly on a pcb.
However, being quite new to all this RF theory, I basically don't really have a clue. Any ideas?