I am designing a four layer stack up PCB having nrf52832 SoC with chip antenna (2450AT18B100: http://www.kynix.com/Detail/744089/2450AT18B100E.html).It is BLE Board (2.45 GHz). This is the first time I have been designing a PCB with an antenna. I am using kicad EDA Software. The stackup of my design is:
- Signal and RF traces with ground copper fill (Green Colour in Picture below)
- Ground Plane
- 3.3V Plane
- Bottom Plane (Basically Solid Ground Plane) (Red colour in Picture below)
I am going to add many vias (at 1/12 of RF frequency which will be 2.45 GHz). The antenna part is not completed yet because I am yet to receive some specification from my PCB fabrication house. I will change the width and shape of antenna feed considering the distance between signal plane and ground plane. I have one question regarding the calculation of width of antenna feed line. Since, I have four layers, Can I use formula of coplanar waveguide with bottom ground plane? Won’t power plane and bottom layer will effect the impedance of coplanar waveguide? Do I need to take into account presence of power layer and bottom layer (actually solid ground plane).
NOTE: The other sensor in the left part of my layout is a CCD (TCD1304) which is basically a linear image sensor.
What I want from the community is suggestion on the pcb and review my design for RF. Since, this is the first time I have designed such a board, I don’t want to design a PCB which won’t work or work with very short range. The pictures of my PCB are given below:
After reviewing the datasheet of my chip antenna and suggestions from Johanson Technology, I can see they have suggested a large ground plane for which I don’t have space.You can check pictures of my layout above as I have marked area for antenna (7mm X 23mm).
The picture below are taken from Johanson Technology’s layout suggestion: