Electronic – Implementing a TI antenna design on an existing PCB

antennapcbpcb-antenna

I'm currently working on a PCB that processes certain sensor measurements. These measurements are then periodically transmitted over the LoRaWAN network (868MHz). I'm using an RFM95 module with an SMA connector and an 868MHz external antenna. This works fine but I'd like to incorporate the antenna into the PCB. I've done some research but I'm very new to antenna technology and I ran into some problems.

I've decided that I want to prototype with Texas Instruments' recommended antenna design for the 868MHz band. Whilst reading the design note I came across very specific antenna measurements (obviously), but also measurements for the ground plane located on the bottom side as visible in the image below.

enter image description here

However, I'm having difficulty understanding what I CAN and CAN'T do with this ground plane. As I'm looking to incorporate this into an existing PCB, I'm wondering whether I can populate the ground plane area with components or not. Furthermore, I'm wondering whether I can extend the ground plane as the current PCB is larger than 63mm x 43mm.

Actual question: Can I extend the ground plane and place components on it as I would do in a regular PCB design.

Best Answer

enter image description here

I imagine that you can do whatever you want in the pink zone so long as you keep all the conductors as-is in the area used by the antenna (green/white zone).

As for ground plane the image is a two layer board and the plane under the microstrip (the vertical; part above the socket) should be retained at the same distance to maintain the impedance match.

If you are using more layers the microstrip could be redesigned for a closer ground plane allowing the other side of the PCB to be populated behind the microstrip.

The zig-zag antenna uses both sides of the board so you can't place components behind it and should not place any conductors close to it.