PCB antenna design problem: too short range?

[angel]

Dear Nordic,

Some time ago we started a project in which we decided to use ANT protocol to communicate wirelessly. However, now that we are going to production in a very very short time, we have spotted a very critical problem in the range of the communication.

Here is the design of the antennas, in emitter and receiver pcb designs:

And here is the schematic for both of them:

The total length of the antenna is 28.13 mm and the width 0.35 mm.

The main problem is that we only have like 1 to 1.5 meters of acceptable range. If I use the nordic DK as TX end, the range is significantly bigger, like 4 to 5 meters. This would be enough for our application.

Also, it is important to state again that the PCBs are already in production, so a solution requiring minimum changes in hardware would be better.

We have already tried different frequency numbers by SW (from 2400 MHz to 2524 MHz), but that only helped a bit (2433 MHz) seems to work a bit better.

Also changed the RADIO_TX_POWER to +4dBm but didn't really do anything.

Anyone has any idea how we could improve the range of our antenna? Again, I know that the same software using the DKs has a really good performance.

Thank you very much for your help.

[Jørn]

Hello Angel. Just to be clear, you say there is a groundplane underneath the antenna. Does the groundplane actually cover the area directly underneath the antenna itself? In other words, have you maintained a keep-out region on all layers underneath the antenna?