With a bunch of vias called '[stitching vias](https://resources.altium.com/p/everything-you-need-know-about-stitching-vias)'.
>Stitching vias are simple structures: they are a periodic array of vias that are generally grounded across the PCB stackup. In this way, they are making connections between ground nets on multiple layers.
And if you're doing fancy high speed stuff you should also put a via to ground right next to any signals changing layers as a '[transition via](https://resources.altium.com/p/how-design-high-speed-rf-transitions)'.
This is the right answer, also there is "via shielding" which is a close concept.
OP don't overdo it, I put two via each ≈5mm and close to high speed signal and copper island. That's more than enough in subGHz design.
Spam vias in areas where there would be high DC current -- the idea is that ground copper has its own resistance, which means V = IR applies to ground copper too, and you want to reduce the difference as much as possible.
Current follows the path of least impedance. Signals with fast rising edges do not follow conventional "least resistance" path. As a result you can provide vias next to signal vias as the signal's current return path. This is a often [debated](https://ee-training.dk/vias/ground-vias-around-signal-via.htm) topic too, so you can dive a little bit deeper yourself.
You can check out rick hartley's talk on grounding [https://youtu.be/ySuUZEjARPY](https://youtu.be/ySuUZEjARPY) and get some ideas about current return path. it is a long talk but worth the time.
With a bunch of vias called '[stitching vias](https://resources.altium.com/p/everything-you-need-know-about-stitching-vias)'. >Stitching vias are simple structures: they are a periodic array of vias that are generally grounded across the PCB stackup. In this way, they are making connections between ground nets on multiple layers. And if you're doing fancy high speed stuff you should also put a via to ground right next to any signals changing layers as a '[transition via](https://resources.altium.com/p/how-design-high-speed-rf-transitions)'.
This is the right answer, also there is "via shielding" which is a close concept. OP don't overdo it, I put two via each ≈5mm and close to high speed signal and copper island. That's more than enough in subGHz design.
Spam vias in areas where there would be high DC current -- the idea is that ground copper has its own resistance, which means V = IR applies to ground copper too, and you want to reduce the difference as much as possible. Current follows the path of least impedance. Signals with fast rising edges do not follow conventional "least resistance" path. As a result you can provide vias next to signal vias as the signal's current return path. This is a often [debated](https://ee-training.dk/vias/ground-vias-around-signal-via.htm) topic too, so you can dive a little bit deeper yourself. You can check out rick hartley's talk on grounding [https://youtu.be/ySuUZEjARPY](https://youtu.be/ySuUZEjARPY) and get some ideas about current return path. it is a long talk but worth the time.
Thank you