Two ZigBee modules in a device

Wireless & IoT
1

Hi all

I am working on designing a device that has two ZigBee modules in it. The reason is to split some functionality and processor intensive tasks between them.

I have heard that if I place them far enough, then its not a big problem to get FCC. However if they are deemed co-located by FCC-lab then it can be quite an expensive problem to get them certified.

IS this right, and of so what minimum distance should separate them.

To make this clear, both device will be using “listen before transmit” so will not be transmitting at the same time. Also the transmit power will be fairly low.

Thanks

2

just checking… you chose ZigBee for its network layer protocol, rather than using IEEE 802.15.4 (e.g., XBee Series 1) itself, which is much, much simpler.

For RF engineering reasons I wouldn’t put two such modules in close (say, 5m) proximity of one another. Even if you choose to put them on different channels (widely spaced), and thus different ZigBee networks. The receiver front ends don’t have channel-wide filters (nor does WiFi).

Listen before transmit (CCA) is in 802.15.4 and should never be disabled.

Why do you feel that two are necessary? Two won’t improve throughput on the air.