Why does my Apple TV cause wifi to drop on my MacBook?
A few suggestions were made in this thread, which could play into it:

1) Check the device (Apple TV) to see if it is under a warranty replacement program
2) Try adjusting the settings on your WiFi router for the broadcast channels. Setting the device to 40MHz only instead of 20/40MHz auto might help alleviate.
3) Try changing the wireless encryption from WPA to WPA2 or vice versa. There may be an issue with how the devices interact with the authentication.