For some reason I always lose my Wi-Fi connection every 30 minutes to an hour, it's probably a router issue I have. What's more annoying is that sometimes it takes up to a minute until my iPad reconnects to my Wi-Fi (even though it could have actually reconnected immediately after the signal was lost). The way I used to solve this problem is to exit out of whatever app I'm running, go to Settings, tap Wi-Fi, and then manually press on the name of my router to force it to connect immediately. Unfortunately even with this method it takes around 10 seconds to connect, not to mention that it requires you to quit your current app.
I found that by far the quickest way to reconnect to Wi-Fi after you lost your signal is to simply lock the iPad, and then press the lock button again to see the "slide to unlock" screen. On the top left where it shows the Wi-Fi signal, you should see it reconnect within a second or two. Now you can unlock the screen and you'll have your connection back, all without ever leaving your app!