My iPhone 4s will not stay connected to my wifi

I have a new D-Link 802.11AC dual band wireless router. My iPhone will only connect on the 2.4Ghz band. I lose connection constantly. When I attmempt to reconnect on my wireless 2.4 netwowk, it will often say "unable to connect." It won't even go to the add password screen. I keep trying many times and no success. Sometimes I will get the password screen. I type the correct password (no caps and I check spelling), but no connection. By the way, my iPad is connected on that neetowk too. I turn router off and on, try again, getto password page but no connection. I keep trying and suddenly the it will take. Nothing i am doing is different that I have described.

I just connected and tried going to the app store. Pinwheel spins until it says no connection.

U G H!!!!!

Anyone know what's the deal.