Unstable Wi-Fi connection or Wi-Fi dropout?

My WiFi connection Keeps drop and the ping is high this is after I bought a brand new D-Link DSL-2750U, the distance between the router and the comput

My WiFi connection Keeps drop and the ping is high this is after I bought a brand new D-Link DSL-2750U, the distance between the router and the computer is about 20cm, the WiFi adapter is b/g/n, when i connect the computer with a regular Ethernet cable the connection is stable and fast, I've tried changing the channel and the bandwidth to every single option and nothing happened. does any one have logical explanation of what is happening here.
note: I've changed the router and the problem still there.

or:My WiFi connection Keeps drop and the ping is high this is after I bought a brand new D-Link DSL-2750U, the distance between the router and the computer is about 20cm, the WiFi adapter is b/g/n, when i connect the computer with a regular Ethernet cable the connection is stable and fast, I've tried changing the channel and the bandwidth to every single option and nothing happened. does any one have logical explanation of what is happening here.note: I've changed the router and the problem still there.

Tags:high,link,brand,