The wifi antenna is a flat piece of copper and it screws to the main body and tapes to the digitizer. If you haven't taken off a digitizer before you almost certainly tore it off.its too easy to,tear off. If you are getting a weak signal you most definitely tore it or pulled the plug,loose. Most likely tore it. The only way to fix it is to take it back apart. Changing the wifi antenna is somewhat tricky. Not that you can't do it but the digitizer cable seems easy to mess up in the process. If you aren't comfortable doing it.,there is a great place in Kalamazoo mi. That can fix you up in no time..
Which iPad do you have ? I have an extra wifi antenna if you have the ipad2