<p>No need to sound impatient or rude. You didn’t seem either in your OP. Why not e-mail, saying “I haven’t received any further communication. Do you have any sense at this point when the interview will be?”</p>
<p>I don’t suggest waiting a month. That’s too long. There’s a chance that the interviewer lost your contact info. Heyalb’s suggestion is tactful and appropriate.</p>
<p>Just send an e-mail saying something along the following.</p>
<p>Dear ____</p>
<p>I haven’t received any further information and so I’m contacting you to follow up on the status of the interview you requested a couple weeks ago. Please contact me at your convenience to set up at time at -INSERT EMAIL HERE- or -INSERT CELL HERE-.</p>