Since your card has an atheros chipset you should be able to do it.
Using madwifi drivers you can create 2 different interfaces on your device and set them up using wlanconfig/iwconfig (or the iw CLI from the new linux wireless extensions, which you can learn how to use here http://wireless.kernel.org/en/users/Documentation/iw) and then set one as AP and the other as client (STA).
It's very easy but depends on your level of knowledge. Basically these are the steps to follow.
If you're already familiar with both AP and client config, then just read Can a Linux machine act as both a wireless client and access point simultaneously using a single physical WLAN interface?. Here it shows how to create the interfaces using the old wireless extensions (wlanconfig+iwconfig):
wlanconfig ath0 create wlandev wifi0 wlanmode sta
wlanconfig ath1 create wlandev wifi0 wlanmode ap
If you are using the new wireless extensions (iw) it's very similar, more or less:
iw phy wifi0 interface add ath0 type sta
iw phy wifi0 interface add ath1 type ap
If you still have trouble I recommend you going through a few tutorials first:
First learn how to install and get familiar with how madwifi drivers works. Help here:
http://madwifi-project.org/wiki/UserDocs/FirstTimeHowTo
Then create the interfaces, help here:
http://madwifi-project.org/wiki/UserDocs#CreatingInterfacesinmadwifi-ng
Then set one as AP, help here:
http://madwifi-project.org/wiki/UserDocs/SimpleAccessPoint
Then set the other as client, as explained here:
http://madwifi-project.org/wiki/UserDocs/802.11i (WPA)
or
http://madwifi-project.org/wiki/UserDocs/SimpleWEPClient (WEP)
A little more help on wireless devices config in linux here:
http://www.wirelessdefence.org/Contents/LinuxWirelessCommands.htm