Do I have to use he same brand external antenna with my wireless product ?

In general, as long as the antenna is designed for the same frequency band -- 2.4GHz for 802.11b and 11g, 5GHz for 802.11a (and has a mating connector) you can use it with a different brand product.

If the antenna cable doesn't have the right connector, you can always purchase another connector/cable from WLAN on-line retailers, just check our links section.