@xmen4u What's the range that you need?
The range on the RFID reader is guaranteed to be at least 3 inches (76mm) if there's nothing blocking the signal. During our manufacturing tests, that's how high the RFID cards are in order to get a passing test. A few inches is about as far as you can get with a passive RFID tag. In order to get further you'll need active RFID tags (basically broadcasting radios).
The RFID antenna is built into the PCB of the RFID chip. Technically you could desolder some components and hook up a bigger antenna, but we haven't tried that. Since the 100mm max is in the datasheet, I'm not sure if that limitation comes from the RFID protocols that the chip implements or their reference design for the antenna.