Antenna for RFID Gun

Hey everyone,

I’m pretty new to electronics so bear with me here because I may be asking something nonsensical. For a little background on my project I’m making an indoor localization system using RFID, we decided to use the localization system to locate packages in a warehouse . Basically we’re imagining something like an RFID gun with an on board screen that will display the location of the tagged packages. With that being said we’re only in the concept development stage of the project so it may change. We’re planning on using the Simultaneous RFID Reader - M6E Nano for the prototype, but the problem is that the on board antenna only has a range of 1-2 feet, and the only long range antennas I can find are massive and won’t suit a handheld device. Do you guys have and suggestions for an antenna we can use? We ideally want it to have a range of at least 4-6 m. Any suggestions and help will be welcomed.