I intend to use semi-passive tags, since I believe that if I use such tags with a passive reader, the range would be somewhat increased—but I don't know by how much. Please correct me if I'm wrong; I'll be extremely grateful for your help.
I think your question is asking how you can increase a passive tag's read distance. One way would be to boost the reader antenna's power output. But most countries place limits on the amount of RF energy that devices can emit—for health reasons, and to prevent them from interfering with other devices.
Another way would be to increase the tag antenna's size. Omni-ID's Ultra tag (see Omni-ID Launches New High-Performance UHF Gen 2 Tags and RFID Journal's 2010 Best in Show Award) has a large antenna, and can be read at a distance of 75 feet (23 meters) or more. Click here for more information.
Adding a battery to create a battery-assisted (sometimes called semi-passive or semi-active) tag also increases read range, because the battery powers the chip, and all of the energy from the reader can be used to communicate with that device. Intelleflex's Extended Capability line of RFID tags offers a read range of 300 feet (91 meters). Click here for more information.
—Mark Roberti, Founder and Editor, RFID Journal
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