A Distanced RFID Dipole for a Metallic Supply Chain Label

摘要

Different versions of dipole antennas are common examples of good low cost antenna solutions for passive RFID tags. They are simple in design and construction and can be printed with electrically conductive ink on low cost substrates such as paper or plastic film. Flexographically printed antennas with a silver ink layer thickness of about 10-12μm gives RFID read range of about 80% compared to the same antennas made of copper [1]. Their unfortunate disadvantage, which is common for all single-layer antennas, is their inability to properly operate when attached near conductive materials. This can cause significant reduction of the operating distance of the RFID tag or its total malfunction. Previous studies have demonstrated that significant changes in input impedance and directivity of the folded dipole antenna happen when it is placed closer than approximately 3-4 wavelengths to a metal plane [2]. Known solutions for direct RFID-tagging of metallic objects include employing PIFA and patch antennas [3-4], but these antenna structures usually require low-loss microwave substrates that are commonly more expensive than is acceptable for many RFID applications.