Omnidirectional miniature RFID tag

Radio frequency identification (RFID) is a widely used technology for contactless data readout. Numerous passive RFID tags are available on the market, and in a vast majority of cases, their designs are based on flat meandered dipole architectures. However, besides technological advantages, those realizations suffer from polarization mismatch issues and limited spatial sectors, from which flat tags can be interrogated. Here, we demonstrate and analyze a miniature omnidirectional tag accessible from all 4π stereo angles with a commercial RFID reader. Our design is based on exploring all three dimensions, which allows achieving close to perfect angular coverage by overlapping several multipole resonances of a structure. An optimized metal strip with a nontrivial geometry is wrapped on a high permittivity ceramic sphere for miniaturization purposes. As a result, a 3 cm device (tenths of an operational wavelength) is demonstrated to be readable from a 1.5 m distance without any dependence on the interrogation direction. Compact omnidirectional tags can remove hard restrictions on a mutual orientation between information holders and interrogating systems. Those capabilities are essential in many applications, including logistics, animal activity monitoring, and security, to name just a few.