-In this paper, an overview of novel integration approaches for improved performance UHF radio frequency identification (RFID) tags and embedded sensors and batteries is presented. Organic substrates, such as paper, that have been very rarely used in UHF and RF applications in the past and could potentially utilize inkjet printing techniques, are also thoroughly investigated for the realization of ultralow-cost RFID/Sensor tags for frequencies ranging from 13.56 MHz up to 950 MHz for the first time ever. The proposed technology could potentially revolutionize wearable and conformal wireless sensor networks (WSN).

In this paper, design, fabrication, assembly and testing of a unique high read-range high-efficiency (95%) Radio Frequency IDentification (RFID) antenna for the 915 MHZ UHF band are discussed. The exceptional characteristics of the RFID are investigated in terms of antenna-IC matching and radiation efficiency. The 915 MHz passive tag is a 3" x 3" omnidirectional tag and yielded a read range of 31 feet compared to a 4" x 4" leading commercial design of 26 feet tested range in lab. This tag also possesses higher read power range (-7dBm to 30 dBm) than the leading commercial design (-5dBm to 30 dBm). The proposed RFID antenna was fabricated on 50 micron thick Liquid Crystal Polymer (LCP) substrate and the read range of the proposed RFID tags was experimentally verified. A large format LCP sheet (300 mm x 300 mm) was used for antenna fabrication and the assembly of the IC was done using low temperature lead free solder alloys that are compatible with the heat distortion temperature of the LCP. I. IntroductionThe demand for flexible antennas with higher efficiency and more compact size has increased in the recent years mainly due to the requirements for a higher and higher read range performance of the increasingly used RFID tags and their almost ubiquitous presence in the industry in securityrelated applications.The passive UHF RFID tags see the widest use in supply-chain and retail applications. One of the biggest advantages of passive UHF tags over the higher frequency tags (i.e. 2.45 GHz RFID tags) is that they have a range, in many environments, of over ten feet (and sometimes as much as tens of feet). Additionally, RFID readers can scan hundreds of UHF tags simultaneously, whereas the lower frequency tags (VLF, LF, and HF bands) already suffering from limited read range (~1-2 feet), can handle about 10% of that scanning capacity with a lower data transfer rate.The proposed 915 MHz RFID tag employs far-field coupling of the real power contained in free-space propagating electromagnetic plane waves due to its shorter wavelength than, for example, the 13.56 MHz HF tags, where the inductive coupling of the transponder tag operates in the near-field as the wavelength is much longer. The IE3D and HFSS design tools are used to perform a system-level optimization of the tag, as well as to design and come up with certain antenna performance parameters such as directivity, radiation pattern, and efficiency.It is well know that the market of the RFID tags is extremely cost sensitive. To address this issue, we have implemented large format fabrication in 300 mm x 300 mm

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-Inductively coupled RFID antennas in two different structures, namely arc-shape and dual-body configurations, are presented. High input resistance can be easily achieved with these structures to realize conjugate impedance matching with some tag chips. 1.99dBi and 5.62dBi directivities at 915MHz are also observed.

Abstract-An overview of design requirements and novel approaches for improved performance UHF radio frequency identification (RFID) tags is presented. Two matching techniques, an inductively coupled structure and a serial stub structure are discussed. Different miniaturized antenna topologies are proposed, focusing on low-profile, high efficiency and high directivity in very compact (less than 3 in 3 in) configurations.