A novel compact RFID tag employing open stubs in a microstrip transmission line is proposed. The prototype of the tag is fabricated on a substrate of dielectric constant 4.4 and loss tangent 0.0018. The tag consists of microstrip open stub resonators and cross polarized transmitting and receiving disc monopole antennas. A prototype of 8 bit data encoded tag is demonstrated in this communication. Method for enhancing the performance of the RFID tag is also proposed. Magnitude or group delay response can be used to decode the tag informations.

A compact asymmetric coplanar strip (ACS) fed dual‐band antenna suitable for DCS/WLAN applications is presented. Dual‐band operation is achieved by modifying the signal strip of the ACS monopole. Parametric studies indicate that operating frequencies of the antenna are determined by the dimensions of the strip monopole. Measurements on the optimized antenna printed on an FR4 substrate with εr = 4.4 and height = 1.6 mm indicate good radiation characteristics with moderate gain. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:1087–1089, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26731

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2287from that part of the trajectory due to the occlusion from the buildings. Instead, signals from BS3 propagate via the identified reflector to this part of the trajectory. These parts of the trajectory are also marked with corresponding NLOS range, via the identified reflector in Fig. 4. Clearly, these markings coincide with the impulse response and explain the NLOS component. Note that the interruption and the NLOS component in Fig. 4 is due to that the van leaves the street with the occlusion for a detour, and when the van returns to the street with the occlusion, the NLOS component is back. Beyond doubt, it is the identified reflector that is active in the NLOS propagation during these segments. VI. CONCLUSIONS AND FUTURE WORKIn this communication we devise a method for estimating a map of NLOS reflectors for a mobile radio network based on multistatic SAR imaging. We apply the back-projection principle for the image creation which is a well known method from computerized tomography and also conventional SAR imaging. The obtained images give promising results where the reflectors are well-correlated with the large buildings detectable in the aerial map of the environment. Also, the possibility to extract which part of the trajectory contributed to different reflectors and from which base station is added. In this way a map where dominating reflectors are present can be built up.The applicability of the estimated reflectors is still unexploited. One possible application area is to consider the estimated reflectors and occlusions in position estimation, [15]. ACKNOWLEDGMENTThe evaluation data from the radio channel measurements has been kindly provided by J. Medbo, Ericsson. REFERENCES[1] M. A. Jensen and J. W. Wallace, "A review of antennas and propagation of channel and radio propagation models for wireless MIMO systems," EURASIP J. Wireless Commun. [3] 3GPP, "Spatial channel model for multiple input multiple output (MIMO) simulations," (TS 25.996). [4] J. Medbo, M. Riback, and J.-E. Berg, "Validation of 3GPP spatial channel model including WINNER wideband extension using measurements," presented at the IEEE Vehicular Technology Conf., 2006. [5] T. Fügen, J. Maurer, T. Kayser, and W. Wiesbeck, "Capability of 3-D ray tracing for defining parameter sets for the specification of future mobile communications systems," IEEE Trans.

A planar, fully printable, frequency signature based multi-resonator circuit for chipless RFID transponder system and swipe card is presented. The amplitude and/or group delay of the spectral signature are utilized for the chipless tag or swipe card multi-resonator circuit, providing a 1: 1correspondence of data bits. It comprises of a bifurcated microstrip transmission line meeting at the far end within which the open circuited shunt stub multiresonators are positioned. The developed structure can be used effectively as a swipe card. The application of the proposed circuit together with its cross-polarized transmitting and receiving microstrip ultra-wideband disc loaded monopole antennas for RFID transponder system is also presented. The experimental and simulated results in support of the potentials of the chipless tag for low cost item tagging such as bank notes and secured documents are explained in this paper. The circuit is having high quality factor and has a very small footprint of 24x10mm 2 .