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.

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A compact ultra wide band (UWB) antenna with dual band notch characteristics is proposed. The antenna consists of a coplanar waveguide (CPW) fed bevelled rectangular patch and a modified rectangular ground plane. A Z-shaped meander line parasitic element and a pair of symmetrical L-shaped quarter-wavelength stubs are employed to realise band-notched functions at WiMAX and WLAN bands respectively. By optimizing the dimensions and positions of these notch structures, the desired notch-bands of WLAN and WiMAX are achieved. Unlike other dual band-notched antennas reported in literature this antenna has a merit of regulating the centre frequency as well as the bandwidth of both the notched bands easily and independently. The measured −10 dB S 11 covers the bandwidth from 2.5 to 11.5 GHz, with two notched bands from 3.3 to 3.6 GHz and 5.2 to 5.75 GHz. The proposed antenna exhibits nearly omni-directional radiation patterns with moderate gain and small group delay variations less than 0.5 ns over the entire operating bandwidth except at the notched bands. Moreover, by using antenna transfer function, the time domain characteristic of the antenna is also studied to confirm its suitability for UWB pulse communication.

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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 .