Chipless radiofrequency identification (chipless-RFID) has emerged as an alternative to RFID systems with tags equipped with chips. The main advantage of chipless-RFID over chipped-RFID is the lower cost of the tags, since the silicon integrated circuits (IC) of chipped tags are replaced with planar passive encoders in chipless tags. The main limitations of chipless-RFID tags are the data storage capability and tag size. In this paper, we propose an approach for the implementation of chipless-RFID systems, based on near-field coupling and sequential bit reading, which alleviates the previous limitations. The tags are implemented by chains of split ring resonators (SRRs) printed on a substrate (including plastic and paper substrates), and the logic state ’1’ or ‘0’ is dictated by the presence or absence of these resonant elements at predefined positions (alternatively, programmable tags can be implemented by detuning certain resonant elements). Tag reading is achieved by means of a transmission line fed by a harmonic signal conveniently tuned, so that such signal is amplitude modulated by tag motion above the line (in proximity to it) due to inductive coupling. Such chipless-RFID system is especially suited for security and authentication applications, by directly printing the planar passive encoders on the items of interest (e.g., corporate and official documents, ballots, exams, etc.). It is demonstrated that the number of achievable bits is only limited by tag size; therefore, the proposed system is compatible with chipped-RFID system in terms of data capacity.
Chipless radiofrequency identification (chipless-RFID) has emerged as an alternative to RFID systems with tags equipped with chips. The main advantage of chipless-RFID over chipped-RFID is the lower cost of the tags, since the silicon integrated circuits (IC) of chipped tags are replaced with planar passive encoders in chipless tags. The main limitations of chipless-RFID tags are the data storage capability and tag size. In this paper, we propose an approach for the implementation of chipless-RFID systems, based on near-field coupling and sequential bit reading, which alleviates the previous limitations. The tags are implemented by chains of split ring resonators (SRRs) printed on a substrate (including plastic and paper substrates), and the logic state ’1’ or ‘0’ is dictated by the presence or absence of these resonant elements at predefined positions (alternatively, programmable tags can be implemented by detuning certain resonant elements). Tag reading is achieved by means of a transmission line fed by a harmonic signal conveniently tuned, so that such signal is amplitude modulated by tag motion above the line (in proximity to it) due to inductive coupling. Such chipless-RFID system is especially suited for security and authentication applications, by directly printing the planar passive encoders on the items of interest (e.g., corporate and official documents, ballots, exams, etc.). It is demonstrated that the number of achievable bits is only limited by tag size; therefore, the proposed system is compatible with chipped-RFID system in terms of data capacity.
This paper is focused on the control of the electrical characteristics of resonant type metamaterial transmission lines, that
is, transmission lines loaded with complementary split ring resonators (CSRRs). The key parameters of metamaterial
transmission lines for microwave and millimetre wave circuit design are the characteristic impedance and the phase
constant (rather than the effective magnetic permeability or dielectric permittivity). Thanks to the presence of reactive
elements loading the host line, metamaterial transmission lines exhibit a major design flexibility that can be useful for
circuit design purposes. Specifically, we can tailor the dispersion diagram and the characteristic impedance to some
extent. By virtue of this, it is possible the design of microwave and millimetre wave components with superior
performance in terms of bandwidth, or the design of multi-band components, both of interest in modern wireless
communication systems. Thanks to the small electrical size of the unit cell of such lines, the resulting metamaterial-based
components are also very small and fully compatible with planar technology (that is, no lumped elements are
used). Different examples are provided to illustrate the possibilities of resonant type metamaterial transmission lines.
This includes hybrid couplers, power dividers and phase shifters, among others. The paper includes also the theoretical
foundations of the approach.
In this paper, electromagnetic bandgap structures are applied to a conventional coplanar waveguide. The EBG is obtained by etching a continuous sinusoidal perturbation pattern either on the central conductor strip or the both ground planes of the CPW. By doing so, a rejected frequency band appears. Since the frequency response of the device can be approximated by the Fourier Transform of the perturbation function, the application of a sinusoidal perturbation gives allows in principle a unique rejected band, without the presence of frequency harmonics. Full wave simulation results are presented for simple reflectors as well as for combination of several simultaneous perturbation functions, tailoring the desired frequency selective behavior.
In the paper, electromagnetic bandgap (EBG) structures in coplanar waveguide (CPW) technology are presented. In order to design this type of circuits, a custom Finite Difference Time Domain (FDTD) code is employed. Due to the fact that simulation is performed in the time domain, a wide frequency response can be obtained in a reasonable amount of time, being a numerically efficient technique. Simulation of several proposed designs are presented and these results are validated with measurements from fabricated prototypes. The results show that the use of FDTD techniques is adequate for the design of EBG devices in planar circuit technology in general.
In this paper, a novel structure in coplanar waveguide (CPW) technology which exhibits an equivalent negative magnetic permeability is described. Such a structure consists in a conventional coplanar waveguide that is loaded with split ring resonator (SRR) cells. Due to the configuration of the magnetic field components in the coplanar waveguide, by adequately placing the SRR cells, quasi-static resonance occurs. In the vicinity of such resonance frequency, the magnetic permeability exhibits a negative value in a certain frequency range. Full wave simulation results as well as measurement from fabricated prototypes validate initial assumptions, providing a new method to implement band rejection filters with very small size.
The use of Electromagnetic Bandgap (EBG) structures has proven to be effective in the implementation of many devices in planar circuit technology, such as filters, couplers and antenna design. In this paper, a low pass filter based in EBG structures in coplanar waveguide (CPW) technology is proposed. The device consists in a periodically loaded CPW with shunt capacitive elements. This way, a low pass frequency response is obtained. The capacitive elements are formed by t-shaped fingers that extend from the central conductor strip to both ground planes. Further enhancement is achieved by introducing a second periodicity in the central conductor strip, modulating the width of the strip. By doing so, effective rejection of undesired frequency harmonics is achieved. Full wave simulation results as well as measurement from fabricated prototypes confirm the performance of the proposed low pass filter, which exhibits low insertion losses in the passband, high rejection slope and effective rejection of undesired harmonics. Another advantage is the small footprint, due to the inherent slow-wave nature of the device.
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