C. M. Nijas

Chipless RFID Tag Using Multiple Microstrip Open Stub Resonators

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.

Low-Cost Multiple-Bit Encoded Chipless RFID Tag Using Stepped Impedance Resonator

A novel compact multiple-bit encoded chipless RFID tag using a stepped impedance resonator (SIR) is proposed. The main advantage of SIR compared with other resonators is the independent control over the fundamental as well as first harmonic frequency by varying either the impedance ratio (K) or length ratio (α). The tag utilizes both the fundamental and the first harmonic frequency of the SIR to represent two bit information with a single resonator. The tag is capable of representing 22N number of bit combinations with N resonators. RFID tags are fabricated on C-MET LK4.3 (εr = 4.3 and tanδ = 0.0018) and RT Duriod (εr = 2.2 and tanδ = 0.0009) substrates. The structural information of the tag is encoded in the frequency spectrum, both in the magnitude and group delay of the backscattered signal. The data encoding capacity of the tag is enhanced by using the frequency shift coding technique. The proposed RFID tags have an operating range of 50 cm in the outdoor environment. Theoretical and numerical methods are used to verify the measured resonant frequencies of the tag.

Analysis of CPW-Fed UWB Antenna for WiMAX and WLAN Band Rejection

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 modifled 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 i10dB S11 covers the bandwidth from 2.5 to 11.5GHz, with two notched bands from 3.3 to 3.6GHz and 5.2 to 5.75GHz. The proposed antenna exhibits nearly omni-directional radiation patterns with moderate gain and small group delay variations less than 0.5ns 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 conflrm its suitability for UWB pulse communication.

High Bit Encoding Chipless RFID Tag Using Multiple E-Shaped Microstrip Resonators

Encoding a large number of bits within a narrow band is an important factor in the development of chipless RFID tags. A novel 8 bit chipless RFID tag with a limited bandwidth of 650 MHz is proposed here. The proposed tag comprises a multi-resonating circuit with eight E-shaped microstrip resonators in the frequency band of 3.12 to 3.77 GHz and two cross-polarized transmitting and receiving monopole antennas. The unique feature of the proposed tag is that a different set of frequencies can be derived by changing a single parameter of the structure. The prototype of the tag is fabricated on a substrate C-MET LK4.3 of dielectric constant 4.3 and loss tangent 0.0018. Different tag combinations are designed and tested using bistatic measurement setup. Measurement results on realized prototypes are provided to ensure the reliability of the proposed design.

A Novel Polarization Independent Chipless RFID Tag Using Multiple Resonators

A novel polarization independent RFID tag employing multiple resonators is proposed. The prototype of the tag is fabricated on a low-cost substrate of dielectric constant 4.4 and loss tangent 0.02. Designing a reader for chipless RFID is a hard task since both the polarization and operating frequency agility have to be implemented. The new tag design proposed in this paper is polarization independent, making the design of the reader easier. A prototype of a 3 bit data encoded tag is demonstrated using single structure which can be extended to any order by cascading. This new design is experimentally validated in the frequency domain using monostatic measurement with magnitude response to decode the information.

A Fan-Shaped Circularly Polarized Patch Antenna for UMTS Band

A simple microstrip circular disc antenna to excite circularly polarized radiation is presented. In a single-probe fed circular disc sector patch, the corners are further truncated to obtain circular polarization characteristics. The truncation helps to reduce the ground plane dimensions making the antenna more compact with overall dimensions of 50mm £ 50mm £ 1:6mm. The lengths of truncation necessary to achieve circular polarization are mathematically expressed. The simulated and experimental results are compared and are found to be in good agreement. Axial ratio bandwidth of 1.3% is obtained. The overall size reduction is 55% in comparison with the original disc sector antenna. The antenna resonates in the UMTS 1900{2170MHz band and can be employed for Mobile Communication applications.

Multi resonance based chipless RFID tag with high data encoding capacity

A chipless RFID tag utilizing fundamental (f0) and first harmonic (fs1) frequencies of the Stepped Impedance Resonator (SIR) for data encoding is proposed in this paper. Impedance Ratio (K) and Length ratio (α) are the two parameters which determine the resonant frequencies of an SIR. The Fundamental or first harmonic frequencies of the SIR can be changed without affecting one another. First harmonic frequency can be selected between the frequency, ranging from 1.16f0 to 3.7f0 by changing K from 0.25 to 7.5. These features along with Frequency Shift Coding technique provide higher bit encoding capacity up to 4bits/cm2. Numerical and experimental analyses are carried out to verify the theoretical results. Data from the tag is decoded using backscattered signal from the tag. Four SIR working in the UWB band is fabricated on an RT Duroid substrate of dielectric constant 2.2 and loss tangent of 0.0009, that can represent 32 bit of information. The tag response is measured inside and outside the anechoic chamber and the data can be measured outside the anechoic chamber up to 50cm distance away from the antenna.

Spectral signature-encoded chipless RFID tag with planar multiresonators

The paper discusses the development of a spectral signature-based chipless Radio Frequency Identification tag using multiple spurline resonators to encode data. Bistatic detection approach is used to decode the tag identity using either the amplitude or the phase of the spectral signature in a spurline resonator. The tag comprises two cross-polarized transmitting and receiving wideband monopole antennas connected to the multiple spurline resonators. The prototype of the tag is fabricated on a substrate C-MET/LK4.3 of dielectric constant 4.3 and loss tangent 0.0018. The measured results show that group delay response can also be used to decode the tag’s identity.

Optimisation of quarter wave microstrip open stub resonators for chipless RFID applications

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. A prototype of 8 bit data encoded tag is demonstrated in this paper. Method for finding the resonant frequency and enhancing the performance of the RFID tag are proposed. Magnitude response can be used to decode the tag informations.

Open loop multi-resonator based chipless RFID tag

A simple, compact, planar open loop multi-resonator for chipless RFID tag with high quality factor is presented. It is a spectral signature based chipless RFID transponder. It consists of a set of cascaded open loop resonators. The prototype fabricated on a substrate of dielectric constant 3.7 and thickness 1.6mm is having an overall dimension of 28×13.2 mm2. 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 verified. The proposed circuit can be used for near filed identification and security systems.