S. Mridula

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.

CPW-Fed UWB Compact Antenna for Multiband Applications

A planar UWB antenna with added GSM 1800/WMTS and UMTS bands is presented. A CPW-fed circular patch is used to obtain wideband characteristic covering the UWB range. A novel slot formed by merging the alternate sides of a hexagon with isosceles triangles is inserted in the patch to obtain dual-band operation with the lower band suitable for GSM 1800 operation. By inserting a bent monopole in the space created by the slot, a triple-band antenna is developed with two lower bands suitable for WMTS and UMTS operation. The antenna prototype is fabricated and tested. Simulated and experimental results are in good agreement. The antenna exhibits stable radiation characteristics and nearly constant group delay in the UWB range.

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.

Frequency signature based chipless RFID tag using shorted stub resonators

A chipless RFID tag using shorted stub resonators is discussed in this paper. The tag has a data capacity of 8 bits. The tag identity can be encoded in the spectral domain either using absence/presence encoding technique or Frequency Shift coding technique. Bistatic detection approach is used to decode the tag identity from either the amplitude or group delay information. The tag comprises two cross polarized transmitting and receiving wide band monopole antennas connected to shorted stub 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. Measurement results on realized prototypes are provided to ensure the reliability of the proposed design.

Metamaterial Inspired CPW Fed Compact Low-Pass Filter

A metamaterial inspired co-planar waveguide (CPW) fed compact low-pass filter is presented in this paper. The 3 dB cutoff frequency of the filter is 1.4 GHz. The roll-off rate achieved for this filter is 47.4 dB/GHz. Sharp roll-off is obtained by introducing an additional resonance using an inductor in series with the shunt capacitor. The usage of chip inductor also results in a compact filter structure. The overall filter dimensions are 39 mm × 32 mm × 1.6 mm. The filter uses defected ground structure (DGS) for attaining stop band attenuation. The measured insertion loss of the filter in the pass band is less than 0.8 dB and average stop band attenuation is better than 23 dB. The equivalent circuit of the proposed filter is similar to that of a dual-CRLH (D-CRLH) transmission line.

U slot multi-resonator RFID tag with enhanced bit encoding capacity

Multi-resonator based 6 bit chipless RFID tag using U slot resonators is presented in this paper. The multi-resonators are designed and fabricated on substrate C-MET LK4.3 of dielectric constant 4.3 and loss tangent 0.0018. The tag identity can be encoded in the spectral domain either using absence/presence encoding technique or Frequency Shift coding technique. Bistatic measurement is used to decode the tag identity from either the amplitude,phase or group delay information. The tag consists of two cross polarised wide band antennas integrated to multi-resonator, for transmission and reception of signals. Various RFID tags are designed and tested using bistatic measurement setup. Measurement results on realized prototypes are provided to ensure the reliability of the proposed design.

CPW-fed fractal antenna with improved UWB response

This paper presents a CPW-fed dual band antenna for improved UWB response. A slotted circular monopole is used to attain dual band operation suitable for GSM 1800 and UWB applications. A fractal pattern is introduced in the design to improve matching in the UWB range. The antenna has an overall size of 34 × 51mm2 and operates in the 1.5-2 GHz and 3.4-11 GHz frequency bands (S11≤-10dB). The measured characteristics of the prototype antenna are in good agreement with the simulation.

Artificial Neural Network Model for Soil Moisture Estimation at Microwave Frequency

This paper reports a neural-network-based methodology to estimate the amount of moisture content in soil at L, S and C frequency bands. A multilayered artificial neural network, using the Levenberg-Marquardt algorithm, is used as the ANN model. The input training data comprise the measured values of dielectric constant of soil in the dry and moist states. Dielectric constant is measured using microwave free-space transmission technique. Measurement has been performed using Vector Network Analyzer (VNA), microstrip patch antenna and soil sample holder. One great advantage with this method is that there is no need to test the pH value of the soil sample, and hence all the associated pre-processing steps, such as drying, pulverizing, can be avoided.

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.

FPGA implementation of one-dimensional reduced mapped real transform-based digital beamformer

ABSTRACT The paper presents the field-programmable gate array implementation of a digital beamformer. This beamformer is based on one-dimensional reduced mapped real transform. The computational complexity and computational time of conventional beamformers is reduced with the application of one-dimensional reduced mapped real transform. The digital beamformer model is created using Xilinx system generator, and its hardware implementation is performed on Spartan 3A FPGA using an Altium NB3000 board.