U. Deepak

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.

A Compact UWB MIMO Antenna With Reflector to Enhance Isolation

A compact ultrawideband (UWB) multiple-input multiple-output (MIMO) antenna, with high isolation, is proposed for portable UWB MIMO systems. Two coplanar stripline-fed staircase-shaped radiating elements are connected back-to-back. The prototype is designed on a substrate of dielectric constant 4.4 with an overall dimension of 25 mm × 30 mm × 1.6 mm. This antenna configuration with an isolating metal strip placed in between the two radiating elements ensures high isolation in the entire UWB band. The proposed antenna exhibits a good 2:1 VSWR impedance bandwidth covering the entire UWB band (3.1-10.6 GHz) with a high isolation better than 20 dB, peak gain of 5.2 dBi, peak efficiency of 90%, and guaranteed value of envelope correlation coefficient (ECC) ≤0.1641.

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.

A Compact Tri-Band Dual-Polarized Corner-Truncated Sectoral Patch Antenna

A coaxial probe-fed sector shaped patch antenna with the three corners truncated generates a triple band resonance by employing the higher order modes of the patch. A fourth sectoral indentation is used to tune the third band. The antenna is fabricated on an FR4 substrate of size 40 mm × 50 mm × 1.6 mm and experimentally investigated. The resonances cover the UMTS (1.92-2.17 GHz), WiMAX (3.3-3.6 GHz), and the ISM 5.2 (5.1-5.3 GHz) bands with 10 dB return loss bandwidths of 11.2%, 5.14%, and 3.9%, respectively, and 3-dB axial ratio bandwidth of 5.8% in the first band. The polarization is circular in the UMTS band and linearly orthogonal in the other two bands. The frequency ratio of the two linearly polarized bands is tunable in the range 1.39-1.51. Area reductions of 6.6% in the patch and 64% in the ground plane with respect to the work on disc sector patch antenna by Hsu et al. are obtained.

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.

A compact Coplanar 4-port MIMO antenna for high-speed UWB applications

This paper proposes a compact 4-port Co-Planar Stripline (CPS) fed Ultra WideBand (UWB) antenna for Multiple-Input Multiple-Output (MIMO) applications. The antenna is fabricated on a 43 mm × 43 mm × 1.588 mm substrate with relative permittivity of 4.3. The antenna possess a 2:1 VSWR impedance matching bandwidth from 3 - 11 GHz, covering the required UWB bandwidth, specified by Federal Communication Commission (FCC) and a good isolation of over 20 dB in the operating band. Stable radiation patterns with stable gain, good efficiency, low envelope correlation coefficient are the attractive features of this antenna.

A 3-port UWB MIMO antenna with enhanced isolation

A novel compact Coplanar Stripline (CPS)-fed 3-port MIMO antenna for UWB (Ultra-Wideband) application is investigated. The proposed antenna consists of three staircase-shaped radiating elements, which are integrated on a single 45mm × 25mm × 1.6mm FR-4 substrate. Spatial and polarization diversity within the antenna elements provided an average isolation of more than 20 dB throughout the UWB band. Good pattern diversity with a low Envelope Correlation Coefficient of ≤ 0.0026 are obtained within the UWB band.

An SIR excited ESA for 2.4 GHz band

A novel Electrically Small Antenna (ESA) for 2.4 GHz ISM band applications is proposed. The antenna element occupies an area of 15mm × 10 mm on a substrate of thickness 1.6mm and relative permittivity 4.4. A Stepped Impedance Resonator (SIR) is employed for obtaining the resonance. The 2:1 VSWR impedance bandwidth of the proposed antenna is 44 MHz. The radiation patterns are slightly directional and the maximum measured gain is -1.3 dBi at 2.42 GHz.

An SIR loaded modified dipole antenna

This paper proposes a novel compact coplanar dual band antenna for 2.4 & 5.2GHz ISM band applications. The antenna occupies an area of 25×9 mm2 on an FR4 substrate of thickness 1.6mm and permittivity 4.3. A bended dipole gives the higher resonance and an SIR, electrically coupled to the dipole gives the lower resonance. The 2:1 VSWR impedance bandwidth of the proposed antenna is 90MHz for the first resonance around 2.4GHz and 2.5GHz for the second resonance. The radiation patterns are nearly omnidirectional. The maximum measured gain is 3.33dBi and 5.9dBi for 2.46GHz and 5.42GHz respectively.

Compact CPW fed ZOR antenna for WLAN application

A compact Zeroth Order Resonance (ZOR) antenna which can be used for 2.4 GHz WLAN applications is presented in this paper. The resonance of the structure is achieved by implanting a chip inductor in between the center conductor of an open ended coplanar waveguide transmission line and a short metal strip. As a result the total electrical size of the fabricated ZOR antenna is reduced by 0.096 λ0 × 0.08 λ0. The reflection, radiation and the variation studies of the antenna are discussed in this paper.