Basudev Majumder

Low-RCS and Polarization-Reconfigurable Antenna Using Cross-Slot-Based Metasurface

This letter presents a polarization-reconfigurable compact slot antenna with reduced radar cross section (RCS) using an asymmetric cross-shaped metasurface (MS). The proposed MS can reconfigure the polarization of the slot antenna between right-hand circular polarization (RHCP), left-hand circular polarization (LHCP), and linear polarization (LP) by rotating it with respect to the center of the slot antenna. In addition, the MS reduces the RCS of the slot antenna significantly in all polarization states. The cross-slot MS is placed just over the planar slot antenna without any air gap. The simulated monostatic RCS of -19.5 dBsm is observed at 4.4 GHz for LHCP and RHCP cases and -17.0 dBsm for LP mode of operation. Antenna performance in terms of its input matching, far-field parameters, monostatic RCS, and axial ratio are measured at its three polarization states, which are in agreement with simulated results.

Dual-Band Circularly Polarized Split Ring Resonators Loaded Square Slot Antenna

A dual-band circularly polarized (CP) microstrip line fed slot antenna using a set of split ring resonators (SRRs) is proposed in this communication. Outer ring connected SRRs are placed on the back side of the slot to create the CP upper band. Diagonally opposite corners of the slot are truncated, which together with the SRRs give CP response in the lower band. The proposed dual-band CP antenna provides design flexibility to control the resonance frequency and sense of polarization at the dual bands, independently. The proposed antenna is designed to operate at 3.1 and 4.7 GHz, which is fabricated and tested. The experimental results show the -10-dB impedance bandwidths of 400 MHz in both the bands and the 3-dB axial ratio bandwidth of 3.1% (from 3.05 to 3.15 GHz) and 4.2% (from 4.65 to 4.85 GHz) in lower and upper bands, respectively. Finally, a metallic cavity is used with the antenna to achieve a unidirectional radiation pattern with front-to-back ratio of more than 15 dB without affecting the impedance bandwidth and CP performance of the antenna.

Dual band dual polarized frequency reconfigurable antenna using meta-surface

A frequency re-configurable dual band dual polarized antenna is proposed. This consists of a rectangular feed patch layer and two MS layers of same thickness. MS layers are made of rectangular loop based unit cells periodically placed in both X and Y direction. The total profile of the antenna is 0.07 λ0 only. Simulation result shows that the operating frequency of the antenna can be changed by physically rotating both the MS layers with respect to the centre of the patch antenna. As the MS is rotated the excitation and the polarization with the electric field of the patch to the MS layers change which changes the effective permittivity of the whole substrate and hence the frequency of the operation also changes. Measured results are well matched with the simulation results. At all the frequencies antenna has peak gain of more than 5.5 dB and the minimum efficiency is more than 89%.

A novel compact comb shaped EBG structure for coupling reduction in WIMAX band

A novel dual band compact near to edge located via-comb shape EBG (NELV-CEBG) has been proposed and its compactness has been studied. A good reduction level of 8-21 dB has been observed when 7×3 matrix of the proposed structure has been applied to enhance the isolation between the patch antenna arrays operating over WIMAX band.

Compact Broadband Directive Slot Antenna Loaded With Cavities and Single and Double Layers of Metasurfaces

In this paper, a compact wideband directive metasurface (MS)-based antenna is proposed. A pair of edge-fed slots, assisted by a fictitious short, is used to excite the MS layer which is made up of a periodic arrangement of rectangular loop-based unit cells along both the x- and y-directions. The proposed MS-based slot antenna is compact and provides good matching over the entire bandwidth with a broadside radiation pattern. A metallic cavity and an artificial magnetic conductorbased cavity are integrated on the MS-based antenna to reduce its backward radiation. Finally, a pair of edge-fed slot antennas combined with two layers of MSs having compact ground plane area of 1.04 λ02 (λ0 is the operating wavelength in free space) is proposed for the improvement of gain, bandwidth, and forward radiation. The overall antenna has a low profile of 0.05 λ0. The proposed configuration shows a 21% measured bandwidth with an average gain of 9.6 dB over its bandwidth. Over its bandwidth, the antenna efficiency is >89%. The design is validated by a fullwave simulation study followed by the experimental verification.

Frequency-Reconfigurable Slot Antenna Enabled by Thin Anisotropic Double Layer Metasurfaces

A frequency-reconfigurable slot antenna using metasurface (MS) is proposed. Two identical anisotropic MS layers are loaded on top of a slot to achieve the frequency reconfigurability. The MS layer is composed of a periodic arrangement of I-shaped metallic inclusions placed in both the horizontal and vertical directions. The MS layers are fed by a linearly polarized slot antenna. The operating frequency of the proposed antenna is tuned by physically rotating the two MS layers with respect to the centre of the slot antenna. Rotation of the MS layers changes the effective permittivity and the loading on the slot antenna and hence the operating frequency changes. The proposed antenna has a low profile with the thickness of the antenna including the two MS layers being 0.07λ0. The simulated and measured results show that using the proposed technique, the operating frequency can be tuned from 2.55 to 3.45 GHz with a fractional tuning range of around 28%. The antenna provides a minimum gain of 5.3 dB with the peak gain being 8.3 dB. The efficiency of the proposed antenna is more than 90% over its tuning range.

Design of SRR loaded reconfigurable antenna for UWB and narrow band applications

In this paper, a reconfigurable antenna utilizing the property of negative permeability of split ring resonators is proposed for band notched UWB and narrow band applications. The proposed design yield the resonant frequency of the narrow band operation and notch frequency of UWB operation coinciding at 5.8 GHz frequency. The proposed antenna is simulated and measured. Radiation efficiency of 80% and 50% is observed for the UWB and the narrow band operation, respectively.

A novel circularly polarized / dual band dual polarized antenna using metasurface

In this paper a novel circular polarized/dual band dual polarized antenna has been proposed, which is validated experimentally using the meta-surface. First a 450 rotated rectangular loop based meta-surface is excited with a patch radiator to obtain the dual band dual polarized operation. Thereafter another same meta-surface is loaded on top of it to merge the two dual polarized band to obtain circular polarization. Appropriate rotation of the top meta-surface ensures maximum coupling with the X directed electric field from the bottom MS. Impedance bandwidth for dual band dual polarized operation is from 5GHz-5.28 GHz and from 5.6 GHz-5.75 GHz. For circular polarization response, impedance band width is from 4.8 GHz-5.77 GHz (Fractional Bandwidth of 19%). and 3 dB axial ratio is from 5.15 GHz-5.76 GHz. Measured gain of the antenna is 7.4 dB.

A high gain EBG backed slot antenna loaded with anisotropic mu-negative superstrate

A reduced profile directional and high gain slot antenna loaded with Electromagnetic Band Gap (EBG) cavity and anisotropic negative permeability medium (NPM) is proposed which is investigated numerically as well as experimentally. Measured result shows a good agreement with the simulation result. Bandwidth of the proposed antenna extends from 3.4 GHz-4.1 GHz (Fractional Bandwidth (FBW) of 19%). Significant improvement in gain about 7 dB is achieved as compared to the conventional slot antenna with E and H plane beam-width of 35.30 and 36.80, respectively.

Compact dual band notched printed UWB MIMO antenna with pattern diversity

A planar multiple-input multiple-output (MIMO) antenna with a compact size of 34×26 mm2 for ultra wideband applications is presented. It consists of orthogonally placed microstrip fed planar monopole antenna with rectangular split ring resonator (SRR) slots to notch WiMAX and WLAN bands. The isolation between the monopoles is improved by using meander shaped ground stubs. The compact antenna provides impedance bandwidth from 3 to 10.7GHz. It also exhibits inter-port isolation of > 15dB for complete UWB. In addition the antenna provides good radiation characteristics, moderate gain across the band and good envelope correlation coefficient value which makes it a suitable candidate for UWB diversity applications.