A wideband compact antenna with quad-circular polarized bands in its operating regions Anumoy Ghosh, Sk. Nurul Islam, Santanu Das International Journal of RF and Microwave Computer Aided Engineering, 2020 This article presents the design of an offset CPW-fed slot antenna which exhibits a narrow impedance bandwidth (IBW; |S11| ≤ −10 dB) extending from 1.20 GHz to 1.45 GHz and another wide impedance bandwidth from 1.86 GHz to 8.4 GHz thus covering almost all the conventional operating frequencies. The antenna is loaded with semicircular and rectangular stubs and meandered microstrip lines to realize circular polarization at 1.35 GHz, 3.3 GHz, 4.9 GHz, and 7.5 GHz with axial ratio bandwidth (axial ratio ≤ 3 dB) of 19.25% (1.2-1.46 GHz), 4.24% (3.24-3.38 GHz), 4.1%(4.8-5 GHz), and 5.2% (7.3-7.69 GHz) respectively thus covering the GPS, WiMAX, WLAN, and X-band downlink satellite communication application bands. The mechanism of generation of CP is discussed using vector analysis of surface current density distribution. The gain is fairly constant in the wide IBW region with maximum fluctuation of 1.2 dB. The structure is compact with an overall layout area of 0.27λ × 0.27λ, where λ is the free-space wavelength corresponding to the lowest circular polarized (CP) frequency. A comparison of the proposed antenna with previously reported structures is performed with respect to impedance bandwidth, compactness, number of CP bands, LHCP to RHCP isolation and gain to comprehend the novelty of the proposed design. A prototype of the proposed antenna is fabricated and the measured results are in accord with the simulated results.
Design of filtering directional coupler with improved performance Mukesh Kumar, Sk Nurul Islam, Gobinda Sen, Susanta Kumar Parui, Santanu Das International Journal of RF and Microwave Computer Aided Engineering, 2020 This letter presents a filtering directional coupler (FDC) with enhanced coupling and high directivity simultaneously. The proposed FDC is composed of a pair of coupled lines instead transmission line of a directional coupler. This coupled lines resonator increases the design parameters by which even/odd mode phase velocity can be compensated to improve the directivity and coupling level. The coupling enhancement can be explained by analyzing the even mode and odd mode circuit of the proposed coupler. A prototype of the proposed coupler is designed which provides a high directivity of 44 dB for 6 dB coupling level at 1 GHz frequency. The proposed coupler is designed, fabricated, and tested.
Miniaturization and harmonic suppression of power divider using coupled line section for high power applications M. Kumar, G. Sen, Sk N. Islam, S. K. Parui, S. Das Radioengineering, 2020 This paper presents a compact transmission line based on the coupled line section to reduce the circuit size of Gysel power divider (GPD). The line is composed of one direct line and one coupled line section. The coupled line section consists of two series lines and one coupled line. The proposed line is symmetrical and analyzed with evenodd mode analysis to derive design equations. The line not only reduces circuit size but also improves the out-off band performance. To validate the properties of the line, a GPD is designed at 1 GHz. The physical size of this GPD occupies only 38% (0.32 g 0.16 g , g is the guided wavelength) circuit area compared to reference GPD. Furthermore, the proposed design includes 2 nd order harmonic suppression with attenuation level better than -20 dB. The proposed GPD is designed and fabricated on an Arlon substrate of relative dielectric constant of 2.2, thickness of 0.787 mm, and loss tangent 0.0009.
Miniaturisation of branch line couplers with a compact transmission line topology based on coupled line section Mukesh Kumar, Sk Nurul Islam, Gobinda Sen, Tannistha Mitra Das, Susanta Kumar Parui, Santanu Das Iet Microwaves Antennas and Propagation, 2020 This study presents a compact transmission line topology to reduce the circuit size of single‐ and two‐section branch line couplers (BLCs). The proposed transmission line is composed of a high impedance series line and one coupled line section. The coupled line section consists of two high impedance series lines and one coupled line. The proposed line is analysed with even–odd mode analysis to derive closed‐form design equations. To validate the equations, a compact single‐ and two‐section BLCs are designed at 0.85 GHz based on the proposed line. The physical size occupied by the proposed single‐ and two‐section BLCs is 23 and 19.5%, respectively, compared to conventional BLCs. Moreover, the proposed transmission line demonstrates the harmonic suppression characteristic due to the coupled line section. As a result of which, the second‐ and third‐order harmonic of the proposed BLCs are suppressed. The proposed BLCs are designed, fabricated, and tested.
Isosceles triangular resonator based compact triple band quad element multi terminal antenna Sk. N. Islam, S. Das Radioengineering, 2020 A triple band quad element multi-input-multioutput (MIMO) antenna is proposed for Bluetooth (2.4 GHz), WLAN (2.5/4.9 GHz) and LTE (3.7 GHz) applications. A compact triangular ring-shaped structure is used as an antenna element. An isosceles triangular ring resonator is designed in such a way that it offers dual-band and another ring resonator is placed inside the empty space of the first resonator to obtain the third band. The antenna element is studied in terms of |S 11 | and also the current distributions are observed at three resonance frequencies to find out the resonance mechanism. The proposed quad element MIMO antenna is compact in total area (0.45 0 0.45 0 ). Isolation better than 20 dB is achieved with minimum inter-element spacing of 0.07 0 without extra isolation circuit. Gain, radiation patterns, envelope correlation coefficient (ECC), diversity gain (DG), channel capacity loss (CCL) and total active reflection coefficient (TARC) values are studied to comprehend the MIMO performance of the proposed design.
Dual-band CPW fed MIMO antenna with polarization diversity and improved gain Sk Nurul Islam, Santanu Das International Journal of RF and Microwave Computer Aided Engineering, 2020 A dual-band MIMO slot antenna with polarization diversity and improved gain is proposed in this article. The antenna is composed of two C-type back-to-back connected slot resonators and offers resonances at 3.5 and 5.2 GHz. This antenna element is further used to design a MIMO antenna. By introducing one U-shaped slot between two antenna elements, isolation between the ports of this MIMO antenna is improved further. Finally, an artificial magnetic conductor (AMC) is placed below the MIMO antenna to enhance its gain. Gain enhancement of 1.5 and 2.2 dB is achieved at lower and upper band, respectively. S-parameters, radiation patterns, gain, envelope correlation coefficient, and channel capacity loss are investigated to conclude about its performances in MIMO applications. Dual band dual polarization (circular and linear), improved isolation, polarization diversity (right-hand circular polarization and left-hand circular polarization), gain enhancement all are presented in a simple design represents the novelty of the proposed MIMO antenna.
Design and Analysis of a Compact Penta-Band Polarization-Insensitive Bandstop Frequency Selective Surface Anumoy Ghosh, Mukesh Kumar, Sk Nurul Islam, Santanu Das IEEE Antennas and Wireless Propagation Letters, 2020 A novel design of a compact penta-band frequency selective surface (FSS) is presented in this letter. The FSS unit cell consists of five metallic structures, two at the top surface and three at the bottom surface of the dielectric, which provide five stopbands in PCS, WiFi, CBRS, lower WLAN, and X-band downlink satellite communication frequency ranges. The mechanisms of stop-band generations are elaborated with current distribution patterns and equivalent circuit modeling. The structure is polarization-insensitive and shows a stable response under oblique incidence up to ±54°. The FSS unit cell is compact with dimensions 0.1λ × 0.1λ, where λ signifies the free-space wavelength corresponding to the lowest resonant frequency. A prototype of the proposed FSS is fabricated, and the measured results are in accord with the simulated results.
A miniaturized microwave absorber based on interdigital capacitor and lumped resistance for X-band radome applications Gobinda Sen, Mukesh Kumar, Sk Nurul Islam, Tannistha Mitra Das, Anumoy Ghosh, Santanu Das 2019 IEEE MTT S International Microwave and RF Conference Imarc 2019, 2019 In this work, a polarization insensitive compact X-band microwave absorber with miniaturized electric field coupled (ELC) resonator is presented. The ELC resonator is integrated with interdigital capacitor for synthesis of miniaturized unit cell area. The structure is also loaded with lumped resistances to achieve wideband absorption. The absorption band with more than 90% absorption covers mostly X-band frequencies from 8.16 GHz to 12.16 GHz with relative absorption bandwidth (RAB) of 39%. The size of the unit cell is 0.16 λL × 0.16 λL and overall thickness of the structure is only 3 mm (0.08 λL, with respect to lowest resonance frequency). The simulated absorption performances of the proposed miniaturized absorber are analyzed for different incident and polarization angles and found to be insensitive and hence can be well suited for Radome application.
An Ultra-Thin Polarization Insensitive Microwave Absorber with a Transmission Window Gobinda Sen, Mukesh Kumar, Sk Nurul Islam, Tannistha Mitra Das, Santanu Das 2019 3rd International Conference on Electronics Materials Engineering and Nano Technology Iementech 2019, 2019 This paper presents an ultra-thin microwave absorber with a transmission window on a low-cost substrate material. The unit cell of the proposed absorber consists of metallic cross dipole patch on top plane and a ring slot at the conductive bottom plane. The substrate height is 0.8 mm, which is ultrathin. The low profile ultra-thin planar structure makes it valuable for electromagnetic interference (EMI) reduction at 5.9 GHz which is industrial, scientific and medical (ISM) frequency band and a transparent window at 4 GHz (C-band). The surface current distributions on the top and bottom planes are studied to elaborate the absorption and transmission mechanism of the structure. The orthogonal symmetry of the structure makes it polarization insensitive and hence suitable for realization in real time environment. The measured results are verified with the simulated ones to test its performance and found to be similar.
CPW-fed capacitor loaded miniaturized dual band antenna Arijit Mitra, Sk Nurul Islam, Tapan Mandal, Santanu Das Proceedings of the 2016 IEEE International Conference on Wireless Communications Signal Processing and Networking Wispnet 2016, 2016
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