Articles written in Sadhana

    • Cylindrical air spaced high gain dielectric resonator antenna for ultra-wideband applications


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      A new geometry of ultra-wideband (UWB) hollow dielectric resonator antenna (DRA) has been designed, simulated, and fabricated. The antenna consists of a rectangular dielectric resonator and excited by a transformer type microstrip feedline. A hollow cylindrical-shaped structure is extracted from a rectangular DR to improve the gain and impedance bandwidth of the antenna. The present work shows that the shifting within the UWB range along with the gain enhancement is observed by increased diameter of the hollow structure and the use of defective ground structure in the ground plane. The antenna provides four different radiating modes, namely TE11d at 3.8 GHz, TE22d at 6.4 GHz, TE231Z at 8.8 GHz, and TE33d at 10 GHz that support to give widen impedance bandwidth. The simulated and measured results are in good agreement as an impedance bandwidth of 104.09% (3.28 to 10.4 GHz) and 103.86% along with a peak gain of 7.2 dB.

    • Broadband circularly polarized dielectric resonator antenna for UWB applications


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      In this paper, a compact circularly polarized asymmetric dielectric resonator antenna (DRA) excited by a quarter-wave transformer (QWT) feedline is proposed for ultra-wideband (UWB) applications. The DRA consists of two rectangular ceramic blocks with the same permittivity (εDR = 9.8) and an F-shaped metallic strip combined with the partial ground. The proposed antenna is supported first and third-order modes as TEδ11 and TEδ13 at 9.1 and 11.28 GHz. The proposed antenna covers ultra-wideband (UWB) range from 6.4 to 12.4 GHz (impedance bandwidth of 63.8 %) with a peak gain of 6.01 dBi at 11.5 GHz. The broad AR bandwidth of the proposed antenna is achieved by the asymmetric structure of DR and the modified ground. The simulated AR bandwidth (≤ 3 dB) of the proposed antenna is 63.8% (6.4 to 12.4 GHz), and the measured AR bandwidth is 2.5% (5.8 to 6.1 GHz) and 43.7% (6.9 to 10.9 GHz). The proposed antenna can be used for C, X band applications.

    • Polarization independent frequency selective surface for marine and air traffic radar applications


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      This article presents a polarization independent frequency selective Surface (FSS) with pass band characteristics for the ‘S’ (1.45–4.63 GHz.) and the ‘X’ (6.33–12.15 GHz) band. The proposed FSS has a miniaturized unit cell structure with optimized dimensions of 13 91391.605 mm3 that is imprinted on acommercially available FR4 substrate. Four stubs each of length 0.115 λ interleaved at the centre of each inner loop to achieve the required pass band performance. Since it is a symmetric structure, it gives a polarizationindependent performance for the pass band response (for S and X bands) with both TE and TM modes of operation. The AR bandwidth (<3 dB) for the ‘S’ and ‘X’ bands is 3.2 GHz and 5.82 GHz, respectively. The prototype of the proposed FSS is fabricated and tested using Agilent’s E 5063A a two port vector networkanalyser and two horn antennas with a calibrated gain of 12 dBi each (operating from 20 KHz to 20 GHz). The measured transmission parameters of the FSS that match well with the simulated ones allow its practical applicability for filtering out unwanted signals for the communication satellites, surface ship radars andmetrological satellites used in the ‘S’ and ‘X’ wireless communication bands respectively. It finds practical applicability in filtering out unwanted signals for the communication satellites, surface ship radars and metrological satellites used in the ‘S’ and ‘X’ wireless communication bands respectively.

    • A low cost and efficient breast cancer detection method with a staircase shaped ultrawide band dielectric resonator antenna using monostatic radar based microwave imaging technique


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      In this article, a staircase-shaped ultra-wide band dielectric resonator antenna (DRA) has been used as a sensor for the detection of breast tumor by monostatic radar-based microwave imaging (MRMWI). The proposed DRA has fractional bandwidth (BW) 98.5% and a high peak gain 5.98 dB along with dual polarization behaviour from 5.12 to 8.2 GHz and 11.02-13.8 GHz. In the MRMWI setup, DRA is placed over the breast phantom at a distance of 7 mm and provides a safe exposure of radiation (<1.6 W/Kg). For simulation, it rotatesaround the phantom at a fixed interval in elevation (0-180°) and azimuthal (0-360°) planes. It works as a radiate and receives the reflected signals towards and from the scanned area simultaneously. To validate the results, fabricated DRA is connected to a vector network analyzer and rotates (as done for simulation) around the artificial breast phantom. That is a replica of the human breast made from gelatin+sugar, Vaseline and wheat flour+water equivalent to skin, fat and tumor respectively. Afterward S11 responses are recorded in the presence and absence of tumor inside the phantom. A significant variation in recorded values leads to the detection of tumors that are processed further in beam-forming algorithms; delay and sum (DAS) and delay-multiply andsum (DMAS) to reform the 2-dimensional image of tumor in MATLAB.

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