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Rajkishor Kumar

Bio: Rajkishor Kumar is an academic researcher from Indian Institutes of Technology. The author has contributed to research in topics: Dielectric resonator antenna & Wideband. The author has an hindex of 10, co-authored 34 publications receiving 297 citations. Previous affiliations of Rajkishor Kumar include K L University & Colorado School of Mines.

Papers
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Journal ArticleDOI
TL;DR: In this article, a new frequency selective surface (FSS)-based isolation technique is proposed for multiple-input-multiple-output (MIMO) antennas, and two FSS designs have been presented, and they are named as FSS and M_FSS.
Abstract: In this communication, a new frequency selective surface (FSS)-based isolation technique is proposed for multiple-input-multiple-output (MIMO) antennas. In the proposed method, a conventional ground plane of monopole-based MIMO antenna is replaced with FSS to improve the isolation between the antenna elements as well as to reduce MIMO antenna radar cross section (RCS). In this communication, two FSS designs have been presented, and they are named as FSS and M_FSS. M_FSS is a slightly modified version of FSS. With FSS, isolation enhancement and RCS reduction have been achieved by altering antenna characteristics. With M_FSS, the same can be achieved by preserving the antenna characteristics. The RCS reductions of 25 and 20 dBsm have been achieved by replacing the PEC ground plane with FSS and M_FSS, respectively. Also, by using the proposed FSS, a stable RCS reduction up to 60° for TE polarization and up to 45° for TM polarization has been achieved. The proposed MIMO antenna with FSS has been fabricated, and the simulation results are experimentally verified.

86 citations

Journal ArticleDOI
TL;DR: In this article, a cubic-shaped dielectric resonator antenna (DRA) with a new question-mark-shaped microstrip feed was proposed, which provides two orthogonal modes with a quadrature phase difference, hence generating circular polarization.
Abstract: A wideband circularly polarized cubic-shaped dielectric resonator antenna (DRA) was excited with a new question-mark-shaped microstrip feed, which provides two orthogonal modes with a quadrature phase difference, hence generating circular polarization. The proposed antenna offers measured - 10-dB impedance bandwidth of 35.35% (at center frequency 3.14 GHz) and measured 3-dB axial-ratio bandwidth of 20.62% (centered on 3.29 GHz) in the broadside direction. The proposed DRA shows the maximum gain and radiation efficiency of 1.51 dB and 90.65%, respectively, in the operating band. It was observed that the proposed antenna is left-hand circular polarized. This antenna is useful for WiMAX (3.3-3.7 GHz) applications.

77 citations

Journal ArticleDOI
TL;DR: In this article, a four-port multiple-input-multiple-output (MIMO) antenna for dual-band wireless local area network applications is designed using meander line concept.
Abstract: In this study, to design a compact four-port multiple-input-multiple-output (MIMO) antenna for dual-band wireless local area network applications, both frequency and isolation between antennas are made as reconfigurable. Both antenna element and decoupling network shown in this study are designed using meander line concept. The frequency reconfigurable capability of the antenna is achieved by incorporating positive-intrinsic-negative (PIN) diodes in the meander line resonator. By making PIN diodes ON and OFF, four antenna elements switch their operating frequency in between 2.4-2.5 and 5.1-5.8 GHz bands. Isolation between the antenna elements also made as reconfigurable by placing PIN diodes in the decoupling network. In ON state, isolation is found in 2.4-2.5 GHz band, whereas in OFF state, isolation is achieved in 5.1-5.8 GHz band. Overall, in both the bands, excellent isolation (more than 15 dB) between the antenna elements has been achieved. The proposed antenna design is printed on the FR-4 substrate and its overall area is 38 × 38 mm 2 . Each antenna element is in polarisation diversity with the adjacent antenna element which makes the proposed design suitable for achieving good MIMO performance.

31 citations

Journal ArticleDOI
TL;DR: In this article, a dual-mode wideband circularly polarized (CP) DRA is implemented by using a stair-shaped microstrip feed line, a pair of L-shaped slots in the ground plane, and a rectangular DR.
Abstract: An examination of a new kind of rectangular dielectric resonator antenna (DRA) demonstrates that it delivers better gain and radiation efficiency for operating in the Worldwide Interoperability for Microwave Access (Wi-MAX) (3.3-3.7 GHz) band. The new dual-mode wideband circularly polarized (CP) DRA is implemented by using a stair-shaped microstrip feed line, a pair of L-shaped slots in the ground plane, and a rectangular DR.

30 citations

Journal ArticleDOI
TL;DR: In this paper, a modified microstrip-line-fed rectangular dielectric resonator antenna coupled with slotted ground plane for circular polarization is proposed, which offers 3-dB axial ratio bandwidth of 16.52% in the broadside direction and −10 dB impedance bandwidth of 17.87% at center frequency 3.58 GHz.
Abstract: A new modified microstrip-line-fed rectangular dielectric resonator antenna coupled with slotted ground plane for circular polarization, is proposed in this article. The circular polarization is achieved due to combination of modified microstrip-line-fed aperture slot on ground plane. The proposed antenna offers 3-dB axial ratio bandwidth of 16.52% (at center frequency 3.57 GHz) in the broadside direction and −10 dB impedance bandwidth of 17.87% (at center frequency 3.58 GHz). The average gain and radiation efficiency is 4.69 dB and 74.84% in the working band. It is observed that the proposed antenna is right hand circularly polarized in broadside direction. The proposed antenna is suitable for Wi-MAX applications. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:206–210, 2016

26 citations


Cited by
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Journal ArticleDOI
TL;DR: Different types of effective implementation techniques for reconfigurable antennas used in various wireless communication systems such as satellite, multiple-input multiple-output (MIMO), mobile terminals and cognitive radio communications are investigated.
Abstract: Due to the fast development of wireless communication technology, reconfigurable antennas with multimode and cognitive radio operation in modern wireless applications with a high-data rate have drawn very close attention from researchers. Reconfigurable antennas can provide various functions in operating frequency, beam pattern, polarization, etc. The dynamic tuning can be achieved by manipulating a certain switching mechanism through controlling electronic, mechanical, physical or optical switches. Among them, electronic switches are the most popular in constituting reconfigurable antennas due to their efficiency, reliability and ease of integrating with microwave circuitry. In this paper, we review different implementation techniques for reconfigurable antennas. Different types of effective implementation techniques have been investigated to be used in various wireless communication systems such as satellite, multiple-input multiple-output (MIMO), mobile terminals and cognitive radio communications. Characteristics and fundamental properties of the reconfigurable antennas are investigated.

86 citations

Journal ArticleDOI
TL;DR: A four-port MIMO antenna array with wideband and high isolation characteristics for imminent wireless systems functioning in 5G New Radio (NR) sub-6 GHz n77/n78/n79 and 5 GHz WLAN bands is proposed.
Abstract: A four-port MIMO antenna array with wideband and high isolation characteristics for imminent wireless systems functioning in 5G New Radio (NR) sub-6 GHz n77/n78/n79 and 5 GHz WLAN bands is proposed. Each array antenna element is a microstrip-line fed monopole type. The novelty of the antenna lies in loading an “EL” slot into the radiating element along with two identical stubs coupled to the partial ground in order to improve the impedance matching and radiation characteristics across the bands of interest. To further attain high port isolation without affecting the compactness and radiation performance of each antenna element, the technique of introducing an innovative un-protruded multi-slot (UPMS) isolating element (of low-profile 2 × 19 mm2) between two closely spaced antenna elements (with an edge-to-edge distance of approx. 0.03λ at 4.6 GHz) is also presented. Besides demonstrating a small footprint of 30 × 40 × 1.6 mm3, the proposed four-port MIMO antenna array has also shown wide 10-dB impedance bandwidth of 58.56% (3.20–5.85 GHz), high isolation of more than 17.5 dB, and good gain and efficiency of around 3.5 dBi and 85%, respectively, across the bands of interest. Finally, the MIMO performance metrics of the proposed antenna are also analyzed.

83 citations

Journal ArticleDOI
Wen Jiang1, Cui Yangqiang1, Bo Liu1, Wei Hu1, Yan Xi1 
TL;DR: By introducing the decoupling structures, the isolation between inner antenna elements is improved from 10dB to 15.1dB in 3.45-GHz band and the coupling effect between the antenna elements and the proposed decoupled structures are promising for solving the problem of terminal space shortage.
Abstract: In this paper, a compact dual-band MIMO antenna array for 5G smartphone applications is proposed. The MIMO antenna consists of eight folded monopole antennas operating at 3.45-GHz band (3300~3600MHz). And the antenna elements with a size of $6.8\times 6.6\times4$ mm3 (about $0.078\lambda \times 0.075\lambda \times 0.046\lambda $ at 3.45 GHz), are disposed along each edge of the system circuit board. By introducing the decoupling structures, the isolation between inner antenna elements is improved from 10dB to 15.1dB in 3.45-GHz band (3300~3600MHz). Meanwhile the inner antenna units can generate an additional operating band covering 2400~2700MHz due to the coupling effect between the antenna elements and the proposed decoupling structures, which is promising for solving the problem of terminal space shortage. To verify the design principle of the proposed MIMO antenna array, the antenna is fabricated and measured. The measured results of efficiency and ECC are analyzed as well to demonstrate the performance of the proposed MIMO array. Channel capacity, user proximity and SAR analysis and are also given in this paper.

68 citations

Journal ArticleDOI
29 Apr 2020-Sensors
TL;DR: Numerical comparisons show that the proposed antenna is superior to other published designs, which makes the proposed single antenna an excellent candidate for a multiple-input multiple-output (MIMO) system constructed from a number of properly allocated elements for 5G mobile communications with excellent diversity schemes.
Abstract: A compact dual-frequency ( 38 / 60 GHz ) microstrip patch antenna with novel design is proposed for 5G mobile handsets to combine complicated radiation mechanisms for dual-band operation. The proposed antenna is composed of two electromagnetically coupled patches. The first patch is directly fed by a microstrip line and is mainly responsible for radiation in the lower band ( 38 GHz ). The second patch is fed through both capacitive and inductive coupling to the first patch and is mainly responsible for radiation in the upper frequency band ( 60 GHz ). Numerical and experimental results show good performance regarding return loss, bandwidth, radiation patterns, radiation efficiency, and gain. The impedance matching bandwidths achieved in the 38 GHz and 60 GHz bands are about 2 GHz and 3.2 GHz , respectively. The minimum value of the return loss is − 42 dB for the 38 GHz band and − 47 for the 60 GHz band. Radiation patterns are omnidirectional with a balloon-like shape for both bands, which makes the proposed single antenna an excellent candidate for a multiple-input multiple-output (MIMO) system constructed from a number of properly allocated elements for 5G mobile communications with excellent diversity schemes. Numerical comparisons show that the proposed antenna is superior to other published designs.

60 citations

Journal ArticleDOI
Xiao-Ting Yuan1, Wei He, Kai-Dong Hong1, Han Chongzhi1, Zhe Chen1, Tao Yuan1 
TL;DR: The effects caused by user’s hands and head are analyzed to guarantee the robustness of the MIMO antenna system in practical applications.
Abstract: In this paper, we presented an ultra-wideband multiple-input multiple-output (MIMO) antenna system with high element-isolation for the application in 5G metal-frame smartphones. We proposed T-shaped and C-shaped slots on the metal frame generating four resonances to enhance the bandwidth. What’s more, we introduce modified H-shaped slots between each antenna-element to improve the element-isolation of MIMO antenna system. As a result, the MIMO antenna system has a wide bandwidth of 58% ranging from 3.3 to 6 GHz and the element-isolation is over 18 dB crossing the effective frequency band. Thanks to the decent element-isolation, the envelope correlation coefficient (ECC) between each antenna-element is below 0.05 providing a reliable anti-interference for the MIMO antenna system. In addition, the measured radiation efficiencies of the MIMO antenna system are higher than 40%. At last, we analyze the effects caused by user’s hands and head to guarantee the robustness of the MIMO antenna system in practical applications.

58 citations