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Kapil R. Dandekar

Bio: Kapil R. Dandekar is an academic researcher from Drexel University. The author has contributed to research in topics: Reconfigurable antenna & Antenna (radio). The author has an hindex of 27, co-authored 223 publications receiving 3035 citations. Previous affiliations of Kapil R. Dandekar include Polytechnic University of Milan & United States Naval Research Laboratory.


Papers
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Journal ArticleDOI
TL;DR: Being the most conductive, as well as water-dispersible, among solution-processed 2D materials, MXenes open new avenues for manufacturing various classes of RF and other portable, flexible, and wearable electronic devices.
Abstract: With the development of the Internet of Things (IoT), the demand for thin and wearable electronic devices is growing quickly The essential part of the IoT is communication between devices, which requires radio-frequency (RF) antennas Metals are widely used for antennas; however, their bulkiness limits the fabrication of thin, lightweight, and flexible antennas Recently, nanomaterials such as graphene, carbon nanotubes, and conductive polymers came into play However, poor conductivity limits their use We show RF devices for wireless communication based on metallic two-dimensional (2D) titanium carbide (MXene) prepared by a single-step spray coating We fabricated a ~100-nm-thick translucent MXene antenna with a reflection coefficient of less than −10 dB By increasing the antenna thickness to 8 μm, we achieved a reflection coefficient of −65 dB We also fabricated a 1-μm-thick MXene RF identification device tag reaching a reading distance of 8 m at 860 MHz Our finding shows that 2D titanium carbide MXene operates below the skin depth of copper or other metals as well as offers an opportunity to produce transparent antennas Being the most conductive, as well as water-dispersible, among solution-processed 2D materials, MXenes open new avenues for manufacturing various classes of RF and other portable, flexible, and wearable electronic devices

333 citations

Journal ArticleDOI
TL;DR: New reconfigurable antenna array is demonstrated for multiple input multiple output (MIMO) communication systems that improves link capacity in closely spaced antenna arrays that includes a new definition of spatial correlation coefficient to include the effects of antenna mismatch and radiation efficiency when quantifying the benefit of pattern diversity.
Abstract: New reconfigurable antenna array is demonstrated for multiple input multiple output (MIMO) communication systems that improves link capacity in closely spaced antenna arrays. The antenna system consists of an array of two printed dipoles separated by a distance of a quarter wavelength. Each of the dipoles can be reconfigured in length using PIN diode switches. The switch configuration can be modified in a manner adaptive to changes in the environment. The configuration of switches effects the mutual coupling between the array elements, and subsequently, the radiation pattern of each antenna, leading to different degrees of pattern diversity which can be used to improve link capacity. The PIN diode-based reconfigurable antenna solution is first motivated through a capacity analysis of the antenna in a clustered MIMO channel model. A new definition of spatial correlation coefficient is introduced to include the effects of antenna mismatch and radiation efficiency when quantifying the benefit of pattern diversity. Next, the widespread applicability of the proposed technique is demonstrated, relative to conventional half wavelength printed dipoles, using computational electromagnetic simulation in an outdoor and indoor environment and field measurements in an indoor laboratory environment. It is shown for the 2 times 2 system considered in this paper, that an average improvement of 10% and 8% is achieved in link capacity for a signal to noise ratio (SNR) respectively of 10 dB and 20 dB in an indoor environment compared to a system employing non reconfigurable antenna arrays.

299 citations

Journal ArticleDOI
TL;DR: Experimental results and computer simulations show that the mutual coupling compensation technique improves up-link DOA algorithm performance primarily by reducing unwanted sidelobe levels and allows DOA-based down-link beamforming algorithms to perform similarly to spatial signature-based algorithms.
Abstract: This paper investigates the benefit of mutual coupling compensation via a method of moments (MoM) approach in a uniform circular antenna array operating at 1.8 GHz. This mutual coupling compensation technique is applied to a direction of arrival (DOA) study of up to two cochannel mobile users. Field measurements and computer simulations are examined to explore the assumptions of the technique and verify its effect when using the Bartlett and MUSIC DOA algorithms. Computer simulations considering the application of the technique to down-link beamforming are also included. Experimental results show that the mutual coupling compensation technique improves up-link DOA algorithm performance primarily by reducing unwanted sidelobe levels. This reduction in sidelobe levels aids in down-link beamforming weight design. Specifically, simulation results show that use of the compensation technique allows DOA-based down-link beamforming algorithms to perform similarly to spatial signature-based algorithms. All field measurements were made using the smart antenna testbed at the University of Texas at Austin.

151 citations

Journal ArticleDOI
TL;DR: The design and application of a wearable strain sensor, which can be used for biomedical monitoring such as contraction, respiration, or limb movements, is discussed and results show that breathing and non-breathing patterns can be successfully classified.
Abstract: Recent advancements in conductive yarns and fabrication technologies offer exciting opportunities to design and knit seamless garments equipped with sensors for biomedical applications. In this paper, we discuss the design and application of a wearable strain sensor, which can be used for biomedical monitoring such as contraction, respiration, or limb movements. The system takes advantage of the intensity variations of the backscattered power (RSSI) from an inductively-coupled RFID tag under physical stretching. First, we describe the antenna design along with the modeling of the sheet impedance, which characterizes the conductive textile. Experimental results with custom fabricated prototypes showed good agreement with the numerical simulation of input impedance and radiation pattern. Finally, the wearable sensor has been applied for infant breathing monitoring using a medical programmable mannequin. A machine learning technique has been developed and applied to post-process the RSSI data, and the results show that breathing and non-breathing patterns can be successfully classified.

97 citations

Journal ArticleDOI
TL;DR: This paper uses field measurements collected in an indoor environment to determine the channel capacity achievable with the RCPAs when used at one or at both ends of the communication link and shows the difference in performance achievable when employed in narrowband or broadband communication systems.
Abstract: In this paper, we investigate the performance achievable with pattern and polarization multielement reconfigurable antennas in narrowband and broadband multiple-input-multiple-output (MIMO) systems by means of two-port reconfigurable circular patch antennas (RCPAs). We use field measurements collected in an indoor environment to determine the channel capacity achievable with the RCPAs when used at one or at both ends of the communication link. To conduct this analysis, we use two types of RCPAs: 1) an RCPA with two different antenna configurations, exploiting only pattern diversity and 2) an RCPA with three different antenna configurations, exploiting both pattern and polarization diversity. The benefits offered by each state (i.e., excited radiation pattern and polarization) of the RCPAs are investigated in both line-of-sight (LOS) and nonline-of-sight (NLOS) scenarios. The analysis shows the effectiveness of each array configuration in increasing the diversity level of the system and the amount of signal power received in LOS and NLOS communication links. The radiation efficiency and the level of pattern and polarization diversity of each configuration are investigated to explain the performance offered by this class of antennas in MIMO systems. Finally, we show the difference in performance achievable with these antennas when employed in narrowband or broadband communication systems.

86 citations


Cited by
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Christopher M. Bishop1
01 Jan 2006
TL;DR: Probability distributions of linear models for regression and classification are given in this article, along with a discussion of combining models and combining models in the context of machine learning and classification.
Abstract: Probability Distributions.- Linear Models for Regression.- Linear Models for Classification.- Neural Networks.- Kernel Methods.- Sparse Kernel Machines.- Graphical Models.- Mixture Models and EM.- Approximate Inference.- Sampling Methods.- Continuous Latent Variables.- Sequential Data.- Combining Models.

10,141 citations

Journal ArticleDOI

2,415 citations

Book
17 Nov 2016
TL;DR: This is the first complete guide to the physical and engineering principles of Massive MIMO and will guide readers through key topics in multi-cell systems such as propagation modeling, multiplexing and de-multiplexing, channel estimation, power control, and performance evaluation.
Abstract: "Written by the pioneers of the concept, this is the first complete guide to the physical and engineering principles of Massive MIMO. Assuming only a basic background in communications and statisti ...

1,115 citations

Journal ArticleDOI
27 Aug 2019-ACS Nano

1,114 citations

Journal ArticleDOI
TL;DR: This paper reviews recent research findings concerning antennas and propagation in MIMO systems and considers issues considered include channel capacity computation, channel measurement and modeling approaches, and the impact of antenna element properties and array configuration on system performance.
Abstract: Multiple-input-multiple-output (MIMO) wireless systems use multiple antenna elements at transmit and receive to offer improved capacity over single antenna topologies in multipath channels In such systems, the antenna properties as well as the multipath channel characteristics play a key role in determining communication performance This paper reviews recent research findings concerning antennas and propagation in MIMO systems Issues considered include channel capacity computation, channel measurement and modeling approaches, and the impact of antenna element properties and array configuration on system performance Throughout the discussion, outstanding research questions in these areas are highlighted

985 citations