Adam Narbudowicz - Academia.edu (original) (raw)

Papers by Adam Narbudowicz

The paper discusses recent developments and challenges in the design of small omnidirectional cir... more The paper discusses recent developments and challenges in the design of small omnidirectional circularly-polarized (CP) antennas. Although omnidirectional CP coverage is easily achievable using antenna arrays, it is just recently that small and low-cost antennas delivered this functionality. The paper addresses practical design problems for these antennas, not reported in previous publications. This includes selection of the omnidirectional plane relative to the ground plane and measurement challenges. Future perspectives on how these antennas can provide electronically steerable beams are investigated using simulated results.

The paper investigates a new approach to analysis and design of inhomogeneous linear antenna arra... more The paper investigates a new approach to analysis and design of inhomogeneous linear antenna arrays. The approach relies on omnidirectional antennas, which exhibit linear phase variation of the radiation pattern in the far-field. By appropriately combining different phase variations with a spacing between antennas, one can obtain a performance not achievable with standard linear arrays. Most notably, the approach allows to decrease size of the aperture required for a given beamwidth. The radiation pattern can be easily calculated by a simple equation (if coupling is neglected).

A bidirectional circularly polarised (CP) antenna for 1.575 GHz GPS L1 band is presented. The ant... more A bidirectional circularly polarised (CP) antenna for 1.575 GHz GPS L1 band is presented. The antenna consists of two back-to-back coupled patches and is fed directly by 50 Coplanar Waveguide (CPW). It is compact and relatively easy to manufacture compared to other antennas with similar properties. The bidirectional CP pattern is achieved by proper adjustment of patch dimensions as well as feed parameters. A study of the key parameter is provided.

2022 19th International Conference on Electrical Engineering/Electronics, Computer, Telecommunications and Information Technology (ECTI-CON), May 24, 2022

IEEE Antennas and Wireless Propagation Letters, 2023

IEEE Transactions on Antennas and Propagation, 2013

A dual-band omnidirectional circularly polarized antenna is proposed. The antenna comprises back-... more A dual-band omnidirectional circularly polarized antenna is proposed. The antenna comprises back-to-back microstrip patches fed by a coplanar waveguide. A very low frequency ratio of 1.182 has been achieved, which can be easily tuned by adjusting four lumped capacitors incorporated into the antenna. An analysis of the omnidirectional circular polarization mechanism as well the dual band operation is provided and confirmed by numerical and experimental data. Key parameters to tune the resonant frequencies and the axial ratio have been identified. The prototype antenna provides omnidirectional circular polarization in one plane with cross polar isolation better than 12 dB for both frequency bands.

IEEE sensors letters, Mar 1, 2023

This work proposes compact multimode Multiple-Input-Multiple-Output (MIMO) antennas for Angle of ... more This work proposes compact multimode Multiple-Input-Multiple-Output (MIMO) antennas for Angle of Arrival (AoA) estimation in miniaturized Internet of Things (IoT) systems. The method excites different orthogonal radiating modes (TM 21 , TM 02 , and TM 31 modes) for beamforming capabilities, and the AoA performance is investigated using the Multiple Signal Classification (MUSIC) algorithm, executed using numerical and experimental data. The technique is tested at 2.238 GHz, while using an antenna diameter < 7.5 cm. Overall, an envelope correlation coefficient < 0.01 is realized between all antenna ports, and a 360 • field of view AoA estimation is demonstrated across the entire azimuthal plane with mean absolute errors smaller than 0.098 •. Furthermore, it is shown that the capability of separating multiple simultaneous impinging signals is comparable to that of state-of-the-art circular arrays with similar number of RF transceivers, while offering, respectively, up to 35% and 71% antenna diameter and height miniaturization.

arXiv (Cornell University), Jan 15, 2023

This work proposes an energy-efficient Directional Modulation (DM) scheme for on-body Internet of... more This work proposes an energy-efficient Directional Modulation (DM) scheme for on-body Internet of Things (IoT) devices. DM performance is tested using a 5-port stacked-patch MIMO antenna under two scenarios: free space case and using a four-layer human forearm phantom to simulate the user's wrist. It is demonstrated that the scheme achieves steerable secure transmissions across the entire horizontal plane. With low Bit Error Rate (BER) of 1.5 × 10 −5 at the desired directions, eavesdroppers experience a high error rate of up to 0.498. Furthermore, this work investigates the DM performance using a subset of the stacked patches in the MIMO antenna, revealing that some combinations achieve a low BER performance using a lower antenna profile, albeit high side-lobes of BER< 10 −2 seen outside the desired region. Overall, the solution is proposed as a good candidate to enable secure wireless communications in emerging wearable IoT devices that are subject to size and energy-constraints.

arXiv (Cornell University), Jan 14, 2023

This work proposes compact, flexible Multiple Input Multiple Output (MIMO) antennas. The design p... more This work proposes compact, flexible Multiple Input Multiple Output (MIMO) antennas. The design principle is based on the excitation of different orthogonal radiating modes within the same antenna volume. Via phase control of the excited modes, beamforming is demonstrated in azimuth and elevation planes using single-layered structures. For flexibility, the antennas are designed using Polydimethylsiloxane (PDMS) as the substrate. Numerical results demonstrate that isolation better than 23 dB is realized in all investigated antennas under different bend configurations. Moreover, the proposed technique demonstrates an antenna with unidirectional beamsteering across the entire elevation plane, and a second design realizes a bidirectional beamsteering in the horizontal plane. Overall, the results highlight the potential of multimode-based beamforming for flexible MIMO antennas in Internet of Things (IoT) systems.

This paper proposes a new approach to reduce weight and complexity of VHF/UHF cubesat antennas by... more This paper proposes a new approach to reduce weight and complexity of VHF/UHF cubesat antennas by utilizing a dual band antenna, rather than standard two-antenna system routinely implemented in cubesats. Three systems are compared: A standard system with separate transmit/receive dipoles, a dual-band dipole for both transmit and receive and a dual-band monopole, which uses the body of 1U cubesat (10 × 10 × 10cm) as a “groundplane”. Additionally it is demonstrated that with appropriate feed the dipole might be used in monopole configuration in case of deployment system malfunction.

An electrically small pattern reconfigurable antenna is proposed. It allows adjustment of the rad... more An electrically small pattern reconfigurable antenna is proposed. It allows adjustment of the radiation pattern by applying a phase shift between its two ports. The structure is a cylinder with /5 diameter. Simulated results show good operation at 2.44 GHz and three different radiation patterns are demonstrated by applying three different phase shifts. The antenna's principles of operation and limitations are explained based on the theory of spherical modes.

arXiv (Cornell University), May 31, 2023

In this paper, the privacy of wireless transmissions is improved through the use of an efficient ... more In this paper, the privacy of wireless transmissions is improved through the use of an efficient technique termed dynamic directional modulation (DDM), and is subsequently assessed in terms of the measure of information leakage. Recently, a variation of DDM termed low-power dynamic directional modulation (LPDDM) has attracted significant attention as a prominent secure transmission method due to its ability to further improve the privacy of wireless communications. Roughly speaking, this modulation operates by randomly selecting the transmitting antenna from an antenna array whose radiation pattern is well known. Thereafter, the modulator adjusts the constellation phase so as to ensure that only the legitimate receiver recovers the information. To begin with, we highlight some privacy boundaries inherent to the underlying system. In addition, we propose features that the antenna array must meet in order to increase the privacy of a wireless communication system. Last, we adopt a uniform circular monopole antenna array with equiprobable transmitting antennas in order to assess the impact of DDM on the information leakage. It is shown that the bit error rate, while being a useful metric in the evaluation of wireless communication systems, does not provide the full information about the vulnerability of the underlying system.

2023 17th European Conference on Antennas and Propagation (EuCAP)

arXiv (Cornell University), Jan 20, 2023

This work proposes an electrically small 3D beamforming antenna for PHYsical Layer (PHY-layer) se... more This work proposes an electrically small 3D beamforming antenna for PHYsical Layer (PHY-layer) security. The antenna comprises two layers of stacked patch structures, and is a five-mode five-port MIMO system operating around 1.85 GHz with electrical size ka = 0.98 and radiation efficiency of up to 55%. By studying the properties of the excited modes, phase and amplitude control allow for unidirectional beam scanning towards any direction around the elevation and azimuth planes. PHY-layer security is investigated using the directional modulation (DM) technique, which transmits unscrambled baseband constellations symbols to a pre-specified secure direction, while simultaneously spatially distorting the same constellations in all other directions. Bit Error Rate (BER) calculations reveal very low values of 2 × 10 −5 for the desired direction of the legitimate receiver, with BER< 10 −2 beamwidths of 55 • and 58 • for the azimuth and elevation planes, respectively.

IEEE Internet of Things Magazine

This tutorial discusses the problem of Angle-of-Arrival (AoA) estimation from small Internet of T... more This tutorial discusses the problem of Angle-of-Arrival (AoA) estimation from small Internet of Things (IoT) devices. It reviews the limitations and challenges of existing miniaturization strategies, which involve classical antenna arrays. As larger distance between antennas is typically needed for increased precision, the miniaturization without loss of accuracy is a significant problem. The article demonstrates that the use of electrically small antennas does not directly solve the problem, since smaller antennas may require increased distance to avoid coupling between elements. Therefore, this work proposes a new technique to perform AoA estimation in small platforms-a Multiple-Input Multiple-Output (MIMO) antenna. MIMO antennas are commonly used to increase the communication throughput, however few works have studied their usage for AoA estimation in line-of-sight environment. The proposed solution offers performance similar to state-of-the-art arrays, however at a substantially reduced size. Performance study is carried out to confirm and validate the proposed technique accuracy and miniaturization efficacy. Size reduction up to 75% compared to linear arrays is achieved with mean absolute errors smaller than 0.11 •. The method also demonstrates a resolution of 5 • with peak mean absolute error of 0.3 • for two simultaneous impinging signals.

IEEE Antennas and Wireless Propagation Letters

2017 11th European Conference on Antennas and Propagation (EUCAP)

2022 16th European Conference on Antennas and Propagation (EuCAP)

This work proposes compact multiport antennas for directional modulation (DM) on wrist-wearable d... more This work proposes compact multiport antennas for directional modulation (DM) on wrist-wearable devices to improve the secrecy and privacy of the transmitted data. The DM performance is investigated using the antenna in free-space and with a human forearm-phantom. The system achieves a low Bit Error Rate (BER) < 10 −1 with 44 • beamwidth, in a unique steerable secure direction over the entire azimuth plane. Full-wave simulations including the phantom at 5 GHz show realized gains of up to 4.26 dBi. The specific absorption rate is below the standard limits, with maximum values of 0.487 W/kg and 1.42 W/kg for the wrist-worn and next-to-mouth conditions, respectively.

2017 International Symposium on Antennas and Propagation (ISAP), 2017

An adaptive radio system combining compact switchless reconfigurable antenna with Software Define... more An adaptive radio system combining compact switchless reconfigurable antenna with Software Defined Radio is proposed. The system allows control of the direction of the transmitted signal solely by adjusting the baseband I and Q components of the modulated signal, while maintaining small antenna size through the use of compact multiport antenna. The system is demonstrated in a line-of-sight configuration with QPSK modulation. Experimental results demonstrate good received power and low error vector magnitude of the demodulated signals.