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Author

Nghia Nguyen-Trong

Bio: Nghia Nguyen-Trong is an academic researcher from University of Queensland. The author has contributed to research in topics: Antenna (radio) & Wideband. The author has an hindex of 20, co-authored 85 publications receiving 1049 citations. Previous affiliations of Nghia Nguyen-Trong include Ton Duc Thang University & University of Adelaide.

Papers published on a yearly basis

Papers
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Journal ArticleDOI
TL;DR: In this article, a stub-loaded microstrip patch antenna with reconfigurable operation in both frequency and polarization is presented, using 12 varactors with two independent voltages, achieving a fractional bandwidth of around 40% while allowing selection between circular polarization with both rotating senses and linear polarization (LP).
Abstract: A stub-loaded microstrip patch antenna with reconfigurability in both frequency and polarization is presented. Using 12 varactors with two independent voltages, reconfigurability is achieved in a fractional bandwidth of around 40% while allowing selection between circular polarization (CP) with both rotating senses and linear polarization (LP). The design is optimized based on an analytical model, which significantly speeds up the process while yielding reasonably accurate predictions. For illustration of the concept, an antenna is designed, optimized, and manufactured for reconfigurable operation in the 2.4–3.6 GHz frequency range. A good agreement between simulations and measurements is obtained which validates the proposed method. A full reconfigurability is demonstrated in the operation band with the ability to both tune the antenna to a given frequency and select a polarization state among left-hand or right-hand CP or various states of LP.

124 citations

Journal ArticleDOI
TL;DR: In this article, a dual-function slot antenna at microwave and millimeter-wave (mm-wave) band is proposed, which consists of a slot printed on the edge of the structure ground plane.
Abstract: A dual-function slot antenna at microwave and millimeter-wave (mm-wave) band is proposed. The design consists of a slot printed on the edge of the structure ground plane. A short-circuited varactor diode (VAR) is used to achieve the frequency tunability from 2.05 to 2.7 GHz (4G, WLAN) with a maximum realized gain of 4.5 dBi. For mm-waveband, the slot works as a connected slot antenna array (CSAA) by using eight periodic feeders with a wide bandwidth of 23–29 GHz (5G) and a maximum realized gain of 12.5 dBi. To enhance the functionality, two slots are orthogonally arranged for multiple-input multiple-output (MIMO) application. The whole structure is implemented using Rogers 5880 substrate with a board size of $70\times 60\times 0.381$ mm3. The envelope correlation coefficient (ECC) and isolation are calculated, showing satisfactory MIMO characteristics. The minimum ECC value is 0.01, while the isolation is more than 20 dB among different feeding ports. Due to the integration of 4G and 5G operations into a single narrow slot, the proposed antenna system is compact, simple, and planar in structure and, thus, attractive for future mobile handheld devices.

93 citations

Journal ArticleDOI
TL;DR: A frequency- and pattern-reconfigurable two-element array antenna based on a stub-loaded configuration using varactor diodes loaded with open stubs is presented, which validates the proposed concept.
Abstract: A frequency- and pattern-reconfigurable two-element array antenna based on a stub-loaded configuration is presented. The frequency-tuning mechanism is implemented using varactor diodes loaded with open stubs. Two independent bias voltages allow to independently add pattern reconfigurability to the array. This is achieved by slightly detuning the resonances of the two patches, thus introducing a beam-steering relative phase difference between them. The design is optimized for a relative frequency tuning range of $\text{10}\%$ extending from 2.15 to 2.38 GHz, within which it presents a continuously beam-steerable radiation pattern covering scanning angles from $-\text{23}^{\circ }$ to $+ \text{23}^{\circ }$ across broadside. An antenna prototype is experimentally characterized, which validates the proposed concept.

88 citations

Journal ArticleDOI
TL;DR: In this paper, a frequency and pattern-reconfigurable antenna based on a center-shorted microstrip patch is presented, which utilizes two resonance modes of a microstrip antenna with shorting vias at the patch center.
Abstract: A frequency- and pattern-reconfigurable antenna based on a center-shorted microstrip patch is presented. The novel design utilizes two resonance modes of a microstrip antenna with shorting vias at the patch center. To set up the antenna tuning mechanism, two groups of varactors with a measured tuning range of [0.149, 1.304] pF are placed at two opposite sides of the antenna, followed by open-circuited loading stubs. For a particular bias voltage configuration, the structure operates as a dual-band antenna with broadside radiation at the upper resonance frequency and monopole-like radiation at the lower band. By varying the dc bias voltage, both resonance frequencies can be changed simultaneously. Based on the proposed concept, a demonstration antenna has been designed so that the two types of aforementioned patterns can be reconfigured across a continuous fractional frequency range of more than 20%. Experimental results are provided, which validate the proposed concept and design procedure.

81 citations

Journal ArticleDOI
TL;DR: In this paper, a flexible high-permittivity dielectric substrate is developed using silicon-based poly-di-methyl-siloxane (PDMS) matrix and microscale of aluminium oxide (Al2O3) and graphite (G) powders.
Abstract: An approach toward designing and building of a compact, low-profile, wideband, unidirectional, and conformal imaging antenna for electromagnetic (EM) head imaging systems is presented. The approach includes the realization of a custom-made flexible high-permittivity dielectric substrate to achieve a compact sensing antenna. The developed composite substrate is built using silicon-based poly-di-methyl-siloxane (PDMS) matrix and microscale of aluminium oxide (Al2O3) and graphite (G) powders. Al2O3 and G powders are used as fillers with different weight-ratio to manipulate and control the dielectric properties of the substrate for attaining better matched with the human head and reducing antenna’s physical size while keeping the PDMS flexibility feature. Using the custom-made substrate, a compact, wideband, and unidirectional on-body matched antenna for wearable EM head imaging system is realized. The antenna is configured as a multi-slot planar structure with four shorting pins, working as electric and magnetic dipoles at different frequency bands. The measured reflection coefficient (S11) shows an operating frequency band of 1–4.3 GHz. The time-average power density and the amplitude of the received signal inside the MRI-based realistic head phantom demonstrate a unidirectional propagation and high-fidelity factor (FF) of more than 90%. An array of 13 antennas are fabricated and tested on a realistic 3-D head phantom to verify the imaging capability of the proposed antenna. The reconstructed images of different targets inside the head phantom demonstrate the possibility of utilizing the conformal antenna arrays to detect and locate abnormality inside the brain using multistatic delay-multiply-and-sum beamforming algorithm.

80 citations


Cited by
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01 Nov 1984
TL;DR: In this article, a substrate-superstrate printed antenna geometry which allows for large antenna gain is presented, asymptotic formulas for gain, beamwidth, and bandwidth are given, and the bandwidth limitation of the method is discussed.
Abstract: Resonance conditions for a substrate-superstrate printed antenna geometry which allow for large antenna gain are presented. Asymptotic formulas for gain, beamwidth, and bandwidth are given, and the bandwidth limitation of the method is discussed. The method is extended to produce narrow patterns about the horizon, and directive patterns at two different angles.

568 citations

Journal ArticleDOI
TL;DR: A wide overview of key early-stage concepts of metematerial-based designs as a thorough reference for specialist antennas and microwave circuits designers are provided.
Abstract: In this review paper, a comprehensive study on the concept, theory, and applications of composite right/left-handed transmission lines (CRLH-TLs) by considering their use in antenna system designs have been provided. It is shown that CRLH-TLs with negative permittivity (e <; 0) and negative permeability (μ <; 0) have unique properties that do not occur naturally. Therefore, they are referred to as artificial structures called “metamaterials”. These artificial structures include series left-handed (LH) capacitances (C L ), shunt LH inductances (L L ), series right-handed (RH) inductances (LR), and shunt RH capacitances (CR) that are realized by slots or interdigital capacitors, stubs or via-holes, unwanted current flowing on the surface, and gap distance between the surface and ground-plane, respectively. In the most cases, it is also shown that structures based on CRLH metamaterial-TLs are superior than their conventional alternatives, since they have smaller dimensions, lower-profile, wider bandwidth, better radiation patterns, higher gain and efficiency, which make them easier and more cost-effective to manufacture and mass produce. Hence, a broad range of metamaterial-based design possibilities are introduced to highlight the improvement of the performance parameters that are rare and not often discussed in available literature. Therefore, this survey provides a wide overview of key early-stage concepts of metematerial-based designs as a thorough reference for specialist antennas and microwave circuits designers. To analyze the critical features of metamaterial theory and concept, several examples are used. Comparisons on the basis of physical size, bandwidth, materials, gain, efficiency, and radiation patterns are made for all the examples that are based on CRLH metamaterialTLs. As revealed in all the metematerial design examples, foot-print area decrement is an important issue of study that have a strong impact for the enlargement of the next generation wireless communication systems.

188 citations

Journal ArticleDOI
TL;DR: In this article, a varactor-tunable second-order bandpass frequency-selective surface (FSS) for microwave frequencies is presented, which is composed of three stacked metallic layers.
Abstract: A varactor-tunable second-order bandpass frequency-selective surface (FSS) for microwave frequencies is presented in this article. The FSS is composed of three stacked metallic layers. The wire grid in each layer in combination with metallic vias provides the bias for the varactors. This configuration eliminates the need for a dedicated bias network for the varactors, and thus avoids undesirable responses associated with the added bias grid. An equivalent circuit model together with an analytical design method is provided to simplify the design procedure of the FSS. The performance of the proposed structure is experimentally validated in a parallel-plate waveguide setup. Measurements show that by changing the varactor capacitance from 0.12 to 0.38 pF, the center frequency of the filter is tuned from 5.2 to 3.7 GHz with a consistent fractional bandwidth of 9% and with an insertion loss between 3 and 6 dB.

149 citations

Journal Article
TL;DR: In this paper, the authors presented a reconfigurable antenna capable of independently reconfiguring the operating frequency, radiation pattern and polarization, using a switched grid of small metallic patches known as pixel surface as a parasitic layer to provide reconfiguration capabilities to existing antennas acting as driven element.
Abstract: This communication presents a reconfigurable antenna capable of independently reconfiguring the operating frequency, radiation pattern and polarization A switched grid of small metallic patches, known as pixel surface, is used as a parasitic layer to provide reconfiguration capabilities to existing antennas acting as driven element The parasitic pixel layer presents advantages such as low profile, integrability and cost-effective fabrication A fully operational prototype has been designed, fabricated and its compound reconfiguration capabilities have been characterized The prototype combines a patch antenna and a parasitic pixel surface consisting of 6 $\,\times\,$ 6 pixels, with an overall size of $06 \lambda \times 06 \lambda$ and 60 PIN-diode switches The antenna simultaneously tunes its operation frequency over a 25% frequency range, steers the radiation beam over ${\pm 30^\circ}$ in E and H-planes, and switches between four different polarizations ( ${\mathhat{\rm x}},$ ${\mathhat{\rm y}}$ , LHCP, RHCP) The average antenna gain among the different parameter combinations is 4 dB, reaching 6–7 dB for the most advantageous combinations The distance between the driven and the parasitic layers determines the tradeoff between frequency tuning range (12% to 25%) and radiation efficiency (45% to 55%)

140 citations