
Gregory HuffTexas A&M University | TAMU · Department of Electrical and Computer Engineering
Gregory Huff
PhD, MS, BS
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117
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Publications (117)
The Swarm-enabled Distributed Sensing (SDS) project was funded to provide a feasibility study to analyze the use of a swarm as a distributed sensor array to enhance the Navy’s battlespace awareness through intelligence collection. This study informs the design of swarm-based sensors and platforms that will use them. The goal of characterizing and u...
This work investigates and analyzes collaborative beamforming for a swarm-enabled distributed sensing project. It investigates the use of a three-dimensional, randomly populated, and uniformly-distributed array in three configurations: spherical, cylindrical, and cubical. These topologies uniquely act like a practical bound to contain the elements...
Flexible hybrid electronic (FHE) materials and devices exploit the interaction of mechanical and electromagnetic properties to operate in new form factors and loading environments, which are key for advancing wearable sensors, flexible antennas, and soft robotic skin technologies. Dielectric elastomer (DE) architectures offer a novel substrate mate...
Multi-material additive manufacturing enables transformative capabilities in customized, low-cost, and multi-functional electromagnetic devices. However, process-specific fabrication anomalies can result in non-intuitive effects on performance; we propose a framework for identifying defect mechanisms and their performance impact by mapping geometri...
Recent studies demonstrate the benefit of integrating origami in many engineering applications, where computational methods facilitate the origami design process. An emerging concept utilizes origami design for physically and functionally flexible electromagnetic devices. However, coupled mechanical and electromagnetic design tools are needed to sy...
This work presents the design and fabrication of two multi-element structurally embedded vascular antennas (SEVAs). These are achieved through advances in additively manufactured sacrificial materials and demonstrate the ability to embed vascular microchannels in both planar and complex-curved epoxy-filled quartz fiber structural composite panels....
This report details a theoretical feasibility study to investigate the performance of circular antenna arrays. The radiation performance of circularly bound random arrays with various distributions are analyzed statistically to identify regions of deterministic, transitional, and random behavior.
Ring (Annular) Antenna Array, Linear Antenna Array,...
In this work a novel technique using closed form expressions is rigorously surveyed to collaboratively nullsteer uniformly distributed, planar ring and volumetric shell distributions. To assess the radiation behavior of these geometries circular tapers are of interest for their attractiveness in derivation, design, application and mathematical simp...
A polarization reconfigurable microstrip patch antenna is achieved using eutectic gallium indium (EGaIn) confined in microfluidic channels. The antenna topology is derived from an orthogonal overlay of two linearly polarized narrow-width microstrip patch antennas. The resulting structure isolated each patch around a common feed structure that has a...
Filtering of electromagnetic signals is key for improved signal to noise ratios for a broad class of devices. However, maintaining filter performance in systems undergoing large changes in shape can be challenging, due to the interdependency between element geometry, orientation and lattice spacing. To address this challenge, an origami-based, reco...
Lay-language version of our presentation on origami-inspired reconfigurable FSS on the ASA’s online press room:
https://acoustics.org/1asp-from-paper-cranes-to-new-tech-gains-frequency-tuning-through-origami-folding-kazuko-fuchi/
Embedded electromagnetic devices on adaptive structures could be an effective strategy to address increasingly demanding requirements for multi-functional aerospace components, when designed with a comprehensive understanding of the coupling between structural and electromagnetic functions. This article proposes a method to conduct coupled structur...
Frequency selective surfaces (FSS) filter specific electromagnetic (EM) frequencies are defined by the geometry and often fixed periodic spacing of a conductive element array. By embedding the FSS pattern into an origami structure, we expand the number of physical configurations and periodicities of the FSS, allowing for fold-driven frequency tunin...
This final report summarizes the activities and achievements of Grant #W911NF-09-1-0429 (“PECASE:Multifunctional Antenna Techniques”). Significant progress was made in all aspects of the proposed research program. This includes theory, design, and experiments on Aperchassis (structural antenna concepts), Antensors (sensor-antenna hybrids), and dyna...
This work examines the characteristic modes and measurement of a circular canonical family (CCF) of ad-hoc array topologies in which element radiators are used independently to deliver both sum and difference beams under lossy conditions. An associated moment generating function is derived, such that analytical patterns use even-odd symmetries for...
Two design strategies are presented to create dual-band frequency selective surfaces based on multi-arm Archimedean spirals. A single-band element is first presented as the basis for the surface. The individual arm lengths of the spirals are utilised as the primary design parameter to synthesise the passband and stopband responses. The first approa...
A nontoxic liquid metal, such as eutectic gallium-indium (EGaIn) alloy, has been used to develop tunable radio frequency (RF) components, such as antennas, inductors, or capacitors, for enabling large tunable range, better linearity, and low loss, using fluidic displacement of the liquid metal. However, EGaIn residue, due to its fast oxidation, lim...
Antenna arrays are widely used in applications such as mobile networks, radar and other wireless communication systems. Traditional phased arrays, with uniformly spaced elements, are typically used in these applications as the design approach is straightforward and control of the elements in the array is well known due to the fixed, known physical...
There are a growing number of plug-and-play options to enable wireless connectivity, but there is not a simple to use design environment for wireless that can unleash the same creative spirit that fueled the maker movement which brought additive manufacturing to the masses or the wiring/Processing moment that lowered the entry barrier for microcont...
A wideband antenna has been aerodynamically functionalized for flight capability. The antenna is based on a planar dipole/Vivaldi metallization scheme. The aerodynamic structure was based on the Nutball flier, a hobbyist flight architecture. The resulting codesign achieved a large VSWR 2∶1 bandwidth from 100 MHz to over 2 GHz and omnidirectional di...
An Unmanned Aerial System (UAS) has been developed which is based on an aerodynamically functionalized planar wideband antenna. The antenna utilizes a planar circular dipole metallization scheme. The aerodynamic structure implements a planform similar to the Nutball flier, a hobbyist flight architecture. The resulting codesign achieved a large impe...
This work examines the array behavior of randomly distributed antennas in both planar and volumetric element distributions, particularly for pattern control. The generation of sum and difference radiation patterns in radially symmetric array topologies is of particular interest, and this is explored in detail along with scanning behavior for a plan...
This work proposes a polarization-reconfigurable antenna composed of two independent, co-located, and orthogonal (“crossed”) narrow microstrip patch antennas with a novel pressure-driven fluidic loading network. Repeating and alternating high-low dielectric constant fluids in the network excite the two patches independently through capacitive coupl...
This communication examines the relationship of metal width and arm spacing of a planar printed spiral antenna on its constant input impedance. Observations on the current and electric field distribution are made first to establish the physical mechanisms responsible for the impedance behavior. An analytical model is proposed to analyze the excited...
This work examines the integration of a spherical inverted-F antenna (SIFA) and a spherical buoy structure. The resulting multifunctional antenna system includes an inertial measurement unit (IMU), microcontroller (MCU), rechargeable battery, and wireless radio. The IMU collects motion-dynamic information from the structure and relays this informat...
A uniformly distributed random planar array is analyzed using a unified probabilistic approach. The expected beam pattern and maximum peaking sidelobe is derived in closed form considering an arrangement of randomly distributed elements within a uniform distribution that are confined to a square geometry. Theoretical and numerical beampatterns are...
Random arrays bound by a spherical volume are rigorously analyzed through a stochastic approach for uniform and Gaussian element distributions. The full mathematical derivation and process to determine the array characteristics are discussed and a key result is the form solution which describes both the sidelobe behavior and main beam characteristi...
A new method for metallization of a polymer substrate has been demonstrated. This method allows for RF devices, including integrated circuits, to be fabricated on substrates which may feature microfluidic channels for cooling. Conventional hot-embossing was used to integrate copper mesh into a poly(methyl methacrylate) (PMMA), forming a microwave l...
This paper examines the transmission line structure of a planar Archimedean spiral antenna. A novel analysis is performed by unwinding the spiral into an equivalent straight transmission line to understand its impedance properties and the radiating mechanism. A relation between the input impedance of the spiral antenna and the characteristic impeda...
This paper presents an analysis of stripline Archimedean snail antenna on its impedance properties and radiation mechanism. The Archimedean snail antenna has similar structure to the spiral one but with asymmetric spiral turns. Power can be transmitted from stripline mode to spiral radiating mode because of impedance matching between the two transm...
This work proposes a novel fluidic switch topology on coplanar waveguide transmission lines for high power applications. The bridge is created from a transverse fluidic network over the coplanar waveguide containing dispersions of spherical and high aspect ratio nanoparticles. In particular, the volume fraction of gold or silver nanoparticles dispe...
An interactive framework for cognitive radio applications is proposed in which a user-equipped Android smartphone and a phased array controller are wirelessly tethered. Algorithms on the smartphone pull inertial, geolocation, and networking data to coordinate tracking and beamsteering, and the smartphone itself serves as a wireless communications b...
This article examines candidate technologies that can jointly and rapidly improve the performance of wireless networks. Specifically, the rise of pragmatic reconfigurable antenna technology tailored to mobile devices offers new possibilities in establishing reliable communication links while limiting interference to nearby users. The operation of t...
A frequency-agile antenna design is proposed that uses a fluidic-enabled reconfigurable reactive loading mechanism. The tuning mechanism offers the ability to change the capacitance of an electrically short, hollow coaxial line that is filled with a low-loss dielectric fluid. The frequency response of the antenna can be tuned by altering the materi...
While Archimedean spiral antennas were invented a half-century ago, only self-complementary impedance can be evaluated directly from the Babinet's principle. This paper examines the effects of metal width and arm spacing on printed spiral's input impedance. A model is proposed based on examination by decomposition of planar spiral. A closed-form ex...
The advent of the smartphone and its impact on manufacturing are changing the technology landscape. The cost of smartphone components has decreased drastically in recent years due to mass production. Elements that have benefited from this revolution include sensing modules. It is now reasonable to assume that advanced wireless devices are orientati...
The use of liquid metal as a switching mechanism for a frequencyreconfigurable edge-fed microstrip patch antenna designed to operate in either the 2.4 GHz ISM band or the 1.6 GHz GPS band is illustrated. A partitioned fluidic manifold bonded to the top of the antenna enables the pressure-driven displacement of a low-loss dielectric fluid and the li...
A design for a reconfigurable antenna is proposed which has polarization reconfigurability, tunable impedance bandwidth, and a modular hexagonal topology for array tiling. A fluid channel with alternating plugs of Eutectic Gallium-Indium alloy and a low-loss perfluorocarbon heat transfer fluid provide variable control of the coupling between a cent...
form only given. GPS is very powerful and provides variety of positioning services for both GPS is very powerful and provides variety of positioning services for both civilian and military purposes. Unfortunately GPS cannot reliably be used inside, because the GPS signal is seriously attenuated by many structures. Increasing demands for indoor posi...
The proposed analytical close-form solutions for the input impedance of planar two-arm Archimedean spiral antenna in free space is a function of metallization ratio and can fulfill the Babinet's principle fundamentally. Therefore, the applications of proposed model to other planar frequency-independent (FI) antennas are examined and discussed in th...
This paper investigates the effects of changing the superstrate above a sub-wavelength Archimedean spiral frequency selective surface. The first part of the paper outlines the design procedure taken to create the FSS geometry for both the band-pass and band-stop. The effects of adding a PDMS bonding layer and a fluidic channel layer above the FSS a...
This paper presents an analytical formula for quasi-static evaluation of even- and odd-mode characteristics of infinitely parallel coplanar waveguides. The analysis yields closed-form expressions based on the conformal mapping method and partial capacitance technique with quasi-TEM assumption. Calculated results show that both the even- and odd-mod...
A cavity model for a spherical inverted-F antenna (SIFA) is proposed using a custom curvilinear coordinate system. The coordinate transformation maps the spherical structure into an equivalent rectangular topology to which conventional cavity method procedures can be applied. The wave equation under this transformation is solved to predict the moda...
Electromagnetic compensation of mechanical bending and thermoregulation are examined for a deformable rectangular microstrip patch antenna. The pressure-driven transport of particles within the circulatory system of the human skin is used as a biologically-inspired model which is applied to provide both thermoregulation and compensation of physical...
This paper presents an analysis of a stripline Archimedean snail antenna on its impedance properties and radiation mechanism. The Archimedean snail antenna has similar structure to the spiral one but with asymmetric spiral turns on arm structures. Power can be transmitted from stripline mode to spiral radiating mode because of impedance matching be...
This paper proposes a quasi-static conformal mapping analysis to analytically evaluate the input resistance of Archi-medean spiral antenna at its radiation region. The deviation from the original constructs of band theory for two-wire spiral antennas leads to the concept of common slot-line mode radiation. The per-unit-length capacitance and the ch...
This paper details the analysis of a variable substrate integrated waveguide resonator enabled by dielectric material perturbations. A circuit model and closed-form expressions are developed. Fluidic dispersions composed of low dielectric oil and high dielectric particles are utilized in a prototype resonator to provide proof-of-concept demonstrati...
This letter proposes a concept for frequency-reconfigurable slot antennas enabled by pressure-driven capacitive microfluidic switches. The switches are operated by pneumatically displacing a plug of eutectic gallium indium alloy (EGaIn) within an air-filled microchannel that traverses the slot orthogonally. Frequency reconfigurability is achieved b...
Planar and volumetric arrays are for their ability to mitigate aliasing in direction of arrival (DOA) estimation using the multiple signal classification (MUSIC) algorithm. The arrangements of elements within the array are based on classic array topologies and lattice configurations native to crystal microstructures. Both an eight channel switched...
form only given. This work considers the performance of wireless communication systems that utilize reconfigurable or pattern-dynamic antennas. The focus is on finite-state channels with memory and performance is assessed in terms of discounted throughput. In a wireless setting, when a slow fading channel enters a deep fade, the corresponding commu...
This paper presents an analytical formula to evaluate even- and odd-mode characteristics of infinitely parallel coplanar waveguides (CPW) with the same dimensions in each CPW, given name as periodic coplanar waveguides (PCPW). The analysis yields a closed-form expression based on the quasi-TEM assumption and conformal mapping transformation. Calcul...
This article considers the performance of wireless communication systems that
utilize reconfigurable or pattern-dynamic antennas. The focus is on
finite-state channels with memory and performance is assessed in terms of
real-time behavior. In a wireless setting, when a slow fading channel enters a
deep fade, the corresponding communication system f...
This article examines a femtocell-based scheme as a prospective means to enhance the performance of current cellular systems. In the adopted framework, femtocells are tasked with connecting local devices to the network of a mobile operator without creating undue interference to cellular users. The access point of a femtocell only possesses limited...
Volumetric distributions of receiving antennas are investigated for their ability to mitigate aliasing and enhance the direction of arrival (DOA) estimation. Surface and volumetric distributions in canonical arrangements (cubic and spherical) of elements and configurations inspired by crystallographic lattices (cubic, tetragonal, etc.) are investig...
The design and operation of an automated system to monitor bending and coordinate fluid displacement in a flexible patch antenna is discussed. This includes the impact of mixing nano-scale particles into the fluid for electromagnetic operations on the flow rate and ability of the fluidic system to regulate the temperature of the antenna and surroun...
Geometrically bound linear, planar, and volumetric random array topologies are analyzed through a probabilistic approach to study the topological impact on beam pattern. The analysis assumes randomly distributed elements with uniform distribution to evaluate the statistically averaged beam pattern for linear, planar (square and circular), and volum...
A biologically-inspired fluidic network based on the human vascular system and transport of colloidal dispersions is proposed as an antenna reconfiguration mechanism. The impact of fluidic colloidal dispersion properties on the impedance behaviour is predicted. Trends in analytical, simulated and measured results show good agreement.
This work presents three iterations of a phase-reconfigurable reflectarray element using fluidic networks. Altering the volume fraction of colloidal dispersions within these networks creates a phase-shift in the reflected signal. The design evolution is discussed through three different design iterations. The 1st iteration demonstrates 200° of meas...
An inward-fed two-arm Archimedean spiral antenna is proposed, which integrates a stripline feed network into one of the spiral arms. A broadband stripline tapered impedance transformer conformal to the spiral's winding provides a novel matching network between the input impedance of the spiral and the characteristic impedance of the stripline. The...
A reconfigurable patch antenna with capillary structure is presented. A thermal analysis of resistive heating due to electromagnetic excitation was performed along with proposed cooling mechanism due to convective capillary thermoregulation. Simulated results are shown for transient and steady-state scenarios that link the fluids thermal properties...
A fluidic-based approach is proposed as a means to reconfigure the reflected phase of a microstrip reflectarray element. Reactive loading for reconfiguration is provided by altering the volume fraction of a fluidic colloidal dispersion within a device. Aspects of design, modeling, and measurement are discussed for a unit-cell prototype design. The...
The design and experiment of a phase reconfigurable RA unit cell enabled by a COSMIX was proposed. A phase shift of 200° was demonstrated at 3 GHz with only 1.2 dB of loss. Deviations were observed between the measured and simulated results but the trends are in agreement. The 0.4 dB baseline loss shown is a measurement of the waveguide with no pat...
This paper examines the frequency reconfiguration of an SIW bandpass filter for frequency-agile operations. Dispersions of dielectric nanoparticles are used as vertically aligned fluidic material perturbations in these devices to provide electromagnetic agility for reconfiguration. Analytical modeling, simulated, and measured data for a single-pole...
The design of wireless communication schemes tailored to real-time traffic requires an analysis framework that goes beyond the traditional criterion of data throughput. This work considers an approach that relates physical system parameters to the queueing performance of wireless links. The potential benefits of multi-rate techniques such as hybrid...
This letter proposes a coaxial stub microfluidic impedance transformer and discusses its design, theory, and operation. Electrostatically-stabilized colloidal dispersions using non-aqueous fluids facilitate its electromagnetic agility by altering their effective medium properties. Theoretical, simulated, and measured results at 400 MHz, 800 MHz, an...
The vertical displacement of a columnar fluidic colloidal dispersion is examined as a frequency reconfigurable dielectric resonator antenna (DRA). The coaxial probe-fed structure has tunable impedance properties that are reversibly controlled by adjusting the columnar height of the dispersion. Colloidal barium strontium titanate was dispersed in hy...
This work presents the design, theory, and measurement of a linearly polarized microstrip patch antenna with a substrate-integrated compensation mechanism to mitigate the detuning effects from a physical deformation (e.g., bending and twisting). In particular, we investigate the ability of an antenna to maintain its impedance bandwidth as it bends...
This work presents the design, theory, and measurement of a linearly polarized microstrip patch antenna with a substrate-integrated compensation mechanism to mitigate the detuning effects from a physical deformation (e.g., bending and twisting). In particular, we investigate the ability of an antenna to maintain its impedance bandwidth as it bends...
This letter proposes a spherical inverted-F antenna (SIFA). The radiating element of this antenna is conformally integrated onto one quadrant of a metal-coated foam sphere. The substrate has been recessed into the spherical volume to remain conformal to the spherical host chassis. Design variables are provided in spherical coordinates to describe t...
Introduction The Reconfigurable Antenna Case Studies in Reconfigurable Large Aperture Antennas Case Studies in Reconfigurable Small Aperture Antennas Advanced Reconfigurable Antenna Applications Summary References
In this work, applications involving a radiation reconfigurable antenna are presented and discussed. The antenna is capable of reconfiguring its radiation pattern from broadside to endfire over a common impedance bandwidth. After outlining the operation and radiation behavior of the single element its use in multiple antenna systems, such as multip...
This work covers the design and experiment of a finite-ground stripline-based spiral antenna with a Dyson-style balun and feed network (including broadband impedance transformer) that have been integrated into a multi-layer (via-free) structure. The spiral antenna uses the finite grounds of the stripline feed network (including the balun and impeda...