2019 IEEE International Symposium on Measurements & Networking (M&N)
The aim of this work is to develop a gas sensor integrated into a 2.4 GHz patch antenna. The dete... more The aim of this work is to develop a gas sensor integrated into a 2.4 GHz patch antenna. The detection mechanism is to track the resonant behavior of an antenna coupled to an interdigitated capacitor (IDC) on which a sensing material is deposited. When the target gas is adsorbed on the material surface, the effective permittivity changes and a variation in the antenna resonant frequency is observed. In order to avoid compromising either the antenna performance or the sensor performance after deposition of the sensing material, the coupling between the patch radiator and the IDC should be weak. For this reason, an aperture coupled patch (ACP) antenna weakly coupled to an IDC is employed. In this paper, the authors describe the ACP antenna design and its integration with an IDC, its fabrication and testing.
Gas sensors have wide applications in several fields, spanning diverse areas such as environmenta... more Gas sensors have wide applications in several fields, spanning diverse areas such as environmental monitoring, healthcare, defense, and the evaluation of personal and occupational exposure to hazardous chemicals. Different typologies of gas sensors have been proposed over the years, such as optical, electrochemical, and metal oxide gas sensors. In this paper, a relatively new typology of gas sensors is explored: the microwave gas sensor. It consists of a combination of a microwave transducer with a nanostructured sensing material deposited on an interdigitated capacitor (IDC). The device is designed and fabricated on a Rogers substrate (RO4003C) using microstrip technology, and investigated as a microwave transducer over the frequency range from 1 GHz to 6 GHz by measuring the scattering (S) parameters in response to gas adsorption and desorption. The sensing material is based on a nano-powder of barium titanate oxalate with a coating of urea (BaTiO(C2O4)2/CO(NH2)2). It is deposited...
2017 IEEE International Instrumentation and Measurement Technology Conference (I2MTC), 2017
Graphene is a monolayer of carbon atoms with remarkable electronic and mechanical properties amen... more Graphene is a monolayer of carbon atoms with remarkable electronic and mechanical properties amenable to sensor applications. While the plasmonic nature of graphene at terahertz frequency has been widely reported, investigations on the practical utility of graphene at the microwave frequencies used in wireless sensor nodes are sparse. In this paper, graphene films with different amounts of graphene (12.5 wt%, 25 wt%) are characterized at the microwave frequencies. Dielectric spectroscopy is used to study variation in surface impedance of the film. A simple circuit model of the film based on lumped elements is obtained by fitting the measured scattering parameters with the ADS simulations on graphene loaded microstrip lines.
2017 11th European Conference on Antennas and Propagation (EUCAP), 2017
Graphene is a monolayer of carbon atoms with remarkable electronic and mechanical properties amen... more Graphene is a monolayer of carbon atoms with remarkable electronic and mechanical properties amenable to sensor applications. While the plasmonic nature of graphene at terahertz frequency has been widely reported, investigations on the practical utility of graphene at the microwave frequencies used in wireless sensor nodes are sparse. In this paper, a printed RF slot ring resonator is configured with a graphene thin-film for sensor application. The conductive losses in the graphene film are characterized by dielectric spectroscopy and considered in the design. The graphene sensing element comprising the slot ring can be integrated with control electronics as a passive wireless sensor node, but the sensor aspect is not addressed in this paper. The novelty of the paper is that RF losses are minimized by capacitively loading the ring at selective locations along its periphery. Dielectric spectroscopy is used to study variation in surface impedance of the film for various graphene loadings, and RF simulations are corroborated with measurements on graphene loaded slot ring resonators.
Wave polarization and polarimetry play vital roles in radar target identification comprising the ... more Wave polarization and polarimetry play vital roles in radar target identification comprising the three phases of target detection, discrimination, and recognition. This chapter presents an introduction to radar polarimetry emphasizing the polarization behavior as described by the scattering matrix. After a brief review of linear, circular, and elliptical polarization and the geometrical parameters of polarization ellipse, such as tilt and ellipticity angles and axial ratio, Stokes parameters and scattering matrices are introduced and explained using examples on canonical targets. The projection of polarization states on the Poincare sphere is discussed. The transformation of the scattering matrix from one polarization state basis to another (e.g., linear to circular and vice versa) is derived. Unitary transformations are applied to the scattering matrix for fully polarized targets and eigen-polarization states corresponding to maximum and minimum backscattered power are derived. The location of null polarization states on the Poincare sphere is discussed, and the Huynen polarization fork is introduced as a useful tool in the visualization of optimal polarimetric parameters. Stokes reflection or Mueller matrix is derived for partially polarized waves. The distinction between Kennaugh's and Huynen's formulations of the target scattering matrix (partially polarized case) is discussed. To demonstrate the application of radar polarimetry, the scattering matrix measurements of a cone with grooves (resembling a missile reentry vehicle) are processed to extract key features such as specular scattering and edge contributions, and the usefulness of polarimetric signatures to discriminate between coated and uncoated bodies is discussed. The polarimetric behavior of precipitation clutter, sea clutter, and ground clutter is also discussed. A radar instrumentation setup for scattering matrix measurement in block diagram form is described, and implications on the setup imposed by colocation of transmit and receive antennas for monostatic measurements and the need to measure amplitude and phase of each orthogonal channel relative to a coherent source are discussed.
AbstractThis paper presents the design of a dual frequency oscillator that simultaneously genera... more AbstractThis paper presents the design of a dual frequency oscillator that simultaneously generates rivo signals of different frequencies. The dual frequency oscillator was implemented in a novel multi layer laminate-type process technology that nses multiple ...
IEEE Transactions on Instrumentation and Measurement, 2021
Wireless sensor elements integrated with miniaturized antennas are useful in various applications... more Wireless sensor elements integrated with miniaturized antennas are useful in various applications such as wearable chemical and environmental sensors and Internet-of-Things (IoT) sensor nodes. A major problem in antenna operation is detuning of the antenna bandwidth due to loading by the sensor element. In this article, we report on the integration of an interdigitated capacitor (IDC), acting as a sensor, into an aperture coupled patch (ACP) antenna, such that weak coupling is established between the IDC and the rectangular patch resonator. Because of low mutual coupling, during the sensing process the antenna is not detuned out of its operational bandwidth and its performance is not compromised by the presence of the sensor and vice versa. A sensing material (barium titanate film) is deposited on the IDC located at the edge of the microstrip line used to slot-feed the ACP antenna. A change in the material permittivity is transduced into a variation of resonant frequency of the antenna. We describe the design and fabrication of the IDC sensor-integrated ACP antenna and demonstrate the measured sensing performance at different temperatures and relative humidity concentrations.
Non-invasive measurement of vital signs (circulatory and respiratory physiological movements of t... more Non-invasive measurement of vital signs (circulatory and respiratory physiological movements of the thorax) using Doppler radar is important to rescue missions (e.g., extricating survivors from wreckage, earthquake rubble etc.). A major challenge for biomedical radar systems is detecting the heartbeat of a subject with high accuracy. A novel algorithm based on one-dimensional (1-D) block processing state-space method (SSM) is considered in this paper to extract vital signs from data measured on a human subject using UWB radar. The 1-D block processing SSM produces range/Doppler-dependent system poles uniquely identified in a parametric manner with signal peaks at the cardiac and respiratory frequencies. It is shown that accurate estimates of vital signs can be obtained without producing high harmonics and inter-modulation products that plague signal resolution in 2-D FFT images.
Carbon nanotube sensors offer sensitivity and compactness, and provide a versatile chemical platf... more Carbon nanotube sensors offer sensitivity and compactness, and provide a versatile chemical platform for ambient monitoring of environmental pollutants such as ozone, ammonia and volatile organic compounds, known to cause acute respiratory health problems (e.g., exacerbations of asthma and COPD). The advances in electronics and the feasibility to interface complex sensor materials with low-resistance metallic contacts enable novel sensor configurations, such as passive nodes scattered on ground and remotely monitored by drones or radar. Under an NIH Grant, we are developing sensor arrays to detect ambient environmental triggers of respiratory diseases in the personal microenvironment. Our approach makes use of the unique electronic properties of single-walled nanotubes (SWNTs) and the tremendous potential to modulate their sensitivity and selectivity using tailored chemical functionalization to adsorb specific molecules. In this paper, we present the first results to demonstrate the...
In this work a preliminary study of the state space method applied to the electromagnetic cloakin... more In this work a preliminary study of the state space method applied to the electromagnetic cloaking problem is presented. A dielectric coated circular cylinder cloaked with a metasurface based on a sinusoidally modulated unit cell is considered. The state space method is used to examine the object’s scattered field and to analyze its composition in terms of specular, trapped and creeping wave modes around the cloaking working frequency.
Carbon nanotubes (CNTs) have several advantages as sensor elements, including large surface area ... more Carbon nanotubes (CNTs) have several advantages as sensor elements, including large surface area for electrical conductivity, low cost, low-temperature operation and the ability to be functionalized with a variety of polymers for enhanced sensitivity. Using CNTs several researchers have demonstrated laboratory detectors of common environmental gases such as ammonia, nitrogen and carbon dioxide. Most of these sensors are based on DC operation and do not offer the sensitivity and selectivity to be useful in ambient sensing of environmental pollutants. In this paper, the design and performance of ozone sensors comprising pristine CNTs functionalized by covalent modification with octadecylamine (ODA) groups is investigated. These CNTs are dispersed and sonicated into an ink formulation spray-coated onto interdigitated electrodes on alumina substrate. The complex AC (1 kHz) impedance of the sensor, measured under ozone exposure between 200 to 500 ppb, reveals impedance change $>50\%$ at 75°C and nearly total sensor retractability upon removal of gas exposure. The selectivity is demonstrated by cross-sensitivity determination for various gases such as methane, carbon dioxide, ammonia and water vapor.
Proceedings of National Aerospace and Electronics Conference (NAECON'94), 1994
Microstrip and coplanar transmission line components have been analyzed by the finite-difference ... more Microstrip and coplanar transmission line components have been analyzed by the finite-difference time-domain (FDTD) method. The FDTD computational mesh is truncated by imposing absorbing boundary conditions on the walls of the mesh, thus simulating outgoing waves appropriate to an open structure. The residual reflection from these boundaries introduces significant error in the frequency-domain parameters derived by Fourier transformation of the time-domain voltages and currents. In this paper, we have developed a new computationally-efficient method called the geometry rearrangement technique (GRT) to cancel the dominant contribution to such reflection. We have applied the GRT to compute the effective dielectric constant of planar transmission lines and the scattering parameters of MMIC components. The computed results have been found to be in good agreement with published data, thus indicating the effectiveness of the GRT in canceling boundary reflection. This research is applicable to efficient characterization of MMIC elements and high-density microwave and millimeter-wave packages, which are currently being investigated in aerospace research
1998 IEEE MTT-S International Microwave Symposium Digest (Cat. No.98CH36192), 1998
... IN THE FDTD ANALYSIS OF WAVEGUIDES Zhian Lin and Krishna Naishadham Department of Electrical ... more ... IN THE FDTD ANALYSIS OF WAVEGUIDES Zhian Lin and Krishna Naishadham Department of Electrical Engineering Wright State University Dayton, OH 45435 ... Here, we employ the Hanning window func-tion to alter the rising slope of the excitation from zero to steady state. ...
2010 IEEE International Symposium on Phased Array Systems and Technology, 2010
ABSTRACT Light-weight phased array antennas for aerospace applications require utilizing the same... more ABSTRACT Light-weight phased array antennas for aerospace applications require utilizing the same antenna aperture to provide multiple functions with dissimilar radiation pattern specifications (e.g., multi-band operation for communications and tracking). Multi-functional antennas provide advantages over aggregate antenna clusters by reducing space requirements, and can aid in the optimal placement of all required apertures to provide adequate isolation between channels. To achieve needed isolation between antenna bands when multiple radiators are in close proximity requires proper selection of antenna topology and the feed network design. This paper seeks to highlight design challenges in the implementation of an X-band (12 GHz) microstrip patch array into a superstrate layer covering printed dual-band slot loop antennas. We describe a novel feature in the proposed design wherein the high frequency array conforms to a specific topology allowed by lower frequency elements to create a single multi-band, multi-functional aperture.
2019 IEEE International Symposium on Measurements & Networking (M&N)
The aim of this work is to develop a gas sensor integrated into a 2.4 GHz patch antenna. The dete... more The aim of this work is to develop a gas sensor integrated into a 2.4 GHz patch antenna. The detection mechanism is to track the resonant behavior of an antenna coupled to an interdigitated capacitor (IDC) on which a sensing material is deposited. When the target gas is adsorbed on the material surface, the effective permittivity changes and a variation in the antenna resonant frequency is observed. In order to avoid compromising either the antenna performance or the sensor performance after deposition of the sensing material, the coupling between the patch radiator and the IDC should be weak. For this reason, an aperture coupled patch (ACP) antenna weakly coupled to an IDC is employed. In this paper, the authors describe the ACP antenna design and its integration with an IDC, its fabrication and testing.
Gas sensors have wide applications in several fields, spanning diverse areas such as environmenta... more Gas sensors have wide applications in several fields, spanning diverse areas such as environmental monitoring, healthcare, defense, and the evaluation of personal and occupational exposure to hazardous chemicals. Different typologies of gas sensors have been proposed over the years, such as optical, electrochemical, and metal oxide gas sensors. In this paper, a relatively new typology of gas sensors is explored: the microwave gas sensor. It consists of a combination of a microwave transducer with a nanostructured sensing material deposited on an interdigitated capacitor (IDC). The device is designed and fabricated on a Rogers substrate (RO4003C) using microstrip technology, and investigated as a microwave transducer over the frequency range from 1 GHz to 6 GHz by measuring the scattering (S) parameters in response to gas adsorption and desorption. The sensing material is based on a nano-powder of barium titanate oxalate with a coating of urea (BaTiO(C2O4)2/CO(NH2)2). It is deposited...
2017 IEEE International Instrumentation and Measurement Technology Conference (I2MTC), 2017
Graphene is a monolayer of carbon atoms with remarkable electronic and mechanical properties amen... more Graphene is a monolayer of carbon atoms with remarkable electronic and mechanical properties amenable to sensor applications. While the plasmonic nature of graphene at terahertz frequency has been widely reported, investigations on the practical utility of graphene at the microwave frequencies used in wireless sensor nodes are sparse. In this paper, graphene films with different amounts of graphene (12.5 wt%, 25 wt%) are characterized at the microwave frequencies. Dielectric spectroscopy is used to study variation in surface impedance of the film. A simple circuit model of the film based on lumped elements is obtained by fitting the measured scattering parameters with the ADS simulations on graphene loaded microstrip lines.
2017 11th European Conference on Antennas and Propagation (EUCAP), 2017
Graphene is a monolayer of carbon atoms with remarkable electronic and mechanical properties amen... more Graphene is a monolayer of carbon atoms with remarkable electronic and mechanical properties amenable to sensor applications. While the plasmonic nature of graphene at terahertz frequency has been widely reported, investigations on the practical utility of graphene at the microwave frequencies used in wireless sensor nodes are sparse. In this paper, a printed RF slot ring resonator is configured with a graphene thin-film for sensor application. The conductive losses in the graphene film are characterized by dielectric spectroscopy and considered in the design. The graphene sensing element comprising the slot ring can be integrated with control electronics as a passive wireless sensor node, but the sensor aspect is not addressed in this paper. The novelty of the paper is that RF losses are minimized by capacitively loading the ring at selective locations along its periphery. Dielectric spectroscopy is used to study variation in surface impedance of the film for various graphene loadings, and RF simulations are corroborated with measurements on graphene loaded slot ring resonators.
Wave polarization and polarimetry play vital roles in radar target identification comprising the ... more Wave polarization and polarimetry play vital roles in radar target identification comprising the three phases of target detection, discrimination, and recognition. This chapter presents an introduction to radar polarimetry emphasizing the polarization behavior as described by the scattering matrix. After a brief review of linear, circular, and elliptical polarization and the geometrical parameters of polarization ellipse, such as tilt and ellipticity angles and axial ratio, Stokes parameters and scattering matrices are introduced and explained using examples on canonical targets. The projection of polarization states on the Poincare sphere is discussed. The transformation of the scattering matrix from one polarization state basis to another (e.g., linear to circular and vice versa) is derived. Unitary transformations are applied to the scattering matrix for fully polarized targets and eigen-polarization states corresponding to maximum and minimum backscattered power are derived. The location of null polarization states on the Poincare sphere is discussed, and the Huynen polarization fork is introduced as a useful tool in the visualization of optimal polarimetric parameters. Stokes reflection or Mueller matrix is derived for partially polarized waves. The distinction between Kennaugh's and Huynen's formulations of the target scattering matrix (partially polarized case) is discussed. To demonstrate the application of radar polarimetry, the scattering matrix measurements of a cone with grooves (resembling a missile reentry vehicle) are processed to extract key features such as specular scattering and edge contributions, and the usefulness of polarimetric signatures to discriminate between coated and uncoated bodies is discussed. The polarimetric behavior of precipitation clutter, sea clutter, and ground clutter is also discussed. A radar instrumentation setup for scattering matrix measurement in block diagram form is described, and implications on the setup imposed by colocation of transmit and receive antennas for monostatic measurements and the need to measure amplitude and phase of each orthogonal channel relative to a coherent source are discussed.
AbstractThis paper presents the design of a dual frequency oscillator that simultaneously genera... more AbstractThis paper presents the design of a dual frequency oscillator that simultaneously generates rivo signals of different frequencies. The dual frequency oscillator was implemented in a novel multi layer laminate-type process technology that nses multiple ...
IEEE Transactions on Instrumentation and Measurement, 2021
Wireless sensor elements integrated with miniaturized antennas are useful in various applications... more Wireless sensor elements integrated with miniaturized antennas are useful in various applications such as wearable chemical and environmental sensors and Internet-of-Things (IoT) sensor nodes. A major problem in antenna operation is detuning of the antenna bandwidth due to loading by the sensor element. In this article, we report on the integration of an interdigitated capacitor (IDC), acting as a sensor, into an aperture coupled patch (ACP) antenna, such that weak coupling is established between the IDC and the rectangular patch resonator. Because of low mutual coupling, during the sensing process the antenna is not detuned out of its operational bandwidth and its performance is not compromised by the presence of the sensor and vice versa. A sensing material (barium titanate film) is deposited on the IDC located at the edge of the microstrip line used to slot-feed the ACP antenna. A change in the material permittivity is transduced into a variation of resonant frequency of the antenna. We describe the design and fabrication of the IDC sensor-integrated ACP antenna and demonstrate the measured sensing performance at different temperatures and relative humidity concentrations.
Non-invasive measurement of vital signs (circulatory and respiratory physiological movements of t... more Non-invasive measurement of vital signs (circulatory and respiratory physiological movements of the thorax) using Doppler radar is important to rescue missions (e.g., extricating survivors from wreckage, earthquake rubble etc.). A major challenge for biomedical radar systems is detecting the heartbeat of a subject with high accuracy. A novel algorithm based on one-dimensional (1-D) block processing state-space method (SSM) is considered in this paper to extract vital signs from data measured on a human subject using UWB radar. The 1-D block processing SSM produces range/Doppler-dependent system poles uniquely identified in a parametric manner with signal peaks at the cardiac and respiratory frequencies. It is shown that accurate estimates of vital signs can be obtained without producing high harmonics and inter-modulation products that plague signal resolution in 2-D FFT images.
Carbon nanotube sensors offer sensitivity and compactness, and provide a versatile chemical platf... more Carbon nanotube sensors offer sensitivity and compactness, and provide a versatile chemical platform for ambient monitoring of environmental pollutants such as ozone, ammonia and volatile organic compounds, known to cause acute respiratory health problems (e.g., exacerbations of asthma and COPD). The advances in electronics and the feasibility to interface complex sensor materials with low-resistance metallic contacts enable novel sensor configurations, such as passive nodes scattered on ground and remotely monitored by drones or radar. Under an NIH Grant, we are developing sensor arrays to detect ambient environmental triggers of respiratory diseases in the personal microenvironment. Our approach makes use of the unique electronic properties of single-walled nanotubes (SWNTs) and the tremendous potential to modulate their sensitivity and selectivity using tailored chemical functionalization to adsorb specific molecules. In this paper, we present the first results to demonstrate the...
In this work a preliminary study of the state space method applied to the electromagnetic cloakin... more In this work a preliminary study of the state space method applied to the electromagnetic cloaking problem is presented. A dielectric coated circular cylinder cloaked with a metasurface based on a sinusoidally modulated unit cell is considered. The state space method is used to examine the object’s scattered field and to analyze its composition in terms of specular, trapped and creeping wave modes around the cloaking working frequency.
Carbon nanotubes (CNTs) have several advantages as sensor elements, including large surface area ... more Carbon nanotubes (CNTs) have several advantages as sensor elements, including large surface area for electrical conductivity, low cost, low-temperature operation and the ability to be functionalized with a variety of polymers for enhanced sensitivity. Using CNTs several researchers have demonstrated laboratory detectors of common environmental gases such as ammonia, nitrogen and carbon dioxide. Most of these sensors are based on DC operation and do not offer the sensitivity and selectivity to be useful in ambient sensing of environmental pollutants. In this paper, the design and performance of ozone sensors comprising pristine CNTs functionalized by covalent modification with octadecylamine (ODA) groups is investigated. These CNTs are dispersed and sonicated into an ink formulation spray-coated onto interdigitated electrodes on alumina substrate. The complex AC (1 kHz) impedance of the sensor, measured under ozone exposure between 200 to 500 ppb, reveals impedance change $>50\%$ at 75°C and nearly total sensor retractability upon removal of gas exposure. The selectivity is demonstrated by cross-sensitivity determination for various gases such as methane, carbon dioxide, ammonia and water vapor.
Proceedings of National Aerospace and Electronics Conference (NAECON'94), 1994
Microstrip and coplanar transmission line components have been analyzed by the finite-difference ... more Microstrip and coplanar transmission line components have been analyzed by the finite-difference time-domain (FDTD) method. The FDTD computational mesh is truncated by imposing absorbing boundary conditions on the walls of the mesh, thus simulating outgoing waves appropriate to an open structure. The residual reflection from these boundaries introduces significant error in the frequency-domain parameters derived by Fourier transformation of the time-domain voltages and currents. In this paper, we have developed a new computationally-efficient method called the geometry rearrangement technique (GRT) to cancel the dominant contribution to such reflection. We have applied the GRT to compute the effective dielectric constant of planar transmission lines and the scattering parameters of MMIC components. The computed results have been found to be in good agreement with published data, thus indicating the effectiveness of the GRT in canceling boundary reflection. This research is applicable to efficient characterization of MMIC elements and high-density microwave and millimeter-wave packages, which are currently being investigated in aerospace research
1998 IEEE MTT-S International Microwave Symposium Digest (Cat. No.98CH36192), 1998
... IN THE FDTD ANALYSIS OF WAVEGUIDES Zhian Lin and Krishna Naishadham Department of Electrical ... more ... IN THE FDTD ANALYSIS OF WAVEGUIDES Zhian Lin and Krishna Naishadham Department of Electrical Engineering Wright State University Dayton, OH 45435 ... Here, we employ the Hanning window func-tion to alter the rising slope of the excitation from zero to steady state. ...
2010 IEEE International Symposium on Phased Array Systems and Technology, 2010
ABSTRACT Light-weight phased array antennas for aerospace applications require utilizing the same... more ABSTRACT Light-weight phased array antennas for aerospace applications require utilizing the same antenna aperture to provide multiple functions with dissimilar radiation pattern specifications (e.g., multi-band operation for communications and tracking). Multi-functional antennas provide advantages over aggregate antenna clusters by reducing space requirements, and can aid in the optimal placement of all required apertures to provide adequate isolation between channels. To achieve needed isolation between antenna bands when multiple radiators are in close proximity requires proper selection of antenna topology and the feed network design. This paper seeks to highlight design challenges in the implementation of an X-band (12 GHz) microstrip patch array into a superstrate layer covering printed dual-band slot loop antennas. We describe a novel feature in the proposed design wherein the high frequency array conforms to a specific topology allowed by lower frequency elements to create a single multi-band, multi-functional aperture.
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