Georgios C. Trichopoulos

Georgios C. Trichopoulos
Arizona State University | ASU · Department of Electrical Engineering

Electrical and Computer Engineering, PhD

About

88
Publications
9,346
Reads
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1,295
Citations
Introduction
Our group specializes in the area of electromagnetics, antennas, and microwave circuits. We focus on mmWave/THz technology and relevant applications. More specifically: Reconfigurable antennas and circuits High resolution, large-scale lensless imaging systems Non-line-of-sight imaging Skin imaging for medical applications and biometrics
Additional affiliations
August 2015 - November 2016
Arizona State University
Position
  • Professor (Assistant)
May 2013 - present
The Ohio State University
Position
  • Postodoctoral Researcher
January 2005 - July 2006
National Technical University of Athens
Position
  • Research Assistant

Publications

Publications (88)
Preprint
Full-text available
Traditional imaging systems, such as the eye or cameras, image scenes that lie in the direct line-of-sight (LoS). Most objects are opaque in the optical and infrared regimes and can limit dramatically the field of view (FoV). Current approaches to see around occlusions exploit the multireflection propagation of signals from neighboring surfaces eit...
Article
Full-text available
This study presents findings in the terahertz (THz) frequency spectrum for non-contact cardiac sensing applications. Cardiac pulse information is simultaneously extracted using THz waves based on the established principles in electronics and optics. The first fundamental principle is micro-Doppler motion effect. This motion based method, primarily...
Article
Reconfigurable intelligent surfaces (RISs) have promising coverage and data-rate gains for wireless communication systems in 5G and beyond. Prior work has mainly focused on analyzing the performance of these surfaces using simulations or lab-level prototypes. To draw accurate insights about the actual performance of these systems, this paper develo...
Preprint
Full-text available
This study presents findings at Terahertz (THz) frequency band for non-contact cardiac sensing application. For the first time, cardiac pulse information is simultaneously extracted using THz waves based on the two established principles in electronics and optics. The first fundamental principle is micro-Doppler (mD) motion effect, initially introd...
Article
Full-text available
In this work, we present a rigorous full-wave eigenanalysis for the study of nanoantennas operating at both terahertz (THz) (0.1–10 THz), and infrared/optical (10–750 THz) frequency spectrums. The key idea behind this effort is to reveal the physical characteristics of nanoantennas such that we can transfer and apply the state-of-the-art antenna de...
Preprint
Full-text available
Reconfigurable intelligent surfaces (RISs) have promising coverage and data rate gains for wireless communication systems in 5G and beyond. Prior work has mainly focused on analyzing the performance of these surfaces using computer simulations or lab-level prototypes. To draw accurate insights about the actual performance of these systems, this pap...
Article
Due to a production error, in the original article [1] , Fig. 5 was incorrectly published. We apologize for this error. The correct figure, with the corresponding caption, is shown below.
Preprint
We present a method for the mitigation of quantization lobes in single-bit reconfigurable reflective surfaces (RRSs). Typically, RRSs are planar beamforming structures consisting of hundreds or thousands of antennas with integrated tunable switches. Under plane-wave illumination, single-bit RRSs suffer from undesired side lobes or quantization lobe...
Preprint
We present a method for the mitigation of quantization lobes in single-bit reconfigurable reflective surfaces (RRSs). Typically, RRSs are planar beamforming structures consisting of hundreds or thousands of antennas with integrated tunable switches. Under plane-wave illumination, single-bit RRSs suffer from undesired side lobes or quantization lobe...
Article
Full-text available
We present an analysis of graphene-loaded transmission line switches for sub-millimeter wave and terahertz applications. As such, we propose equivalent circuit models for graphene-loaded coplanar waveguides and striplines and examine the switching performance under certain parameters. Specifically, we identify the optimum design of graphene switche...
Preprint
We present an analysis of graphene loaded transmission line switches. Namely, we propose equivalent circuit models for graphene loaded coplanar waveguides and striplines and examine the switching performance under certain design parameters. As such, the models account for the distributed effects of electrically-large shunt switches in coplanar wave...
Preprint
We present an analysis of graphene loaded transmission line switches. Namely, we propose equivalent circuit models for graphene loaded coplanar waveguides and striplines and examine the switching performance under certain design parameters. As such, the models account for the distributed effects of electrically-large shunt switches in coplanar wave...
Article
Full-text available
We present a method for the mitigation of quantization lobes in single-bit reconfigurable reflective surfaces (RRSs). Typically, RRSs are planar beamforming structures consisting of hundreds or thousands of antennas with integrated tunable switches. Under plane-wave illumination, single-bit RRSs suffer from undesired side lobes or quantization lobe...
Chapter
We present a novel non-contact probing approach for on-wafer metrology of high-speed devices and integrated circuits. The new method has been developed under the ONR DATE MURI and enables, for the first time, contact-free multi-port S-parameter measurements on-wafer. The main motivation to develop this new method was the inherent issues in the stat...
Article
The authors present a fabrication process for the development of high-frequency (>30 GHz) on-wafer graphene devices with the use of titanium sacrificial layers. Graphene patterning requires chemical processes that have deleterious effects on graphene resulting in very low yield. The authors prevent delamination of the delicate graphene from the sub...
Article
We propose a novel quasi-optical topology to enable ultra-wideband on-wafer characterization in the THz regime. Using quasi-optical components, we implement a highperformance directional coupler and a non-contact probing scheme, to interrogate on-wafer devices and circuits. The use of quasi-optics allows superior signal isolation and wideband opera...
Article
Full-text available
We present a novel imaging method for compact, low-profile imagers in millimeter wave (mmW) and terahertz (THz) frequencies. The method borrows the principles of computerized tomography (CT) to generate 2D or 3D high-resolution images using simplified RF-front-ends. To perform imaging the proposed scheme implements the projection-slice theorem. Spe...
Article
At mmW and THz band, on-wafer testing is very critical for on-wafer electronics devices and circuits as well as spectroscopy. Nevertheless, current measurement capabilities are limited by contact probe technology and vector network analyzers (VNAs). Recently, we proposed a non-contact method to tackle the issue of using expensive and brittle contac...
Article
Full-text available
Frequencies from 100 GHz to 3 THz are promising bands for the next generation of wireless communication systems because of the wide swaths of unused and unexplored spectrum. These frequencies also offer the potential for revolutionary applications that will be made possible by new thinking, and advances in devices, circuits, software, signal proces...
Preprint
Full-text available
In this work, we propose a novel approach for high accuracy user localization by merging tools from both millimeter wave (mmWave) imaging and communications. The key idea of the proposed solution is to leverage mmWave imaging to construct a high-resolution 3D image of the line-of-sight (LOS) and non-line-of-sight (NLOS) objects in the environment a...
Article
Full-text available
A hybrid full-wave/quasi-optical electromagnetic model for the design of lens-integrated THz antennas for high frequency non-contact device characterization (30 GHz – 3 THz) is presented. Experimental validation of the antenna properties (input impedance and radiation pattern) is also provided to demonstrate the accuracy of the proposed model.
Article
Full-text available
We propose a novel technique for efficient and robust modeling of multistatic, multi-dimensional, large-format millimeter-wave/terahertz (mmW/THz) imaging systems. The proposed method significantly reduces the necessary computational resources for the design of electrically large systems of multiple sensors that acquire multi-frequency images, such...
Article
The W-Band ($75-110\; \mathrm{GHz}$) sky contains a plethora of information about star formation, galaxy evolution and the cosmic microwave background. We have designed and fabricated a dual-purpose superconducting circuit to facilitate the next generation of astronomical observations in this regime by providing proof-of-concept for both a millimet...
Conference Paper
Full-text available
In this study a novel THz system is presented for 2D or 3D radar imaging. The system implements a Computerized Tomography's (CT's) algorithm that records the Radon Transform (RT) of an object and reconstructs the image using the Inverse Radon Transform (IRT). As such, the imaging system is comprised of a simple linear antenna that significantly sim...
Article
Full-text available
The aim of this paper is the investigation of nonreciprocal phenomena in anisotropically loaded 2-D periodic structures. For this purpose, our well-established 2-D curvilinear finite difference frequency domain method is combined with periodic boundary conditions and extended toward the eigenanalysis of periodic structures loaded with both isotropi...
Conference Paper
We propose a compact, low profile imaging array for active imaging applications and focused illumination capability. As such, the object scene is illuminated and imaged by the same array. The new topology allows for the implementation of densely packed, large-format sensors that operate in the millimeter (mmW) and sub-mmW region. RF sources, antenn...
Article
Full-text available
We present a broadband lumped-element parasitic equivalent circuit to accurately capture the frequency response of electromagnetic (EM) interactions inside the structure and surrounding environment of high electron-mobility transistors (HEMTs). A new mutual inductance term is included to account for the high-frequency magnetic field coupling betwee...
Article
Full-text available
We present a novel THz computed tomography system that enables fast 3-dimensional imaging and spectroscopy in the 0.6-1.2 THz band. The system is based on a new real-time broadband THz camera that enables rapid acquisition of multiple cross-sectional images required in computed tomography. Tomographic reconstruction is achieved using digital images...
Conference Paper
We present a broadband lumped-element parasitic equivalent circuit extraction procedure based on full-wave modeling of electromagnetic interactions within the pad layout of millimeter-wave high electron mobility transistors (HEMTs). The proposed method is illustrated using a conventional two-finger HEMT topology within a coplanar waveguide environm...
Conference Paper
We propose a compact endoscopic probe for tissue margin detection through reflection measurements in the terahertz band (0.1 – 3 THz). Compared to scalar reflectivity measurements, a fully polarimetric characterization of tissue and malignancy margins provides order-of-magnitude better differentiation, facilitating medical diagnosis of internal org...
Article
Full-text available
We present significant performance improvements of non-contact probes for the mmW and sub-mmW device characterization. Repeatability and accuracy of the measurement setup is studied using an automated non-contact probe system and compared with conventional contact-probes. Owing to the planar, non-contact nature of the new setup, only 2-axis automat...
Article
This paper reports on the design and performance of a terahertz (THz) linear camera with 50 pW/√Hz noise-equivalent power (NEP). This camera is sensitive to four bands of vertically and horizontally polarized THz radiation (0.22, 0.32, 0.42, and 0.52 THz). The heart of the camera is a diode-based focal plane array (FPA) that has a 10 nV thermal noi...
Article
Full-text available
We present a novel non-contact metrology approach for on-wafer characterization of sub-millimeter-wave devices, components, and integrated circuits. Unlike existing contact probes that rely on small metallic tips that make physical contact with the device on the chip, the new non-contact probes are based on electromagnetic coupling of vector networ...
Conference Paper
Full-text available
We demonstrate, for the first time, on-wafer 2-port characterization of passive millimeter wave components using a novel, non-contact measurement probe technique in the G-band (140-220 GHz). This new non-contact approach enables fast, repeatable, low-cost, wear&tear-free, robust, and large-scale evaluation of integrated circuits (IC) and devices. O...
Conference Paper
We develop a new terahertz (THz) imaging approach with 90 μm image resolution at 750 GHz using an inverse-microscope quasi-optical setup with an extended hemispherical high-resistivity silicon lens and a vector network analyzer frequency extender with horn-antenna output port. Owing to the large refractive index of silicon lens (n∼3.5), the achieve...
Conference Paper
Full-text available
We present a novel, non-contact, on-wafer device characterization method covering both THz (300 GHz-3 THz) and mmW bands (60-300 GHz). Unlike existing contact probes which rely on fragile tips and physical contact with the device on the chip, the new non-contact probe setup is based on radiative coupling of vector network analyzer test ports into t...
Conference Paper
We have developed a cost-effective, quad-frequency band THz imager for real-time THz imaging applications operating at 220GHz, 320GHz, 420GHz, and 520GHz frequency bands. The new sensor is based on antimonide-based heterostructure backward diodes impedance matched and monolithically integrated with high-gain, narrowband planar antennas. The antenna...
Conference Paper
Due to the low penetration depth of THz waves, research in biomedical THz imaging has been primarily focused on the reflection-mode spectroscopy for the diagnosis of various types of cancer (breast, skin, cervical and colon) as well as the classification of skin burns. However, alternative techniques have been around for many decades. For instance,...
Conference Paper
We present a non-contact, on-wafer, broadband device and component testing methodology scalable to the THz band. The “contactless” probe setup is based on radiative coupling of vector network analyzer test ports onto the coplanar waveguide environment of monolithic devices and integrated circuits. Efficient power coupling is achieved via planar, br...
Conference Paper
We present a hybrid full-wave/quasi-optical electromagnetic model for the design of lens-integrated THz antennas for high frequency non-contact device characterization (0.1-3 THz). The new non-contact probe setup consists of on-chip receiving and transmitting THz antennas in a co-planar waveguide environment. Commercially available THz-frequency ex...
Conference Paper
Full-text available
We present a novel approach for on-wafer device characterization in the THz band. A non-contact method eliminating the need for physical contact with test wafer is proposed. Non-contact method is based on radiative coupling of Network Analyzer's test ports into coplanar environment of monolithic device (DUT) through integrated planar THz antennas....
Conference Paper
We present a large-format focal plane array sensor for THz imaging. Each pixel of the sensor array consists of an 85μm×92μm lithographically fabricated wideband dual-slot antenna, monolithically integrated with an ultra-fast diode tuned for the 0.6-1.2 THz band. The small antenna footprint enables a densely packed THz imaging array. Concurrently, o...
Article
Full-text available
We present a large-format, sub-millimeter-resolution, focal plane array sensor for THz imaging. Each pixel in the sensor array consists of broadband THz antennas monolithically integrated with ultra-fast heterostructure backward diodes for THz sensing. With the aid of in-house hybrid electromagnetic modeling tools, the focal plane array is optimize...
Conference Paper
Sub-millimeter scale image resolution afforded by the THz frequency band, coupled with the ability of THz waves to penetrate through packaging materials have sparked significant interest in THz frequencies for security screening. Conventionally, large-format THz images have been solely acquired using a raster scan of a single pixel, taking several...
Article
Full-text available
We develop a simple and robust impedance characterization method for planar THz antennas with micron- and submicron-size port geometries. Such antennas are often encountered in THz sensing applications where an ultrafast electronic device, such as a Schottky junction or a heterostructure backward diode, is integrated with a planar antenna structure...
Conference Paper
Full-text available
We propose a contactless characterization approach for evaluating semiconductor devices and integrated circuits that operate in the THz regime (0.1-3 THz). The non-contact probe consists of on-chip receiving and transmitting THz antennas in a co-planar waveguide environment. Commercially available frequency extension modules with horn antennas are...
Conference Paper
We present the performance characterization of a large-format, sub-millimeter resolution, real-time focal plane array (FPA) sensor for THz imaging. With the aid of in-house hybrid electromagnetic modeling tools, the FPA is optimized for diffraction limited image resolution and conjugate impedance matching for highest THz sensitivity. The sensor ope...
Conference Paper
We present a new “non-contact” approach for device and circuit testing at THz frequencies. The new non-contact probe design is based on beam-tilted THz antennas integrated into the coplanar environment of the monolithic circuits and devices, such as high-speed transistors and diodes. Commercially available THz vector network analyzers (VNAs) (with...
Conference Paper
We develop a hybrid approach for computing the system-level imaging performance of THz focal plane arrays (FPAs). We use the full-wave moment method to analyze the performance of THz FPA antennas. Antenna topology is optimized for impedance matching with the integrated THz sensors and pattern matching to external optical components. The effects of...
Conference Paper
Full-text available
THz applications have been limited by the lack of a cost-effective, real-time, large format THz camera. This paper discusses the recent experimental results of a real-time (100 Hz), large-format (80x64 pixel), broadband (0.6 - 1.2THz) THz camera.
Article
Full-text available
The widespread adoption of THz based applications has been hindered by the lack of a real-time, broad-band, cost-effective THz camera with sufficient sensitivity to enable applications in markets as diverse as security, non-destructive evaluation, and biomedical imaging. This technological gap can be filled through the development of an 80 × 64 pix...
Article
Full-text available
We present an indirect port-impedance characterization technique for monolithically manufactured THz antennas. Due to the exceedingly small geometrical details, standard contact-probe measurements cannot be carried out at the desired port locations. Alternatively, several contact-probe measurements are carried out at remote locations while the inpu...
Article
Full-text available
We present an impedance characterization method for THz antennas using coplanar probe measurements. The antenna structure, which is typically monolithically integrated with detector diodes, is represented as a two-port network. The impedance seen by the diode can be analytically extracted using reflection coefficient measurements from the other rem...
Article
Full-text available
A new broadband monolithic THz antenna design that covers the entire 0.6 - 1.2 THz band is developed as the imaging pixel of THz focal plane array (FPA). Heterostructure backward diodes are integrated monolithically with the THz antennas and are used as the detectors to reproduce digital images from the 2- dimensional received power distribution. A...
Article
A novel broadband monolithic THz antenna design that covers the 0.625 THz–1.125 THz band is developed as the imaging pixel of THz focal plane array. Each pixel consists of heterostructure backward diodes monolithically integrated with impedance tuned THz antennas. Since THz responsivity of the pixel is optimized by conjugate matching between the an...