Gregory D. Durgin

• PhD Virginia Tech 2000
• Professor at Georgia Institute of Technology

Accurate RF propagation modeling in urban environments is critical for developing digital spectrum twins and optimizing wireless communication systems. We introduce OpenGERT, an open-source automated Geometry Extraction tool for Ray Tracing, which collects and processes terrain and building data from OpenStreetMap, Microsoft Global ML Building Foot...

Discuss the general solution of the transmission line equations and explore the meaning of a “one-dimensional wave.”

Our previous lectures have considered un-energized lines, and focused on the mechanism by which they charged to a steady-state voltage. In this lecture, we consider the reverse situation: lines that are being discharged. The starting point for analyzing charged lines is the steady-state situation considered in previous lectures. In the steady-state...

Closely-spaced transmission lines exhibit parasitic capacitance and inductance that can couple signals between them. In this chapter we consider a pair of symmetrical, coupled lines and develop equations for the analysis of signals guided by those lines. One application of strong coupling is a device such as a directional coupler, useful in measure...

A common source of noise in both analog and digital systems arises from parasitic mutual capacitance and inductance between closely-spaced conductors. Mutual capacitance and inductance provides a path between two traces that are not physically connected, allowing signals to jump from one circuit to another. In the following, we develop a methodolog...

Walk through the evolution of a transmission line problem for a line terminated with a resistive load.

Up until now, we have considered transmission lines driven by DC sources. In this chapter, we turn our attention to the case of a signal with a short temporal (time) duration.

Previous chapters have explored transmission lines terminated with resistive loads. In reality, most line terminations contain some reactance, such as the shunt capacitance arising from the pads of an integrated circuit. For example, Table 8.1 shows typical values of resistance and capacitance associated with several types of digital logic. The pur...

Provide motivation by introducing the finite velocity of electrical signals and the remedy afforded by transmission line theory.

Continue to illustrate the application of transmission line theory to resistively-loaded lines excited by DC generators, using examples. Introduce power definitions, and present a variety of termination schemes that eliminate or reduce reflections from mismatched loads.

A resistively terminated transmission line system is shown in Figure 9.1. In previous chapters, we approached a resistively-loaded system by solving the appropriate equations analytically, introducing reflection coefficients and other simplifications. In the event that the load is a nonlinear device, however, we must revert back to first principles...

In circuits of even modest complexity, a transmission line will often need to be cascaded with another transmission line that has different impedance. Or the signal pathway may need to branch out to two or more separate transmission lines in a fan-out. In this chapter, we learn how to treat the junctions of these types of lines.

High-speed, accurate RF propagation models are essential for interference prediction between different spectrum users. We propose a simple and effective regression-based estimation method that can be used both for correcting errors in existing propagation models, such as the Terrain Integrated Rough Earth Model (TIREM), and also as a stand-alone em...

The IEEE Journal of Radio Frequency Identification (JRFID) hosts a Special Issue collecting journal papers that were presented at the IEEE International Conference on Digital Twins and Parallel Intelligence (DTPI) 2022 Conference , held in two simultaneous venues on opposite sides of the world on October 28-30, 2022. The first venue was in Ningbo...

This paper outlines the components of a digital spectrum twin (DST) and potential application maps that can inform automated or enhanced spectrum management decisions. The DST is fundamentally a map and image database, with environmental, measurement, and prediction maps that allow parallel intelligence operations to generate useful information usi...

This special issue in the IEEE Journal of Radio Frequency Identification (JRFID) was born as an initiative of the IEEE Council Of Radio Frequency Identification (CRFID) Technical Committee on “Motion Capture and Localization” (TC-MoCap) ( https://mocap.ieee-rfid.org/ ). The latter ( Fig. 1 ) was established in Spring 2021 to promote activities an...

This paper explains non-Keplerian orbital behavior for thin, large earth-based satellites with very low area density. We demonstrate a unique new solution that produces a new, quasi-geostationary earth orbit (QGEO) that can help with economical deployment of space solar power satellites as well as the mitigation of space debris for all satellites.

Passive backscatter radio frequency (RF) tags have been used for many terrestrial applications and have the potential for use in many identification and sensing applications in space. Passive RF tags do not require a battery, but operate by harvesting energy from an RF signal emitted by a reader and communicate by modulating the signal scattered fr...

Tunneling tags have already shown their long-range capability for communications and localization in line-of-sight (LoS) with a reader operating in the 5.8 GHz band. In this paper, a received signal phase-based positioning method is investigated using semi-passive and tunneling radio frequency identification (RFID) tags in various non-line-of-sight...

This paper introduces a wireless power transfer system using a 5-coil asymmetric topology to mitigate range limitations when powering devices requiring small coils. The efficiency of a traditionally coupled wireless power transfer system falls sharply at distances beyond the diameter of the coils used. In order to power devices requiring small pack...

Ambient Scatter Communications (ASC) is an emergent field of scatter-based-radio which promises low-power, lowcost, and “regulation-free” wireless communications. Ambient Scatter Communication Systems (ASCS) uniquely employ previously modulated and transmitted ambient RF energy as its RF carrier, creating non-trivial complexity in matters of signal...

This work demonstrates the ability to extend the positioning range of low-powered RFID tags to distances usually not achievable with other wireless or conventional RFID technologies. The technique is performed through a Received Signal Phase (RSP)-based method on a 5.8 GHz backscatter tunneling tag, in multipath-rich indoor and outdoor environments...

Simple, low-power, reliable backscatter communication systems must overcome the severe, double-fading nature of the backscatter channel. In this article, we show experimentally that when a conventional transponder is replaced by a retrodirective transponder in backscatter systems, those deep fading nulls are reduced by as much as two orders-of-magn...

Prior to the 21st century, positioning technologies had limited applications including air traffic control, air and sea navigation, satellite communications and related military uses. Today, positioning technologies have deeply merged with daily life and enabled many novel sensors, systems and services. For example, navigation systems are the enabl...

This article summarizes the history and present state of the IEEE Council on Radio-Frequency Identification (CRFID). The aim, scope, and achievement of CRFID on technical & academic activities, academic publications, and membership services & education are highlighted, which describe how CRFID commits and grows resources to achieve its goals for it...

Precise estimation of object position and orientation using RF tags is an emerging application of RFID technology. In this work, we present a novel wireless two-dimensional position and orientation estimation and tracking technique that illustrates the concept of sensor fusion —using multiple, disparate sensor measurements to synthesize a single,...

Over the past 30 years, optically transparent conductors have revolutionized electronics in many televisions, smartphones, and solar panels. These conductors are materials that simultaneously allow the transmission of light and provide electrical conductivity [1]. Transparent conducting films (TCFs), the most widely used optically transparent condu...

The round-trip nature of backscatter communications subjects the radio link to unusually severe small-scale fading. Over fading channels, the received signal envelope in backscatter-based systems such as radio-frequency identification (RFID) systems fades worse than a standard one-way communication. In this paper, we study spatial fading of the rec...

Hybrid inertial microwave reflectometry (HIMR) is one of the most promising technologies for achieving the elusive, ultimate goal of wireless localization, i.e., motion-capture grade position tracking at long-range distances. In this paper, we introduce and analyze Kalman filter-based real-time position estimators for HIMR systems. Results from mea...

The Intraoral Tongue Drive System (iTDS) is an embedded wireless tongue-operated assistive technology developed for people with tetraplegia to provide them a higher level of independence in performing daily living tasks, such as accessing computers, smartphones, and driving wheelchairs. The iTDS was built as an arch-shaped dental retainer hermetica...

Radio frequency identification (RFID) is the driving technology behind many compelling applications, such as internet-of-things (IoT), smart cities, and inventory tracking. However, it is always challenging to make a small, low-cost transceiver with little power consumption. This paper presents the design and characterization of a low-power, compac...

A robust wireless communication is critical for wireless intraoral devices since it is adversely affected by the external radio frequency (RF) interference and impedance variations of the transmitter (Tx) antenna in the dynamic mouth environment. We present a three-band (27 MHz, 433 MHz, and 915 MHz) Tx with an adaptive antenna impedance matching s...

Movement towards mm-wave backscatter communications in radio-frequency identification (RFID) systems necessitates seeking designs that compensate for the path loss introduced by the radio channel. A viable, simple, and power-efficient solution is to equip RFID tags with retrodirective arrays, which guarantee reflection with maximal gain in the dire...

This paper presents a new technique for suppressing specular reflection using binary reflective surfaces (such as those easily fabricated on a printed circuit board) that maximally suppress mean currents on the reflector using the theory of perfect pulses. We simulate multiple versions (or orders) of these structures to characterize the nulling dep...

Backscatter modulation in radio frequency identification (RFID) tags will potentially connect billions of tomorrow's devices to the Internet-of-Things. Current passive RFID systems have power constraints that limit RFID tag communication to short ranges, but these limitations can be overcome by employing reflection amplifiers. In this paper, we sho...

Movement towards mm-wave backscatter communications in radio-frequency identification (RFID) systems necessitates seeking designs that compensate for the path loss introduced by the radio channel. A viable, simple, and power-efficient solution is to equip RFID tags with retrodirective arrays, which guarantee reflection with maximal gain in the dire...

This paper presents the effects of partitioning scattering arrays with specific attention to retrodirective structures. By segmenting large arrays, total data transmission can be drastically increased while severely reducing design concerns associated with retrodirective feed networks. The behavior of partitioned retrodirective arrays is observed a...

The intraoral Tongue Drive System (iTDS), is a tongue-controlled wireless assistive technology, operated by a number of user-defined voluntary tongue gestures to issue control commands. In this paper, we present a new arch-shaped iTDS, occupying the buccal shelf space in the mouth, without limiting the available space for tongue motions. We describ...

The Simon Cipher is a low complexity, symmetric cipher that was designed for pervasive computing applications, such as RFID and IoT; however, there has not been a hardware implementation of the Simon Cipher that addresses the unique low-power and low-device count demands for RFID. We present a bit-serial hardware implementation guide and the simont...

In this paper, we explore the use of the Simon Cipher 4-block key expansion as the basis for an unkeyed hash function that is targeted toward RFID and Internet of Things applications with the benefit of reusing existing hardware. A modified Simon Cipher 4-block key expansion is used to create a construction that can be implemented to operate on the...

This paper explains how to construct and apply perfect pulses – antipodal binary waveforms with extraordinary DC-nulling properties – to an ambient scatter communications link. Several methods for employing perfect pulses in digital modulation schemes, with particular emphasis on backscatter (and simply scatter) radio modulation, are demonstrated....

The selection of channel codes for backscatter RFID tag-to-reader communications has always been preoccupied with minimal cost, low chip complexity, low power consumption, and the poor sensitivities of early-2000s RFID readers. For example, the ISO 18000-6C standard for UHF RFID tags employs FM0 modulation – an extraordinarily simple scheme that do...

Tagless identification and tracking with throughwall received signal strength-based radio tomographic imaging (RTI) allows emergency responders to learn where people are inside of a building before entering the building. Use of directional antennas in RTI nodes focuses RF power along the link line, improving system performance. However, antennas pl...

In the United States, government and commercial entities have begun sharing the 3550–3650 MHz military Radar band. The key to ensuring successful sharing is robust interference prediction based on accurate and reliable propagation models. This paper presents the results of a comprehensive propagation measurement and modeling campaign for the 3.5 GH...

Antenna detuning can be used for a variety of sensing applications. In this paper, the performance of an E-patch and a conventional patch antenna was evaluated in the presence of dielectric materials. The gain penalty and the reflection coefficient of both the antennas were simulated and measured using a vector network analyzer. The performance of...

Despite recent gains in turn-on sensitivity, passive RFID tags are approaching fundamental limits imposed by diode conversion of RF-to-DC power. However, an RF-to-thermal-to-DC energy conversion process can be shown to outperform existing diode conversion techniques at very low power levels, in terms of both conversion efficiency and output voltage...

Object localization is one of the most important applications of RFID technology. In this paper, we demonstrate how fine-scale orientation can be estimated from a multi-antenna backscatter tag. Three basic orientation changes — tag roll, pitch and yaw — were considered, where roll and pitch maneuvers were successfully identified from the direction...

Six broadband measurements were made of the transmission at 3–4 GHz between two horn antennas 30 cm above the ground through 80 cm tall grass. Water was sprayed over the tall grass, and the variation in transmission was captured as the water evaporated. The results show an increase in transmission through the wet grass of 6.5 dB at an 8 m distance....