A5081281241- Indoor and Outdoor Localization Technologies
- Antenna Design and Analysis
- RFID technology advancements
- Microwave Imaging and Scattering Analysis
- Energy Harvesting in Wireless Networks
- Ultra-Wideband Communications Technology
- Full-Duplex Wireless Communications
- Millimeter-Wave Propagation and Modeling
- Terahertz technology and applications
- Metamaterials and Metasurfaces Applications
- Microwave and Dielectric Measurement Techniques
- Radio Wave Propagation Studies
- Power Line Communications and Noise
- Advanced SAR Imaging Techniques
- Wireless Power Transfer Systems
- Antenna Design and Optimization
- Image Processing Techniques and Applications
- Radio Frequency Integrated Circuit Design
- Immunotherapy and Immune Responses
- Radar Systems and Signal Processing
- Superconducting and THz Device Technology
- Spacecraft Design and Technology
University of Washington
2016-2018
Intellectual Ventures (United States)
2017-2018
Seattle University
2016
Duke University
2013
Applied Radar (United States)
2013
Graz University of Technology
2009-2012
Signal Processing (United States)
2008-2011
Institut für Informationsverarbeitung
2010
Abstract We demonstrate a low-profile holographic imaging system at millimeter wavelengths based on an aperture composed of frequency-diverse metasurfaces. Utilizing measurements spatially-diverse field patterns, diffraction-limited images human-sized subjects are reconstructed. The is driven by single microwave source swept over band frequencies (17.5–26.5 GHz) and switched between collection transmit receive metasurface panels. High fidelity image reconstruction requires precise model for...
In this paper, we present the extension of a recently published two-frequency continuous-wave (CW) ultra-high-frequency RF identification ranging technique to multiple carriers. The proposed system concept relies on exact phase information; hence, passive tag cannot be accurately modeled as frequency-flat linear device. A linearized model tag's reflection coefficient is devised bridge gap between nonlinear reality and CW radar theory. Estimation error bounds are derived effects caused by...
In this paper the impact of signal bandwidth on performance frequency modulated continuous wave (FMCW) radar based ranging to ultra high (UHF) radio identification (RFID) tags is investigated. The analyses are ultra-wideband (UWB) channel measurements performed in a warehouse portal, which severe multipath environment. It illustrated that available usual ISM bands at 900 MHz, 2.5 GHz and 5.8 only sufficient for precise RFID tag localization if moderate or low conditions given. However,...
Emerging metasurface antenna technology enables flexible and low cost massive multiple-input multiple-output (MIMO) millimeter-wave (mmW) imaging for applications such as personnel screening, weapon detection, reconnaissance, remote sensing. This work proposes an orthogonal coded active illumination (OCAI) approach which utilizes simultaneous, mutually transmit signals to illuminate the scene being imaged. It is shown that OCAI robust code amplitude phase imbalance introduced by imperfect...
A proof of concept for ultra-wideband (UWB)-based ranging in passive UHF RF identification (RFID) is presented. The proposed method uses the tag's backscatter modulation and thus does not require processing UWB signal by tag. It evaluated using measurements an indoor environment similar to a warehouse portal terms channel impulse responses. accuracy comparable classical inherently robust multipath propagation.
A comprehensive characterization and model of the UHF RFID channel is presented for narrowband through ultra-wideband tag localization systems. The analyses are based on measurements in a warehouse portal, centered around 900 MHz. Measured scenarios include an electromagnetically transparent pallet containing liquids, each portal shielded by metal backplanes absorbing material. cover individual channels to from tag, feedback channel, backscatter bi- monostatic reader setups. We find that...
Since the time of Nikola Tesla, dream ubiquitous wireless power transfer (WPT) has tantalized generations inventors and engineers. A practical, WPT infrastructure could offer tremendous benefits for mobile devices, such as extending battery lifetime, on-the-fly recharging, or, in some cases, eliminating batteries pesky charging cords altogether. But these can be achieved only if spatial temporal distribution controlled. The authors consider approaches to achieving control over long-range...
We present an efficient method for enhancing far-field wireless power transfer (WPT) to highly power-constrained mobile devices such as UHF and microwave RFID transponders using a multiple-input-multiple-output (MIMO) base station system. Existing techniques channel estimation are prohibitively complex consume too much be integrated into milliwatt- or microwatt-class wirelessly powered devices. show that can optimized transponder's backscatter signal alone, without requiring measurement...
The wireless channel of backscatter radio systems is a two-way pinhole channel, created by the concatenation two standard channels. We present method to calculate wideband parameters channels based on constituent one-way focus characteristics that are vital for narrowband and ranging, such as K-factor w.r.t. direct (line-of-sight) path RMS delay spread. presented analyses include uncorrelated well correlated pairs thus valid bistatic monostatic antenna setups. also show scattering (US)...
We present a detailed analysis of an indoor UWB channel measurement campaign. The focus is on the modeling deterministic part multipath using a-priori known relevant reflections and scatterers, found from available floor plan. Our approach uses virtual signal sources, whose locations visibilities can be calculated simple ray-launching techniques. steps exploit these results, effective cancellation method that introduces virtually no artifacts. show corresponding multipath-components explain...
This paper presents an extension of synthetic aperture radar (SAR) techniques to enable simultaneous imaging, sensor tag localization, and backscatter-based data uplink from multiple tags in a cluttered environment. A unified system model is presented that leverages coherent processing backscattered signals gathered over the for all three these purposes. The proposed approach, using balanced orthogonal codes SAR-based localization as well backscatter uplink, shown have several favorable...
We present a method for enhancing far-field wireless power transfer (WPT) to nonlinear, passive UHF RFID backscatter transponders using multi-input multi-output (MIMO) base station. The proposed does not require on-tag measurements or channel estimation, either of which would add significant complexity and consumption microwatt-class wirelessly powered devices such as tags. show in measurement-based proof concept that WPT optimization nonlinear is possible solely based on the signal, without...
We present a 5.8 GHz Fresnel-zone microwave wireless power transfer experiment leveraging large planar holographic metasurface reflectarray to form focused spot at distance of 6.5 m. The 1.5 m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> is fabricated from 15 panels having total dimensions 122×127 cm, and comprised over 4,000 reflective patch resonators on the top surface 3.0 mm thick FR-4 substrate. A constrained hologram approach...
We present a low cost X-band microwave backscatter communication testbed incorporating integrated planar wideband bow-tie antennas. This leverages silicon germanium (SiGe) circuits intended for the satellite television market to provide an experimental capability experimentation in 10.0 GHz 11.1 band. The antennas have 10 dB return loss bandwidth of 9.63-13.15 and gain 6 dBi. transmitter consists single-chip frequency synthesizer buffer amplifier with output power -2 dBm. receive...
We present a localization and multiple access method for backscatter sensor networks based on synthetic aperture radar (SAR) techniques. Two tags, each consisting of wideband bow-tie antenna, PIN switch, an Arduino Nano, were designed indoor measurement over the 10–13 GHz band. With size 0.6 m, tags can be imaged separately or in combination at ranges up to 4 m. A cross-range resolution 8 cm range 4.6 achieved with errors less than cm.
High-accuracy localization remains a much desired but elusive feature for passive radio transponders as used in radio-frequency identification (RFID). We believe that the principle of cognitive radar can overcome fundamental physical limitations hindering its implementation. propose to jointly employ narrowband interrogate and an adaptive (ultra) wideband backscatter target tracking actuating, sensing, learning environment. This paper explores system model key processing perception-action...
Real time locating systems (RTLS) and wireless sensor networks are currently a hot challenging research topic. Ultra wideband (UWB) shows promising properties for these systems, such as low-power transmitter designs highly accurate ranging, where cm-level accuracy is achievable even in multipath intensive environments. A high-performance reference receiver architecture based on coherent processing presented this paper. It used to define quality metrics of the received signals, example peak...
A chip manufacturing process requires extensive support of CAD-tools in order to predict the behavior embedded circuitry and ensure intended system functionality. Past experience shows that overall performance UHF RFID systems is mainly limited by multipath propagation detuning. In this context, system-level simulations are vital assess improve circuit. We present a simulator framework capable handling chip-level tag models, fading MIMO radio channels, interrogator building blocks on signal...
Computational imaging is a proven strategy for obtaining high-quality images with fast acquisition rates and simpler hardware. Metasurfaces provide exquisite control over electromagnetic fields, enabling the radiated field to be molded into unique patterns. The fusion of these two concepts can bring about revolutionary advances in design systems security screening. In context computational imaging, each pattern serves as single measurement scene; scene then interpreted estimating...
We present a modulated ultrawideband backscatter calibration target (fiducial) intended for group delay in large-aperture multitransceiver millimeter-wave imagers. The fiducial is designed to resemble point scatterer across the K-band (17.5-26.5 GHz). Multiple such fiducials may be used mitigate thermal and mechanical drift multiple transceivers comprising imager. This approach allows tracking removing both time-varying amplitude phase RF hardware associated cables. Backscatter modulation of...
Undesired local oscillator (LO) leakage and dc offset impairments are commonly observed when direct conversion (or homodyne) receivers (RXs) used for coherent millimeter-wave (mmW) active imaging, particularly severe imaging short-range, slow-moving targets where the target's baseband response is close to dc. This letter proposes a binary phase shift keying (BPSK) coding scheme, which modulates illumination source mitigate self-jamming in receiver I/Q demodulator. modulation permits...