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Durgin, Gregory D.

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Now showing 1 - 5 of 5
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    Optimal sliding correlator channel sounder design
    (Georgia Institute of Technology, 2008-09) Pirkl, Ryan J. ; Durgin, Gregory D.
    The sliding correlator technique remains one of the most versatile and effective methods for sounding the radio propagation channel in next-generation wireless systems. Despite their utility, there has never been a comprehensive set of metrics and rules for the design of a sliding correlator channel sounder. This paper presents quantitative guidelines for balancing the many system parameters to achieve optimal levels of temporal resolution, dynamic range, processing. gain, and Doppler resolution. The design procedure presented at the end of the paper will allow researchers to probe the new radioscapes that result as wireless systems are pushed to higher carrier frequencies, wider bandwidths, multiple antennas, and ubiquitous operation.
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    Gains for RF tags using multiple antennas
    (Georgia Institute of Technology, 2008-02) Griffin, Joshua D. ; Durgin, Gregory D.
    Backscatter radio systems, including high frequency radio frequency identification (RFID), operate in the dyadic backscatter channel - a two-way pinhole channel that has deeper small-scale fades than that of a conventional one-way channel. This paper shows that pinhole diversity is available in a rich scattering environment caused by modulating backscatter with multiple RF tag antennas - no diversity combining at the reader, channel knowledge, or signaling scheme change is required. Pinhole diversity, along with increased RF tag scattering aperture, can cause up to a 10 dB reduction in the power required to maintain a constant bit-error-rate for an RF tag with two antennas. Through examples, it is shown that this gain results in increased backscatter radio system communication reliability and up to a 78% increase in RF tag operating range.
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    Link envelope correlation in the backscatter channel
    (Georgia Institute of Technology, 2007-09) Griffin, Joshua D. ; Durgin, Gregory D.
    High-frequency backscatter radio systems operate in the dyadic backscatter channel, a pinhole channel whose envelope probability density function and bit-error-rate performance are strongly affected by link envelope correlation – the envelope correlation between the forward and backscatter links of the dyadic backscatter channel. This paper shows that link envelope correlation is most detrimental for backscatter radio systems using co-located reader transmitter and receiver antennas and a single RF transponder antenna. It is shown that using separate reader antennas and multiple RF transponder antennas will decrease link envelope correlation effects and a near maximum bit-error-rate can be achieved with link envelope correlation less than 0.6.
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    RF tag antenna performance on various materials using radio link budgets
    (Georgia Institute of Technology, 2006) Griffin, Joshua D. ; Durgin, Gregory D. ; Haldi, Andreas ; Kippelen, Bernard
    Passive radio frequency (RF) tags in the UHF and microwave bands have drawn considerable attention because of their great potential for use in many radio frequency identification (RFID) applications. However, more basic research is needed to increase the range and reliability of a passive RF tag’s radio link, particularly when the RF tag is placed onto any lossy dielectric or metallic surface. This paper presents two new useful forms of the radio link budget that describe the power link of an RF tag system when the tag is attached to an object. These radio link budgets are dependent upon the gain penalty, a term which quantifies the reduction in RF tag antenna gain due to material attachment. A series of measurements, or radio assay, was used to measure the far-field gain pattern and gain penalty of several flexible 915 MHz antennas when attached to cardboard, pine plywood, acrylic, deionized water, ethylene glycol, ground beef, and an aluminum slab. It is shown that the gain penalty due to material attachment can result in more than 20 dB of excess loss in the backscatter communication link.
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    Wideband measurements of angle and delay dispersion for outdoor and indoor peer-to-peer radio channels at 1920 MHz
    (Georgia Institute of Technology, 2003-05) Durgin, Gregory D. ; Kukshya, Vikas ; Rappaport, Theodore S.
    This paper presents spatio-temporal measurements for the peer-to-peer radio channel at a center frequency of 1920 MHz with 140 MHz of radio-frequency bandwidth. The measurements were taken using a spread-spectrum channel sounder and an automated spatial probing system that uses precise computer- controlled positioning and orientation of omnidirectional and directional (30° beamwidth) antennas to measure both the angles-of-arrival and time-delays of multipath components. Transmitter-receiver configurations included six outdoor-to-outdoor cross-campus locations at Virginia Polytechnic Institute and State University (17–219 ns rms delay spread, 0.36–0.91 angular spread—using the unitless definition of angular spread defined in [1]), three outdoor-to-indoor locations (27–34 ns rms delay spread, 0.78–0.98 angular spread), and three indoor-to-indoor locations (29–45 ns rms delay spread, 0.73–0.90 angular spread). The paper also quantitatively describes a trend that shows how angular spread increases with increasing delay spread.