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Rodriguez D.,Arizona State University | Gorur R.S.,Arizona State University | Hansen P.M.,Systems Center
IEEE Transactions on Dielectrics and Electrical Insulation | Year: 2010

The paper reports about the role of humidity on the breakdown of air in non-uniform fields at 30 kHz - a frequency within the VLF/LF bands used for long distance communication. Experiments were conducted using rod/rod and rod/plane configurations with gap lengths ranging from 8 to 1000 mm. The results indicate that the breakdown voltage at 30 kHz is affected by humidity with varying impact based on gap length. Short (8-45 mm) gaps show a reduction in the breakdown voltage with humidity, while no significant variation is observed for long gaps (125-1000 mm). Breakdown voltages are observed to be markedly lower for 30 kHz when compared to the same gap at 60 Hz. Breakdown mechanisms for explaining this phenomenon are proposed. A correction factor to calculate breakdown voltage as a function of humidity for VLF is presented. © 2010 IEEE.

Harris F.,San Diego State University | Bologna F.,Systems Center
European Signal Processing Conference | Year: 2015

Digital receivers often contain a cascade of two filters in the base-band signal-conditioning path. The first is a square-root raised-cosine Nyquist matched filter designed to maximize SNR and suppress out-of-band interference, while the other is a decision-directed (T/2)-spaced equalizer which removes the spectral distortion introduced by the channel. This paper presents an equalizer modified to permit a single filter to converge simultaneously to a (T/2)-spaced zero forcing equalizer and a matched filter. © 2002 EUSIPCO.

Allen J.C.,Systems Center | Rockway J.W.,Systems Center
Circuits, Systems, and Signal Processing | Year: 2012

Multiport transformers offer enhanced matching capabilities for multiport loads. These transformers are analyzed to characterize wideband matching designs. An eigenvalue decomposition of the multiport load produces a geometric description of the sublevel sets of the matching transformers and identifies those frequency bands where multiport transformers are effective. A multiport antenna provides a concrete design example. © Springer Science+Business Media, LLC 2011.

Hansen P.,Systems Center | Adams R.,Systems Center
IEEE Antennas and Propagation Magazine | Year: 2011

The classic work of Chu and others has been extended to determine the minimum radiation Q for the TM case of electrically small antennas contained within a spheroid (prolate and oblate) with no energy stored inside. The results of numerical calculations have been used to give an analytic formula that can be used to determine the electrically small bound on Qr as a function of aspect ratio for prolate and oblate spheroids. These formulas have been used to develop a lower bound for antennas contained within a cylinder, and a comparison has been made to several practical antennas as a function of aspect ratio. An antenna suggested by Wheeler is shown to have the best (lowest), Qr of the antennas examined over a wide range of aspect ratios. © 2011 IEEE.

Lopez J.,Texas Tech University | Lie D.Y.C.,Texas Tech University | Meadow B.K.,Systems Center | Cothern J.,Systems Center
Proceedings of the IEEE Bipolar/BiCMOS Circuits and Technology Meeting | Year: 2010

A fully-monolithic 3-element array of coupled voltage-controlled-oscillator (VCO) network was fabricated in a 0.18μm SiGe BiCMOS process for potential use in a Rx/Tx modules. A digitally controlled on-chip passive network was designed and used for controlling the coupling strength across the array VCO units. The operational bandwidth of this core network resides in the S-Band from 1.2GHz to 1.7GHz. The integrated VCO network can be injection-locked via an external RF source to achieve excellent phase noise performance. These characteristics make this coupled-VCO network a very attractive choice for possible use in phased-array radar applications. The chip's total power consumption is 30mW (12mA at 2.5V). ©2010 IEEE.

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