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Multiple and time-varying spectral nulls have been observed in wideband HF-NVIS channel. These nulls cause rapid fading in narrowband HF-NVIS links. This paper offers one physical explanation of these observations — the rapid fading is caused by interference between the ordinary (O mode) and extraordinary (X mode) waves carrying the signal in opposite sense polarization at the receiver. This explanation...
This work presents a comparison of RCS and Doppler spectrograms of a 10 m tall Vertical Axis Wind Turbine using the Physical Optics and Multilevel Fast Multipole Method numerical techniques. The MLFMM results are then compared with measurements. Simulations and measurements were performed at 1.5GHz, 3.6GHz, 5.8GHz, and 9.7GHz corresponding to electrical dimensions of 50λ–323λ. The average RCS using...
Channel measurements of 2×2 MIMO channels at 300 MHz in an urban environment are made with the purpose of comparing the usable degrees of freedom in the channel to simulation and to assess suitability of MIMO in outdoor UHF channels. It was found that the average measured condition number over the receiver path was 16.7 dB while the mean condition number for a 2×2 uncorrelated Rayleigh fading environment...
This work presents the capacity achieved in a 3-D simulation of BS-MIMO versus conventional MIMO and SISO. An ESPAR antenna was used as the directional antenna in the BS-MIMO configuration for both the transmitter and the receiver. The MIMO and SISO configuration used dipole antennas. The channel of each configuration was calculated in a 3-D model of Rosslyn, VA. The channel results were then used...
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