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Microwave and millimeter-wave rectifying circuit arrays and ultra-wideband antennas for wireless power transmission and communicationsRen, Yu-Jiun 15 May 2009 (has links)
In the future, space solar power transmission and wireless power transmission will
play an important role in gathering clean and infinite energy from space. The rectenna,
i.e., a rectifying circuit combined with an antenna, is one of the most important
components in the wireless power transmission system. To obtain high power and high
output voltage, the use of a large rectenna array is necessary.
Many novel rectennas and rectenna arrays for microwave and millimeter-wave
wireless power transmission have been developed. Unlike the traditional rectifying
circuit using a single diode, dual diodes are used to double the DC output voltage with
the same circuit layout dimensions. The rectenna components are then combined to form
rectenna arrays using different interconnections. The rectennas and the arrays are
analyzed by using a linear circuit model. Furthermore, to precisely align the mainbeams
of the transmitter and the receiver, a retrodirective array is developed to maintain high
efficiency. The retrodirective array is able to track the incident wave and resend the
signal to where it came from without any prior known information of the source location. The ultra-wideband radio has become one of the most important communication
systems because of demand for high data-rate transmission. Hence, ultra-wideband
antennas have received much attention in mobile wireless communications. Planar
monopole ultra-wideband antennas for UHF, microwave, and millimeter-wave bands are
developed, with many advantages such as simple structure, low cost, light weight, and
ease of fabrication. Due to the planar structures, the ultra-wideband antennas can be
easily integrated with other circuits. On the other hand, with an ultra-wide bandwidth,
source power can be transmitted at different frequencies dependent on power availability.
Furthermore, the ultra-wideband antenna can potentially handle wireless power
transmission and data communications simultaneously. The technologies developed can
also be applied to dual-frequency or the multi-frequency antennas.
In this dissertation, many new rectenna arrays, retrodirective rectenna arrays, and
ultra-wideband antennas are presented for microwave and millimeter-wave applications.
The technologies are not only very useful for wireless power transmission and
communication systems, but also they could have many applications in future radar,
surveillance, and remote sensing systems.
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Signal constellations of a retrodirective array phase modulatorKoo, Gregory Andre 05 April 2011 (has links)
A quadrature phase shift keying (QPSK) retrodirective array phase modulator (RAPM) was designed and fabricated to characterize its backscatter signal constellation when placed near objects with varying conductivities and relative permittivities. The signal constellations produced when the RAPM was placed near objects were compared to a constellation in free space to determine relative magnitude and phase changes. When conductors and high permittivity dielectrics were placed close behind the RAPM, constellation points were found to shrink in magnitude by up to twenty percent and shift in phase by up to eight degrees. When conductors were placed between the RAPM and an interrogator, the signal constellation was found to collapse, shrinking by up to 95.6 percent. For materials similar to free space, minimal constellation shrinkage resulted, but signal constellation rotation by up to 68 degrees occurred. The power consumption of a RAPM was also characterized and found to decrease as the number of bits per symbol increased. This result demonstrates that in comparison to conventional backscatter tags, which implement one bit per symbol, the RAPM can implement a greater number of bits per symbol, reduce its power consumption, and increase its range in a passive backscatter communication system. To characterize the beamwidth of the RAPM's retrodirective array, a radar cross section (RCS) measurement of the RAPM was performed over a scan angle range of -90 to +90 degrees. The structural component generated by the RAPM's patch antenna ground plane was found to dominate the antenna mode of the retrodirective array. As a result, a novel homodyne receiver based RCS measurement was performed to filter out the structural RCS component and measure the pure antenna mode of the RAPM.
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