Phased Arrays in Radar and Communication Systems. Pattern Characteristics and Synthesis of Linear and Planar Arrays. Patterns of Nonplanar Arrays. Elements, Transmission Lines, and Feed Architectures for Phased Arrays. Summary of Element Pattern and Mutual Impedance Effects. Array Error Effects. Special Array Feeds for Limited Field of View and Wideband Arrays.

Phased Array Antenna Handbook

RF harvesting circuits have been demonstrated for more than 50 years, but only a few have been able to harvest energy from freely available ambient (i.e., non-dedicated) RF sources. In this paper, our objectives were to realize harvester operation at typical ambient RF power levels found within urban and semi-urban environments. To explore the potential for ambient RF energy harvesting, a city-wide RF spectral survey was undertaken from outside all of the 270 London Underground stations at street level. Using the results from this survey, four harvesters (comprising antenna, impedance-matching network, rectifier, maximum power point tracking interface, and storage element) were designed to cover four frequency bands from the largest RF contributors (DTV, GSM900, GSM1800, and 3G) within the ultrahigh frequency (0.3-3 GHz) part of the frequency spectrum. Prototypes were designed and fabricated for each band. The overall end-to-end efficiency of the prototypes using realistic input RF power sources is measured; with our first GSM900 prototype giving an efficiency of 40%. Approximately half of the London Underground stations were found to be suitable locations for harvesting ambient RF energy using our four prototypes. Furthermore, multiband array architectures were designed and fabricated to provide a broader freedom of operation. Finally, an output dc power density comparison was made between all the ambient RF energy harvesters, as well as alternative energy harvesting technologies, and for the first time, it is shown that ambient RF harvesting can be competitive with the other technologies.

Ambient RF Energy Harvesting in Urban and Semi-Urban Environments

Far-field patterns and Gaussian-beam coupling efficiencies are investigated for a double-slot antenna placed on hemispherical lenses with varying extension lengths. The radiation patterns of a double-slot antenna on a silicon dielectric lens are computed using ray-tracing inside the dielectric lens and electric and magnetic field integration on the spherical dielectric surface. The measured radiation patterns at 246 GHz and Gaussian-beam coupling efficiencies show good agreement with theory. The theoretical results are presented in terms of extension-length/radius and radius/ lambda , and therefore result in universal design curves for silicon lenses of different diameters and at different frequencies. The theoretical and experimental results indicate that for single units, there exists a wide range of extension lengths which result in high Gaussian-coupling efficiencies (50-60%) to moderately high f 's. These Gaussian-coupling efficiencies can be increased to 80-90 degrees % with the use of a lambda /sub m//4 matching-cap layer. For imaging array applications with high packing densities, an extension-length/radius of 0.38 to 0.39 (depending on frequency) will result in peak directivity and a corresponding Gaussian-coupling efficiency 15-20% lower than for single units. >

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Double-slot antennas on extended hemispherical and elliptical silicon dielectric lenses

The multiband behavior of the fractal Sierpinski (1915) antenna is described. Due to its mainly triangular shape, the antenna is compared to the well-known single-band bow-tie antenna. Both experimental and numerical results show that the self-similarity properties of the fractal shape are translated into its electromagnetic behavior. A deeper physical insight on such a behavior is achieved by means of the computed current densities over the antenna surface, which also display some similarity properties through the bands.

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On the behavior of the Sierpinski multiband fractal antenna

Many modern satellite and terrestrial point-to-point communications systems use circular polarization (CP) wave propagation in order to maximize the polarization efficiency component of the link budget. Therefore, in an undergraduate electromagnetics syllabus, an introduction to the topic of circular polarization is necessary to promote an understanding of the propagation aspects of modern communications system design. Students new to the antennas and propagation discipline often have difficulty in grasping the concept of CP; therefore, in this paper, the essential aspects of this topic are reinforced by a tutorial description of CP in terms of wave propagation, antenna properties, and measurement techniques. A simple laboratory-based project is described that requires the design, fabrication, and measurement of a crossed dipole antenna. The measured input impedance and radiation patterns are correlated with theory to highlight the conditions necessary to support CP wave propagation. By combining basic electromagnetic concepts with a series of simple intuitive laboratory experiments, the students can more easily visualize, and hence understand, CP wave propagation and its use in communications systems design.

Understanding and measuring circular polarization

Introduction to Antennas.Fundamentals of Antennas.Arrays of Discrete Elements.Dipoles and Monopoles.Loop Antennas.Small Antennas.Microstrip Antennas.Slot Antennas.Slot-Antenna Arrays.Leaky-Wave Antennas.Long-Wire Antennas.Surface-Wave Antennas and Surface-Wave Excited Arrays.Helical Antennas.Frequency-Independent Antennas.Horn Antennas.Lens Antennas.Reflector Antennas.Feeds for Lenses and Reflectors.Electromechanical Scanning Antennas.Frequency-Scan Antennas.Phased Arrays.Conformal and Low-Profile Arrays.Adaptive Antennas.Methods of Polarization Synthesis.Low-Frequency Antennas.Medium-Frequency Broadcast Antennas.High-Frequency Antennas.VHF and UHF Communications Antennas.TV and FM Transmitting Antennas.TV Receiving Antennas.Microwave-Relay Antennas, Radiometer Antennas.Radar Antennas.Microwave Beacon Antennas.Tracking Antennas.Satellite Antennas.Earth Station Antennas.Aircraft Antennas.Seeker Antennas.Direction-Finding Antennas and Systems.ECM and ESM Antennas.Radio-Telescope Antennas.Transmission Lines and Waveguide.Impedance Matching and Broadbanding.Radomes.Microwave Propagation.Antenna Measurements.Materials and Design Data.

Henry Jasik

Papers

Antenna engineering handbook