John D. Kraus

Bio: John D. Kraus is an academic researcher from Ohio State University. The author has contributed to research in topics: Radio astronomy & Radio telescope. The author has an hindex of 16, co-authored 109 publications receiving 2421 citations. Previous affiliations of John D. Kraus include University of Michigan.

Antennas For All Applications

Abstract: 1 Introduction 2 Antenna Basics 3 The Antenna Family 4 Point Sources 5 Arrays of Point Sources 6 The Electric Dipole and Thin Linear Antennas 7 The Loop Antenna 8 End Fire Antennas: The Helical Beam Antenna and the Yagi-Uda Array 9 Slot, Patch and Horn Antennas 9II Slot and Horn Antennas II 10 Flat Sheet, Corner and Parabolic Reflector Antennas 11 Broadband and Frequency-Independent Antennas 12 Antenna Temperature, Remote Sensing and Radar Cross-Section 13 Self and Mutual Impedances 14 The Cylindrical Antenna and the Moment Method (MM) 15 The Fourier Transform Relation Between Aperture Distribution and Far-Field Pattern 16 Arrays of Dipoles and of Apertures 17 Lens Antennas 18 Frequency-Selective Surfaces and Periodic Structures by Ben A. Munk 19 Practical Design Considerations of Large Aperture Antennas 20 Some Examples of Large or Unique Antennas 21 Antennas for Special Applications 22 Terahertz Antennas 23 Baluns, etc. By Ben A. Munk 24 Antenna Measurements. By Arto Lehto and Pertti Vainikainen Appendix A Tables for Reference Appendix B Books and Video Tapes Appendix C Computer Programs (Codes) Appendix D Absorbing Materials Appendix E Measurement Error

Radio astronomy receivers

Abstract: A general survey of the principles of radio astronomy receivers is presented. System noise temperature, the sensitivity of different receiver types, and the calibration of receivers are studied. A total-power receiver is analyzed as a basic radio telescope receiver and. the results are used to obtain the performance of other receiver types such as the Dicke receiver, Graham's receiver, correlation receiver, and phase-switching receiver.

The Helical Antenna

Abstract: The helix is a fundamental form of antenna of which loops and straight wires are limiting cases. When the helix is small compared to the wavelength, radiation is maximum normal to the helix axis. Depending on the helix geometry, the radiation may, in theory, be elliptically, plane, or circularly polarized. When the helix circumference is about 1 wavelength, radiation may be maximum in the direction of the helix axis and circularly polarized or nearly so. This mode of radiation, called the axial or beam mode, is generated in practice with great ease, and may be dominant over a wide frequency range with desirable pattern, impedance, and polarization characteristics. The radiation pattern is maintained in the axial mode over wide frequency ranges because of a natural adjustment of the phase velocity of wave propagation on the helix. The terminal impedance is relatively constant over the same frequency range because of the large initial attenuation of waves on the helix. The conditions for circular polarization are analyzed, and the importance of the array factor in determining the radiation pattern of a long helix is discussed.

A backward angle-fire array antenna

Abstract: A new type of array is described which consists of a grid or mesh structure situated parallel and close to a flat conducting sheet. It operates as a linearly polarized traveling-wave antenna with the main lobe of radiation in a backward angle-fire direction. The direction of the beam is a function of the frequency. Operation of the antenna is analyzed by simple array theory and comparisons are made between calculated and measured performance. An application of the array as a radio telescope antenna is mentioned.

Helical Beam Antennas for Wide-Band Applications

Abstract: The helical beam antenna has inherent broad-band properties. Over a wide frequency band the pattern shape, circularity of polarization, and terminal impedance are relatively stable. Measured performance data are presented for a medium-gain helical beam antenna of optimum dimensions with a bandwidth of about 1.7 to 1. A high-gain broadside array of four such helices is described. Other wide-band applications of helical beam antennas, including omnidirectional types, are also discussed.

Table of isotopes

Abstract: A table is presented of a complete list of the radioactive and stable isotopes, with a number of their salient features, as recorded in the literature or by private communications up to February 1958. (W.D.M.)

On the capacity improvement of ad hoc wireless networks using directional antennas

Abstract: The capacity of ad hoc wireless networks is constrained by the interference between concurrent transmissions from neighboring nodes. Gupta and Kumar have shown that the capacity of an ad hoc network does not scale well with the increasing number of nodes in the system when using omnidirectional antennas [6]. We investigate the capacity of ad hoc wireless networks using directional antennas. In this work, we consider arbitrary networks and random networks where nodes are assumed to be static.In arbitrary networks, due to the reduction of the interference area, the capacity gain is proven to be √2π/α when using directional transmission and omni reception. Because of the reduced probability of two neighbors pointing to each other, the capacity gain is √2π/β when omni transmission and directional reception are used. Although these two expressions look similar, the proof technique is different. By taking advantage of the above two approaches, the capacity gain is 2π/√αβ when both transmission and reception are directional.For random networks, interfering neighbors are reduced due to the decrease of interference area when directional antennas are used for transmission and/or reception. The throughput improvement factor is 2π/α, 2π/β and 4π2/αβ for directional transmission/omni reception, omni transmission/direc-tional reception, and directional transmission/directional reception, respectively.We have also analyzed hybrid beamform patterns that are a mix of omnidirectional/directional and a better model of real directional antennas.

Short-Range Ultra-Broadband Terahertz Communications: Concepts and Perspectives

Abstract: We propose the concept of ultra-broadband terahertz communication, based on directed non-line-of-sight (NLOS) transmissions. Potential applications of such a system supporting multi-gigabit data rates are given, and put into the context of currently emerging WLANs/WPANs. The technology and propagation constraints serve as boundary conditions for the determination of the required antenna gain to support ultra-broadband communication. Resulting high-gain antenna requirements will necessitate highly directed transmissions. We propose the use of omni-directional dielectric mirrors to support directed NLOS paths. Their performance is investigated with ray-tracing simulations of a terahertz propagation channel in a dynamic office environment, which is calibrated with measured building-material and mirror parameters. We demonstrate that a directed NLOS path scheme will make a terahertz communication system robust to shadowing. Furthermore, we show that dielectric mirrors covering only parts of the walls will significantly enhance the signal coverage in a typical indoor scenario.

Optical antenna thermal emitters

Abstract: Optical antennas are a critical component in nanophotonics research1 and have been used to enhance nonlinear2,3 and Raman4 cross-sections and to make nanoscale optical probes5. In addition to their ‘receiving’ properties, optical antennas can operate in ‘broadcasting’ mode, and have been used to modify the emission rate6 and direction7 of individual molecules. In these applications the antenna must operate at frequencies given by existing light emitters. Using thermal excitation of optical antennas, we bypass this limitation and realize emitters at infrared frequencies where sources are less readily available. Specifically, we show that the thermal emission from a single SiC whisker antenna is attributable to well-defined, size-tunable Mie resonances8. Furthermore, we derive a fundamental limit on the antenna emittance and argue theoretically that these structures are nearly ideal black-body antennas. Combined with advancing progress in antenna design, these results could lead to optical antenna emitters operating throughout the infrared frequency range. Single SiC whiskers can be made into infrared emitters by thermal excitation. The broadband thermal emission is coupled to the electromagnetic resonances of the whisker, allowing relatively narrowband emission at infrared frequencies. The emission frequency can be tuned by adjusting the size of the whiskers.