New large-scale CO surveys of the first and second Galactic quadrants and the nearby molecular cloud complexes in Orion and Taurus, obtained with the CfA 1.2 m telescope, have been combined with 31 other surveys obtained over the past two decades with that instrument and a similar telescope on Cerro Tololo in Chile, to produce a new composite CO survey of the entire Milky Way. The survey consists of 488,000 spectra that Nyquist or beamwidth ( °) sample the entire Galactic plane over a strip 4°-10° wide in latitude, and beamwidth or ° sample nearly all large local clouds at higher latitudes. Compared with the previous composite CO survey of Dame et al. (1987), the new survey has 16 times more spectra, up to 3.4 times higher angular resolution, and up to 10 times higher sensitivity per unit solid angle. Each of the component surveys was integrated individually using clipping or moment masking to produce composite spatial and longitude-velocity maps of the Galaxy that display nearly all of the statistically significant emission in each survey but little noise. The composite maps provide detailed information on individual molecular clouds, suggest relationships between clouds and regions widely separated on the sky, and clearly display the main structural features of the molecular Galaxy. In addition, since the gas, dust, and Population I objects associated with molecular clouds contribute to the Galactic emission in every major wavelength band, the precise kinematic information provided by the present survey will form the foundation for many large-scale Galactic studies. A map of molecular column density predicted from complete and unbiased far-infrared and 21 cm surveys of the Galaxy was used both to determine the completeness of the present survey and to extrapolate it to the entire sky at |b| 5°), X shows little systematic variation with latitude from a mean value of (1.8 ± 0.3) × 1020 cm-2 K-1 km-1 s. Given the large sky area and large quantity of CO data analyzed, we conclude that this is the most reliable measurement to date of the mean X value in the solar neighborhood.

https://iopscience.iop.org/article/10.1086/318388/pdf

The Milky Way in Molecular Clouds: A New Complete CO Survey

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

A theore tical analysis is made of the effect of antenna s ize on parameters such as gain, bandwidth, and efficiency . Both near-zone and far-zon e direct ive gains are considered . It is found that t he maximum gain obtainable from a broad-band antenna is approxima tely equal t o that of the uniformly illumina ted aper t ure. If higher gain is desired , the antenna mus t necessarily be a narrow-band device. In fact, th e input impedance becomes frequency sensitive so r apidly that, for large antennas, no significant increase in gain over tha t of the uniformly illuminated aper t ure is possible. Also, if t he antenn a is lossy, t he efficiency falls rapidly as the gain is increased over that of the uniformly illumina ted aperture.

/pdf/effect-of-antenna-size-on-gain-bandwidth-and-efficiency-xloahnda8i.pdf

Effect of antenna size on gain, bandwidth, and efficiency

We present quantitative predictions of the performance of nanotubes and nanowires as antennas, including the radiation resistance, the input reactance and resistance, and antenna efficiency, as a function of frequency and nanotube length. Particular attention is paid to the quantum capacitance and kinetic inductance. We develop models for both far-field antenna patterns as well as near-field antenna-to-antenna coupling. In so doing, we also develop a circuit model for a transmission line made of two parallel nanotubes, which has applications for nanointerconnect technology. Finally, we derive an analog of Hallen's integral equation appropriate for single-walled carbon nanotube antennas

Quantitative theory of nanowire and nanotube antenna performance

Aspects of the subject disclosure may include, for example, receiving, by a feed point of a dielectric antenna, electromagnetic waves from a dielectric core coupled to the feed point without an electrical return path, where at least a portion of the dielectric antenna comprises a conductive surface, directing, by the feed point, the electromagnetic waves to a proximal portion of the dielectric antenna, and radiating, via an aperture of the dielectric antenna, a wireless signal responsive to the electromagnetic waves being received at the aperture. Other embodiments are disclosed.

Method and apparatus for coupling an antenna to a device

* Chapter 1: Survey of microwave antenna design problems * Chapter 2: Circuit relations, reciprocity theorems * Chapter 3: Radiation from current distributions * Chapter 4: Wavefronts and rays * Chapter 5: Scattering and diffraction * Chapter 6: Aperture illumination and antenna patterns * Chapter 7: Microwave transmission lines * Chapter 8: Microwave dipole antennas and feeds * Chapter 9: Linear-array antennas and feeds * Chapter 10: Waveguide and horn feeds * Chapter 11: Dielectric and metal-plate lenses * Chapter 12: Pencil-beam and simple fanned-beam antennas * Chapter 13: Shaped-beam antennas * Chapter 14: Antenna installation problems * Chapter 15: Antenna measurements - techniques * Chapter 16: Antenna measurements - equipment

Microwave antenna theory and design

During World War II intensive efforts of radio engineers and physicists resulted in the invention of many new types of antennas and in advances in fundamental antenna theory. The paper presents the results of this work in relation to the principal problem areas that were recognized during that period: 1) sidelobe suppression; 2) beam-shaping techniques; 3) beam-scanning techniques; 4) broadbanding; 5) antenna siting. In each of these areas major advances were made, both in operating hardware and in theoretical understanding.

Contributions to the Antenna Field during World War II

Expressions are derived for the external field produced by a slot of arbitrary shape in the wall of a circular wave guide (of infinite extent and infinite conductivity), the tangential components of the electric field in the slot being assumed to have been prescribed. This is accomplished by matching a Fourier representation of the external field, built up by superposition of basic sets of cylindrical waves, to a Fourier expansion of the prescribed field over the surface of the cylindrical wave guide. The far‐zone field is obtained by applying the method of steepest descent to the Fourier integrals that constitute the coefficients in the expansion for the external field. The results satisfy the radiation conditions for far‐zone fields.

The External Field Produced by a Slot in an Infinite Circular Cylinder

Various studies of diffraction of electromagnetic waves motivated by and applied to work on microwave aperture antennas are reviewed in relation to their significance to the study of optics. A critique of the Kirchhoff formula is presented to show the essentially heuristic nature of the formula and its range of applicability. Other approaches to high-frequency approximations for diffraction problems are indicated together with various experimental results showing the structure of the electromagnetic field in the neighborhood of the aperture or scatterer. The results illustrate how studies in the microwave region have enlarged the scope of optics and provide a rich body of material for teaching the subject of diffraction in physical optics.

Microwave aperture antennas and diffraction theory.

The problem of determining a harmonic time-varying electromagnetic field where the electric vector assumes prescribed values for its tangential components over given spherical or conical boundaries and which has proper radiation characteristics at infinity is considered by a procedure very much like that used in the theory of slots in waveguide walls. The technique used in solving this type of boundary value problem is to establish, by an application of the Lorentz Reciprocity Theorem, a Green's function which represents the electric and magnetic fields of a point generator (infinitesimal dipole) applied at an arbitrary position on the conducting surface where the fields satisfy homogeneous boundary conditions. The total fields for an arbitrary source are then obtained by superposition; i.e., direct integration over the aperture. Since detailed results for the case of a sphere have been obtained by many authors, we confine the details of the technique to the infinite cone. It is assumed that in each case the tangential components of the electric vector are given functions over the entire boundary surface. The results apply directly to the theory of radiating apertures in a perfectly conducting spherical wall or a cone, since the tangential components of the electric vector are different from zero only in the area of the aperture, where it is presumed they are known. The results are also applicable to scattering by conducting spheres and cones, since the tangential electric field components over the boundary surfaces are the negative of those of the incident field. To illustrate the applicability and the limitations of the results, we shall present the formal solutions for arbitrarily shaped apertures on cones and apply them to the several types of delta slots which are usually discussed in connection with other radiating structures.

S. Silver

Papers

Microwave antenna theory and design

Contributions to the Antenna Field during World War II

The External Field Produced by a Slot in an Infinite Circular Cylinder

Microwave aperture antennas and diffraction theory.

Exterior electromagnetic boundary value problems for spheres and cones