Radiowave Propagation Research Research Articles

Maximum Gain of Array Antenna With Closely Placed Dipole Elements

A double integral operation is required to obtain gain in an array antenna in general, and only an omnidirectional antenna is represented in a closed form. In this letter, as a result of radio-wave propagation research, a closed-form expression that can be applied to a small dipole antenna or a half-wavelength dipole antenna is shown by using an equation applicable to spatial correlation in a three-dimensional multipath environment. In addition, the maximum gain characteristics of the half-wavelength dipole element linear array antenna are analyzed using the equation.

Polarization Weather Radar Development from 1970–1995: Personal Reflections

The modern era of polarimetric radar begins with radiowave propagation research starting in the early 1970s with applications to measurement and modeling of wave attenuation in rain and depolarization due to ice particles along satellite–earth links. While there is a rich history of radar in meteorology after World War II, the impetus provided by radiowave propagation requirements led to high-quality antennas and feeds. Our journey starts by describing the key institutions and personnel responsible for development of weather radar polarimetry. The early period was dominated by circularly polarized radars for propagation research and at S band (frequency near 3 GHz) for hail detection. By the mid to late 70s, a paradigm shift occurred which led to the dominance of linear polarizations with applications to slant path attenuation prediction as well as estimation of rain rates and inferences of precipitation physics. The period from the early 1980s to 1995 can be considered as the “golden” period of rapid research that brought in meteorologists, cloud physicists, and hydrologists. This article describes the evolution of this technology from the vantage point of the authors. Their personal reflections and “behind the scenes” descriptions offer a glimpse into the inner workings at several key institutions which cannot be found elsewhere.

ELF and VLF radio waves

This review covers developments in ELF and VLF radio-wave propagation research over the last 50 years of the Journal of Atmospheric and Solar-Terrestrial Physics. A review of such a large field, over such a long period, cannot be fully comprehensive and the authors have therefore covered important areas which have they themselves have found interesting. The survey begins with a review of work on natural and man made sources of ELF and VLF radiation. This is followed by sections on experimental and theoretical studies of unperturbed (ambient) ELF and VLF radio propagation. Schumann resonance research, which is currently undergoing a renaissance, is then reviewed. A review of research into transient perturbations of ELF and VLF propagation follows, extending from the early work on nuclear explosions up to the current work on sprites. The review concludes with a brief summary of the VLF navigation systems of the USSR and USA, (Alpha and Omega) whose development and life-span covered most of the last 50 years.

A low cost data processing system for radio wave propagation research

A small low-cost data recording system, built around personal computers, is described for testing the European Space Agency (ESA) data acquisition (receiving) systems of the proposed experimental satellite known as Olympus. The recording system is used for observing the propagation behavior of the 12.5 GHz beacon signal of an existing communication satellite and the data of a university meteorological station. Three small units were designed; one unit to record three signals over a period of four days with a sampling rate of 1 Hz; a second for nine signals over a period of ten days with a sampling rate of 6 samples/minute, and a third unit that is still under development. An analysis program gives a quick view of the recorded signals and can store and process events (unexpected behavior of the signals). >

Radio-wave propagation research in China and the 1988 Beijing international symposium on radio propagation

Radio-wave propagation research in China and the 1988 Beijing international symposium on radio propagation

Radio-Wave Propagation during World War II

Many publications have appeared which describe the very extensive wartime radio-wave propagation research. References to some of these summaries are given which cover some aspects of this research as carried out in the United States, England, the U.S.S.R., Japan and Germany. These summaries are most complete for the work done in the United States, England and Japan. A summary is then given of some of the wartime research in the United States on direction finders and the polarization of downcoming ionospheric radio waves. This is followed by some heretofore unpublished material on Japanese ionospheric research which, by way of example, clearly indicates that an April, 1942, paper by Maeda, Uyeda and Shinkawa contains the first definite identification and interpretation of the F2-layer longitude effect. Finally a brief summary is given of a few selected topics in propagation research which arose out of the wartime development of radar.

Radio-wave propagation research in the Department of Scientific and Industrial Research during the years 1937–1946

The fundamental study of the propagation of radio waves has formed an important part of the programme of the Radio Research Board, which was established under the Department of Scientific and Industrial Research in 1920. The object of the present paper is to survey the progress made in this field during the decade ending in 1946, and to indicate the manner in which the investigations concerned have been developed to meet the requirements of those responsible for applying radio waves to various practical uses. The researches described cover the radio-frequency spectrum from about 10 kc/s up to 50000 Mc/s or more. They deal with the transmission of radio waves along the surface of the earth, and illustrate the manner in which this transmission is influenced by the electrical properties of the ground and the curvature of the earth and by the corresponding properties and slopes of natural and man-made protuberances on the ground. The characteristics of the ionosphere have been studied intensively for over twenty years, and during the past decade considerable advance has been made in our knowledge of this region of the atmosphere and of the manner in which radio waves are propagated through it. With the advance of radio technique and developments to shorter and shorter wavelengths, it has become clear that wave propagation in the lower atmosphere is greatly affected by the vertical gradient of the temperature and humidity of the air; the associated phenomena have been studied directly, and, in addition, the electrical properties of the constituents of the atmosphere, solid, liquid and gaseous, have been determined at the very high radio frequencies relevant to this portion of the investigation. Finally, the important part played by radio noise of either atmospheric or extraterrestrial origin has been studied with a view to understanding more clearly the manner and circumstances in which such noise can either influence the successful transmission of intelligence by radio waves, or provide a means of increasing our knowledge of such phenomena as those associated with thunderstorms and activity on the surface of the sun. This survey attempts to show what an important part the study of wave propagation plays in numerous applications of radio technique, and demonstrates that there is still much further work to be done before the full requirements of those using the technique can be met in a satisfactory manner.