Radio Propagation Studies Research Articles

GPS phase-delay measurement: Technique for the calibration and analysis in millimetre-wave radio propagation studies

Observation of phase delay from GPS satellites, followed by signal and data processing allows the quantity of water vapour in the atmosphere to be continuously monitored. At millimetre-wavelengths, water vapour has significant impact on radiowave propagation, along with rain, cloud and oxygen. Comparisons are presented of integrated precipitable water vapour measured by GPS with a co-sited radiometer and with radiosonde measurements from a nearby site. Data are also presented in which the liquid water (cloud and rain) attenuation is separated from radiometer predicted total attenuation using the measurement of water vapour by GPS. The GPS technique thus represents a new tool to study radiowave propagation, and aids in the calibration of radiometers operating in frequency bands that are sensitive to water vapour.

Results from clear-air propagation studies on Franco–UK paths at 1.3 and 11 GHz

The paper presents results from statistical studies of radio propagation at frequencies between 1.3 GHz and 11.7 GHz on radio paths of 153-297 km, with data collected over 8 years. Data from the first 3 years were used in COST Project 210 and related to annual average conditions. More recent data, included in the paper, have been used to study worst month statistics, signal attenuation in propagation over coastal zones and 1.3/11.7 GHz frequency scaling.

High-Performance Computing and Plasma Physics

The physics of ionized gases is a relatively new science. Not until the development of the electrical industry were controlled experiments on ionized gases possible, and so plasma physics is only about 100 years old. The early part of this century saw some pioneering studies of gas discharges and radio propagation in the ionosphere. However, the real impetus came with the initiation of the controlled thermonuclear reaction programs in the 1950s and with the discoveries of the Van Allen belts and the solar wind in the 1960s. Studies in these areas showed that plasma behavior is much more complex than had been anticipated.

Statistical AR models for the frequency selective indoor radio channel

A statistical model of the indoor radio channel is proposed that is derived from a second order autoregressive process representation of the channel frequency response. The accuracy of the statistical model is examined by comparing the cumulative distribution functions of the RMS delay spread and the 3dB width of the frequency correlation function computed from the regenerated data with that of the measurements performed in two indoor radio propagation studies in the 0.9–1.1 GHz band.

Experimental studies of daytime LF radio propagation and their implications for D-region electron densities

Measurements are presented of interference phenomena in amplitude and phase of VLF and LF signals along propagation paths from central England to the Norwegian Sea. The data are interpreted by means of the ‘wave-hop’ propagation theory, incorporating full wave evaluation of ionospheric reflection coefficients with realistic D-region models. No published electron density profiles are found which completely satisfy the experimental data, but modified profiles are presented which provide a better fit to the observations.

New algorithm for (9 GHz) range-gated radar system

A new rain rate estimation algorithm is presented for simple terrestrial range-gated radars commonly used in radio propagation studies. Use of the algorithm permits the effective elimination of ground-based reflections from objects which are independent of precipitation conditions. Results from simulations on a 9 GHz terrestrial radar system are presented.

A microcomputer-based real-time data system for radio wave propagation studies

A microcomputer-based real-time data system has been implemented and tested for data collection and processing. The paper presents the main system components, together with special features tailored for radio propagation studies. The computer system is designed to control a data acquisition system (DAS) and to perform other data processing functions. The system is built using Hewlett-Packard hardware: the low-cost HP9825 microcomputer together with the HP3497 automatic data acquisition and control system. The main features of the system are: (i) Menu-driven system, (ii) user friendly interactive operation, (iii) optimized tape utilization and DAS scanning speed, (iv) on-line help facility. The paper starts by introducing the system layout and then describes the system hardware, which includes the microcomputer, the data acquisition system and the various sensors. System design is then presented with emphasis on tape and speed optimization. It is hoped that the present paper will be useful for engineers and scientists planning environmental, meteorological and engineering studies involving real-time data acquisition.

A Tethered Psychrosonde for Radio Refractivity Profile Measurements

The Indian sub-continent is subject to a varied and complex pattern of anomalous propagation conditions. These have a direct and significant influence on the performance of radar and microwave equipment.This paper describes the instruments and a recoverable Kytoon facility, developed for the first time in India to measure the gradient of temperature, humidity and pressure with height in the lower atmosphere upto 400 metres (extendable to 1.5 km) from the ground in which the major anomalous propagation conditions exist.The gradient of Radio Refractive Index is derived from the three meteorological parameters which enables the study of radio propagation in the VHF, UHF, and microwave spectra.

A Discussion on the early days of ionospheric research and the theory of electric and magnetic waves in the ionosphere and magnetosphere - Phase integral methods for studying the effect of the ionosphere on radio propagation

The phase integral method is a form of ray theory, extended to use complex values of the space coordinates. Its application to radio propagation studies was pioneered by T. L. Eckersley who showed how to use it for calculating (a) the reflexion coefficient of the ionosphere, (b) the propagation constant for radio waves guided by the Earth’s surface and by the ionosphere or troposphere, and (c) the coefficient for coupling of an ordinary and an extraordinary wave in the ionosphere. The method involves the evaluation of integrals along suitably chosen contours in complex space. It is approximate but often capable of high accuracy and often quicker to use than more exact methods. Its justification is based on the physical principles of analytic continuation and of uniform approximation. For reflexion and coupling problems in a horizontally stratified ionosphere, the contours used for the phase integrals are determined by those real or complex heights called ‘reflexion’ or ‘coupling’ points, where two roots of the Booker quartic equation are equal. The study of the behaviour of the governing equations near these points shows when failure of the phase integral method may be expected.

Lloyd Berkner Memorial: The President's Page, Guest Editorial

For forty years Lloyd Berkner was a vigorous participant in geophysics. His career began with his short‐wave radio propagation studies in Minnesota and Antarctica in the 1920's, and continued, with a wider and wider group of colleagues, in studies of the ionosphere, the arctic and antarctic regions, meteorology, and the origin of the atmosphere. His achievements included his remarkable leadership of the American Geophysical Union and the International Council of Scientific Unions, his profoundly expansive vision which was brought to reality in the International Geophysical Year, his chairmanship over landmark National Academy reports in meteorology and space sciences, his leadership in the Associated Universities Incorporated, the Institute of Radio Engineers, in the formation of the Graduate Center of the Southwest (now the University of Texas at Dallas), the Environmental Science Services Administration, and the Institute of Electrical and Electronics Engineers. His untimely death in 1967 at age 62 came in the midst of his exciting new personal research on the origin and the chronology of the earth's atmosphere.

Lloyd V. Berkner (1905-1967)

Lloyd V. Berkner, a Fellow of the Arctic Institute and one of the outstanding American scientists of modern time, suffered a fatal heart attack in Washington on 4 June 1967 while attending a meeting of the National Academy of Sciences. On 7 June he was buried in Arlington National Cemetery. Dr. Berkner was known widely as the "Father of the International Geophysical Year" and more than anyone else in North America developed the idea and gave early impetus to that worldwide effort that did much to promote and improve scientific co-operation throughout the world. He was born in 1905 in Milwaukee, Wisconsin. At the time of his death his legal residence was in Florida. After graduating in 1927 with a B.S. degree in Electrical Engineering, he really had three careers: one as a research scientist, one as a research administrator, and one as a naval officer. He excelled in all three. Early in his career he supervised the installation of the first radio range system. A little later he became a member of the first Byrd Antarctic Expedition and played an important part in designing and installing the communications system for that expedition. Part of that time he spent in New Zealand and established the relay system for antarctic communications. He made constructive studies of long-range radio propagation, and also designed and constructed the first sweep frequency ionospheric sounder. Berkner was appointed the first Executive Secretary of the Research and Development Board of the newly created Department of Defence, and strongly influenced the coordination of the research and development programs of the three armed services. In 1950, at the request of the Secretary of State, he carried out a study of the relationships of science and foreign policy. In his report, Berkner recommended the establishment of the post of Science Adviser to the Secretary of State, as well as the appointment of science attaches in the principal embassies of the United States. These recommendations now have been put into effect. In 1951 he became head of Associated Universities, Inc., and in that capacity for ten years supervised the operation of the Brookhaven National Observatory for the Atomic Energy Commission. Next he accepted the invitation of a group of southwestern businessmen to organize the Graduate Research Centre of the Southwest, with headquarters in Texas. The purpose was to stimulate graduate education and advanced training in that region. In 1927 Berkner was commissioned an Ensign in the U.S. Naval Reserve and designated a Naval Aviator. From 1941 to February 1946 he served in the active naval service. He worked in electronics in the Bureau of Aeronautics and rose to the rank of Captain in 1945. Early that year he was assigned to the Pacific Fleet and served aboard the U.S.S. Enterprise in the Okinawa campaign. Although he was returned to inactive duty in February 1946, he kept up his Naval Reserve status and in 1955 was promoted to Rear Admiral. Doctor Berkner was awarded many honours during his active and productive career. He held at least eight honorary degrees from universities in the United States and from the universities of Calcutta, Uppsala, and Edinburgh. Among his military and civilian awards were: Commendation Ribbon of the Secretary of the Navy; Legion of Merit; Honorary Officer, Order of the British Empire; Special Congressional Gold Medal; Gold Medal of the City of New York; and Silver Medal of the Aeronautical Institute.

ELECTROMAGNETIC FIELDS OF A DIPOLE OVER AN ANISOTROPIC HALF-SPACE

An oscillating electric dipole located over a homogeneous anisotropic conducting half-space is considered. The conductivity tensor is taken to have a simple diagonal form which is appropriate for a finely stratified medium. Expressions for the electromagnetic fields are derived for both vertical and horizontal dipole excitation. It is shown that the horizontally polarized fields are independent of the vertical component of the conductivity. On the other hand, the vertically polarized fields are influenced both by the horizontal and the vertical components of the conductivity. The results have possible application to electromagnetic investigations of the earth's crust and in radio propagation studies.

Microwave Measurements of Partially Coherent Fields

This paper describes a new technique for producing an extended incoherent microwave source and its use in generating calibrated partially coherent fields. The source consists of a planar array of commercial fluorescent lamps for which the thermal radiation corresponds to electron temperatures of over 10,000°K. The technique is significant in that, heretofore, laboratory measurements of radiation from extended microwave sources have been restricted principally to coherent fields, even though many radio propagation studies involve partially coherent fields. Radiometric measurements were made of the coherence of the extended microwave source fields and found to agree well with the van Cittert–Zernike theorem. Diffraction patterns of circular apertures illuminated by partially coherent fields were also measured and showed similar good agreement with theory.

Oblique-Sounding and HF Radio Communication

The sweep-frequency oblique sounder is a powerful tool for the study of ionospheric propagation over actual communication circuits. In addition, since it provides the pulse response of the ionosphere as a function of frequency it is potentially a powerful tool for improving communication via the ionsphere. The Defence Research Telecommunications Establishment's (DRTE) experience in using sweep-frequency sounding for the study of HF radio propagation over both short and long paths is described. These include difficult communication circuits in the auroral zone where unreliability is frequently encountered. These studies have revealed many inadequacies in our present prediction systems. Preliminary attempts to use oblique-sounding information for improving present HF communication circuit reliability have been made, but to obtain full advantage of this technique improved communication systems are required. A description is given of a proposal, which is only one of many possible, for using the obliquesounding technique on HF radio circuits to obtain more reliable long distance communication.

Propagation measurements at 3480 Mc/s over a 173-mile path

The paper presents an account of an experimental study of beyond-the horizon radio scatter propagation at a frequency of 3480 Mc/s over a path of 173 statute miles between Start Point and Wembley. Details of the path and brief details of the transmitting, receiving and recording equipment are given. Propagation data, collected from May, 1956, to April, 1957, are presented. The performance of the link is measured by the hourly median transmission loss, L, defined as the ratio, expressed in decibels, of the power transmitted to that received. The diurnal and seasonal variations in L are discussed. The distribution of the amplitude of the received signal within a period of an hour is used to investigate the characteristic rapid fading of the scattered signal. Some attempt has been made to associate variations in L with general trends in the weather. Experimental estimates of the aerial coupling loss are given and compared with various theoretical predictions. Preliminary measurements on double diversity, using aerials which can be separated in the vertical direction by distances varying from 9 to 17 ft, are reported. The effects produced by aircraft flying through the beam are discussed, and a series of tests in which a naval aircraft flew both along and transversely across the transmission path are described.

Back-scatter sounding: an aid to radio propagation studies

An historical account is given of investigations of back-scatter, and the evidence indicating the ground as the source is discussed. By means of the radar equation the echo intensity is calculated, and the effects of layer curvature and thickness are indicated. The marked seasonal variations in the echo patterns observed at Slough are discussed. Back-scattering after two or more ionospheric reflections is also considered, while very long distance scattering, sometimes with no intermediate ground reflection, is reported. Tests are described which show that, although good accuracy in skip distance measurement is possible, errors may be high if aerials with a large beamwidth are used. The utility of the rotating-aerial back-scatter sounder with plan position indicator for study of propagation over a wide area is stressed and some samples of records obtained with such an instrument are given.

Magnetic work of the United States Coast and Geodetic Survey from July 1, 1949 to June 30, 1950

Geomagnetic information is an essential element of navigational charts. It is also required to surveyors in retracing old property lines originally defined by compass bearings. Important collateral uses occur in geophysical exploration for oil‐bearing structures, in the study and prediction of radio propagation affecting communications and radio navigational aids, in the study of sunspot activities and of auroral and ionospheric disturbances, and in certain military applications.The magnetic survey of the United States has required the accumulation, over many years, of observed values of magnetic declination, intensity, and dip at several thousand places in the United States and territorial areas. The declination in the United States, directly needed for navigational and surveying uses, varies from 22° West in Maine to 24° East in the Pacific Northwest. To evaluate the constantly changing components of the magnetic field, repeat observations at a limited number of key stations are made on a regular schedule, whereas continuous readings of the changing components are made at fixed observatories.