摘要:

A theory is presented giving far‐field radiation patterns and surface‐wave behavior for vertically polarized antennas located at zero height over flat ground, with a surface impedance which can be discontinuous along a radius from the antenna. The theory is based on the radiation from the surface electric and magnetic currents as determined by the Sommerfeld attenuation function. Both sky‐wave and surface‐wave solutions are obtained simultaneously, with applications to ground screens, recovery phenomena, Fresnel zones, and similar engineering problems discussed with examples. In general, the results agree with those obtained using the compensation

ISSN:0048-6604    

DOI:10.1029/RS010i012p01011

年代:1975

数据来源: WILEY

摘要:

Digital radar reflectivity data may be used to estimate the slant path attenuation which would have been obtained on a ground‐to‐satellite path using a frequency higher than that of the original radar. The crucial role of the small intense cells is illustrated and the necessity of maintaining the radar data at their highest spatial resolution is discussed. A technique to simulate path diversity systems is demonstrated for a squall line case and shows that diversity pair orientation perpendicular to the elongation of the precipitation line studied yields the best diversity performa

ISSN:0048-6604    

DOI:10.1029/RS010i012p01019

年代:1975

数据来源: WILEY

摘要:

The problem of microwave thermal emission from a half‐space random medium is solved. We consider a laminar structure which has a nonuniform temperature distribution in the vertical direction. A radiative transfer approach is applied. For constant absorption and scattering coefficients, the brightness temperature is determined by a simple closed‐form formula. Physical interpretations and numerical results are illustrated and discussed for the various ca

ISSN:0048-6604    

DOI:10.1029/RS010i012p01025

年代:1975

数据来源: WILEY

摘要:

It is shown that the correlation ellipse bears no relationship to the “average” shape of irregularities in the amplitude pattern formed at the ground from the interference of radio waves reflected or scattered from the ionosphere. The concept that the correlation ellipse should be related to the average shape arose because it was considered that the cross‐correlation coefficient for zero delay between two fading records (with spatial separationr) was related to the average normalized amplitude of the irregularities at a displacementrfrom the center of the average irregularity. As shown in this paper, the cross‐correlation coefficient for zero delay depends only on the mean fading period and the mean and variance of the time delays between corresponding fades. It retains its usual significance only ifris in the direction o

ISSN:0048-6604    

DOI:10.1029/RS010i012p01035

年代:1975

数据来源: WILEY

摘要:

Irradiance fluctuations of a plane wave propagating through a strongly refracting thin turbulent slab are treated. The parabolic wave equation of the fourth‐order moment of the field is solved by an operational method and the triple integral form of the solution is obtained. Numerical results of the variance function show the saturation effect and the values of the covariance are given for the under‐ and over‐saturation re

ISSN:0048-6604    

DOI:10.1029/RS010i012p01037

年代:1975

数据来源: WILEY

摘要:

The estimation of the power spectrum of a time series by fitting a finite autoregressive model to the data has recently found widespread application in the physical sciences. The extension of this method to the analysis of vector time series is presented here through its application to ULF waves observed in the magnetosphere by the ATS 6 synchronous satellite. Autoregressive spectral estimates of the power and cross‐power spectra of these waves are computed with computer programs developed by the author and are compared with the corresponding Blackman‐Tukey spectral estimates. The resulting spectral density matrices are then analyzed to determine the direction of propagation and polarization of the observed wa

ISSN:0048-6604    

DOI:10.1029/RS010i012p01043

年代:1975

数据来源: WILEY

摘要:

Equations for the two‐frequency two‐position mutual coherence functions are derived under the usual parabolic and Markov approximations. These equations are then solved numerically. It is shown that the mutual coherence functions occur naturally in the study of pulse distortion through a random communication channel and in the investigation of signal correlations. Contour plots of correlation functions show the possibility of having equal values at two frequency separations for a given spatial separation. This behavior is explainable in terms of overlapping Fresnel zo

ISSN:0048-6604    

DOI:10.1029/RS010i012p01055

年代:1975

数据来源: WILEY

摘要:

A modulated beam of charged particles is represented as an infinite line antenna carrying a current distribution traveling along it at a prescribed speed. The radiation from such an antenna is calculated theoretically, and typical patterns are presented for conditions appropriate to the ionosphere and magnetosphere.

ISSN:0048-6604    

DOI:10.1029/RS010i012p01063

年代:1975

数据来源: WILEY

摘要:

When cylindrical electron beams, density modulated at a prescribed repetition frequency (f≈ 3 to 6 MHz), are injected into plasmas along a magnetic field, cylindrical electron Bernstein waves are found to be launched nearly perpendicular to the electron beams. The wave amplitude and frequency are controlled easily. The mechanism of the excitation of cylindrical electron Bernstein waves by electron beams is investigated theoretically to explain the experimental result

ISSN:0048-6604    

DOI:10.1029/RS010i012p01071

年代:1975

数据来源: WILEY