摘要:

The edge effect of planar phased hexagonal arrays is numerically investigated by comparing exact solutions of active impedance and array element pattern of finite arrays with those determined with infinite array approximation. The analysis incorporates the improved circuit theory, which has a higher accuracy than the electro‐motive‐force method. Considerations are also made for the edge effect on the total array pattern. It is found that the edge effect is in reverse proportion to array size. It can be neglected for arrays composed of more than 200 elements, for which the array pattern can be well approximated by the product of the array factor and array element pattern of an infinite ar

ISSN:0048-6604    

DOI:10.1029/RS021i001p00001

年代:1986

数据来源: WILEY

摘要:

The formulas for the complete electromagnetic field in region 1 (z≥ 0,k1) due to a horizontal electric dipole also located in region 1 near its plane boundary with region 2 (z≤ 0,k2; |k2|2« |k1|2) are reviewed and applied to determine the moment of a magnetic dipole that effectively generates the field in region 2. Use is made of this field to determine the locus of the Poynting vector, the maximum depth of penetration into region 2 of the lateral wave part of the field, and the fraction of power associated with the lateral wave in a specified range. Application is made to the use of horizontal antennas on the seafloor for geophysical exploration of the lithosp

ISSN:0048-6604    

DOI:10.1029/RS021i001p00013

年代:1986

数据来源: WILEY

摘要:

Wideband measurements (100 kHz) of medium frequency atmospheric noise have been made over the past several years in the southwestern United States. In part 1 of a two‐part paper the measurement and data transcription system and the statistical analysis software used to analyze the data are presented. In part 2, representative first‐ and higher‐order statistics and the impact of the data on bandwidth and system performance are described. Measurement results presented in part 1 include the temporal structure of atmospheric noise, the distribution and time variation of the measured average noise power, and comparisons with predictions by the International Radio Consultative Committee (

ISSN:0048-6604    

DOI:10.1029/RS021i001p00025

年代:1986

数据来源: WILEY

摘要:

As part of a larger experiment to measure the cosmic microwave background radiation spectrum, frequent simultaneous measurements of microwave thermal emissions from the earth's atmosphere have been made at 10, 33, and 90 GHz. We have performed these measurements at two separate locations, Berkeley, California, and the White Mountain Research Station located near Bishop, California, which differ greatly in altitude and climatic conditions. Typical values of the atmospheric antenna temperature measured in Berkeley (250‐m elevation) during good weather are 2.54±0.29, 12.4±0.3, and 34.3±0.5 K for 10, 33, and 90 GHz, respectively. Corresponding values measured at White Mountain (3800 m) are 1.11± 0.04, 4.48±0.18, and 11.0±0.1 K. Because the measurements are simultaneous in nature, correlations between the measurements taken at the various frequencies provide constraints on models of the microwave emission of the earth's atmosphere, especially models describing atmospheric emission as a function of precipitable water

ISSN:0048-6604    

DOI:10.1029/RS021i001p00047

年代:1986

数据来源: WILEY

摘要:

A numerical consideration is performed on degradation of element properties and array patterns of a planar phased array owing to the effects of antenna element structure. By using a crossed 3‐subelement Yagi antenna specially designed for the VHP‐band MST radar in Japan (the MU radar) as a model of antenna element, the following two subjects are investigated: (1) mutual coupling effects induced by deviation of the intersecting point of a pair of crossed subelements from each subelement center, and (2) effects of vertical current which flows on the mast supporting the antenna subelements. It is concluded that neither of them provide significant degradation of either element properties or array patterns. Although this conclusion is derived for specific phased arrays composed of specific antenna elements, it will be essentially valid for ordinary planar phased arrays composed of dipoles or Yagi anten

ISSN:0048-6604    

DOI:10.1029/RS021i001p00056

年代:1986

数据来源: WILEY

摘要:

The simple attenuation model has been improved from an earlier version and now includes the effect of wave polarization. The model is for the prediction of rain attenuation statistics on earth‐space communication links operating in the 10–35 GHz band. Simple calculations produce attenuation values as a function of average rain rate. These together with rain rate statistics (either measured or predicted) can be used to predict annual rain attenuation statistics. In this paper model predictions are compared to measured data from a data base of 62 experiments performed in the U.S., Europe, and Japan. Comparisons are also made to predictions from other mod

ISSN:0048-6604    

DOI:10.1029/RS021i001p00065

年代:1986

数据来源: WILEY

摘要:

Probability‐density functions of directional slopes of the wind‐disturbed water surface were measured with an optical scanner. The upwind‐downwind and crosswind components of mean‐square slopes were found to vary with the logarithm of wind‐friction velocity. The angular variation of mean‐square slopes was found to follow an elliptical, Gaussian joint probability‐density function, with its variance again related to the wind‐fr

ISSN:0048-6604    

DOI:10.1029/RS021i001p00073

年代:1986

数据来源: WILEY

摘要:

We present mathematical methods for the interpretation of high frequency radar sea‐echo measured by narrow‐beam and CODAR systems. (CODAR is a small transportable radar with a scanning broad beam). These methods are based Barrick's equations for the ocean radar cross section in terms of the directional ocean waveheight spectrum and surface current, using a dimensionless mathematical formulation. In this paper, we describe the simulation of narrow‐ and broad‐beam radar sea‐echo from both deep and shallow water, discussing the effect of ocean surface currents, including vertical and horizontal current shear. This paper provides the mathematical tools for the modeling of common experimental situations in HF radar oceanography; such models are used in subsequent papers that describe the extraction of sea‐state information from HF radar se

ISSN:0048-6604    

DOI:10.1029/RS021i001p00081

年代:1986

数据来源: WILEY

摘要:

A simple user interactive technique that allows digital ionosonde sky map echo location data to be dealiased uniquely is described. Unambiguous tracking of large‐scale ionospheric features is thus made possible. The method utilizes the frequency dependence of the relationship between obliquity of propagation and signal phas

ISSN:0048-6604    

DOI:10.1029/RS021i001p00101

年代:1986

数据来源: WILEY

摘要:

A simple surface propagation model is commonly used to estimate the effects of ionospheric disturbances on extremely low frequency (ELF) propagation. Though often adequate, one shortcoming of the model is its failure to allow for excitation by the broadside component of a horizontal electric dipole. That excitation can be quite significant in a sporadicEenvironment because the modal polarization can then contain a substantial mixture of transverse electric component. This is demonstrated by considering a flat earth geometry with a vertical geomagnetic field superimposed on a laterally homogeneous, cylindrically symmetric disturbance centered over the transmitter. The method utilizes normal mode decomposition. Matching equations at the boundary of the disturbance are developed by evaluating height gain integrals, and it is shown that this method is tantamount to simply matching the ground vertical electric and azimuthal magnetic fields at the boundary. Results for a sporadicEtype environment indicate substantial departures from other model predictions.

ISSN:0048-6604    

DOI:10.1029/RS021i001p00106

年代:1986

数据来源: WILEY